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  • AERODYNAMICS  (2,975)
  • 1985-1989  (2,967)
  • 1940-1944  (8)
  • 1
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    Application of a semianalytical technique for sensitivity analysis of unsteady aerodynamic computations (1988)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: A semianalytical approach is developed for the sensitivity analysis of linear unsteady aerodynamic loads. The semianalytical approach is easier to implement than the analytical approach. It is also computationally less expensive than the finite difference approach when used with panel methods which require a large number of panels. The semianalytical approach is applied to an isolated airfoil in a two-dimensional flow and rotating propfan blades in three-dimensional flow. Sensitivity coefficients with respect to nonshape-dependent variables are shown for some cases.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2377 , Structures, Structural Dynamics and Materials Conference; Apr 18, 1988 - Apr 20, 1988; Williamsburg, VA; United States
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  • 2
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    Some numerical calculations by using linear classical sonic theories approached from sub- or supersonic speeds (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The unsteady aerodynamics of a two-dimensional wing at sonic speed are studied by using so-called classical sonic theories (linear), approached from supersonic flow (M=1+0) or subsonic flow (M=1-0). In the former approach, the exact expressions of lift and lift distribution are obtained in terms of Fresnel integrals, while in the latter approach an integral equation must be solved, the kernel function of which is obtained from the subsonic Possio's equation and has a root singularity. The discrete analysis is adopted on the basis of the semicircle method (SCM) and the weighting function for subsonic-flow-Gauss-quadrature, as well as modified characteristics obtained from both approaches agree quite well with each other. The results obtained by the present computations are compared with those of DLM-C (subsonic 2D code) developed by ANDO et al, and are found to give a reasonable outer boundary for subsonic unsteady aerodynamics.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20112 , NAS 1.77:20112
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  • 3
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    The Aerodynamic Optimization of Wings at Subsonic Speeds and the Influence of Wingtip Design (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Some of the objectives of modern aircraft development are related to the achievement of reduced fuel consumption and aircraft noise. This investigation is mainly concerned with the aerodynamic aspects of aircraft development, i.e., reduction of induced drag. New studies of wing design, and in particular wing tips, are considered. Induced drag is important since, in cruising flight, it accounts for approximately one-third of the entire drag for the aircraft, and one-half while climbing. A survey is presented for the wing geometries and wing tip designs studied, and theoretical investigations of different planar wings with systematically varied wing tip forms are conducted. Attention is also paid to a theoretical study of some planar and nonplanar wings and their comparison with experimental data.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88534 , NAS 1.15:88534
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  • 4
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    Aeronautical engineering: A continuing bibliography with indexes (supplement 225) (1988)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: This bibliography lists 429 reports, articles, and other documents introduced into the NASA scientific and technical information system in March, 1988.
    Keywords: AERODYNAMICS
    Type: NASA-SP-7037(225) , NAS 1.21:7037(225)
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  • 5
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    Finite element calculations for aerodynamic coefficients of a 3-dimensional body in subsonic flow using Green's function method (1988)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: An accurate method for evaluating the derivatives along circular paths on the surface is proposed. Calculations are made on various practical configurations such as wing-body combinations, tandem wings, wings with dihedral angles at sideslip, ground effects, interference between a sphere and wind tunnel, etc. Comparisons with experiment show good agreement.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20208 , NAS 1.77:20208
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  • 6
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    Calculation of non-stationary aerodynamic forces in the near sonic range (1988)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The development of a mathematical method for calculating nonstationary supersonic flow in the near-sonic range is described. A perturbation formula is derived based on the exact stationary values; it is applicable to the equation for potential. The problem can thus be divided into stationary and nonstationary fields. The pressure distribution in an oscillating profile is determined, based on hyperbolic differential equations. It is shown that there are important corollaries concerning the application of linear theory. With suitable extrapolations, linear theory can be used up to about Mach 0.8. Linear theory is not applicable, however, when determining the moment coefficients; for this case, a special technique is described.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20310 , NAS 1.77:20310
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  • 7
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    Aeronautical engineering: A continuing bibliography with indexes (supplement 219) (1987)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: This bibliography lists 586 reports, articles, and other documents introduced into the NASA scientific and technical information system in October, 1987.
    Keywords: AERODYNAMICS
    Type: NASA-SP-7037(219) , NAS 1.21:7037(219)
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  • 8
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    Calculation of aerodynamic heat transfer for blunt-nosed thin wings at different angles of attack at supersonic speeds (1987)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: A method for calculating aerodynamic heat transfer on thin wings at angles of attack is provided, based on the assumption of small cross flow and the calculation of an infinite cylinder. It is valid in the range of supersonic and hypersonic speeds. The method does not require calculation of the details of the stream lines and can be used for various swept wings at moderate angle of attack or yaw angle. A comparison between theoretical and experimental results is given.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20127 , NAS 1.77:20127
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  • 9
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    Calculation of the distributed loads on the blades of individual multiblade propellers in axial flow using linear and nonlinear lifting surface theories (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: In recent years much attention has been given to the development of methods and programs for the calculation of the aerodynamic characteristics of multiblade, saber-shaped air propellers. Most existing methods are based on the theory of lifting lines. Elsewhere, the theory of a lifting surface is used to calculate screw and lifting propellers. In this work, methods of discrete eddies are described for the calculation of the aerodynamic characteristics of propellers using the linear and nonlinear theories of lifting surfaces.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20173 , NAS 1.77:20173 , (ISSN 0321-3429)
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  • 10
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    Aeronautical engineering: A cumulative index to a continuing bibliography (1988)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: This bibliography is a cumulative index to the abstracts contained in NASA SP-7037(210) through NASA SP-7037(221) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, foreign technology, contract number, report number, and accession number indexes.
    Keywords: AERODYNAMICS
    Type: NASA-SP-7037(222) , NAS 1.21:7037(222)
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  • 11
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    The interference of the model support mast with measurements of the longitudinal and lateral aerodynamic coefficients (1987)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The effects the single-bottom support masts used in the ONERA S1 and S4 wind tunnels have on aerodynamic data collected with scale model aircraft were examined experimentally and analytically. Systematic studies were performed on the flow characteristics around different diameters for the mounts. Scaling methods used to make data from one wind tunnel correspond to data from the other are described. Airbus 320 models were introduced into the tests and mast-body flow interactions were observed. A summary is presented of restrictions on the mast diameters, relative to cylindrical model diameters, which will minimize the effects the masts have on longitudinal and lateral aerodynamic stability data.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20079 , NAS 1.77:20079 , ONERA-TP-1986-181
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  • 12
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    Hypersonic aerodynamic coefficients and convection flow estimation in a HERMES type project (1987)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: An analysis of all the experimental and computation requirements of the HERMES project is presented. The discussion includes the influence of the upper atmosphere composition and possible chemical reactions, the information collected in Orbiter experiments, the possibility of utilizing plasma generators and CF4 in wind tunnel tests, the development of parabolized Navier-Stokes models and solutions, and the computing capacity requirements.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20019 , NAS 1.77:20019
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  • 13
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    Aerodynamics of the Viggen 37 aircraft. Part 1: General characteristics at low speed (1986)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: A description of the aerodynamics of the Viggen 37 and its performances, especially at low speeds is presented. The aerodynamic requirements for the design of the Viggen 37 aircraft are given, including the basic design, performance requirement, and aerodynamic characteristics, static and dynamic load test results and flight test results. The Viggen 37 aircraft is designed to be used for air attack, surveillance, pursuit, and training applications. It is shown that this aircraft is suitable for short runways, and has good maneuvering, acceleration, and climbing characteristics. The design objectives for this aircraft were met by utilizing the effect produced by the interference between two triangular wings, positioned in tandem.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88403 , NAS 1.15:88403
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  • 14
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    Formation of asymmetric separated flow past slender bodies of revolution at large angles of attack (1986)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The paper examines the problem of determining stationary positions of pairs of vortices of unequal intensity in the flow behind a cylinder modeling the axisymmetric separated flow past a slender body at large angles of attack. The possible asymmetric stationary positions of two vortices are calculated, and their stability with respect to small perturbations is determined. Bifurcations of the flow field with changes in vortex intensity are analyzed.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88441 , NAS 1.15:88441 , (ISSN 0321-3249)
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  • 15
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    Mutual effect of thermochemical surface decomposition and viscous interaction during hypersonic flow past a sharp cone (1986)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Numerical results on the hypersonic gas flow in viscous interaction regime past sharp circular cones with thermally destructible Teflon surface are presented. Characteristics of the mutual influence between the thermochemical decomposition of the surface and the viscous interaction are revealed.
    Keywords: AERODYNAMICS
    Type: NASA-TM-78015 , NAS 1.15:78015
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  • 16
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    Three-dimensional boundary layer analysis program Blay and its application (1986)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The boundary layer calculation program (BLAY) is a program code which accurately analyzes the three-dimensional boundary layer of a wing with an undefined plane. In comparison with other preexisting programs, the BLAY is characterized by the following: (1) the time required for computation is shorter than any other; (2) the program is adaptable to a parallel processing computer; and (3) the program is associated with a secondary accuracy in the z-direction. As a boundary layer modification to transonic nonviscous flow analysis programs, it is used to adjust viscous and nonviscous interference problems repeatedly. Its efficiency is an important factor in cost reduction in aircraft designing.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77962 , NAS 1.15:77962 , Jun 30, 1983 - Jul 01, 1983; Tokyo; Japan
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  • 17
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    Comparison of computational results of a few representative three-dimensional transonic potential flow analysis programs (1986)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The development of transonic aerodynamic computation methods and specific examples, as well as examples of three-dimensional transonic computation in design, are discussed. The case of the transonic transport and the case of the small transport are analyzed. Requirements for programs of the future are itemized.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77963 , NAS 1.15:77963 , Jun 30, 1983 - Jul 01, 1983; Tokyo; Japan
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  • 18
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    NASA's hypersonic fluid and thermal physics program (Aerothermodynamics) (1985)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: This survey paper gives an overview of NASA's hypersonic fluid and thermal physics program (recently renamed aerothermodynamics). The purpose is to present the elements of, example results from, and rationale and projection for this program. The program is based on improving the fundamental understanding of aerodynamic and aerothermodynamic flow phenomena over hypersonic vehicles in the continuum, transitional, and rarefied flow regimes. Vehicle design capabilities, computational fluid dynamics, computational chemistry, turbulence modeling, aerothermal loads, orbiter flight data analysis, orbiter experiments, laser photodiagnostics, and facilities are discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-0922
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  • 19
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    Deceleration of a supersonic flow behind a curved shock wave with isentropic precompression (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Three-dimensional supersonic flows of an ideal fluid in the neighborhood of bodies formed by being cut out along the streamlines of an axisymmetric flow are investigated. The flow consists of a region of isoentropic compression and a region of vortex flow. An exact solution with variable entropy is used to describe the flow in the vortex region. In the continuous flow region an approximate solution is constructed by expanding the solution in a series in a small parameter. The effect of the shape of the excision and the vorticity of the flow on compression of the jet and and the total pressure loss coefficient is studied.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77920 , NAS 1.15:77920
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  • 20
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    Presentation of the acoustic and aerodynamic results of the Aladin 2 concept qualification testing (1985)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Wind tunnel tests were conducted of a scale model of the Aladin 2 aircraft. The propulsion system configuration is described and the air flow caused by jet ejection is analyzed. Three dimensional flow studies in the vicinity of the engine installation were made. Diagrams of the leading and trailing edge flaps are provided. Graphs are developed to show the aerodynamic performance under conditions of various airspeed and flap deflection.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77883 , NAS 1.15:77883 , CP-143
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  • 21
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    Discussion of the paper, Some Aspects of Propulsion for the Augmenter-Wing Concept, by D. C. Whittley (1985)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Many modern concepts for STOL and V/STOL aircraft rely on integration of the propulsion system with the wing to create favorable lift interactions, and are known as powered lift concepts. A study of powered lift, concerning management and control of the various propulsive streams or jets is presented, each concept having its own particular objectives and requirements. Some specific objectives of this kind are described which relate to the augmentor wing. Consideration is given to three aspects of the subject, namely the augmentor flap itself, the wind ducting and augmentor primary nozzle, and the choice of powerplant or engine cycle. More generally, comments are made regarding noise attenuation and the prospect for achieving a low overall noise level for jet STOL aircraft of the future.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77884 , NAS 1.15:77884
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  • 22
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    Periodic vortex shedding in the supersonic wake of a planar plate (1985)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Vortex sheets in the wake have been mainly studied in incompressible flows and in the transonic region. Heinemann et al. (1976) have shown that for the subsonic region the Strouhal number is nearly independent of the Mach number. Motallebi and Norbury (1981) have observed an increase in the Strouhal number in transonic supersonic flow at Mach numbers up to 1.25. The present investigation is concerned with an extension of the studies of vortex shedding to higher supersonic Mach numbers, taking into account questions regarding the possibility of a generation of stable von Karman vortex paths in the considered Mach number range. It is found that the vortex sheet observed in a supersonic wake behind a rough plate is only stable and reproducible in cases involving a certain surface roughness and certain aspects of trailing edge geometry.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77854 , NAS 1.15:77854
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  • 23
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    Three-dimensional unsteady lifting surface theory in the subsonic range (1985)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The methods of the unsteady lifting surface theory are surveyed. Linearized Euler's equations are simplified by means of a Galileo-Lorentz transformation and a Laplace transformation so that the time and the compressibility of the fluid are limited to two constants. The solutions to this simplified problem are represented as integrals with a differential nucleus; these results in tolerance conditions, for which any exact solution must suffice. It is shown that none of the existing three-dimensional lifting surface theories in subsonic range satisfy these conditions. An oscillating elliptic lifting surface which satisfies the tolerance conditions is calculated through the use of Lame's functions. Numerical examples are calculated for the borderline cases of infinitely stretched elliptic lifting surfaces and of circular lifting surfaces. Out of the harmonic solutions any such temporal changes of the down current are calculated through the use of an inverse Laplace transformation.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77812 , NAS 1.15:77812 , European Aeron. Congr.; Sep 25, 1956 - Sep 29, 1956; Scheveningen; Netherlands
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  • 24
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    High-alpha aerodynamic characteristics of crescent and elliptic wings (1989)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Static longitudinal and lateral-directional forces and moments were measured for elliptic- and crescent-wing models at high angles of attack in the NASA Langley 14-by-22-ft Subsonic Tunnel. The forces and moments were obtained for an angle-of-attack range including stall and post-stall conditions at a Reynolds number based on the average wing chord of about 1.8 million. Flow-visualization photographs using a mixture of oil and titanium-dioxide were also taken for several incidence angles. The force and moment data and the flow-visualization results indicated that the crescent wing model with its highly swept tips produced much better high-angle-of-attack aerodynamic characteristics than the elliptic model. Leading-edge separation-induced vortex flow over the highly swept tips of the crescent wing is thought to produce this improved behavior at high angles of attack. The unique planform design could result in safer and more efficient low-speed airplanes.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-2240 , AIAA Applied Aerodynamics Conference; Jul 31, 1989 - Aug 02, 1989; Seattle, WA; United States
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  • 25
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    Stability characteristics of a supersonic boundary layer and their relation to the position of the laminar-turbulent transition point (1987)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: By comparing the calculated results with experimental data, it is demonstrated that the position of the laminar-boundary transition point of a boundary layer can be estimated by using the e-exp-n method. The effect of the Mach number, pressure gradient, and heat transfer on the laminar-turbulent transition is discussed. It is found that under conditions of strong cooling, the effect of the pressure gradient on the position of the transition point is less pronounced than in the absence of heat transfer.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88533 , NAS 1.15:88533
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  • 26
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    Aerodynamic characteristics of general aviation at high angle of attack with the propeller slipstream (1986)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: The aerodynamic characteristics of the FA-300 business aircraft at high angle of attack with the propeller stream are described. The FA-300 offers two types, FA-300-700 for 340 HP, and -710 for 450 Hp of the engine. The effects of the propeller slipstream on the high angle of the attack are discussed.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88503 , NAS 1.15:88503 , (ISSN 0021-4663)
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  • 27
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    Supersonic flow with feeding of energy (1985)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: The present work discusses the results of some experimental studies on the possibility of attenuating shock waves in a supersonic flow. The shock waves were formed by an external source of electrical energy. An electromechanical method is described that permits partial recovery of the expended energy.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77912 , NAS 1.15:77912
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  • 28
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    NASA's CFD Validation Program (1989)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: With computational fluid dynamics (CFD) becoming a productive research and design tool, the requirement to validate CFD codes has grown significantly. NASA had emphasized CFD validation activities since 1986 when a separate work element was formed to fund experimental activities related to validation. NASA's CFD and CFD validation programs are closely coordinated to ensure that experimental data bases are available as soon as possible for validating codes. In response to industry and academic requirements, four levels of experimental research have been defined as part of CFD validation with NASA's Aeronautics Advisory Committee (AAC) support although only the fourth level actually has the detailed information necessary for validating codes. Critical flow physics especially turbulence modeling are key to improved CFD codes. NASA has focused additional resources on transition and turbulence physics to meet these requirements. With improved turbulence models, CFD codes will be more accurate, robust, and efficient. However, with the level of detailed information available from CFD codes, highly accurate and detailed experiments are required to capture the critical information for validating codes. Advanced instrumentation especially non-intrusive instrumentation is required to acquire this information in validation experiments. The CFD validation program is being coordinated and managed to address these critical activities. A list of experiments which are currently being supported at least partially are included.
    Keywords: AERODYNAMICS
    Type: NASA, Ames Research Center, NASA Computational Fluid Dynamics Conference. Volume 1: Sessions 1-6; p 123-134
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  • 29
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    A preliminary investigation of drag reduction and mechanism for a blunt body of revolution with slanted base (1988)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: This is a preliminary study of the drag reduction effect and its mechanism of a blunt body of revolution with a 21-deg slant angle by using a series of base plates. Drag coefficients were measured to investigate the effect of base installation position and plate height. An effective drag reduction device was found. Through the measurement of base pressure and total pressure distribution and flow pattern display, flow characteristics and drag reduction mechanism in the vortex near the wake were investigated.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20349 , NAS 1.77:20349
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  • 30
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    Oscillating airfoils and their wake (1985)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: The unsteady phenomena in the wake of an oscillating wing or rotor blade are examined theoretically using the Prandtl approximation of the vortex-transport equation. A mathematical model is developed and applied to such problems as the effect of winglets on the performance of fixed wings and the possibly of employing similar designs in rotor blades. Model predictions for several profiles are compared with published and experimental measurements, and good agreement is found. Graphs and diagrams are provided.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77831 , NAS 1.15:77831 , REPT-42
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  • 31
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    Airflow Research (1985)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: This is an overview of research being done in laminar flow at Ames Dryden Flight Research Center and Langley Research Center. Airflow research at Ames Dryden has resulted in a special wing covering that will artificially induce laminar flow on the wing surface; this specially adapted wing is shown being tested in different flying conditions. This video also features research done at Langley in producing a chemical covering for wings that will make visible natural laminar flow and turbulent airflow patterns as they occur. Langley researchers explain possible use of this technology in supersonic flight.
    Keywords: AERODYNAMICS
    Type: ASR-239 , NASA-TM-109372 , NONP-NASA-VT-94-198219
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  • 32
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    Unsteady aerodynamic characterization of a military aircraft in vertical gusts (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The effects of 2.5-m/sec vertical gusts on the flight characteristics of a 1:8.6 scale model of a Mirage 2000 aircraft in free flight at 35 m/sec over a distance of 30 m are investigated. The wind-tunnel setup and instrumentation are described; the impulse-response and local-coefficient-identification analysis methods applied are discussed in detail; and the modification and calibration of the gust-detection probes are reviewed. The results are presented in graphs, and good general agreement is obtained between model calculations using the two analysis methods and the experimental measurements.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77810 , NAS 1.15:77810 , AAAF-NT-83-16 , Appl. Aerodyn. Colloq.,; Nov 08, 1983 - Nov 10, 1983; Toulouse; France
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    Variable Sweep Transition Flight Experiment (VSTFE)-Parametric Pressure Distribution Boundary Layer Stability Study and Wing Glove Design Task (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: The Variable Sweep Transition Flight Experiment (VSTFE) was initiated to establish a boundary-layer transition data base for laminar flow wing design. For this experiment, full-span upper-surface gloves will be fitted to a variable sweep F-14 aircraft. The results of two initial tasks are documented: a parametric pressure distribution/boundary-layer stability study and the design of an upper-surface glove for Mach 0.8. The first task was conducted to provide a data base from which wing-glove pressure distributions could be selected for glove designs. Boundary-layer stability analyses were conducted on a set of pressure distributions for various wing sweep angles, Mach numbers, and Reynolds number in the range of those anticipated for the flight-test program. The design procedure for the Mach 0.8 glove is described, and boundary-layer stability calculations and pressure distributions are presented both at design and off-design conditions. Also included is the analysis of the clean-up glove (smoothed basic wing) that will be flight-tested initially and the analysis of a Mach 0.7 glove designed at the NASA Langley Research Center.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3992 , NAS 1.26:3992 , D6-52511
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    Sensitivity of F-106B Leading-Edge-Vortex Images to Flight and Vapor-Screen Parameters (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: A flight test was undertaken at NASA Langley Research Center with vapor-screen and image-enhancement techniques to obtain qualitative and quantitative information about near-field vortex flows above the wings of fighter aircraft. In particular, the effects of Reynolds and Mach numbers on the vortex system over an angle-of-attack range were sought. The relevance of these flows stems from their present and future use at many points in the flight envelope, especially during transonic maneuvers. The aircraft used in this flight program was the F-106B because it was available and had sufficient wing sweep (60 deg) to generate a significant leading-edge vortex system. The sensitivity of the visual results to vapor screen hardware and to onset flow changes is discussed.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2818 , L-16395 , NAS 1.60:2818
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    Numerical Simulation of Subsonic and Transonic Propeller Flow (1988)
    In:  CASI
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    Publication Date: 2019-08-14
    Description: The numerical simulation of 3-D transonic flow about a system of propeller blades is investigated. In particular, it is shown that the use of helical coordinates significantly simplifies the form of the governing equation when the propeller system is assumed to be surrounded by an irrotational flow field of an inviscid fluid. The unsteady small disturbance equation, valid for lightly loaded blades and expressed in helical coordinates, is derived from the general blade-fixed potential equation, given for an arbitrary coordinate system. The use of a coordinate system which inherently adapts to the mean flow results in a disturbance equation requiring relatively few terms to accurately model the physics of the flow. Furthermore, the helical coordinate system presented here is novel in that it is periodic in the circumferential direction while, simultaneously, maintaining orthogonal properties at the mean blade locations. The periodic characteristic allows a complete cascade of blades to be treated, and the orthogonality property affords straightforward treatment of blade boundary conditions. An ADI numerical scheme is used to compute the solution of the steady flow as an asymptotic limit of an unsteady flow. As an example of the method, solutions are presented for subsonic and transonic flow about a 5 percent thick bicircular arc blade of an 8-bladed cascade. Both high and low advance ratio cases are computed and include a lifting as well as nonlifting cases. The nonlifting solutions obtained are compared to solutions from a Euler code.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100163 , E-3725 , NAS 1.15:100163 , GRC-E-DAA-TN22557
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    Shuttle Tethered Aerothermodynamics Research Facility (STARFAC) Instrumentation Requirements (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: The instrumentation requirements for the Shuttle Tethered Aerothermodynamic Research Facility (STARFAC) are presented. The typical physical properties of the terrestrial atmosphere are given along with representative atmospheric daytime ion concentrations and the equilibrium and nonequilibrium gas property comparison from a point away from a wall. STARFAC science and engineering measurements are given as are the TSS free stream gas analysis. The potential nonintrusive measurement techniques for hypersonic boundary layer research are outlined along with the quantitative physical measurement methods for aerothermodynamic studies.
    Keywords: AERODYNAMICS
    Type: NASA, Washington Applications of Tethers in Space: Workshop Proceedings, Vol. 2; p 251-263
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  • 37
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    Losses in Channels with Increased External Turbulence (1986)
    In:  CASI
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    Publication Date: 2019-08-14
    Description: An approximate method for determining the effect of the level of turbulence on the aerodynamic characteristics of convergent and diffuser channels is examined. A momentum equation for the boundary layer is in the method, introducing external flow turbulence on the basis of experimental values of the coefficient of friction and the form factor. It is found that at significant levels of external turbulence, losses must be considered not only in the boundary layer but also in the central region of the channel.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77995 , NAS 1.15:77995
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  • 38
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    On the Solution of the Three-Dimensional Flowfield About a Flow-Through Nacelle (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: The solution of the three dimensional flow field for a flow through nacelle was studied. Both inviscid and viscous inviscid interacting solutions were examined. Inviscid solutions were obtained with two different computational procedures for solving the three dimensional Euler equations. The first procedure employs an alternating direction implicit numerical algorithm, and required the development of a complete computational model for the nacelle problem. The second computational technique employs a fourth order Runge-Kutta numerical algorithm which was modified to fit the nacelle problem. Viscous effects on the flow field were evaluated with a viscous inviscid interacting computational model. This model was constructed by coupling the explicit Euler solution procedure with a flag entrainment boundary layer solution procedure in a global iteration scheme. The computational techniques were used to compute the flow field for a long duct turbofan engine nacelle at free stream Mach numbers of 0.80 and 0.94 and angles of attack of 0 and 4 deg.
    Keywords: AERODYNAMICS
    Type: NASA-TM-87448 , NAS 1.15:87448 , N85-22371
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  • 39
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    Development of supersonic computational aerodynamic program using panel method (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: An aerodynamic program for steady supersonic linearized potential flow using a higher order panel method was developed. Boundary surface is divided into planar triangular panels on each of which a linearly varying doublet and a constant or linearly varying source are distributed. Distributions of source and doublet on the panel assemblies of the panels can be determined by their strengths at nodal points, which are placed at the vertices of the panels for linear distribution or on each panel for constant distribution.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20113 , NAS 1.77:20113
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  • 40
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    Integral method of wall interference correction in low-speed wind tunnels (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The analytical solution of Poisson's equation, derived form the definition of vortex, was applied to the calculation of interference velocities due to the presence of wind tunnel walls. This approach, called the Integral Method, allows an accurate evaluation of wall interference for separated or more complicated flows without the need for considering any features of the model. All the information necessary for obtaining the wall correction is contained in wall pressure measurements. The correction is not sensitive to normal data-scatter, and the computations are fast enough for on-line data processing.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20055 , NAS 1.77:20055
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  • 41
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    Vortex systems on slender rotating bodies and their effect on the aerodynamic coefficients (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The turbulent flow of rotational bodies up to a length of 20 diameters with various head shapes and cylindrical tails was examined in the subsonic wind tunnel with the Mach number of M = 0.1. At angles of incidence lower than 30 degrees, a pair of symmetrical eddies rests stationary from head to tail on the trailing side, very close to the body. At angles between 30 and 60 degrees, the stationary eddies are asymmetrically pushed off. Between 60 and 90 degrees, the eddies detach themselves in an instationary manner. This includes, for example, the turbulent flow at the start-up of flying bodies in the presence of lateral winds. The results of measurments obtained by Mello at M = 2, an impulse method, and the cross flow theory according to Allen are used for comparison.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88490 , NAS 1.15:88490 , ISL-10/66
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  • 42
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    Propulsion and control propellers with thruster nozzles primarily for aircraft applications (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: A propulsion and control propeller with thruster nozzles, primarily for aircraft application is described. Adjustability of rotor blades at the hub and pressurized gas expulsion combined with an air propeller increase power. Both characteristics are combined in one simple device, and, furthermore, incorporate overall aircraft control so that mechanisms which govern lateral and horizontal movement become superfluous.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77715 , NAS 1.15:77715
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    Vortex conception of rotor and mutual effect of screw/propellers (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: A vortex theory of screw/propellers with variable circulation according to the blade and its azimuth is proposed, the problem is formulated and circulation is expanded in a Fourier series. Equations are given for inductive velocities in space for crews, including those with an infinitely large number of blades and expansion of the inductive velocity by blade azimuth of a second screw. Multiparameter improper integrals are given as a combination of elliptical integrals and elementary functions, and it is shown how to reduce elliptical integrals of the third kind with a complex parameter to integrals with a real parameter.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77979 , NAS 1.15:77979
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    Experimental investigations on airfoils with different geometries in the domain of high angles of attack-flow separation (1985)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: Wind tunnel tests were conducted on airfoil models in order to study the flow separation phenomena occurring for high angles of attack. Pressure distribution on wings of different geometries were measured. Results show that for three-dimensional airfoils layout and span lift play a role. Separation effects on airfoils with moderate extension are three-dimensional. The flow domains separated from the air foil must be treated three-dimensionally. The rolling-up of separated vortex layers increases with angle in intensity and induction effect and shows strong nonlinearities. Boundary layer material moves perpendicularly to the flow direction due to the pressure gradients at the airfoil; this has a stabilizing effect. The separation starts earlier with increasing pointed profiles.
    Keywords: AERODYNAMICS
    Type: NASA-TM-77892 , NAS 1.15:77892
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    Transonic Symposium: Theory, Application, and Experiment, volume 1, part 2 (1989)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: In order to assess the state of the art in transonic flow disciplines and to glimpse at future directions, NASA-Langley held a Transonic Symposium. Emphasis was placed on steady, three dimensional external, transonic flow and its simulation, both numerically and experimentally. The symposium included technical sessions on wind tunnel and flight experiments; computational fluid dynamic applications; inviscid methods and grid generation; viscous methods and boundary layer stability; and wind tunnel techniques and wall interference. This, being volume 1, is unclassified.
    Keywords: AERODYNAMICS
    Type: NASA-CP-3020-VOL-1-PT-2 , L-16501-VOL-1-PT-2 , NAS 1.55:3020-VOL-1-PT-2 , Apr 19, 1988 - Apr 21, 1988; Hampton, VA; United States
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    Transonic Symposium: Theory, Application, and Experiment, Volume 1, Part 1 (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Topics addressed include: wind tunnel and flight experiments; computational fluid dynamics (CFD) applications, industry overviews; and inviscid methods and grid generations.
    Keywords: AERODYNAMICS
    Type: NASA-CP-3020-VOL-1-PT-1 , L-16501-VOL-1-PT-1 , NAS 1.55:3020-VOL-1-PT-1 , Apr 19, 1988 - Apr 21, 1988; Hampton, VA; United States
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    Numerical study of a delta planform with multiple jets in ground effect (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The flow past a 60-deg delta wing equipped with two thrust-reverser jets near the inboard trailing edge has been analyzed by numerical solution of the 3D thin-layer Navier-Stokes equations. An implicit, partially flux-split, approximately-factored Navier-Stokes solver coupled with a multiple grid embedding scheme has been adapted to this problem. Studies of the impact of numerical parameters (e.g., grid refinement and dissipation levels), and flow-field parameters such as the height of the delta wing above the ground plane and the jet size on the solution, were performed. Results of these numerical studies indicate some challenges in the accurate resolution of complex 3D free shear layers and jets. Nevertheless, flow features such as jet deformation and ground vortex formation observed in experimental flow visualizations are captured. Further, comparisons with experimental data confirm the ability to simulate the loss of wing-borne lift, commonly referred to 'suckdown, as the delta planform flies at slow speeds in close proximity to the ground. Detailed analysis of the numerical results has also given additional insight into the structure of the ground vortex and the mechanisms of lift loss.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 892283 , ; 15 p.|SAE, Aerospace Technology Conference and Exposition; Sept. 25-28, 1989; Anaheim, CA; United States
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    Prediction of transitional (laminar-turbulent) hypersonic flows using the parabolized Navier-Stokes equations (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Hypersonic transitional flow predictions have been made using the parabolized Navier-Stokes equations with an algebraic transition/turbulence model by appropriately modulating the turbulent viscosity with the available intermittency functions for incompressible and compressible flows. A comparison between the predictions with and without a low Reynolds number correction has also been made. The predictions are compared with the available experimental data and with the theory over a range of Mach number. A simple Re(theta)/M(delta) criterion is shown to satisfactorily predict the meridional variation of the onset location of transition on a cone at a small angle of attack, whereas none of the correlations discussed can do that. Various available correlations are discussed vis-a-vis the predictions as to the locations of the onset and the end of transition.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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    On hypersonic shock layer and its extension beyond the Navier-Stokes level (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: An extension of the continuum model beyond the Navier-Stokes (NS) level and related issues on problem formulation are examined for a hypersonic shock layer on the basis of Grad's thirteen-moment equations for a Maxwell gas. The 13-moment system, simplified consistently with a fully viscous version of the thin shock-layer approximation, permits correlation with the corresponding NS-based solution. With the exception of pressure and density, several flow properties including normal stress, shear stress and normal heat flux along a streamline are unaffected by translational nonequilibrium and are therefore predicted correctly by the NS solution to the leading order, even in a domain far from translational equilibrium where molecular-transport processes rank equally with the convection.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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    2-D and 3-D mixing flow analyses of a scramjet-afterbody configuration (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A cold simulant gas study of propulsion/airframe integration for a hypersonic vehicle powered by a scramjet engine is presented. The specific heat ratio of the hot exhaust gases are matched by utilizing a cold mixture of argon and Freon-12. Solutions are obtained for a hypersonic corner flow and a supersonic rectangular flow in order to provide the upstream boundary conditions. The computational test examples also provide a comparison of this flow with that of air as the expanding supersonic jet, where the specific heats are assumed to be constant. It is shown that the three-dimensional computational fluid capabilities developed for these types of flow may be utilized to augment the conventional wind tunnel studies of scramjet afterbody flows using cold simulant exhaust gases, which in turn can help in the design of a scramjet internal-external nozzle.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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    Hypersonic rarefied-flow aerodynamics inferred from Shuttle Orbiter acceleration measurements (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Data obtained from multiple flights of sensitive accelerometers on the Space Shuttle Orbiter during reentry have been used to develop an improved aerodynamic model for the Orbiter normal- and axial-force coefficients in hypersonic rarefied flow. The lack of simultaneous atmospheric density measurements was overcome in part by using the ratio of normal-to-axial acceleration, in which density cancels, as a constraint. Differences between the preflight model and the flight-acceleration-derived model in the continuum regime are attributed primarily to real gas effects. New insights are gained into the variation of the force coefficients in the transition between the continuum regime and free molecule flow.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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    Review of a code development and calibration program in support of the aeroassist flight experiment (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The code development and calibration program for the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) is reviewed, with emphasis directed toward support of the Aeroassist Flight Experiment (AFE). The flight project is designed to obtain data which will be used in the validation of computational fluid dynamic approximation methods. Comparisons between experimental data and numerical simulation focus on perfect-gas tests over a scale model of the AFE and on flight and ground tests which challenge some aspect of the thermochemical nonequilibrium model. In the first case, the gas model is simple, but the grid-related problems of defining the real vehicle are present. In the second case, the vehicle geometries are simple, but thermochemical processes must be modeled correctly in order to compare with the experimental data. These comparisons are described as calibration runs because they test elements of the numerical simulation, but no single data set adequately simulates the full-scale AFE flight conditions. Comparisons between computation and experiment over a broad range of data sets show generally good agreement, though some aspects of the numerical model require further development.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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    Computation of three dimensional turbulent boundary layers in internal flows, including turbomachinery rotor blades (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A method is developed for predicting three-dimensional turbulent boundary layers occurring in internal flows, including rotor blades of turbomachinery. These boundary layers are complex, turbulent, and are subject to Coriolis and centrifugal forces. The algebraic Reynolds stress model (ARSM) developed in this paper satisfies the realizability conditions exactly and captures the changes in turbulenet structure arising from curvature and rotation. The prediction of pressure driven secondary flow agrees well with the data and all the three turbulent models (k-e, algebraic eddy viscosity, and ARSM) show the same level of agreement. The prediction of boundary layer on rotor blades shows much better agreement with the ARSM. It is essential to employ the higher order models to capture the effects of rotation and curvature and three-dimensional boundary layers in turbomachinery.
    Keywords: AERODYNAMICS
    Type: International Symposium on Air Breathing Engines; Sept. 3-8, 1989; Athens; Greece
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    Progress towards the development of an inviscid-viscous interaction method for unsteady flows in turbomachinery cascades (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The velocity and heat transfer characteristics of blade passage flows subject to onset velocities that vary in space and time are calculated by means of a general method involving the solution of inviscid and boundary-layer equations coupled with the Hilbert integral. The performance of this boundary layer method for flows with prescribed pressure distribution is evaluated in terms of two model problems that give attention to the stagnation region. One model corresponds to an oscillating airfoil with moving stagnation point; the other is a simulation of a blade which is subject to a uniform onset velocity.
    Keywords: AERODYNAMICS
    Type: Intl. Symposium on Unsteady Aerodynamics and Aeroelasticity of Turbomachines and Propellers; Sept. 6-10, 1987; Aachen; Germany
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    The unsteady aerodynamics of an oscillating cascade in a compressible flow field (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Fundamental experiments were performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate and quantify the unsteady aerodynamics of a cascade of biconvex airfoils executing torsion-mode oscillations at realistic reduced frequencies. Flush-mounted, high-response miniature pressure transducers were used to measure the unsteady airfoil surface pressures. The pressures were measured for three interblade phase angles at two inlet Mach numbers, 0.65 and 0.80, and two incidence angles, 0 and 7 deg. The time-variant pressures were analyzed by means of discrete Fourier transform techniques, and these unique data were then compared with predictions from a linearized unsteady cascade model. The experimental results indicate that the interblade phase angle had a major effect on the chordwise distributions of the airfoil surface unsteady pressure, and that reduced frequency, incidence angle, and Mach number had a somewhat less significant effect.
    Keywords: AERODYNAMICS
    Type: Intl. Symposium on Unsteady Aerodynamics and Aeroelasticity of Turbomachines and Propellers; Sept. 6-10, 1987; Aachen; Germany
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  • 56
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    Calculation of unsteady Euler flows in turbomachinery using the linearized Euler equations (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The model used by the present unsteady cascade flow calculation method is based on the linearized unsteady Euler equations and accounts for blade loading and geometry, shock motion, and wake motion. The steady flow that must be determined prior to the unsteady flow is ascertained by means of a Newton iteration procedure. A noteworthy feature of the procedure is the use of shock-fitting to determine steady and unsteady shock positions; the use of the Euler equations in conjunction with the Rankine-Hugoniot shock-jump conditions is found to directly model the generation of entropy and vorticity at shocks. Results are presented for both channel and cascade flows.
    Keywords: AERODYNAMICS
    Type: Intl. Symposium on Unsteady Aerodynamics and Aeroelasticity of Turbomachines and Propellers; Sept. 6-10, 1987; Aachen; Germany
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    Analysis of nonuniform subsonic flows about a row of moving blades (1988)
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    Publication Date: 2019-07-27
    Description: The motion of a nonuniform flow about a row of moving blades is modeled as that of a three-dimensional rotational disturbance convected by the mean flow. The aerodynamic theories for such flows are reviewed for both linearly propagating disturbances and disturbances distorted by the mean flow. Linear theories results are examined to assess the effects of the gust variables, the Mach number, and the blade spacing, on the unsteady blade response. For loaded blades, the upstream disturbances are distorted by the blade mean flow. For a potential mean flow, the governing equations can be reduced to a single inhomogeneous nonconstant coefficient convective wave equation. A numerical procedure is developed using an elliptic grid system. The accuracy of the solutions strongly depends on the far-field radiation condition and the optimum determination of the grid system. Solutions are presently obtained for thick symmetric airfoils in three-dimensional gusts.
    Keywords: AERODYNAMICS
    Type: Intl. Symposium on Unsteady Aerodynamics and Aeroelasticity of Turbomachines and Propellers; Sept. 6-10, 1987; Aachen; Germany
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  • 58
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    Navier-Stokes calculations for DFVLR F5-wing in wind tunnel using Runge-Kutta time-stepping scheme (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A three-dimensional Navier-Stokes code using an explicit multistage Runge-Kutta type of time-stepping scheme is used for solving the transonic flow past a finite wing mounted inside a wind tunnel. Flow past the same wing in free air was also computed to assess the effect of wind-tunnel walls on such flows. Numerical efficiency is enhanced through vectorization of the computer code. A Cyber 205 computer with 32 million words of internal memory was used for these computations.
    Keywords: AERODYNAMICS
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  • 59
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    Navier-Stokes simulation of wind-tunnel flow using LU-ADI factorization algorithm (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The three dimensional Navier-Stokes solution code using the LU-ADI factorization algorithm was employed to simulate the workshop test cases of transonic flow past a wing model in a wind tunnel and in free air. The effect of the tunnel walls is well demonstrated by the present simulations. An Amdahl 1200 supercomputer having 128 Mbytes main memory was used for these computations.
    Keywords: AERODYNAMICS
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    Unsteady transonic airfoil computation using the integral solution of full-potential equation (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The shock-capturing integral-equation scheme developed by Kandil and Hu (1987) for the analysis of steady transonic flow over airfoils is extended to the unsteady case. The full potential formulation of the governing equations is reviewed; the solution method is outlined; and results for a NACA 0012 airfoil in forced pitching oscillation at Mach 0.755 are presented in extensive graphs and briefly characterized. The present technique is shown to require significantly less computation time than finite-difference or finite-volume methods, and to give shock-motion predictions in good agreement with those of an implicit finite-volume Euler solver; the surface-pressure peaks are slightly underpredicted.
    Keywords: AERODYNAMICS
    Type: International Conference on Boundary Element Methods; Sept. 6-9, 1988; Southampton
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  • 61
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    Navier-Stokes simulation of transonic wing flow fields using a zonal grid approach (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The transonic Navier-Stokes code was used to simulate flow fields about isolated wings for workshop wind-tunnel and free-air cases using the thin-layer Reynolds-averaged Navier-Stokes equations. An implicit finite-difference scheme based on a diagonal version of the Beam-Warming algorithm was used to integrate the governing equations. A zonal grid approach was used to allow efficient grid refinement near the wing surface. The flow field was sensitive to the turbulent transition model, and flow unsteadiness was observed for a wind-tunnel case but not for the corresponding free-air case. The specification of experimental pressure at the wind-tunnel exit plane is the primary reason for the difference of these two numerical solutions.
    Keywords: AERODYNAMICS
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  • 62
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    An explicit Runge-Kutta method for 3D turbulent incompressible flows (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A computer code has been developed to solve for the steady-state solution of the 3D incompressible Reynolds-averaged Navier-Stokes equations. The approach is based on the cell-center, central-difference, finite-volume formulation and an explicit one-step, multistage Runge-Kutta time-stepping scheme. The Baldwin-Lomax turbulence model is used. Techniques to accelerate the rate of convergence to a steady-state solution include the preconditioned method, the local time stepping, and the implicit residual smoothing. Improvements in computational efficiency have been demonstrated in several areas. This numerical procedure has been used to simulate the turbulent horseshoe vortex flow around an airfoil/flat-plate juncture.
    Keywords: AERODYNAMICS
    Type: GAMM-Conference on Numerical Methods in Fluid Mechanics; Sept. 9-11, 1987; Louvain-la-Neuve; Belgium
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  • 63
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    Computations of unsteady dissociating nitrogen flows (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A time-accurate computer program has been developed to solve flows involving nonequilibrium chemical reactions and vibrational relaxation. The program is based on a multidomain approach and an explicit MacCormack scheme. Results are presented for three simple test cases, involving nitrogen dissociation in a closed box.
    Keywords: AERODYNAMICS
    Type: GAMM-Conference on Numerical Methods in Fluid Mechanics; Sept. 9-11, 1987; Louvain-la-Neuve; Belgium
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  • 64
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    Use of LEBU-devices for drag reduction at flight conditions (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The practical aspects of drag reduction using LEBU (large-eddy break-up) devices, turbulence manipulators, etc. in flight are discussed with the help of experience from previous flight tests. These tests have shown that appreciable reductions in local skin friction exist under flight conditions, and that the turbulence-manipulating effects can be found for swept tandem devices in transonic as well as supersonic flows. The unsteady loads experienced with the devices are discussed in connection with the frequencies occurring in this type of real flight conditions.
    Keywords: AERODYNAMICS
    Type: Turbulent drag reduction by passive means; Sept. 15-17, 1987; London
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  • 65
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    Modification of turbulent boundary layer structure by large-eddy breakup devices (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The modification of the turbulent boundary layer large-eddy structure by streamlined devices is analyzed using the rapid distortion approximation and unsteady aerodynamic theory. The fluctuating velocity downstream of thin plate and airfoil-shaped devices is calculated throughout the boundary layer for two-dimensional and three-dimensional upstream harmonic disturbances. It is shown that such devices suppress most effectively the fluctuating vertical velocity for a range of reduced frequencies k(1) based on the device chord length. This effect depends on the device geometry and loading, its distance to the wall, and on the upstream disturbance condition. Effective devices suppressing most of the large-scale turbulent energy are such that k(1) varies over the 0.5 to 3.0 range. For airfoil-shaped devices, the device thickness has minimal effect on its performance. On the other hand, lifting devices are more effective than thin plates particularly for two-dimensional disturbances.
    Keywords: AERODYNAMICS
    Type: Turbulent drag reduction by passive means; Sept. 15-17, 1987; London
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  • 66
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    Turbulent drag reduction research at NASA Langley - Progress and plans (1987)
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    Publication Date: 2019-07-27
    Description: Prospective research efforts planned at NASA-Langley in view of results obtained to date in passive turbulent drag reduction experiments are discussed. It has been established that conventional flow-aligned riblets are effective even in the presence of a degree of flow inclination and pressure gradients, and at transonic speeds. No increase in net drag reduction is expected from nonconventional riblet geometries. Large eddy breakup devices promise drag reductions in the 8-15 percent range. Heat transfer-augmentation, noise-reduction, turboprop/fuselage interaction noise reduction, are other advantages expected from this line of research.
    Keywords: AERODYNAMICS
    Type: Turbulent drag reduction by passive means; Sept. 15-17, 1987; London
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  • 67
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    Three-dimensional stability of boundary layers (1987)
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    Publication Date: 2019-07-27
    Description: The most recent efforts on the stability and transition of three-dimensional flows are reviewed. These include flows over swept wings, rotating disks, rotating cones, yawed bodies, corners, and attachment lines. The generic similarities of their stability behavior is discussed. It is shown that the breakdown process is very complex, often leading to contradictory results. Particular attention is paid to opposing observations of stationary and traveling wave disturbances.
    Keywords: AERODYNAMICS
    Type: Perspectives in turbulence studies; May 11, 12, 1987; Goettingen; Germany
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  • 68
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    Detection of large-scale organized motions in a turbulent boundary layer (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: This paper presents and discusses experimental data from an investigation of organized motions in a supersonic turbulent boundary layer. Conditional sampling of crossed-wire and multiple normal-wire signals is performed. A comparison is made between events detected using the VITA conditional sampling technique and those found by thresholding the UV signal. Based on this comparison, limitations of the VITA technique are discussed. The conditional sampling results indicate that most organized motions are consistent with hairpin vortices.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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  • 69
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    Reynolds shear stress development in pressure-driven three-dimensional turbulent boundary-layers (1987)
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    Publication Date: 2019-07-27
    Description: The development of the Reynolds stresses has been examined experimentally in an initially two-dimensional boundary layer which is driven to three dimensionality by a spanwise pressure gradient. The pressure field was imposed by an upstream-facing wedge. Two different wedge angles were used in order to vary the level of boundary layer skewing. Bradshaw's Al parameter was found to decrease with the rate of decrease being dependent on the level of skewing between the freestream and the wall flow. It was also concluded that the ratio of the cross-stream to streamwise shear stress components was governed by the rate of freestream turning.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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  • 70
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    Upwind-biased, point-implicit relaxation strategies for hypersonic flowfield simulations on supercomputers (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: An upwind-biased, point-implicit relaxation algorithm for obtaining the numerical solution to the governing equations for three-dimensional, viscous, hypersonic flows in chemical and thermal nonequilibrium is described. The algorithm is derived using a finite-volume formulation in which the inviscid components of flux across cell walls are described with Roe's averaging and Harten's entropy fix with second-order corrections based on Yee's Symmetric Total Variation Diminishing scheme. The relaxation strategy is well suited for computers employing either vector or parallel architectures, and the relation between computer architecture and algorithm is emphasized. It is also well suited to the numerical solution of the governing equations on unstructured grids. Because of the point-implicit relaxation strategy, the algorithm remains stable at large Courant numbers without the necessity of solving large. block tri-diagonal systems. A single relaxation step depends only on information from nearest neighbors. Predictions for pressure distributions, surface heating, and aerodynamic coefficients compare well with experimental data for Mach 10 flow over a blunt body. Predictions for the hypersonic flow of air in chemical and thermal nonequilibrium (velocity = 8917 m/s, altitude = 78 km.) over the Aeroassist Flight Experiment (AFE) configuration obtained on a multi-domain grid are discussed.
    Keywords: AERODYNAMICS
    Type: ; 10 p.
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  • 71
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    Flow in out-of-plane double S-bends (1987)
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    Publication Date: 2019-07-27
    Description: An experimental investigation of developing flows through a combination of out-of-plane S-bend ducts was conducted to gain insight into the redirection of flow in geometries similar to those encountered in practical aircraft wing-root intake ducts. The present double S-bend was fabricated by placing previously investigated S-ducts and S-diffusers in series and with perpendicular planes of symmetry. Laser-Doppler anemometry was employed to measure the three components of mean velocity, the corresponding rms quantities, and Reynolds stresses in the rectangular cross-section ducts. Due to limited optical access, only two mean and rms velocity components were resolved in the circular cross-section ducts. The velocity measurements were complemented by wall static pressure measurements. The data indicates that the flows at the exit are complex and asymmetric. Secondary flows generated by the pressure field in the first S-duct are complemented or counteracted by the secondary flows produced by the area expansion and the curvature of the S-diffuser. The results indicate the dominance of the inlet conditions and geometry upon the development of secondary flows and demonstrate that the flows are predominantly pressure-controlled. The pressure distribution caused by the duct geometry determines the direction and magnitude of the bulk flow while the turbulence dictates the mixing characteristics and profiles in the near wall region.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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  • 72
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    Properties of a half-delta wing vortex (1987)
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    Publication Date: 2019-07-27
    Description: The mean flow and turbulence structure of a single longitudinal vortex generated by a half-delta wing placed at a small angle of attack were investigated. Particular consideration was given to the near-field properties of the generator in order to establish the role of the generator wake in the initial rolling-up of the vortex, as well as to the far-field properties so that the approach to equilibrium could be studied. Measurements were made on fine cross-plane grids at seven streamwise locations using hot cross wires. The results show that the point of maximum vorticity and the generator wake do not merge until a streamwise distance equivalent to three generator heights is reached. Comparison with previous data on vortices produced by double-branched generators confirmed that the present vortex had achieved a fully developed state, and at a relatively short streamwise distance.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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  • 73
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    The structure of separated flow regions occurring near the leading edge of airfoils - including transition (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Laser Doppler Velocimeter data, static pressure data, and smoke flow visualization data was obtained and analyzed to correlate with separation bubble data. The Eppler 387 airfoil was focused on at a chord Reynolds number of 100,000 and an angle of attack of 2 deg. Additional data was also obtained from the NACA 663-018 airfoil at a chord Reynolds number of 160,000 and an angle of attack of 12 deg. The structure and behavior of the transition separation bubble was documented along with the redeveloping boundary layer after reattachment over an airfoil at low Reynolds numbers. The understanding of the complex flow phenomena was examined so that analytic methods for predicting their formation and development can be improved. These analytic techniques have applications in the design and performance prediction of airfoils operating in the low Reynolds number flight regime.
    Keywords: AERODYNAMICS
    Type: NASA-CR-185853 , NAS 1.26:185853
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  • 74
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    Numerical study of three-dimensional separation and flow control at a wing/body junction (1989)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: The problem of three-dimensional separation and flow control at a wing/body junction has been investigated numerically using a three-dimensional Navier-Stokes code. The numerical code employs an algebraic grid generation technique for generating the grid for unmodified junction and an elliptic grid generation technique for filleted fin junction. The results for laminar flow past a blunt fin/flat plate junction demonstrate that after grid refinement, the computations agree with experiment and reveal a strong dependency of the number of vortices at the junction on Mach number and Reynolds number. The numerical results for pressure distribution, particle paths and limiting streamlines for turbulent flow past a swept fin show a decrease in the peak pressure and in the extent of the separated flow region compared to the laminar case. The results for a filleted juncture indicate that the streamline patterns lose much of their vortical character with proper filleting. Fillets with a radius of three and one-half times the fin leading edge diameter or two times the incoming boundary layer thickness, significantly weaken the usual necklace interaction vortex for the Mach number and Reynolds number considered in the present study.
    Keywords: AERODYNAMICS
    Type: NASA-CR-185819 , NAS 1.26:185819
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  • 75
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    Computational technique for compressible vortex flows using the integral equation solution (1988)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: The steady full-potential equation is written in the form of Poisson's equation, and the solution for the velocity field is expressed in terms of an integral equation. The integral solution consists of two surface integrals and one volume integral. The solution is obtained through successive iteration cycles. Each cycle of iteration consists of two sub-cycles, an inner cycle for wake relaxation and an out cycle for the strength of the source distribution integrals representing the flow compressibility. The density gradients in the source distribution is computed by using a type-differencing scheme of the Murman-Cole type. The method is applied to delta wings and the numerical examples show that a curved shock is captured on the wing suction side beneath the leading edge vortex sheet. Recently, a modified version of the scheme was applied to rectangular wings. In this modified scheme, the surface integral terms were computed by using a bilinear distribution of vorticity on triangular vortex panels which represent the wing and its wake. The results were compared with the available experimental data and they are in good agreement.
    Keywords: AERODYNAMICS
    Type: NASA-CR-182695 , NAS 1.26:182695
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    Investigation of chemically reacting and radiating supersonic internal flows (1986)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: The two-dimensional spatially elliptic Navier-Stokes equations are used to investigate the chemically reacting and radiating supersonic flow of the hydrogen-air system between two parallel plates and in a channel with a ten degree compression-expansion ramp at the lower boundary. The explicit unsplit finite-difference technique of MacCormack is used to advance the governing equations in time until convergence is achieved. The chemistry source term in the species equation is treated implicitly to alleviate the stiffness associated with fast reactions. The tangent slab approximation is employed in the radiative flux formation. Both pseudo-gray and nongray models are used to represent the absorption characteristics of the participating species. Results obtained for specific conditions indicate that the radiative interaction can have a significant influence on the flow field.
    Keywords: AERODYNAMICS
    Type: NASA-CR-180540 , NAS 1.26:180540
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  • 77
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    Simple numerical method for predicting steady compressible flows (1986)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: A numerical method for solving the isenthalpic form of the governing equations for compressible viscous and inviscid flows was developed. The method was based on the concept of flux vector splitting in its implicit form. The method was tested on several demanding inviscid and viscous configurations. Two different forms of the implicit operator were investigated. The time marching to steady state was accelerated by the implementation of the multigrid procedure. Its various forms very effectively increased the rate of convergence of the present scheme. High quality steady state results were obtained in most of the test cases; these required only short computational times due to the relative efficiency of the basic method.
    Keywords: AERODYNAMICS
    Type: NASA-CR-180345 , NAS 1.26:180345
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    An investigation of the feasibility of active boundary layer thickening for aircraft drag reduction (1986)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: The feasibility of using a forward mounted windmilling propeller to extract momentum from the flow around an axisymmetric body to reduce total drag has been studied. Numerical calculations indicate that a net drag reduction is possible when the energy extracted is returned to an aft mounted pusher propeller. However, net drag reduction requires very high device efficiencies. Results of an experimental program to study the coupling between a propeller wake and a turbulent boundary layer are also reported. The experiments showed that a complex coupling exists and simple modes for the flow field are not sufficiently accurate to predict total drag.
    Keywords: AERODYNAMICS
    Type: NASA-CR-177133 , NAS 1.26:177133
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    The use of a panel code on high lift configurations of a swept forward wing (1985)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: A study was done on high lift configurations of a generic swept forward wing using a panel code prediction method. A survey was done of existing codes available at Ames, frow which the program VSAERO was chosen. The results of VSAERO were compared with data obtained from the Ames 7- by 10-foot wind tunnel. The results of the comparison in lift were good (within 3.5%). The comparison of the pressure coefficients was also good. The pitching moment coefficients obtained by VSAERO were not in good agreement with experiment. VSAERO's ability to predict drag is questionable and cannot be counted on for accurate trends. Further studies were done on the effects of a leading edge glove, canards, leading edge sweeps and various wing twists on spanwise loading and trim lift with encouraging results. An unsuccessful attempt was made to model spanwise blowing and boundary layer control on the trailing edge flap. The potential results of VSAERO were compared with experimental data of flap deflections with boundary layer control to check the first order effects.
    Keywords: AERODYNAMICS
    Type: NASA-CR-176968 , NAS 1.26:176968
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  • 80
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    Vortex boundary-layer interactions (1986)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: Parametric studies to identify a vortex generator were completed. Data acquisition in the first chosen configuration, in which a longitudinal vortex pair generated by an isolated delta wing starts to merge with a turbulent boundary layer on a flat plate fairly close to the leading edge is nearly completed. Work on a delta-wing/flat-plate combination, consisting of a flow visualization and hot wire measurements taken with a computer controlled traverse gear and data logging system were completed. Data taking and analysis have continued, and sample results for another cross stream plane are presented. Available data include all mean velocity components, second order mean products of turbulent fluctuations, and third order mean products. Implementation of a faster data logging system was accomplished.
    Keywords: AERODYNAMICS
    Type: NASA-CR-176701 , NAS 1.26:176701
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  • 81
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    An assessment of upper surface blowing for the reduction of tilt rotor download (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A study evaluating the use of upper-surface blowing to reduce the wing download on a V-22 tilt rotor aircraft has been completed. The study assesses the penalties associated with the upper-surface blowing system (compressor weight, compressor power, etc.), and the reduction in wing download, for a wide range of blowing slot heights and blowing pressure ratios. Three wing configurations were investigated: blowing at both leading and trailing edges with no change in wing planform relative to the V-22 tilt rotor aircraft, blowing at both leading and trailing edges with a 25% reduction in wing chord, and blowing at the leading edge only with the flap deflected 75 deg. Predicted download is presented for all of these configurations, and is compared with the download of the baseline V-22 tilt rotor aircraft configuration. The optimum configuration had 15% less net download than the baseline V-22 configuration.
    Keywords: AERODYNAMICS
    Type: ; 9 p.|Aug 01, 1987; Monterey, CA; United States
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  • 82
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    Interference effects on the hypersonic, rarefied flow about a flat plate (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The Direct Simulatiaon Monte Carlo method is used to study the hypersonic, rarefied flow interference effects on a flat plate caused by nearby surfaces. Calculations focus on shock-boundary-layer and shock-lip interactions in hypersonic inlets. Results are presented for geometries consisting of a flat plate with different leading-edge shapes over a flat lower wall and a blunt-edge flat plate over a 5-degree wedge. The problems simulated correspond to a typical entry flight condition of 7.5 km/s at altitudes of 75 to 90 km. The results show increases in predicted local heating rates for shock-boundary-layer and shock-lip interactions that are quantitatively similar to those observed experimentally at much higher densities.
    Keywords: AERODYNAMICS
    Type: Intl. Symposium on Rarefied Gas Dynamics: Theoretical and Computational Techniques; Jul 10, 1988 - Jul 16, 1988; Pasadena, CA; United States
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  • 83
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    Computational aerothermodynamics (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Computational aerothermodynamics concerns the coupling of real gas effects with equations of motion to include thermochemical rate processes for chemical and energy exchange phenomena. These processes concern the creation and destruction of gas species by chemical reactions and the transfer of energy between the various species and between the various energy modes (e.g., translation, rotation, vibration, ionization, dissociation/recombination, etc.) of the species. To gain some insight into when such phenomena occur for current and future aerospace flight vehicles the author shows the flight regimes of some typical vehicles (e.g., Concord, aerospace plane, Space Shuttle, associated space transfer vehicles, Apollo entry vehicle, etc.) in terms of flight altitude and flight speed. Also indicated are regimes where chemical reactions such as dissociation and ionization are important and where nonequilibrium thermochemical phenomena are important.
    Keywords: AERODYNAMICS
    Type: Supercomputing ''89; Nov 13, 1989 - Nov 17, 1989; Reno, NV; United States
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  • 84
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    Comparison of measured induced velocities with results from a closed-form finite state wake model in forward flight (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An unsteady, three-dimensional induced-flow model is applied to compute the induced-flow distribution of a rotor in forward flight, and numerical results are compared against LDV measurements for both time-averaged and unsteady induced flow at the disk. The former flow shows good agreement with measured data, except just behind the pylon at the lowest advanced ratio and near the blade tips for rectangular blades at high advance ratios. The method performs as well or better than other codes that have been applied to these data, takes less computing time, and is better suited to aeroelastic analysis. Results with only four harmonics and 15 state variables converge to all fundamental characteristics of the time-averaged flow.
    Keywords: AERODYNAMICS
    Type: AHS Annual Forum; May 22, 1989 - May 24, 1989; Boston, MA; United States
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    A numerical analysis of the British Experimental Rotor Program blade (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Two Computational Fluid Dynamic codes which solve the compressible full-potential and the Reynolds-Averaged Thin-Layer Navier-Stokes equations were used to analyze the nonrotating aerodynamic characteristics of the British Experimental Rotor Program (BERP) helicopter blade at three flow regimes: low angle of attack, high angle of attack and transonic. Excellent agreement was found between the numerical results and experiment. In the low angle of attack regime, the BERP had less induced drag than a comparable aspect ratio rectangular planform wing. At high angle of attack, the blade attained high-lift by maintaining attached flow at the outermost spanwise locations. In the transonic regime, the BERP design reduces the shock strength at the outer spanwise locations which affects wave drag and shock-induced separation. Overall, the BERP blade exhibited many favorable aerodynamic characteristics in comparison to conventional helicopter rotor blades.
    Keywords: AERODYNAMICS
    Type: AHS Annual Forum; May 22, 1989 - May 24, 1989; Boston, MA; United States
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  • 86
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    Advanced rotor computations with a corrected potential method (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An unsteady Full-Potential Rotor code (FPR) has been enhanced with modifications directed at improving its drag prediction capability. The potential code has been rewritten with modifications to increase the code accuracy. Also, the shock generated entropy has been included to provide solutions comparable to the Euler equations. Two different weakly interacted boundary layer models have also been coupled to FPR in order to estimate skin-friction drag. One is a two-dimensional integral method and the other is a three-dimensional finite-difference scheme. The new flow solver is able to find accurate inviscid drags without recourse to numerical error tares. This permits the resolution of drag distributions resulting from rotor geometric variations. Good comparisons have been obtained between computed and measured torque for a rectangular and a highly swept model rotor.
    Keywords: AERODYNAMICS
    Type: AHS Annual Forum; May 22, 1989 - May 24, 1989; Boston, MA; United States
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  • 87
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    Interactive grid generation for turbomachinery flow field simulations (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The control point form of algebraic grid generation presented provides the means that are needed to generate well structured grids of turbomachinery flow simulations. It uses a sparse collection of control points distributed over the flow domain. The shape and position of coordinate curves can be adjusted from these control points while the grid conforms precisely to all boundaries. An interactive program called TURBO, which uses the control point form, is being developed. Basic features of the code are discussed and sample grids are presented. A finite volume LU implicit scheme is used to simulate flow in a turbine cascade on the grid generated by the program.
    Keywords: AERODYNAMICS
    Type: Intl. Conference on Numerical Grid Generation in Computational Fluid Mechanics ''88; Dec 05, 1988 - Dec 08, 1988; Miami Beach, FL; United States
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  • 88
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    Interactive grid generation for fighter aircraft geometries (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An interactive procedure to construct grids about fighter aircraft configurations using a 'state-of-the-art' workstation is described. A multiple-block grid topology is used to minimize grid skewness. Grid points on the surface of a configuration are precomputed and stored on the faces of appropriate blocks. Grid points at intermediate and far field boundary surfaces are computed with analytical functions and stored on appropriate faces. Grid points in the interior of blocks are computed using transfinite interpolation with Lagrangian and exponential blending functions. Interactive software has been written for the IRIS 3030 graphics workstation to control the shape and spacing of grid points on intermediate and far field boundaries, and to control the interior interpolation.
    Keywords: AERODYNAMICS
    Type: Intl. Conference on Numerical Grid Generation in Computational Fluid Mechanics ''88; Dec 05, 1988 - Dec 08, 1988; Miami Beach, FL; United States
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  • 89
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    Effects of thermochemistry, nonequilibrium, and surface catalysis on the design of hypersonic vehicles (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An account is given of the function of physical aspects of a gas on the characteristics of the flow and of the heating associated with hypersonic flight. At the high temperatures encountered, the thermal and chemical characteristics of the air in a hypersonic vehicle's shock layer are altered in ways which depend on the atomic and molecular structure of N and O and their ions; similar effects exist in scramjet propulsion systems. These properties in turn influence the character of shock waves and expansions, and hence the pressure, temperature, and velocity distributions. Transport properties affecting the boundary-layer structure will also affect heat flux and shear stress.
    Keywords: AERODYNAMICS
    Type: Joint Europe/U.S. Short Course on Hypersonics; Dec 07, 1987 - Dec 11, 1987; Paris; France
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  • 90
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    An in-flight investigation of ground effect on a forward-swept wing airplane (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A limited flight experiment was conducted to document the ground-effect characteristics of the X-29A research airplane. This vehicle has an aerodynamic platform which includes a forward-swept wing and close-coupled, variable incidence canard. The flight-test program obtained results for errors in the airdata measurement and for incremental normal force and pitching moment caused by ground effect. Correlations with wind-tunnel and computational analyses were made. The results are discussed with respect to the dynamic nature of the flight measurements, similar data from other configurations, and pilot comments. The ground-effect results are necessary to obtain an accurate interpretation of the vehicle's landing characteristics. The flight data can also be used in the development of many modern aircraft systems such as autoland and piloted simulations.
    Keywords: AERODYNAMICS
    Type: NASA-TM-101708 , H-1573 , NAS 1.15:101708 , AGARD Symposium on Aerodynamics of Combat Aircraft, Controls, and of Ground Effect; Oct 02, 1989 - Oct 05, 1989; Madrid; Spain
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  • 91
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    Numerical investigations in three-dimensional internal flows (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In order to develop an understanding of flow fields that exist in sidewall compression inlet models, an explicit, time-accurate full Navier-Stokes code was used to model them. Both laminar and turbulent boundary layers were numerically simulated. These simulations were examined as they were influenced by Mach number, changes in sidewall compression angle, hypersonic viscous interaction effects, and thick entering boundary layers. Cause and effect relationships were established. The numerical simulations were compared with the limited data available to aid in understanding both the simulations and the experiments.
    Keywords: AERODYNAMICS
    Type: NASA-CR-186068 , NAS 1.26:186068 , National Aero-Space Technical Symposium; Apr 24, 1989 - Apr 28, 1989; Monterey, CA; United States
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  • 92
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    Unsteady aerodynamic simulation of multiple bodies in relative motion: A prototype method (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A prototype method for time-accurate simulation of multiple aerodynamic bodies in relative motion is presented. The method is general and features unsteady chimera domain decomposition techniques and an implicit approximately factored finite-difference procedure to solve the time-dependent thin-layer Navier-Stokes equations. The method is applied to a set of two- and three- dimensional test problems to establish spatial and temporal accuracy, quantify computational efficiency, and begin to test overall code robustness.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102181 , A-89095 , NAS 1.15:102181 , AIAA Computational Fluid Dynamics Conference; Jun 14, 1989 - Jun 16, 1989; Buffalo, NY; United States
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  • 93
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    Research in Natural Laminar Flow and Laminar-Flow Control, part 3 (1987)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Part 3 of the Symposium proceedings contains papers addressing advanced airfoil development, flight research experiments, and supersonic transition/laminar flow control research. Specific topics include the design and testing of natural laminar flow (NLF) airfoils, NLF wing gloves, and NLF nacelles; laminar boundary-layer stability over fuselage forebodies; the design of low noise supersonic/hypersonic wind tunnels; and boundary layer instability mechanisms on swept leading edges at supersonic speeds.
    Keywords: AERODYNAMICS
    Type: NASA-CP-2487-PT-3 , L-16350-PT-3 , NAS 1.55:2487-PT-3 , Mar 16, 1987 - Mar 19, 1987; Hampton, VA; United States
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  • 94
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    Prediction of Unsteady Blade Surface Pressures on an Advanced Propeller at an Angle of Attack (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The numerical solution of the unsteady, three-dimensional, Euler equations is considered in order to obtain the blade surface pressures of an advanced propeller at an angle of attack. The specific configuration considered is the SR7L propeller at cruise conditions with a 4.6 deg inflow angle corresponding to the plus 2 deg nacelle tilt of the Propeller Test Assessment (PTA) flight test condition. The results indicate nearly sinusoidal response of the blade loading, with angle of attack. For the first time, detailed variations of the chordwise loading as a function of azimuthal angle are presented. It is observed that the blade is lightly loaded for part of the revolution and shocks appear from hub to about 80 percent radial station for the highly loaded portion of the revolution.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102374 , E-5108 , NAS 1.15:102374 , AIAA PAPER 89-1060 , Aeroacoustics Conference; Apr 10, 1989 - Apr 12, 1989; San Antonio, TX; United States
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  • 95
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    Research in Natural Laminar Flow and Laminar-Flow Control, part 2 (1987)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Part 2 of the Symposium proceedings includes papers addressing various topics in basic wind tunnel research/techniques and computational transitional research. Specific topics include: advanced measurement techniques; laminar flow control; Tollmien-Schlichting wave characteristics; boundary layer transition; flow visualization; wind tunnel tests; flight tests; boundary layer equations; swept wings; and skin friction.
    Keywords: AERODYNAMICS
    Type: NASA-CP-2487-PT-2 , L-16350-PT-2 , NAS 1.55:2487-PT-2 , Mar 16, 1987 - Mar 19, 1987; Hampton, VA; United States
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  • 96
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    Numerical simulation of unsteady rotational flow over propfan configurations (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The objective is to develop efficient numerical techniques for the study of aeroelastic response of a propfan in an unsteady transonic flow. A three dimensional unsteady Euler solver is being modified to address this problem.
    Keywords: AERODYNAMICS
    Type: NASA-CR-186037 , NAS 1.26:186037 , AIAA 28th Aerospace Sciences Meeting and Exhibit; Jan 08, 1990 - Jan 11, 1990; Reno, NV; United States
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  • 97
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    A numerical method for predicting hypersonic flowfields (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The flow about a body traveling at hypersonic speed is energetic enough to cause the atmospheric gases to react chemically and reach states in thermal nonequilibrium. In this paper, a new procedure based on Gauss-Seidel line relaxation is shown to solve the equations of hypersonic flow fields containing finite reaction rate chemistry and thermal nonequilibrium. The method requires a few hundred time steps and small computer times for axisymmetric flows about simple body shapes. The extension to more complex two-dimensional body geometries appears straightforward.
    Keywords: AERODYNAMICS
    Type: Sensing, Discrimination, and Signal Processing and Superconducting Materials and Instrumentation; Jan 12, 1988 - Jan 14, 1988; Los Angeles, CA; United States
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  • 98
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    Comparison of shock structure solutions using independent continuum and kinetic theory approaches (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A vehicle traversing the atmosphere will experience flight regimes at high altitudes in which the thickness of a hypersonic shock wave is not small compared to the shock standoff distance from the hard body. When this occurs, it is essential to compute accurate flow field solutions within the shock structure. In this paper, one-dimensional shock structure is investigated for various monatomic gases from Mach 1.4 to Mach 35. Kinetic theory solutions are computed using the Direct Simulation Monte Carlo method. Steady-state solutions of the Navier-Stokes equations and of a slightly truncated form of the Burnett equations are determined by relaxation to a steady state of the time-dependent continuum equations. Monte Carlo results are in excellent agreement with published experimental data and are used as bases of comparison for continuum solutions. For a Maxwellian gas, the truncated Burnett equations are shown to produce far more accurate solutions of shock structure than the Navier-Stokes equations.
    Keywords: AERODYNAMICS
    Type: Sensing, Discrimination, and Signal Processing and Superconducting Materials and Instrumentation; Jan 12, 1988 - Jan 14, 1988; Los Angeles, CA; United States
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  • 99
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    Fundamental problem in computing radiating flow fields with thick shock waves (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Possible reasons for the failure of the Navier-Stokes equations to yield realistic profiles of the temperature and density through the structure of a hypersonic shock wave are investigated. Models for bulk viscosity in a monatomic gas are examined which yield a realistic thickness for the shock-wave density profile, but not the temperature profile, and hence are not satisfactory. A tentative computational model for nitrogen is explored which yields considerably more realistic results than the Navier-Stokes equations. This model involves a nonlinear stress-strain tensor, nonlinear heat flux vector, and nonequilibrium rotational energy.
    Keywords: AERODYNAMICS
    Type: Sensing, Discrimination, and Signal Processing and Superconducting Materials and Instrumentation; Jan 12, 1988 - Jan 14, 1988; Los Angeles, CA; United States
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  • 100
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    Aerodynamic applications of an efficient incompressible Navier-Stokes solver (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A robust and accurate upwind scheme based on flux-difference splitting for three-dimensional, incompressible flows in general coordinates is described. Viscous effects are included through a thin-layer approximation to the Navier-Stokes equations. Turbulent flows are simulated with extensions to the Baldwin-Lomax (1978) turbulence model. The effects of accuracy and gridding on the computed flow field results are assessed. The results obtained from the code for vortical flows over a delta wing, a double delta wing, and a tangent-ogive forebody compare well with experimental data.
    Keywords: AERODYNAMICS
    Type: ICAS Congress; Aug 28, 1988; Jerusalem; Israel
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