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  • AERODYNAMICS  (684)
  • 1990-1994  (684)
  • 1975-1979
  • 1991  (684)
  • 1
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    The hypersonic double ellipse in rarefied flow (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The problem of the hypersonic double ellipse in rarefied flow is treated by a particle method using the collision model first described by McDonald (1988). In the approach used here, the computational overhead is reduced by using simple cubic cells. The problem of the definition of complex geometries is addressed by developing an algorithm to define the relation of a body surface to the network of cells.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 912-923.
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  • 2
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    Application of program LAURA to thermochemical nonequilibrium flow through a nozzle (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Program LAURA (Langley Aerothermodynamic Upwind Relaxation Algorithm) is an upwind-biased, point-implicit relaxation algorithm for obtaining the numerical solution to the governing equations for 3D viscous hypersonic flows in chemical and thermal nonequilibrium. The algorithm is derived using a finite-volume formulation in which the inviscid components of flux across cell walls are described with a modified Roe's averaging and with second-order corrections based on Yee's Symmetric Total Variation Diminishing scheme. The code has been applied to Problem 8.2 of this workshop for the case of thermochemical nonequilibrium flow through a nozzle. Chemical reaction rates are defined with the model of Park (1987). Thermal nonequilibrium is modeled using a two-temperature approximation in which the vibrational energies of all molecules are assumed to be in equilibrium at a single temperature which is generally different from the translational-rotational temperature. Two grids were used to define the flow for the original problem, with a stagnation temperature of 6500 K. A third case with a stagnation temperature of 10,000 K is also presented. The solution domain includes the converging nozzle, subsonic flow domain in which the gas is substantially in thermochemical equilibrium and the diverging nozzle, hypersonic flow domain in which the gas is substantially in thermochemical nonequilibrium.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 1145-1158.
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  • 3
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    Hypersonic cone flow predictions using an implicit upwind space-marching code (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Solutions have been computed and results are presented for Problem 1, the case of Mach 9 transitional flow past a 7 deg half-angle cone at zero incidence. The solutions were computed using a code developed for the integration of the parabolized Navier-Stokes equations. The algorithm employed in the code is based on a Roe-type flux-difference-splitting scheme applied following a finite-volume approach. The basic algorithm has been modified to make it implicit and second-order accurate in the crossflow directions. Results are presented in terms of surface pressure and heat transfer as well as boundary layer profiles of pitot pressure, Mach number, and tangential velocity. The case was recalculated several times in an effort to determine sensitivities to such parameters as grid density, wall temperature, turbulence model parameters, as well as freestream expansion. Comparisons with the experimental data are presented and discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 75-91.
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  • 4
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    Correlation of airloads on a two-bladed helicopter rotor (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Airloads measured on a two-bladed helicopter rotor in flight, from the Tip Aerodynamic and Acoustic Test, are compared with calculations from a comprehensive helicopter analysis (CAMRAD/JA), and the pressures compared with calculations from a full-potential rotor code (FPR). The flight test results cover an advance ratio range from 0.19 to 0.38. The lowest speed case is characterized by the presence of significant blade-vortex interactions. Good correlation of peak-to-peak vortex-induced loads and the corresponding pressures is obtained. The results of the correlation for this two-bladed rotor are substantially similar to the results for three- and four-bladed rotors, concerning the tip vortex core size for best correlation, calculation of the peak-to-peak loads on the retreating side, and calculation of vortex-induced loads on inboard radial stations.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71); 38 p.
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  • 5
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    The development of a CFD potential method for the analysis of tilt-rotors (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A new CFD potential code, FPX (eXtended Full-Potential), has been developed for application to both helicopters and tilt-rotors. The code solves the unsteady, three-dimensional full potential equation and is an extension of the rotor code, FPR. Both entropy and viscosity corrections are included to enhance the physical modeling capabilities. A number of efficiency related modifications have yielded a factor of two speed-up in the code. An axial flow capability has been added to treat tilt-rotor in forward flight (cruise mode). In order to employ streamwise periodicity and accurately solve for the propagation of acoustic signals in the tip region, an H-H topology has been added to the basic O-H grid system. Computations are performed for the XV-15 Standard and ATB blades at high-speed conditions. Comparisons are made for the blade aerodynamics and the induced fuselage cabin pressure for a range of Mach numbers. Grid generation, wake treatment, and far-field wall treatment are identified as problem areas with recommendations for future research.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71); 15 p.
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  • 6
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    Recent developments in rotor wake modeling for helicopter noise prediction (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A preliminary test/theory correlation evaluation is conducted for wake measurement test results obtained by LDV for a B360 helicopter rotor, at conditions critical to the understanding of wake-rollup and blade-vortex interaction phenomena. The LDV data were complemented by acoustic, blade pressure, rotor performance, and blade/control load measurements.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71); 16 p.
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  • 7
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    Grid-refinement study of hypersonic laminar flow over a 2-D ramp (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Computations were made for those test cases of Problem 3 which were designated as laminar flows, viz., test cases 3.1, 3.2, 3.4, and 3.5. These test cases corresponded to flows over a flat plate and a compression ramp at high Mach number and at high Reynolds number. The computations over the compression ramps indicate a substantial streamwise extent of separation. Based on previous experience with separated laminar flows at high Mach numbers which indicated a substantial effect with spatial grid refinement, a series of computations with different grid sizes were performed. Also, for the flat plate, comparisons of the results for two different algorithms were made.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 244-254.
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  • 8
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    Computational fluid dynamics for hypersonic airbreathing aircraft (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A development status evaluation is presented for CFD methods applicable to fuselage-integrated scramjet powerplant incorporating hypersonic vehicles; these methods are critically important due to the unavailability of experimental facilities for such elevated Mach number/high-enthalphy conditions. Advancements are required in algorithm robustness and speed, geometric flexibility, and the inclusion of more complete flow physics. The most serious deficiencies lie in turbulence modeling, the lack of complete transition-prediction methods, and combustion modeling.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: Hypersonic flows for reentry problems. Vol. 1 (A93-42576 17-02); p. 55-71.
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  • 9
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    CFD for hypersonic propulsion (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: An overview is given of research activity on the application of computational fluid dynamics (CDF) for hypersonic propulsion systems. After the initial consideration of the highly integrated nature of air-breathing hypersonic engines and airframe, attention is directed toward computations carried out for the components of the engine. A generic inlet configuration is considered in order to demonstrate the highly three dimensional viscous flow behavior occurring within rectangular inlets. Reacting flow computations for simple jet injection as well as for more complex combustion chambers are then discussed in order to show the capability of viscous finite rate chemical reaction computer simulations. Finally, the nozzle flow fields are demonstrated, showing the existence of complex shear layers and shock structure in the exhaust plume. The general issues associated with code validation as well as the specific issue associated with the use of CFD for design are discussed. A prognosis for the success of CFD in the design of future propulsion systems is offered.
    Schlagwort(e): AERODYNAMICS
    Materialart: In: Hypersonic flows for reentry problems. Vol. 1 (A93-42576 17-02); p. 170-186.
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  • 10
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    Computational methods for shock waves in three-dimensional supersonic flow (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A central artificial-viscosity and an upwind-biased difference method are contrived to solve the Euler equations for flowfields over typical spacecrafts. The spatial discretization is based on either nodal or cell-vertex formulation in the domain extending from free stream to the end of the vehicle. The outer boundary is treated as a bow shock in the first method but is placed in the free stream in the second, which captures both bow and internal shocks using an approximate Riemann solver based on high-order extrapolation to the cell face. These methods were tested for the Shuttle and Hermes orbiters at wind-tunnel conditions and angles of attack ranging from 0 to 60 deg. The artificial-viscosity method incorporated with a shock-fitting procedure shows smeared crossflow and wing-shock positions and required 15 percent more CPU per node than the upwind method. Greater flexibility and robustness is demonstrated by the latter on a fixed grid for all cases considered.
    Schlagwort(e): AERODYNAMICS
    Materialart: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 87; 2-3,
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  • 11
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    High-Reynolds-number test requirements in low-speed aerodynamics (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Research requirements to an ultra-high-Reynolds-number liquid helium facility are reviewed. Aerodynamic research areas under consideration include wave vortex hazard reduction, vortex control and diagnostics for maneuvering fighter aircraft, and performance of high-lift devices.
    Schlagwort(e): AERODYNAMICS
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  • 12
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    Engineering calculations of three-dimensional inviscid hypersonic flowfields (1991)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 628-635
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  • 13
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    Static aeroelastic analysis for generic configuration wing (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A static aeroelastic analysis capability that calculates flexible air loads for generic configuration wings was developed. It was made possible by integrating a finite element structural analysis code (MSC/NASTRAN) and a panel code of aerodynamic analysis based on linear potential flow theory. The framework already built in MSC/NASTRAN was used, and the aerodynamic influence coefficient matrix was computed externally and inserted in the NASTRAN by means of a DMAP program. It was shown that deformation and flexible air loads of an oblique wing configuration including asymmetric wings can be calculated reliably by this code both in subsonic and supersonic speeds.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 801
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  • 14
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    Numerical prediction of subsonic turbulent flows over slender bodies at high incidence (1991)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 2054-206
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  • 15
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    Probe systems for static pressure and cross-stream turbulence intensity (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A recent study of total-pressure probes for use in highly turbulent streams is extended herein by developing probe systems that measure time-averaged static or ambient pressure and turbulence intensity. Arrangements of tubular probes of circular and elliptical cross section are described that measure the pressure at orifices on the sides of the probes to obtain different responses to the cross-stream velocity fluctuations. When the measured data are combined to remove the effect of the presence of the probes on the local pressure, the time-averaged static pressure and the cross-stream components of turbulence intensity can be determined. If a system of total pressure tubes, as described in an accompanying paper, is added to the static pressure group to form a single cluster, redundant measurements are obtained that permit accuracy and consistency checks.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 750-755
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  • 16
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    Implicit flux-split Euler schemes for unsteady aerodynamic analysis involving unstructured dynamic meshes (1991)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1836-184
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  • 17
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    Viscous flow solutions for slender bodies of revolution at incidence (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Flow over slender prolate spheroids at incidence is examined. The incidence angle is chosen high enough to cause streamwise separation of the flow in addition to crossflow separation generally observed at lower incidence angles. The freestream Mach number for the cases investigated here is subsonic, thus precluding the use of parabolized procedures. Laminar, transitional and turbulent flow cases are investigated.
    Schlagwort(e): AERODYNAMICS
    Materialart: Computers and Fluids (ISSN 0045-7930); 20; 3, 19
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  • 18
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    Thermochemical nonequilibrium issues for earth re-entry of Mars mission vehicles (1991)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 552-559
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  • 19
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    Aeroassist flight experiment heating-rate sensitivity study (1991)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 5; 456-462
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  • 20
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    Effect of geometrical disturbance on vortex asymmetry (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 560-566
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  • 21
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    Flight stagnation-point heating calculations on Aeroassist Flight Experiment vehicle (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: NASA's Aeroassist Flight Experiment (AFE) vehicle will be deployed from the Space Shuttle Orbiter in 1994 to make a data-gethering aeropass through the upper atmosphere before returning to orbit for Shuttle pickup. An axisymmetric, chemically-reacting viscous shock-layer code is presently used to calculate AFE heating rates which automatically accounts for the viscous-inviscid interaction and entropy layer-swallowing effects which are ignored by the conventional boundary-layer methods. Results are presented for the stagnation-point heating of the current AFE baseline trajectory.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 125-128
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  • 22
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    Supersonic aerodynamic characteristics of monoplanar missiles with low-profile quadriform tails (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 9-15
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  • 23
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    Fully coupled implicit method for thermochemical nonequilibrium air at suborbital flight speeds (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 31-39
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  • 24
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    Numerical simulation of Shuttle ascent transonic flow using an unstructured-grid approach (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An unstructured-grid, finite-volume method has been developed for simulating the inviscid flow over spacecrafts of realistic configuration. The grid generation is accomplished by a new technique on the basis of the advancing-front concept. This simple technique is shown to be equally as powerful for a complex multibody as for a single vehicle. Second- or third-order accuracy is obtained via an innovative interpolation procedure similar to the conventional MUSCL approach. This method has been applied to the Shuttle orbiter and a representative Shuttle launch vehicle consisting of the orbiter, the external tank, and the solid rocket boosters. A comparison is discussed between the present results and other results obtained from structured- and unstructured-grid methods.
    Schlagwort(e): AERODYNAMICS
    Materialart: Computers and Structures (ISSN 0045-7949); 39; 1-2,
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  • 25
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    Newton's method applied to finite-difference approximations for the steady-state compressible Navier-Stokes equations (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Finite-difference approximations for steady-state compressible Navier-Stokes equations, whose two spatial dimensions are written in generalized curvilinear coordinates and strong conservation-law form, are presently solved by means of Newton's method in order to obtain a lifting-airfoil flow field under subsonic and transonnic conditions. In addition to ascertaining the computational requirements of an initial guess ensuring convergence and the degree of computational efficiency obtainable via the approximate Newton method's freezing of the Jacobian matrices, attention is given to the need for auxiliary methods assessing the temporal stability of steady-state solutions. It is demonstrated that nonunique solutions of the finite-difference equations are obtainable by Newton's method in conjunction with a continuation method.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 93; 108-127
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  • 26
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    Experimental transition investigation of a free-shear layer above a cavity at Mach 3.5 (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 7; 626-634
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  • 27
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    Influence of thickness and camber on the aeroelastic stability of supersonic throughflow fans (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An engineering approach was used to include the nonlinear effects of thickness and camber in an analytical aeroelastic analysis of casecades in supersonic acial flow (supersonic leading-edge locus). A hybrid code using Lighthill's nonlinear piston theory and Lane's linear potential theory was developed to include these nonlinear effects. Lighthill's theory was used to calculate the unsteady pressures on the noninterference surface regions of the airfoils in cascade. Lane's theory was used to calculate the unsteady pressures on the remaining interference surface regions. Two airfoil profiles were investigated (a supersonic throughflow fan design and a NACA 66-206 airfoil with a sharp leading edge). Results show that compared with predictions of Lane's potential theory for flat plates, the inclusion of thickness (with or without camber) may increase or decrease the aeroelastic stability, depending on the airfoil geometry and operating conditions. When thickness effects are included in the aeroelastic analysis, inclusion of camber will influence the predicted stability in proportion to the magnitude of the added camber. The critical interblade phase angle, depending on the airfoil profile and operating conditions, may also be influenced by thickness and camber. Compared with predictions of Lane's linear potential theory, the inclusion of thickness and camber decreased the aerodynamic stiffness and increased the aerodynamic damping at Mach 2 and 2.95 for a cascade of supersonic throughflow fan airfoils oscillating 180 degrees out of phase at a reduced frequency of 0.1.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 7; 404-411
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  • 28
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    A spectral collocation method for compressible, non-similar boundary layers (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An efficient and highly accurate algorithm based on a spectral collocation method is developed for numerical solution of the compressible, two-dimensional and axisymmetric boundary layer equations. The numerical method incorporates a fifth-order, fully implicit marching scheme in the streamwise (timelike) dimension and a spectral collocation method based on Chebyshev polynomial expansions in the wall-normal (spacelike) dimension. The spectral collocation algorithm is used to derive the nonsimilar mean velocity and temperature profiles in the boundary layer of a 'fuselage' (cylinder) in a high-speed (Mach 5) flow parallel to its axis. The stability of the flow is shown to be sensitive to the gradual streamwise evolution of the mean flow and it is concluded that the effects of transverse curvature on stability should not be ignored routinely.
    Schlagwort(e): AERODYNAMICS
    Materialart: International Journal for Numerical Methods in Fluids (ISSN 0271-2091); 13; 713-737
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  • 29
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    Numerical simulation of high-incidence flow over the F-18 fuselage forebody (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 609-617
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  • 30
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    Computation of Navier-Stokes equations for three-dimensional flow separation (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Supersonic flows over a sharp and a flat-faced blunt fin mounted on a flat plate are simulated numerically. Several basic issues involved in the resultant three-dimensional steady flow separation are studied. Using the same number of grid points, different grid spacings are employed to investigate the effects of a grid resolution on the origin of the line of separation. Various shock strengths are used to study the so-called separation and unseparated boundary layer and to establish the existence or absence of secondary separation. The length of separation ahead of the flat-faced blunt fin, bifurcation of a horseshoe vortex, and the accessibility of a closed-type separation are investigated. The usual interpretation of the flow field from previous studies and new interpretations arising from the present simulation are discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1659-166
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  • 31
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    Compressible equilibrium turbulent boundary layers at nonadiabatic wall conditions (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1573-158
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  • 32
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    Oscillation of high-altitude balloons (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The Vaisala-Brunt frequencies of atmospheric waves lie sufficiently near He-filled balloon buoyancy oscillation frequencies to cause a near-resonance condition, especially in the 11.6-24.4 km altitude range. This excitation will hold for such balloons irrespective of size and payload variations due to the independence of balloon buoyant frequencies from size. Vertical perturbations of approximately 5-min period should accordingly be anticipated by balloon flight-control system designers.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 606-608
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  • 33
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    Effect of splitter plate on unsteady flows around a body of revolution at incidence (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Numerical solutions of the thin-layer approximation of the 3D Navier-Stokes equations are presented for flows around an ogive-cylinder body with and without a splitter plate. It is suggested that the presence of the splitter plate prevents the interaction between flows on either side of the symmetry plane. It is concluded that, as a result of the enforced symmetry, the antisymmetric mode of the convective instability near the apex of the body cannot be excited and, therefore, the vortices remain symmetric, staying low and parallel to the upper body surface. The antisymmetric mode of the absolute instability mechanism cannot be initiated, which suppresses the alternate shedding of vortices from the cylindrical portion of the body. High-frequency fluctuations of the shear layer are found to remain virtually unaffected by the presence of the splitter plate.
    Schlagwort(e): AERODYNAMICS
    Materialart: Physics of Fluids A (ISSN 0899-8213); 3; 2122-213
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  • 34
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    Effect of vortex core distortion on blade-vortex interaction (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1355-136
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  • 35
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    Flight tests of external modifications used to reduce blunt base drag (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 517-525
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  • 36
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    Semianalytical technique for sensitivity analysis of unsteady aerodynamic computations (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 481-488
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  • 37
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    Hypersonic rarefied flow about plates at incidence (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1250-125
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  • 38
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    Computational and experimental evaluation of helicopter rotor tips for high-speed flight (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 403-409
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  • 39
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    New device for controlling asymmetric flowfields on forebodies at large alpha (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 456-462
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  • 40
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    Accuracy of an unstructured-grid upwind-Euler algorithm for the ONERA M6 wing (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Improved algorithms for the solution of the three-dimensional, time-dependent Euler equations are presented for aerodynamic analysis involving unstructured dynamic meshes. The improvements have been developed recently to the spatial and temporal discretizations used by unstructured-grid flow solvers. The spatial discretization involves a flux-split approach that is naturally dissipative and captures shock waves sharply with at most one grid point within the shock structure. The temporal discretization involves either an explicit time-integration scheme using a multistage Runge-Kutta procedure or an implicit time-integration scheme using a Gauss-Seidel relaxation procedure, which is computationally efficient for either steady or unsteady flow problems. With the implicit Gauss-Seidel procedure, very large time steps may be used for rapid convergence to steady state, and the step size for unsteady cases may be selected for temporal accuracy rather than for numerical stability. Steady flow results are presented for both the NACA 0012 airfoil and the Office National d'Etudes et de Recherches Aerospatiales M6 wing to demonstrate applications of the new Euler solvers. The paper presents a description of the Euler solvers along with results and comparisons that assess the capability.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 397-402
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  • 41
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    Numerical solutions of forward-flight rotor flow using an upwind method (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 374-380
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  • 42
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    Experimental and predicted pressure and heating distributions for aeroassist flight experiment vehicle (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 5; 301-307
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  • 43
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    Computation of laminar hypersonic compression-corner flows (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1108-111
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  • 44
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    Hypersonic nonequilibrium viscous solutions over slender bodies (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An extension is undertaken of a previous numerical study in order to improve current understanding of nonequilibrium flow effects over slender bodies. Upon extension of the parametric study to encompass smaller nose radii, the downstream influence of equilibrium nonequilibrium flow is found to be much smaller than for the larger nose radii. A comparison of individual stagnation nonequilibrium heating rates demonstrates that a relative comparison of the ratios was not indicative of the actual heating reduction.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 358-360
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  • 45
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    Large-scale advanced propeller blade pressure distributions - Prediction and data (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 7; 452-461
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  • 46
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    Three-dimensional rarefied flow simulations for the Aeroassist Flight Experiment vehicle (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Hypersonic rarefied flow about the Aeroassist Flight Experiment vehicle has been investigated using a three-dimensional direct simulation Monte Carlo method. Calculations are performed for the transitional flows encountered during the vehicle's atmospheric entry for altitudes of 110 and 100 km with an entry velocity of 9.9 km/s. The simulations are performed using a five-species reacting gas model that account for rotational and vibrational internal energies. The solutions indicate that dissociation is important at altitudes of 110 km and below. Results are presented for surface pressures, convective heating, flowfield structure, and aerodynamic coefficient variations with altitude.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 52-57
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  • 47
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    Standard test case for a low-speed, turbulent junction vortex flow (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The mean flow structure upstream, around within, and in the near wake of a turbulent junction or horseshoe vortex is reported for an incompressible subsonic flow. Measurements of the primitive variables of velocity and pressure are reported on all surfaces bounding the region of the vortex flow and on three transverse and one streamwise plane within the flowfield itself for comparisons between the measured and any calculated flow variables. Detailed surface flow visualizations and some direct force measurements of surface shear stress are also available. The data is a highly detailed, coherent, self-consistent set offered to the computational fluid mechanics community as a standard test case for the evaluation of the capability of numerical solvers intended for predicting the flowfield in such a complex, separated, three-dimensional turbulent flow. This data base is available for copying to user supplied tapes or for transmission via BITNET, as well as in two National Technical Information Service (NTIS) reports.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 14
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  • 48
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    Calculation of steady and unsteady pressures on wings at supersonic speeds with a transonic small-disturbance code (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 175-180
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  • 49
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    Asymmetric vortices on a slender body of revolution (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 667-675
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  • 50
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    Computational analysis of underexpanded jets in the hypersonic regime (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 7; 297-299
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  • 51
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    Real gas effects on hypersonic boundary-layer stability (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: High-temperature effects alter the physical and transport properties of a gas, air in particular, due to vibrational excitation and gas dissociation, and thus the chemical reactions have to be considered in order to compute the flow field. Linear stability of high-temperature boundary layers is investigated under the assumption of chemical equilibrium and this gas model is labeled here as real gas model. In this model, the system of stability equations remains of the same order as for the perfect gas and the effect of chemical reactions is introduced only through mean flow and gas property variations. Calculations are performed for Mach 10 and 15 boundary layers and the results indicate that real gas effects cause the first mode instability to stabilize while the second mode is made more unstable. It is also found that the second mode instability shifts to lower frequencies. There is a slight destabilizing influence of real gas on the Goertler instability as compared to the perfect gas results.
    Schlagwort(e): AERODYNAMICS
    Materialart: Physics of Fluids A (ISSN 0899-8213); 3; 803-821
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  • 52
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    Comment on 'Critique of turbulence models for shock-induced flow separation' (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1021-102
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  • 53
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    Laser interferometer/Preston tube skin-friction comparison in shock/boundary-layer interaction (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An evaluation is conducted of the accuracy of the 'Preston tube' surface pitot-pressure skin friction measurement method relative to the already proven laser interferometer skin-friction meter in a swept shock wave/turbulent boundary-layer interaction. The Preston tube was used to estimate the total shear-stress distribution in a fin-generated swept shock-wave/turbulent boundary-layer interaction. The Keener-Hopkins calibration method using the isentropic relation to calculate the Preston-tube Mach number produces the best results.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1007-100
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  • 54
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    Effect of nose bluntness on flowfield over slender bodies in hypersonic flows (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 5; 166-171
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  • 55
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    Flowfield and vehicle parameter influence on results of engineering aerothermal methods (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 16-22
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  • 56
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    Euler analysis of a High-Speed Civil Transport concept at Mach 3 (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 239-245
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  • 57
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    Inverse problem in incompressible, irrotational axisymmetric flow (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A vortex-sheet method for solving the axisymmetric inverse problem is presented, and an iterative, interactive computer program for computing the body shape starting from an assumed shape is developed. The method eliminates the calculation of the direct problem at every iteration using the given velocity. The singular integral that arises in the problem formulation has been integrated analytically. The efficiency of the vortex-sheet method is demonstrated using three test cases, and the obtained body shapes and the corresponding surface velocity distributions are presented.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 94; 419-436
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  • 58
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    Interactive three-dimensional boundary-layer method for transonic flow over swept wings (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 678
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  • 59
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    Aspects and applications of patched grid calculations (1991)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Patched grid calculations within the framework of an implicit, flux vector split upwind/relaxation algorithm for the Euler equations are presented. Aspects of computing on patched grids are discussed including the effect of a metric-discontinuous interface on the convergence rate of the algorithm, and the effect of curvature along an interface. Applications to a converging-diverging nozzle including effects of choking and bypass slots in two dimensions are presented.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 676
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  • 60
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    Effect of exhaust plume/afterbody interaction on installed scramjet performance (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 123-130
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  • 61
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    Numerical simulation of the effect of spatial disturbances on vortex asymmetry (1991)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 344-352
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  • 62
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    Probe shapes for streamwise momentum and cross-stream turbulence intensity (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: When the highly turbulent flowfields at the edges of jets, in augmentors, and in other jet-mixing devices are surveyed with conventional pitot probes, the values indicated by the instruments may contain a significant increment brought about by the dynamics of the eddies. Although the influence of turbulence on the measurements is usually negligible in streams where the turbulence level is 1 percent or less, the effect of turbulence on static and total pressure measurements can be around 20 percent when the turbulence level exceeds 40 percent. This paper describes a theoretical study that develops probe shapes that directly measure the time-averaged total pressure based on the streamwise component of the velocity vector to obtain a direct measurement of the streamwise momentum. The difference between the time-averaged pressure indicated by such a probe and one that measures the total head based on the entire velocity vector yields the cross-stream turbulence intensity.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 741-749
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  • 63
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    Parametric study of dissociation and ionization models at 12 kilometers/second (1991)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 619-627
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  • 64
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    Increased ephemeris accuracy using attitude-dependent aerodynamic force coefficients for inertially stabilized spacecraft (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The FREEMAC program used to generate the aerodynamic coefficients, as well as associated routines that allow the results to be used in other software is described. These capabilities are applied in two numerical examples to the short-term orbit prediction of the Gamma Ray Observatory (GRO) and Hubble Space Telescope (HST) spacecraft. Predictions using attitude-dependent aerodynamic coefficients were made on a modified version of the PC-based Ephemeris Generation Program (EPHGEN) and were compared to definitive orbit solutions obtained from actual tracking data. The numerical results show improvement in the predicted semi-major axis and along-track positions that would seem to be worth the added computational effort. Finally, other orbit and attitude analysis applications are noted that could profit from using FREEMAC-calculated aerodynamic coefficients, including orbital lifetime studies, orbit determination methods, attitude dynamics simulators, and spacecraft control system component sizing.
    Schlagwort(e): AERODYNAMICS
    Materialart: Flight Mechanics(Estimation Theory Symposium, 1991; p 249-264
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  • 65
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    The research progress on Hodograph Method of aerodynamic design at Tsinghua University (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Progress in the use of the Hodograph method of aerodynamic design is discussed. It was found that there are some restricted conditions in the application of Hodograph design to transonic turbine and compressor cascades. The Hodograph method is suitable not only to the transonic turbine cascade but also to the transonic compressor cascade. The three dimensional Hodograph method will be developed after obtaining the basic equation for the three dimensional Hodograph method. As an example of the Hodograph method, the use of the method to design a transonic turbine and compressor cascade is discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: Pennsylvania State Univ., Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-3); p 599-606
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  • 66
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    Study of a new airfoil used in reversible axial fans (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The characteristics of the reverse ventilation of axial flow are analyzed. An s shaped airfoil with a double circular arc was tested in a wind tunnel. The experimental results showed that the characteristics of this new airfoil in reverse ventilation are the same as those in normal ventilation, and that this airfoil is better than the existing airfoils used on reversible axial fans.
    Schlagwort(e): AERODYNAMICS
    Materialart: Pennsylvania State Univ., Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-3); p 553-562
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  • 67
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    An inverse method with regularity condition for transonic airfoil design (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: It is known from Lighthill's exact solution of the incompressible inverse problem that in the inverse design problem, the surface pressure distribution and the free stream speed cannot both be prescribed independently. This implies the existence of a constraint on the prescribed pressure distribution. The same constraint exists at compressible speeds. Presented here is an inverse design method for transonic airfoils. In this method, the target pressure distribution contains a free parameter that is adjusted during the computation to satisfy the regularity condition. Some design results are presented in order to demonstrate the capabilities of the method.
    Schlagwort(e): AERODYNAMICS
    Materialart: Pennsylvania State Univ., Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-3); p 541-552
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  • 68
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    Airfoil optimization with efficient gradient calculations (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The viscous airfoil design analysis code XFOIL was extended to allow optimization using conformal mapping coefficients as design variables. The optimization technique used was the Steepest Descent method applied to a Penalty Function. The gradients of the aerodynamic variables with respect to the design variables were cheaply calculated as by-products of XFOIL's integral boundary layer Newton solver. The speed of the optimization process further increased by updating the Newton system boundary layer variables after each optimization step using the available gradient information. Two examples are presented.
    Schlagwort(e): AERODYNAMICS
    Materialart: Pennsylvania State Univ., Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-3); p 433-444
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    Variational formulation of hybrid problems for fully 3-D transonic flow with shocks in rotor (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Based on previous research, the unified variable domain variational theory of hybrid problems for rotor flow is extended to fully 3-D transonic rotor flow with shocks, unifying and generalizing the direct and inverse problems. Three variational principles (VP) families were established. All unknown boundaries and flow discontinuities (such as shocks, free trailing vortex sheets) are successfully handled via functional variations with variable domain, converting almost all boundary and interface conditions, including the Rankine Hugoniot shock relations, into natural ones. This theory provides a series of novel ways for blade design or modification and a rigorous theoretical basis for finite element applications and also constitutes an important part of the optimal design theory of rotor bladings. Numerical solutions to subsonic flow by finite elements with self-adapting nodes given in Refs., show good agreement with experimental results.
    Schlagwort(e): AERODYNAMICS
    Materialart: Pennsylvania State Univ., Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-3); p 337-346
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    Application of direct inverse analogy method (DIVA) and viscous design optimization techniques (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A direct-inverse approach to the transonic design problem was presented in its initial state at the First International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-1). Further applications of the direct inverse analogy (DIVA) method to the design of airfoils and incremental wing improvements and experimental verification are reported. First results of a new viscous design code also from the residual correction type with semi-inverse boundary layer coupling are compared with DIVA which may enhance the accuracy of trailing edge design for highly loaded airfoils. Finally, the capabilities of an optimization routine coupled with the two viscous full potential solvers are investigated in comparison to the inverse method.
    Schlagwort(e): AERODYNAMICS
    Materialart: Pennsylvania State Univ., Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-3); p 307-324
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  • 71
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    Navier-Stokes calculation of transonic flow past the NTF 65 deg delta wing (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Models of four delta wings were built and tested in the 8 x 8 ft Transonic Wind Tunnel at LaRC. The wings are identical in planform shape with a swept-back angle of 65 degrees, but bear different leading edge profiles. The models were tested under pressurized and cryogenic conditions to simulate true flight Reynolds numbers. Data on the aerodynamic forces and pressure distributions at various locations on the wings were taken at various flight Mach numbers and angles of attack. Effects of high Reynolds number and leading edge radius on the aerodynamic characteristics of the wings are being accessed. To thoroughly understand the turbulent, vortical flow around the wings, an effort to perform computational aerodynamic analysis is being made. The objective of the analysis is to supplement and validate the experimental data and explain the high Reynolds number and leading edge effects. GRIDGEN, a software developed by General Dynamics, is being used to generate the grid topology for the flow field around the wings. The flow solver to be used is CFL3D, a computation fluid dynamics code developed at LaRC. Based on the geometric description of the wings, a FORTRAN program called WINGSURF was written to generate the databases defining the surface geometry of the wings. To match the true geometry of the models in the wind tunnel for realistic comparison with experimental results, databases defining the sting support for the wing models were also created by two other FORTRAN programs, STINJOIN and STINREAR. Listing of the programs are attached and the geometry of a typical wing model with the sting support is shown. Other aspects of the investigation are discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: Old Dominion Univ., NASA/American Society for Engineering Ed; Old Dominion Univ.,
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  • 72
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    Constant-temperature anemometry measurements in hypersonic boundary layers (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: One of the major unresolved issues in fluid dynamics is the nature of apparent stresses, called Reynolds stresses, which occur in turbulent boundary layers. In hypersonic boundary layers, the flow physics is further complicated by the large temperature and density fluctuations and the concomitant contamination of the Reynold stresses by fictitious terms. Because of the severe flow environment and the extraordinary demands on sensors and instruments, the turbulence characteristics of hypersonic boundary layers were studied in only a cursory fashion. The plans for supersonic (HSCT) and hypersonic (NASP) vehicles made supersonic flow physics one of the critical pacing technologies in aerospace science. In particular, experimental data are needed to verify candidate computer models and to reach an important understanding of the turbulence physics. The presented research is the start of a substantial effort to refine existing instrumentation and develop experimental techniques to measure the various component of the Reynolds stress in hypersonic boundary layers.
    Schlagwort(e): AERODYNAMICS
    Materialart: Old Dominion Univ., NASA/American Society for Engineering Ed; Old Dominion Univ.,
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  • 73
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    An evaluation of preliminary Doppler global velocimetry measurements (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A review of Doppler Global Velocimetry (DGV) data obtained during wind tunnel tests on a 75 degree swept delta wing was performed. High frequency variations observed in normalized data files are attributed to image alignment problems. Unfortunately, initial DGV velocity data compared poorly with baseline reference data. Nonlinear DGV system operation during the tests is the likely source of this problem. Corrected data compares much more favorably and suggests that DGV is a valid measurement technique. Future DGV investigations should include a method or means for monitoring laser frequency relative to the ALF transfer function behavior.
    Schlagwort(e): AERODYNAMICS
    Materialart: Old Dominion Univ., NASA/American Society for Engineering Ed; Old Dominion Univ.,
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  • 74
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    The use of artificial neural networks in experimental data acquisition and aerodynamic design (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: It is proposed that an artificial neural network be used to construct an intelligent data acquisition system. The artificial neural networks (ANN) model has a potential for replacing traditional procedures as well as for use in computational fluid dynamics validation. Potential advantages of the ANN model are listed. As a proof of concept, the author modeled a NACA 0012 airfoil at specific conditions, using the neural network simulator NETS, developed by James Baffes of the NASA Johnson Space Center. The neural network predictions were compared to the actual data. It is concluded that artificial neural networks can provide an elegant and valuable class of mathematical tools for data analysis.
    Schlagwort(e): AERODYNAMICS
    Materialart: Old Dominion Univ., NASA/American Society for Engineering Ed; Old Dominion Univ.,
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  • 75
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    A numerical method for unsteady aerodynamics via acoustics (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Formal solutions to the wave equation may be conveniently described within the framework of generalized function theory. A generalized function theory is used to yield a formulation and formal solution of a wave equation describing oscillation of a flat plate from which a numerical method may be derived.
    Schlagwort(e): AERODYNAMICS
    Materialart: Old Dominion Univ., NASA/American Society for Engineering Ed; Old Dominion Univ.,
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  • 76
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    Experiences with optimizing airfoil shapes for maximum lift over drag (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The goal was to find airfoil shapes which maximize the ratio of lift over drag for given flow conditions. For a fixed Mach number, Reynolds number, and angle of attack, the lift and drag depend only on the airfoil shape. This then becomes a problem in optimization: find the shape which leads to a maximum value of lift over drag. The optimization was carried out using a self contained computer code for finding the minimum of a function subject to constraints. To find the lift and drag for each airfoil shape, a flow solution has to be obtained. This was done using a two dimensional Navier-Stokes code.
    Schlagwort(e): AERODYNAMICS
    Materialart: Old Dominion Univ., NASA/American Society for Engineering Educ; Old Dominion Univ.,
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  • 77
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    Leading-edge receptivity to a vortical freestream disturbance: A numerical analysis (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The receptivity to freestream vorticity of the boundary layer over a flat plate with an elliptic leading edge is investigated numerically. The flow is simulated by solving the incompressible Navier-Stokes system in general curvilinear coordinates with the vorticity and stream function as dependent variables. A finite-difference scheme which is second-order accurate in both space and time is used. As a first step, the steady basic-state solution is computed. Then a small amplitude vortical disturbance is introduced at the upstream boundary and the governing equations are solved time-accurately to evaluate the spatial and temporal growth of the perturbations leading to instability waves (Tollmien-Schlichting waves) inside the boundary layer. Preliminary results for a symmetric, 2-D disturbance reveal the presence of Tollmien-Schlichting waves aft of the flat-plate/ellipse juncture.
    Schlagwort(e): AERODYNAMICS
    Materialart: Numerical Simulation of Swept-Wing Flows; p 30-52
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  • 78
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    The computation of induced drag with nonplanar and deformed wakes (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The classical calculation of inviscid drag, based on far field flow properties, is reexamined with particular attention to the nonlinear effects of wake roll-up. Based on a detailed look at nonlinear, inviscid flow theory, it is concluded that many of the classical, linear results are more general than might have been expected. Departures from the linear theory are identified and design implications are discussed. Results include the following: Wake deformation has little effect on the induced drag of a single element wing, but introduces first order corrections to the induced drag of a multi-element lifting system. Far field Trefftz-plane analysis may be used to estimate the induced drag of lifting systems, even when wake roll-up is considered, but numerical difficulties arise. The implications of several other approximations made in lifting line theory are evaluated by comparison with more refined analyses.
    Schlagwort(e): AERODYNAMICS
    Materialart: Stanford Univ., Nonlinear Aerodynanics and the Design of Wing Tips; 9 p
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  • 79
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    Three-dimensional calculations of supersonic reacting flows using an LU scheme (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A 3-D numerical program that incorporates comprehensive real gas property models was developed to simulate supersonic reacting flows. The code employs an implicit, finite volume, Lower-Upper (LU), time-marching method to solve the complete Navier-Stokes and species equations in a fully-coupled and efficient manner. A chemistry model with 9 species and 18 reaction steps is adopted in the program to represent the chemical reactions of H2 and air. To demonstrate the capability of the program, flow fields of underexpanded hydrogen jets transversely injected into the supersonic airstream inside the combustors of scramjets are calculated. Results clearly depict the flow characteristics, including the shock structure, the separated flow regions around the injector, and the distribution of the combustion products.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Lewis Research Center, Center for Modeling of Turbulence and Transition (CMOTT). Research Briefs: 1990; p 151
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  • 80
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    Aerothermodynamics for United States advanced programs (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-29
    Beschreibung: A series of graphics relating to aerothermodynamics is presented. They following topics are shown: space transportation architecture options and systems, vehicle shapes and design goals, aerothermodynamics (including hypersonic entry), computational fluid dynamics, ground based testing, aeroassist environment, and airbreathing propulsion.
    Schlagwort(e): AERODYNAMICS
    Materialart: ESA, Aerothermodynamics for Space Vehicles; p 515-533
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  • 81
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    Streamwise upwind algorithm for computing unsteady transonic flows past oscillating wings (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1668-167
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  • 82
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    Convergence acceleration of viscous and inviscid hypersonic flow calculations (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 29; 1214-122
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  • 83
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    Unsteady blade-surface pressures on a large-scale advanced propeller - Prediction and data (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 7; 866-872
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  • 84
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    Boundary-layer and wake measurements on a swept, circulation-control wing (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 706-712
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  • 85
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    Euler code evaluation of a transatmospheric vehicle at supersonic speeds (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 683-688
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  • 86
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    Computation of three-dimensional turbulent vortical flows on bodies at high incidence (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 28; 689-699
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  • 87
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    Aerodynamic heating on AFE due to nonequilibrium flow with variable entropy at boundary layer edge (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-29
    Beschreibung: A method of predicting the aerobrake aerothermodynamic environment on the NASA Aeroassist Flight Experiment (AFE) vehicle is described. Results of a three dimensional inviscid nonequilibrium solution are used as input to an axisymmetric nonequilibrium boundary layer program to predict AFE convective heating rates. Inviscid flow field properties are obtained from the Euler option of the Viscous Reacting Flow (VRFLO) code at the boundary layer edge. Heating rates on the AFE surface are generated with the Boundary Layer Integral Matrix Procedure (BLIMP) code for a partially catalytic surface composed of Reusable Surface Insulation (RSI) times. The 1864 kg AFE will fly an aerobraking trajectory, simulating return from geosynchronous Earth orbit, with a 75 km perigee and a 10 km/sec entry velocity. Results of this analysis will provide principal investigators and thermal analysts with aeroheating environments to perform experiment and thermal protection system design.
    Schlagwort(e): AERODYNAMICS
    Materialart: ESA, Aerothermodynamics for Space Vehicles; p 371-376
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    Computation of compressible quasi-axisymmetric slender vortex flow and breakdown (1991)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The unsteady, compressible Navier-Stokes equations are used to compute and analyze compressible quasi-axisymmetric isolated vortices. The Navier-Stokes equations are solved using an implicit, upwind, flux difference splitting finite volume scheme. The developed three dimensional solver was verified by comparing its solution profiles with those of a slender, quasi-axisymmetric vortex solver for a subsonic, quasi-axisymmetric vortex in an unbounded domain. The Navier-Stokes solver is then used to solve for a supersonic, quasi-axisymmetric vortex flow in a configured circular duct. Steady and unsteady vortex-shock interactions and breakdown were captured. The problem was also calculated using the Euler solver of the same code; the results were compared with those of the Navier-Stokes solver. The effect of the initial swirl was investigated.
    Schlagwort(e): AERODYNAMICS
    Materialart: Analysis and Control of Asymmetric Vortex Flows and Supersonic Vortex Breakdown; 10 p
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  • 89
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    Nonequilibrium turbulence modeling effects on transonic vortical flows about delta wings (1991)
    In:  CASI
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    Publikationsdatum: 2017-10-02
    Beschreibung: The Johnson-King turbulence model that is a viable method for calculating two dimensional transonic separated flows was extended into three dimensions. The implementation was done for Navier Stokes flow solvers written in general curvilinear coordinates. The present approach used in turbulence modeling is based on streamwise integration of an ordinary differential equation (o.d.e.) that governs the maximum Reynolds shear stress behavior. Streamwise integration of the o.d.e. approach was found to offer great mathematical simplicity and economy for three dimensional Navier Stokes methods. Thus, the new method is quick, simple, and very cheap. The new method was first checked against the data of a well known transonic axisymmetric bump experiment, and a good agreement was obtained. Later, the new method was used to compute the flow around a low aspect ratio wing in a transonic wind tunnel. Finally it was employed to study the nonequilibrium turbulence effects on the transonic vortical flows about a 65 deg sweep round leading edge delta wing.
    Schlagwort(e): AERODYNAMICS
    Materialart: AGARD, Vortex Flow Aerodynamics; 13 p
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  • 90
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    In-flight flow visualization and pressure measurements at low speeds on the NASA F-18 high alpha research vehicle (1991)
    In:  CASI
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    Publikationsdatum: 2017-10-02
    Beschreibung: Inflight results from surface and off surface flow visualizations and from extensive pressure distributions document the vortical flow on the leading edge extensions (LEXs) and forebody of the NASA F-18 high alpha research vehicle (HARV) for low speeds and angles of attack up to 50 deg. Surface flow visualization data, obtained using the emitted fluid technique, were used to define separation lines and laminar separation bubbles (LSB). Off surface flow visualization data, obtained by smoke injection, were used to document both the path of the vortex cores and the location of vortex core breakdown. The location of vortex core breakdown correlated well with the loss of suction pressure on the LEX and with the flow visualization results from ground facilities. Surface flow separation lines on the LEX and forebody corresponded well with the end of pressure recovery under the vortical flows. Correlation of the pressures with wind tunnel results show fair to good correlation.
    Schlagwort(e): AERODYNAMICS
    Materialart: AGARD, Vortex Flow Aerodynamics; 42 p
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    Investigation of vortex breakdown on a delta wing using Euler and Navier-Stokes equations (1991)
    In:  CASI
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    Publikationsdatum: 2017-10-02
    Beschreibung: A numerical investigation of leading edge vortex breakdown in a delta wing at high angles of attack is presented. The analysis was restricted to low speed flows on a flat plate wing with sharp leading edges. Both Euler and Navier-Stokes equations were used and the results were compared with experimental data. Predictions of vortex breakdown progression with angle of attack with both Euler and Navier-Stokes equations are shown to be consistent with the experimental data. However, the Navier-Stokes predictions show significant improvements in breakdown location at angles of attack where the vortex breakdown approaches the wing apex. The predicted trajectories of the primary vortex are in very good agreement with the test data, the laminar solutions providing the overall best comparison. The Euler shows a small displacement of the primary vortex, relative to experiment, due to the lack of secondary vortices. The turbulent Navier-Stokes, in general, fall between the Euler and laminar solutions.
    Schlagwort(e): AERODYNAMICS
    Materialart: AGARD, Vortex Flow Aerodynamics; 12 p
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  • 92
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    Vortex control: Further encounters (1991)
    In:  CASI
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    Publikationsdatum: 2017-10-02
    Beschreibung: The progress of continuing investigations on vortex control techniques is updated. The following topics are briefly discussed: (1) vortex flaps adapted for high-alpha control; (2) alleviation of leading edge extension (LEX) vortex induced twin-tail buffet; (3) controlled decoupling of interactive forebody chine and wing vortices; (4) forebody vortex manipulation by mechanical and pneumatic techniques; and (5) stall-departure alleviation of high aspect-ratio wings. Salient results of exploratory low speed wind tunned experiments are presented. The investigations, primarily aimed at concept validation, were performed on generic configurations utilizing flow visualizations and pressure and balance measurements. Selected results illustrate the efficacy and potential for development of specific vortex control concepts for improved high-alpha configuration aerodynamics.
    Schlagwort(e): AERODYNAMICS
    Materialart: AGARD, Vortex Flow Aerodynamics; 12 p
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  • 93
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    User's guide for a flat wake rotor inflow/wake velocity prediction code, DOWN (1991)
    In:  CASI
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    Publikationsdatum: 2019-06-28
    Beschreibung: A computer code named DOWN was created to implement a flat wake theory for the calculation of rotor inflow and wake velocities. A brief description of the code methodology and instructions for its use are given. The code will be available from NASA's Computer Software Management and Information Center (COSMIC).
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-104139 , NAS 1.15:104139 , AVSCOM-TR-91-B-016 , AD-B161021L
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    Prediction of unsteady aerodynamic loads in cascades using the linearized Euler equations on deforming grids (1991)
    In:  Other Sources
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    Publikationsdatum: 2019-06-28
    Beschreibung: A linearized Euler solver for calculating unsteady flows in turbomachinery blade rows due to both incident gusts and blade motion is presented. Using the linearized Euler technique, one decomposes the flow into a mean (or steady) flow plus an unsteady, harmonically varying, small disturbance flow. Linear variable coefficient equations describe the small disturbance behavior of the flow, and are solved using a pseudo-time marching Lax-Wendroff scheme. For the blade motion problem, a harmonically deforming computational rid that conforms to the motion of vibrating blades eliminates large error producing mean flow gradient terms that would otherwise appear in the unsteady flow tangency boundary condition. The paper also presents a new, numerically exact, nonreflecting far-field boundary condition based on an eigenanalysis of the discretized equations. Computed flow solutions demonstrate the computational accuracy and efficiency of the present method. The solution of the linearized Euler equations requires one to two orders of magnitude less computer time than solution of the nonlinear Euler equations using traditional time-accurate time-marching techniques. In addition, the deformable grid significantly improves the accuracy of the solution.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 91-3378
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    The vortex interaction in a propeller/stator flow field (1991)
    In:  Other Sources
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    Publikationsdatum: 2019-06-28
    Beschreibung: The vortex interaction encounered in the flow field of a propeller and a stator has been investigated using smoke flow visualization. A stator at angle of attack was used to generate a line vortex which interacted with the helical vortex filaments generated by a propeller. Changes in the relative vortex strengths and vortex rotational directions yielded several distinct vortex structures. Axial flow in the vortex cores is determined to influence the development of the vortex interaction.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 91-1818
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    Effects of leading-edge flap oscillation on unsteady delta wing flow and rock control (1991)
    In:  Other Sources
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    Publikationsdatum: 2019-06-28
    Beschreibung: The isolated and interdisciplinary problems of unsteady fluid dynamics and rigid-body dynamics and control of delta wings with and without leading-edge flap oscillation are considered. For the fluid dynamics problem, the unsteady, compressible, thin-layer Navier-Stokes (NS) equations, which are written relative to a moving frame of reference, are solved along with the unsteady, linearized, Navier-displacement (ND) equations. The NS equations are solved for the flowfield using an implicit finite-volume scheme. The ND equations are solved for the grid deformation, if the leading-edge flaps oscillate, using an ADI scheme. For the dynamics and control problem, the Euler equation of rigid-body rolling motion for a wing and its flaps are solved interactively with the fluid dynamics equations for the wing-rock motion and subsequently for its control. A four-stage Runge-Kutta scheme is used to explicitly integrate the dynamics equation.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 91-1796
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    Progress in hypersonic turbulence modeling (1991)
    In:  Other Sources
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    Publikationsdatum: 2019-06-28
    Beschreibung: A compressibility modification is developed for k-omega (Wilcox, 1988) and k-epsilon (Jones and Launder, 1972) models, that is similar to those of Sarkar et al. (1989) and Zeman (1990). Results of the perturbation solution for the compressible wall layer demonstrate why the Sarkar and Zeman terms yield inaccurate skin friction for the flat-plate boundary layer. A new compressibility term is developed which permits accurate predictions of the compressible mixing layer, flat-plate boundary layer, and shock separated flows.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 91-1785
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    Opportunities for applications of natural laminar flow technology at high-subsonic speeds (1991)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The possible profiles of high subsonic speed airfoils with extensive regions of natural laminar flow (NLF) are explored, on the bases of calculations which suggest that high subsonic Mach number NLFs are obtainable for both swept and unswept wing applications at certain Reynolds numbers. Attention is given to the transonic pressure distributions of airfoils for unswept wings at freestream Mach numbers of 0.65-0.80 and chord Reynolds numbers of up to 50 million. The case of 10-30 deg swept-wing NLF airfoils is also investigated for chord Reynolds numbers of 15-50 million.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 91-1773
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
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    Studies of shock/shock interaction on smooth and transpiration-cooled hemispherical nosetips in hypersonic flow (1991)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Experimental studies are conducted to examine the utilization of transpiration cooling to reduce the peak-heating loads in areas of shock/shock interaction. Smooth and transpiration-cooled nosetip models, 12 inches in diameter, were employed in these studies, which focused on defining the pressure distributions and heat transfer in type III and IV interaction areas. Transpiration cooling was determined to significantly increase the size of the shock layer and to move the peak-heating point around the body. A transpiration-cooling rate of more than 30 percent of the freestream maximum flux did not lower the peak-heating level more than 10 percent, but the integrated heating loads were reduced.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 91-1765
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    Stability of a compressible swirling jet (1991)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Temporal linear stability of a compressible swirling axisymmetric jet is considered. It is found that with the addition of a modest amount of swirl, instability growth rates are substantially increased. Additionally, rotating jets are found to be highly unstable for disturbances with high aximuthal wave numbers. Such disturbances are absent for the case of non-swirling jets. Most importantly, it is found that the stabilizing influence of increasing Mach number is diminished with the introduction of swirl to the jet flow.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 91-1770
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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