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  • STRUCTURAL MECHANICS  (1.510)
  • AERODYNAMICS
  • 1970-1974  (2.766)
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  • 1
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    Noise and vibration level reduction by covering metal structures with layers of damping materials (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: One of the most important methods of reducing the noise and vibration level is the damping of the secondary sources, such as metal plates, often used in vehicle structures, by means of covering materials with high internal viscosity. Damping layers are chosen at an optimum thickness corresponding to the frequency and temperature range in which a certain structure works. The structure's response corresponding to various real situations is analyzed by means of a measuring chain including electroacoustical or electromechanical transducers. The experimental results provide the dependence of the loss factor and damping transmission coefficient as a function of the damping layer thickness or of the frequency for various viscoelastic covering materials.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 246-253
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  • 2
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    Vibration and recoil control of pneumatic hammers (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: Vibration sources are described for pneumatic hammers used in the mining industry (pick hammers), in boiler shops (riveting hammers), etc., bringing to light the fact that the principal vibration source is the variation in air pressure inside the cylinder. The present state of the art of vibration control of pneumatic hammers as it is practiced abroad, and the solutions adopted for this purpose, are discussed. A new type of pneumatic hammer with a low noise and vibration level is presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 79-84
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  • 3
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    Vibration control in forge hammers (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: Special measures are discussed for calculating, designing and executing a forge hammer foundation, so that the vibrations that occur during its working will not be transmitted to neighboring machinery, workrooms and offices. These vibrations are harmful to the workers near the forge hammer.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 73-78
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  • 4
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    Experimental determination of the vibration level in 5,100 kW electric locomotive assemblies (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: Because of the high vibration level occurring during the running of electric locomotives, mechanical defects occur in the control mechanisms of auxiliary services. This fact has given rise to the necessity of determining the values of these vibrations in electric locomotives during their running. Measurements were conducted on the Craiova-Drobeta-Turnu Severin line, and measures to reduce the vibration level in electric locomotives were instituted.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 50-54
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  • 5
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    Random vibrations of linear viscoelastic beams with lumped masses (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: A method is presented of determining the mean square transversal deflection of an isotropic and homogeneous linear viscoelastic beam having a certain number of lengthwise distributed lumped masses. It is assumed that the beam is acted upon by a stationary random process uniformly distributed along the beam. The method is useful in vibration level control by means of additional lumped masses.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 36-42
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  • 6
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    Random vibrations of quadratic damping systems (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: An oscillating system with quadratic damping subjected to white noise excitation is replaced by a nonlinear, statistically equivalent system for which the associated Fokker-Planck equation can be exactly solved. The mean square responses are calculated and the optimum damping coefficient is determined with respect to the minimum mean square acceleration criteria. An application of these results to the optimization of automobile suspension damping is given.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 29-35
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  • 7
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    The response of many-storied structures under seismic actions (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: A seismic action which is characterized by the acceleration function of the seismic motion is analyzed. The equations of motion in the direction of the seismic action are determined for a completely rigid ground and for a ground with linear deformability characteristics (rotation deformability). The equation for the rotation motion is derived by considering elastic and viscoelastic properties of the foundation ground. The differential equations are written by treating the mechanical model of a many-storied structure as a fixed vertical beam with a uniformly distributed mass as well as with concentrated masses on each floor.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 43-49
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  • 8
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    Insulation of nonlinear and random vibrations in the mining industry (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: The insulation of nonlinear and random vibrations is considered for some ore preparing and sorting implements: rotary crushers, resonance screens, hammer mills, etc. The appearance of subharmonic vibrations is analyzed, and the conditions for their appearance are determined. A method is given for calculating the insulation of these vibrations by means of elastic elements made of rubber. The insulation of the random vibrations produced by Symons crushers is calculated by determining the transmissability and deformation of the insulation system for a narrow band random response.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 22-28
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  • 9
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    A mathematical model for storied buildings subjected to automatic loom stresses (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: Expressions are derived for the displacements of a many storied building subjected to the action of classical weaving looms located at different levels of the building. The building is regarded as a vertical fixed beam with a uniformly distributed mass as well as concentrated masses at each level. The calculation relations are obtained on the assumption of harmonic variation of the forces acting at each level as well as the assumption of narrow band stationary random excitatory forces.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 15-21
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  • 10
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    Study of vibrations produced by a vibrating beam used for vibrating concretes (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-11
    Beschreibung: For compacting concretes in building, vibrating beams are used. The vibrations are generated by inertial vibrators, and the beam is normally displaced by the operator by means of a handle that is elastically fastened to the beam by means of rubber pads. Considered are vibrations transmitted to the operator, taking into account the beam's shock vibration motions. The steady state motion of a dynamic beam pattern is studied, and results of experimental tests with existing equipment are presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 9-14
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  • 11
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    Stresses in dome-shaped shells of revolution with discontinuities at the apex (1974)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-02
    Beschreibung: Asymptotic solutions of Novozhilov's equations of shells of revolution are derived for axisymmetric and first harmonic loadings. The solutions obtained are valid throughout the shallow and nonshallow regions. Stresses in dome shaped shells of revolution with a discontinuity in the form of a circular hole, a circular rigid insert, or a nozzle at the apex have been investigated. Numerical results are obtained for spheres, ellipsoids, and paraboloids, containing a discontinuity under a internal pressure and moment. Curves depicting stress distributions are given. The influence of three types of discontinuity on the stresses of the shells is also given.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Multivariant Function Model Generation; 118 p
    Format: text
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  • 12
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    Current structural vibration problems associated with noise (1974)
    In:  CASI
    Details
    Publikationsdatum: 2011-10-14
    Beschreibung: As the performance of aerospace vehicles has increased, the noise generated by the propulsion system and by the passage of the vehicle through the air has also increased. Further increases in performance are now underway for space vehicles such as the space shuttle vehicle and for short distance takeoff and landing (STOL) aircraft, and are being planned for supersonic aircraft. The flight profiles and design features of these high-performance vehicles are reviewed and an estimate made of selected noise-induced structural vibration problems. Considerations for the prevention of acoustic fatigue, noise transmission, and electronic instrument malfunction are discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AGARD Noise Mech.; 16 p
    Format: text
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  • 13
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    Lifting-surface theory for a semi-infinite wing in oblique gust (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: An unsteady lifting-surface theory is developed for the calculation of the airload on a semi-infinite-span thin wing in a compressible flow due to interaction with an oblique gust. By using the solutions obtained for a two-dimensional wing, the problem is formulated so that the unknown is taken to be the difference between the airload on the semi-infinite wing and that on a two-dimensional wing under the same gust conditions. Since this airload difference is nonzero only near the wing tip, the control points need be distributed in the tip region only; this significantly simplifies the numerical procedure. Results are presented for a wing with rectangular tip. The implication for noise and unsteady loads due to blade-vortex interaction for helicopter rotors is discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal; 12; Dec. 197
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  • 14
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    Inclusion of transverse shear deformation in finite element displacement formulations (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A stiffness matrix is derived for a beam element with transverse shear deformation. It is shown that straightforward energy minimization yields the correct stiffness matrix in displacement formulations when transverse shear effects are considered. Since the TIM4 beam element does not represent the geometric boundary conditions for a cantilever beam the rotation of the normal must be retained as a grid point degree of freedom.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal; 12; Nov. 197
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  • 15
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    Planetary entry aerothermodynamics. II - Computational analyses and flight experience (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Limitations concerning the possibility to simulate all the significant flow and thermal phenomena occurring during the entry of a space vehicle into a planetary atmosphere make it necessary to rely on computational analyses to obtain the required data for the design of the spacecraft needed for the NASA missions planned for the next two decades. 'Benchmark' computer programs concerned with complete, detailed, and accurate computational solutions of entry problems are considered along with programs representing engineering approximations for cases in which the accuracy provided by the benchmark programs is not needed. The information obtainable by computational analysis has to be supplemented by actual flight experience in order to meet the goals of the NASA entry-technology program. The individual space missions planned for the coming years are examined together with the possibilities for obtaining the data needed to satisfy the entry requirements in each case.
    Schlagwort(e): AERODYNAMICS
    Materialart: Astronautics and Aeronautics; 12; Dec. 197
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  • 16
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    Analysis of acoustic radiation in a jet flow environment (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: The analysis of sound fields from arbitrary source distributions in terms of Legendre and spherical Hankel functions is well known. The purpose of this paper is to extend this classical method of analysis to environments such as jet flows where flow and flow gradients are inherently present. The wave-equation governing the radiation of sound in such an environment is derived. The steady state flow and flow gradients in the axial and transverse directions appear as coefficients in the terms of the wave-equation. A semi-numerical method is used to solve the wave-equation in terms of modified spherical harmonics yielding the phase velocities and the directivities of an infinite set of modes. The directivity of each mode is obtained in terms of modified Legendre functions by numerical integration. Some results of these directivity and phase-velocity calculations are presented for a limited number of frequency and flow parameters. Both convective and shear refraction are shown to be important.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Sound and Vibration; 36; Sept. 8
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  • 17
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    Unified approach to aerodynamic sound generation in the presence of solid boundaries (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A general equation governing aerodynamic sound generation in the presence of solid boundaries is derived. It is shown that all the theories in the literature appear as special cases of this general equation. Derived special equations for propeller and fan noise are likewise shown to be more general than the conventional equations in that they make allowance for variation in retarded time over the blade surfaces.
    Schlagwort(e): AERODYNAMICS
    Materialart: Acoustical Society of America; vol. 56
    Format: text
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  • 18
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    Microcraters formed in glass by projectiles of various densities (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: An experiment was conducted investigating the effect of projectile density on the structure and size of craters in soda lime glass and fused quartz. The projectiles were spheres of polystyrene-divinylbenzene (PS-DVB), aluminum, and iron with velocities between 0.5 and 15 km/sec and diameters between 0.4 and 5 microns. The projectile densities spanned the range expected for primary and secondary particles of micrometer size at the lunar surface, and the velocities spanned the lower range of micrometeoroid velocities and the upper range of secondary projectile velocities. There are changes in crater morphology as the impact velocity increases, and the transitions occur at lower velocities for the projectiles of higher density. The sequence of morphological features of the craters found for PS-DVB impacting soda lime glass for increasing impact velocity, described in a previous work (Mandeville and Vedder, 1971), also occurs in fused quartz and in both targets with the more dense aluminum and iron projectiles. Each transition in morphology occurs at impact velocities generating a certain pressure in the target. High density projectiles require a lower velocity than low-density projectiles to generate a given shock pressure.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Geophysical Research; 79; Aug. 10
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  • 19
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    Automatic numerical generation of body-fitted curvilinear coordinate system for field containing any number of arbitrary two-dimensional bodies (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A method for automatic numerical generation of a general curvilinear coordinate system with coordinate lines coincident with all boundaries of a general multi-connected region containing any number of arbitrarily shaped bodies is presented. With this procedure the numerical solution of a partial differential system may be done on a fixed rectangular field with a square mesh with no interpolation required regardless of the shape of the physical boundaries, regardless of the spacing of the curvilinear coordinate lines in the physical field, and regardless of the movement of the coordinate system. Numerical solutions for the lifting and nonlifting potential flow about Joukowski and Karman-Trefftz airfoils using this coordinate system generation show excellent comparison with the analytic solutions. The application to fields with multiple bodies is illustrated by a potential flow solution for multiple airfoils.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Computational Physics; 15; July 197
    Format: text
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  • 20
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    Approximate techniques of structural reanalysis (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A study is made of two approximate techniques for structural reanalysis. These include Taylor series expansions for response variables in terms of design variables and the reduced-basis method. In addition, modifications to these techniques are proposed to overcome some of their major drawbacks. The modifications include a rational approach to the selection of the reduced-basis vectors and the use of Taylor series approximation in an iterative process. For the reduced basis a normalized set of vectors is chosen which consists of the original analyzed design and the first-order sensitivity analysis vectors. The use of the Taylor series approximation as a first (initial) estimate in an iterative process, can lead to significant improvements in accuracy, even with one iteration cycle. Therefore, the range of applicability of the reanalysis technique can be extended. Numerical examples are presented which demonstrate the gain in accuracy obtained by using the proposed modification techniques, for a wide range of variations in the design variables.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures; 4; Aug. 197
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  • 21
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    Analysis of propagation of waves of acoustic frequencies in curved ducts (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: The propagation of waves of acoustic frequencies in curved ducts of rectangular cross section is studied for the first four modes. The analysis makes use of Bessel functions of the order (n + 1/2) to construct curves of wavenumber in the duct versus imposed wavenumber and to determine the profile of vibrational velocities. A wide range of duct widths and unrestricted radii of curvature have been considered. The characteristics of motion in a bend are compared with propagation of waves in a straight duct, and important differences in the behavior of waves are noted.
    Schlagwort(e): AERODYNAMICS
    Materialart: Acoustical Society of America; vol. 56
    Format: text
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  • 22
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    Axial flow measurements in trailing vortices (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A scanning laser Doppler velocimeter was used to measure the axial velocity defect in the cores of trailing vortices behind a lifting airfoil of rectangular planform. Data were obtained at several different angles of attack and downstream distances ranging from 30 to 1000 chord lengths. The test was designed to obtain continuous data from the near field into the far field while removing uncertainties associated with the interpretation of data obtained by the hydrogen bubble technique. The measured velocities of V sub x/U sub infinity are compared with those predicted. The agreement is remarkably good over the entire range of downstream distances, which supports the credibility of calculating axial velocities using the results of Moore and Saffman (1973).
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal; 12; Aug. 197
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  • 23
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    Vortex measurements behind a swept wing transport model (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A backscatter laser Doppler velocimeter which simultaneously senses the axial and the tangential components of the velocity has been used to measure the velocity distributions in the near wake of a swept wing semispan transport model in a wind tunnel. The model configuration included nacelles, pylons, antishock bodies, and wing flaps which could be deflected 27 deg. Typical wake vortex velocity profiles are presented for the flaps-retracted and the flaps-deployed 27 deg configurations, respectively.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft; 11; June 197
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  • 24
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    Static, stability, and dynamic analysis of shells of revolution by numerical integration - A comparison (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Recent innovations in digital computer technology have enabled engineers to analyze shell structures of complex configurations without unduly restrictive approximations. An attempt is made to compare the various programs now generally available from the point of view of the advantages of the relative technique utilized, as well as the programmed state of the art. Many of the comparisons are based on the sample problems solved by the STARS-2 system of programs. These examples indicate both the structural detail which can be analyzed by, and the analytical capabilities available in, the numerical shell-of-revolution programs. All advantages and differences are demonstrated by use of solutions for realistic shell problems in the areas of statics, stability, vibrations, and dynamic response of shells subjected to time-dependent loadings.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 25
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    Forced vibrations of multi-component compliant tanks and feedlines (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: An analytical and experimental research program was performed to investigate the effects of flexible tanks and lines and the total system dynamic response of a simple physical system which had some of the essential features of a liquid-fueled launch vehicle. Several vessel-wall materials were used to obtain a range of elastic moduli. Water was used to simulate the fuel and an electromagnetic shaker provided external excitation such as might originate from a rocket-propulsion system. Experimental data were compared to values obtained from mathematical models for the many degree-of-freedom lumped-mass representation.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 26
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    Nonproportional loading limit for structures (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: The design of most structures involves ensuring integrity for several independent loading conditions. Often, it is rational to design these, exploiting the ductility of the materials to reduce structural costs. Then, ensuring integrity evokes the need for nonmonotonic limit analyses. A groundwork is laid for implementing these analyses. An alternate limit load characterization to that of Greenberg is provided, a mathematical statement of the problem leading to both monotonic (proportional) and nonmonotonic limit loads values is formulated, a direct limit load analysis procedure for analysis within a finite-element framework is described, and limit loads for sets of simple structures are evaluated. A direct limit analysis process is described, and monotonic limit loads are characterized. The process furnishes 'exact' values of limit loads with increasing efficiency as the number of structural elements and force redundancy decreases. Tests show that the accuracy of predicting nonmonotonic limit loads is very sensitive to the number of degrees of freedom in the analysis compared with the total number in the model.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures; 4; Mar. 197
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  • 27
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    Shock shapes of blunt bodies in hypersonic helium, air, and CO2 flows (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A primary factor governing hypersonic flowfield characteristics of blunt vehicles entering planetary atmospheres is the normal shock density ratio. Hence, a means of duplicating or simulating the high density ratios experienced during planetary entry is needed. One facility having the capability of generating a range of hypersonic-hypervelocity flow conditions in arbitrary test gases is the expansion tube. Preliminary shock shape results obtained in the Langley 6-in. expansion tube at hypersonic conditions are presented. Normal shock density ratios from approximately 4 to 19 were generated using helium, air, and CO2 test gases at freestream velocities from 5 to 7 km/sec. Test models were a flat-faced cylinder and the Viking aeroshell.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal; 12; Mar. 197
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  • 28
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    Adhesive fracture mechanics (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: In studies of fracture mechanics the adhesive fracture energy is regarded as a fundamental property of the adhesive system. It is pointed out that the value of the adhesive fracture energy depends on surface preparation, curing conditions, and absorbed monolayers. A test method reported makes use of a disk whose peripheral part is bonded to a substrate material. Pressure is injected into the unbonded central part of the disk. At a certain critical pressure value adhesive failure can be observed. A numerical stress analysis involving arbitrary geometries is conducted.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Fracture; 10; Mar. 197
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  • 29
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    Computation of transonic flow about lifting wing-cylinder combinations (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Some results are described for a lifting rectangular wing centrally located on a circular-cylindrical body. This simple configuration has been utilized in order to assess the merits of a mapping technique for wing-body configurations. The procedure employed makes use of a coordinate transformation to simplify specification of the surface boundary condition in the computation of the flow about the wing. The method can be extended to incorporate wing sweep, finite length body of noncircular cross section, and arbitrary wing placement; however, these extensions involve a considerable increase in complexity of the problem.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft; 11; Apr. 197
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  • 30
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    A vortex entrainment model applied to slender delta wings (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: A mathematical model of the vortex flow over a slender sharp-edged delta wing is proposed, and is shown to provide good agreement with the experiment. Although the technique requires experimental data in the form of the vortex core locations, it does account for the previously ignored mass entrainment of the vortex core.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal; 12; Jan. 197
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  • 31
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    Extraction of derivatives from flight data for several aircraft, using the LRC interactive computer system (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Results are presented of a procedure for estimating stability and control parameters from flight data, by using maximum likelihood methods employing an interactive computer system, which was established at the NASA Langley Research Center. Problems encountered are discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 49-76
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  • 32
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    Identification of aircraft stability and control derivatives in the presence of turbulence (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A maximum likelihood estimator for a linear system with state and observation noise is developed to determine stability and control derivatives from flight data obtained in the presence of turbulence. The formulation for the longitudinal short-period mode is presented briefly, including a special case that greatly simplifies the problem if the measurement noise on one signal is negligible. The effectiveness and accuracy of the technique are assessed by applying it first to simulated flight data, in which the true parameter values and state noise are known, then to actual flight data obtained in turbulence. The results are compared with data obtained in smooth air and with wind-tunnel data. The complete maximum likelihood estimator, which accounts for both state and observation noise, is shown to give the most accurate estimate of the stability and control derivatives from flight data obtained in turbulence. It is superior to the techniques that ignores state noise and to the simplified method that neglects the measurement noise on the angle-of-attack signal.
    Schlagwort(e): AERODYNAMICS
    Materialart: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 77-114
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  • 33
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    A comparison of two methods of extracting stability derivatives from flight test data (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Two methods for extracting stability derivatives from flight data are compared. A modified Newton-Raphson quasilinearization minimization technique and a digital-analog (hybrid) matching technique were used to analyze the same data maneuvers obtained from two aircraft. About 70 maneuvers from an F-111E aircraft were analyzed over a Mach number range of 0.3 to 2.0 and an angle of attack range of 3 to 19 degrees. About 20 maneuvers were analyzed for the X-24A lifting body at Mach numbers of 0.5, 0.8, and 0.9, and an angle of attack range of 4 to 13 degrees. Stability derivatives were extracted from these maneuvers and the results from the two techniques, along with wind tunnel results, were compared.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Flight Res. Center Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 43-48
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  • 34
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    New triangular plate-bending finite element with transverse shear flexibility (1974)
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    Publikationsdatum: 2011-08-16
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal; 12; Dec. 197
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  • 35
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    Correlation for estimating vortex rotational velocity downstream dependence (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Description of a correlation, derived from water tank measurements in the wake of wings towed under water, that makes it possible to predict the downstream distance behind an aircraft in flight where its trailing vortex will begin to decay. Comparisons of measured and predicted data are discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft; 11; Nov. 197
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  • 36
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    Roll-up of aircraft trailing vortices using artificial viscosity (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The artificial viscosity method of Kuwahara and Takami (1973) is used to calculate the roll-up of trailing vortices behind a number of practical aerodynamic configurations. Where possible, the results are compared for core location with available experimental data.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft; 11; Nov. 197
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  • 37
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    Influence of ablation impurities on blunt body re-entry ionization (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Electron density profiles which include the effect of an ablated sodium impurity were computed for the boundary layer on a blunt-nosed body re-entering the atmosphere at 7.62 km/sec. Profiles are computed from the nose to a distance of four diameters along the RAM C-payload. A finite-difference, laminar, nonequilibrium chemistry boundary-layer program was used. Comparison of theory with S-band diagnostic antenna results, electron concentration deduced from X- and C-band attenuation data, and Langmuir probe data at several different aft body locations show that agreement is good at high altitude. At the lower altitudes there is disagreement between theory and S-band antenna data where the apparent discrepancy is attributed to the three-body recombination rate constant used for deionization of sodium coupled with the effect of angle of attack.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal; 12; June 197
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  • 38
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    Interactive design of large end rings on stiffened conical shells using composites (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Design study methods and results for a composite reinforced base ring for the conical aeroshell structure of the planetary lander vehicle for Project Viking, an unmanned mission to Mars, are presented. The aeroshell is a ring and stringer-stiffened conical shell structure having a half angle of 70 degrees with a large base ring mounted at the outer edge of the cone and a large pay-load ring in the interior with many smaller rings spaced along the inside shell surface. The purpose of the structure is to develop the aerodynamic drag required to decelerate the lander in the Mars atmosphere to facilitiate a soft landing. The design of a shell structure of this complexity requires the use of the latest technology available in a large general-purpose shell buckling program. The large general-purpose non-linear shell buckling program (BOSOR 2) which was used for this purpose is described.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 39
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    Some after-dinner reflections on system identification (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The growth of the field of system identification is discussed along with changes in methodology which have taken place in recent years. The similarity between pattern recognition and system identification is pointed out, involving the modelling in the latter and the feature selection problem in the former. It is stated that once a model is formulated, including the disturbances and measurement errors, the parameter finding can be formulated as a statistical estimation problem. The various techniques and their application are discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Flight Res. Center Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 381-385
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  • 40
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    Systems identification - reprise and projections (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: A state-of-the-arts review is given for the field of system identification. Progress in the field is traced from the early models of dynamic systems by Sir Isaac Newton up to the present day use of advanced techniques for numerous applications.
    Schlagwort(e): AERODYNAMICS
    Materialart: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 375-379
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  • 41
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    A new criterion for modeling systems (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The criterion that is proposed is an expected value of the mean square response error as an alternative to testing a model against new data. Modeling with respect to this new criterion does not change the estimate for a given model format from a maximum likelihood estimate or mean square response error estimate. The new criterion does, however, provide a means of comparing models with different formats and varying complexity. A numerical example is used to illustrate the application of the proposed criteria and the problem of searching for the best model. For all but the most trivial system identification problems, it is shown that a prohibitive number of combinations of terms of the model must be investigated to ensure the final model is best.
    Schlagwort(e): AERODYNAMICS
    Materialart: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 291-313
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  • 42
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    Effects of flight instrumentation errors on the estimation of aircraft stability and control derivatives (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: An error analysis program based on an output error estimation method was used to evaluate the effects of sensor and instrumentation errors on the estimation of aircraft stability and control derivatives. A Monte Carlo analysis was performed using simulated flight data for a high performance military aircraft, a large commercial transport, and a small general aviation aircraft for typical cruise flight conditions. The effects of varying the input sequence and combinations of the sensor and instrumentation errors were investigated. The results indicate that both the parameter accuracy and the corresponding measurement trajectory fit error can be significantly affected. Of the error sources considered, instrumentation lags and control measurement errors were found to be most significant.
    Schlagwort(e): AERODYNAMICS
    Materialart: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 261-280
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  • 43
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    Nonlinear parameter identification: Ballistic range experience applicable to flight testing (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The parameter identification scheme being used is a differential correction least squares procedure (Gauss-Newton method). The position, orientation, and derivatives of these quantities with respect to the parameters of interest (i.e., sensitivity coefficients) are determined by digital integration of the equations of motion and the parametric differential equations. The application of this technique to three vastly different sets of data is used to illustrate the versatility of the method and to indicate some of the problems that still remain.
    Schlagwort(e): AERODYNAMICS
    Materialart: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 191-195
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  • 44
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    Boundary value problems with incremental plasticity in granular media (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Discussion of the critical state concept in terms of an incremental theory of plasticity in granular (soil) media, and formulation of the governing equations which are convenient for a computational scheme using the finite element method. It is shown that the critical state concept with its representation by the classical incremental theory of plasticity can provide a powerful means for solving a wide variety of boundary value problems in soil media.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 45
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    A solution to the contact of two rough spherical surfaces (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The influence of roughness on the interfacial pressure distribution in the contact of two spherical surfaces is considered. An approximate general solution is presented and it is shown that the pressure for all radii can be determined solely from a reference pressure which is, in turn, a function of two parameters - a dimensionless roughness and a dimensionless hardness. Values for the radius of contact are also presented.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 46
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    Aerodynamics of jet flap and rotating cylinder flap STOL concepts (1974)
    In:  CASI
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    Publikationsdatum: 2012-05-22
    Beschreibung: The aerodynamic effectiveness of various propulsive lift concepts to provide for the low speed performance and control required for short takeoff and landing aircraft is discussed. The importance of the interrelationship between the propulsion system and aerodynamic components of the aircraft is stressed. The relative effectiveness of different lift concepts was evaluated through static and wind tunnel tests of various aerodynamic models and propulsion components, simulations of aircraft, and in some cases, flight testing of research aircraft incorporating the concepts under study. Results of large scale tests of lift augmentation devices are presented. The results of flight tests of STOL research aircraft with augmented jet flaps and rotating cylinder flaps are presented to show the steeper approach flight paths at low forward speeds.
    Schlagwort(e): AERODYNAMICS
    Materialart: AGARD V/STOL Aerodyn.; 6 p
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  • 47
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    Mixed mode stress field effect in adhesive fracture (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Numerical or analytical analyses were performed on seven different test specimens including blister test, 90-degree peel test, torsion test, and various cone tests. These specimens are in general subjected to complex stress fields having various amounts of Mode I, Mode II, and Mode III loads. The specimens were then constructed using polymethyl methacrylate for the adherends and a transparent polyurethane elastomer (Solithane 113) for the adhesive. This combination permitted direct observation of the bondline as load was applied. Although initial debonds as well as bond end termination singularities were present in all specimens, in some cases the debond did not initiate at the singularity points as would normally have been expected. An explanation for this behavior is presented, as well as a comparison of loading mode effect on those specimens for which the debond did propagate from a bond terminus singular point.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Fracture; 10; Dec. 197
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  • 48
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    Dependence of plate-bending finite element deflections and eigenvalues on Poisson's ratio (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal; 12; Oct. 197
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  • 49
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    A generalized-capacity-matrix technique for computing aerodynamic flows (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: A numerical generalized-capacity-matrix technique is developed for application to aerodynamic flow computations. This technique allows the very fast direct (noniterative) numerical elliptic solvers to be used in problems with arbitrary internal boundaries and with a wide class of boundary conditions, including numerical application of the Kutta condition on an airfoil without iteration. Accuracy, speed, and usefulness of the technique are demonstrated with linear problems for potential flows over airfoil shapes. The method's main advantages, however, can be exploited within iterative procedures for a variety of complex flow problems governed by systems of equations not necessarily elliptic or linear.
    Schlagwort(e): AERODYNAMICS
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  • 50
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    Fast direct numerical solution of the nonhomogeneous Cauchy-Riemann equations (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: A fast direct (noniterative) 'Cauchy-Riemann Solver' is developed for solving the finite-difference equations representing systems of first-order elliptic partial differential equations in the form of the nonhomogeneous Cauchy-Riemann equations. The method is second-order accurate and requires approximately the same computer time as a fast cyclic-reduction Poisson solver. The accuracy and efficiency of the direct solver are demonstrated in an application to solving an example problem in aerodynamics: subsonic inviscid flow over a biconvex airfoil. The analytical small-perturbation solution contains singularities, which are captured well by the computational technique. The algorithm is expected to be useful in nonlinear subsonic and transonic aerodynamics.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Computational Physics; 15; May 1974
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  • 51
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    Estimation of longitudinal aerodynamic coefficients and comparison with wind-tunnel values (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Some recent experience at Ames Research Center in the estimation of aerodynamic coefficients for the Lear-Jet and the Augmentor Wing Jet STOL Research Aircraft is reviewed. The coefficients estimated from flight data are compared with values based on large-scale wind-tunnel tests. The results obtained by the regression and quasilinearization identification techniques are also compared. The regression method generally provides the lower standard deviation in the coefficient estimates and provides the better fit to the wind-tunnel values. The addition of nonlinear terms in the aerodynamic equations decreases the difference between the estimated and measured time histories but also increases the standard deviation in the estimated coefficient values.
    Schlagwort(e): AERODYNAMICS
    Materialart: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 125-148
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  • 52
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    Fracture initiation and propagation in a cylindrical shell containing an initial surface flaw (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: An attempt is made to provide the necessary analytical tools for the application of two different types of fracture criteria to shell structures. Of particular interest is the problem of fracture propagation and arrest in a cylindrical pressure vessel containing an initial surface flaw. It is assumed that the flaw has the most unfavorable geometry and orientation, namely, it is a crack lying on a meridional plane. Stress intensity factor for a part-through crack, and a surface or internal crack with a fully yielded net ligament are considered. Attention is given to constant delta curves for depressurization studies and to depressurization and crack arrest in pressure vessels.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 53
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    Vortex-induced heating to cone flaps at Mach 6 (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Discussion of the local heating effect on the lee-side control flaps of supersonic configurations due to the interaction between vortices and leeward control surfaces at an angle of attack. Considerations are given for an appropriate positioning of control flaps to alleviate such interactions and the resulting thermal effect. Tests are carried out on a sharp right circular cone with two types of flap configurations in a study of oil flow patterns about the cone at selected angles of attack. Splitting of flaps and moving them to positions away from the symmetry plane did reduce the heating but also reduced the average flap pressure and increased flow complexity.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets; 11; Mar. 197
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  • 54
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    An improved static probe design (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: A new static probe design is described in which the static holes are located much closer to the tip than in conventional probes. The new probe shows promise for use in some situations where conventional probes become highly inaccurate. An additional advantage of the new design is that, when used in static pressure survey rakes, the probes can be located much closer together than in conventional designs and still ensure that disturbances from neighboring probe tips do not affect the static readings.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal; 12; Apr. 197
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  • 55
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    Vortex-induced heating to a cone-cylinder body at Mach 6 (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Presented data on vortex-induced heating in a cone-cylinder body at Mach 6 show that the most severe heating need not occur as a result of the interaction of the primary vortices with the lee surface, even though this interaction produces a large, well-defined featherline oil smear. It is pointed out that the severity of vortex-induced heating is extremely sensitive to Reynolds number and geometry and that there exists a 'threshold Reynolds number' below which vortex-induced heating decreases abruptly.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets; 11; Feb. 197
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  • 56
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    Simulation of real-gas effects for Mars entry (1974)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The changes in aerodynamic characteristics due to real-gas effects associated with high speed flight (characterized by large shock density ratios) are primarily the result of changes in surface pressures acting on the forebody. The surface pressures are affected by a change in shock density ratio (real-gas effects) in two ways. First, the level of pressure at the stagnation point relative to freestream dynamic pressure is changed, and second, the distribution of surface pressure relative to stagnation-point pressure is changed. The density-ratio effect on the stagnation point pressure level can be estimated by considering the flow of a perfect gas about a blunt body.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets; 11; Jan. 197
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    V/STOL aerodynamics: A review of the technology (1974)
    In:  CASI
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    Publikationsdatum: 2012-05-22
    Beschreibung: An analysis of the development and technological applications of V/STOL aircraft is presented. The use of V/STOL aircraft to overcome the limitations of conventional aircraft is discussed. The aspects of V/STOL aircraft which are considered are: (1) economic penalties of propulsive lift, (2) advantages of propulsive lift, (3) potential improvements in V/STOL aircraft, (4) the aerodynamics of V/STOL aircraft, and (5) proposals for additional research in V/STOL development.
    Schlagwort(e): AERODYNAMICS
    Materialart: AGARD V/STOL Aerodyn.; 13 p
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  • 58
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    An overview of high temperature metal fatigue: Aspects covered by the 1973 International Conference on Creep and Fatigue (1974)
    In:  CASI
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    Publikationsdatum: 2012-05-22
    Beschreibung: A summary of papers is presented which covers the following broad aspects of high temperature metal fatigue: (1) materials development and characterization; (2) environmental factors, including air, vacuum, helium, iodine, sodium, and radiation environments; (3) general fatigue life relationships; (4) crack growth laws; (5) design code activities; and (6) design and service experience. Illustrative tables accompany the summary.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AGARD Low Cycle High Temp. Fatigue; 47 p
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    A general purpose stabilised balloon platform (1974)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: The development of a three axis stabilized balloon platform capable of being operated in three modes of increasing accuracy is discussed. The system relies on angular motion sensing for primary feedback with linear accelerometers, magnetometers, and a star sensor for positional information. When under primary control the system will acquire and stabilize on any accessible part of the celestial sphere. A video verification system is included to provide pointing confirmation. Under improved accuracy control, the star sensor is used to lock onto a target star.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 284-293
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  • 60
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    Air Force Cambridge Research Laboratories balloon operations (1974)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: The establishment and functions of the AFCRL balloon operations facility are discussed. The types of research work conducted by the facility are defined. The facilities which support the balloon programs are described. The free balloon and tethered balloon capabilities are analyzed.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 160-164
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  • 61
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    Balloon platform for extended-life astronomy research (1974)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: A configuration has been developed for a long-life balloon platform to carry pointing telescopes weighing as much as 80 pounds (36 kg) to point at selected celestial targets. A platform of this configuration weighs about 375 pounds (170 kg) gross and can be suspended from a high altitude super pressure balloon for a lifetime of several months. The balloon platform contains a solar array and storage batteries for electrical power, up and down link communications equipment, and navigational and attitude control systems for orienting the scientific instrument. A biaxial controller maintains the telescope attitude in response to look-angle data stored in an on-board computer memory which is updated periodically by ground command. Gimbal angles are computed by using location data derived by an on-board navigational receiver.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 136-144
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  • 62
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    An orientable, stabilized balloon-borne gondola for around-the-world flights (1974)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: A system capable of pointing a balloon-borne telescope at selected celestial objects to an accuracy of approximately 10 arc minutes for an extended period (weeks to months) without reliance on telemetry is described. A unique combination of a sun/star tracker, an on-board computer, and a gyrocompass is utilized for navigation, source acquisition and tracking, and data compression and recording. The possibilities for intelligent activities by the computer are also discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 71-80
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  • 63
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    Identification of structural parameters from helicopter dynamic test data (1974)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: A method is presented for obtaining the mass, stiffness, and damping parameters of a linear mathematical model, having fewer degrees of freedom than the structure it represents, directly from dynamic response measurements on the actual helicopter without a priori knowledge of the physical characteristics of the fuselage. The only input information required in the formulation is the approximate natural frequency of each mode and mobility data measured proximate to these frequencies with sinusoidal force excitation applied at only one point on the vehicle. The practicality and numerical soundness of the theoretical development was demonstrated through a computer simulation of an experimental program.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Ames Res. Center Rotorcraft Dyn.; p 239-248
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  • 64
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    Experimental and analytical studies in tilt-rotor aeroelasticity (1974)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: An overview of an experimental and analytical research program underway for studying the aeroelastic and dynamic characteristics of tilt-rotor VTOL aircraft is presented. Selected results from several investigations of scaled models in the transonic dynamics tunnel, as well as some results from a test of a flight-worthy proprotor in the full-scale wind tunnel are shown and discussed with a view toward delineating various aspects of dynamic behavior peculiar to proprotor aircraft. Included are such items as proprotor/pylon stability, whirl flutter, gust response, and blade flapping. Theoretical predictions are shown to be in agreement with the measured stability and response behavior.
    Schlagwort(e): AERODYNAMICS
    Materialart: Its Rotorcraft Dyn.; p 171-184
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  • 65
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    Theory and comparison with tests of two full-scale proprotors (1974)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: A nine degrees-of-freedom theoretical model was developed for investigations of the dynamics of a proprotor operating in high inflow axial flight on a cantilever wing. The theory is described, and the results of the analysis are presented for two proprotor configurations: a gimballed, stiff-inplane rotor, and a hingeless, soft-inplane rotor. The influence of various elements of the theory are discussed, including the modeling used for the blade and wing aerodynamics, and the influence of the rotor lag degree of freedom. The results from full-scale tests of the two proprotors are presented and compared with the theoretical results.
    Schlagwort(e): AERODYNAMICS
    Materialart: Its Rotorcraft Dyn.; p 159-169
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  • 66
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    Application of antiresonance theory to helicopters (1974)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: Antiresonance theory is the principle underlying nonresonant nodes in a structure, and covers both nonresonant nodes occurring naturally and those introduced by devices such as dynamic absorbers and antiresonant isolators. The dynamic antiresonant vibration isolator (DAVI) and the nodale module are examples of the applications of transfer antiresonances. It is shown that antiresonances are eigenvalues, and that they can be determined by matrix iteration. Applications of antiresonance theory to helicopter engineering problems, using the antiresonant eigenvalue equation are suggested.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Ames Res. Center Rotorcraft Dyn.; p 101-106
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  • 67
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    Correlation of finite-element structural dynamic analysis with measured free vibration characteristics for a full-scale helicopter fuselage (1974)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The correlation achieved with each program provides the material for a discussion of modeling techniques developed for general application to finite-element dynamic analyses of helicopter airframes. Included are the selection of static and dynamic degrees of freedom, cockpit structural modeling, and the extent of flexible-frame modeling in the transmission support region and in the vicinity of large cut-outs. The sensitivity of predicted results to these modeling assumptions are discussed. Both the Sikorsky Finite-Element Airframe Vibration analysis Program (FRAN/Vibration Analysis) and the NASA Structural Analysis Program (NASTRAN) have been correlated with data taken in full-scale vibration tests of a modified CH-53A helicopter.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Ames Res. Center Rotorcraft Dyn.; p 67-80
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  • 68
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    Comparison of the experimental aerodynamic characteristics of theoretically and experimentally designed supercritical airfoils (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A lifting airfoil theoretically designed for shockless supercritical flow utilizing a complex hodograph method has been evaluated in the Langley 8-foot transonic pressure tunnel at design and off-design conditions. The experimental results are presented and compared with those of an experimentally designed supercritical airfoil which were obtained in the same tunnel.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-3082 , L-9548 , NAS 1.15:X-3082
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  • 69
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    A study of the nonlinear aerodynamics of bodies in nonplanar motion (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Concepts from the theory of functionals are used to develop nonlinear formulations of the aerodynamic force and moment systems acting on bodies in large-amplitude, arbitrary motions. The analysis, which proceeds formally once the functional dependence of the aerodynamic reactions upon the motion variables is established, ensures the inclusion, within the resulting formulation, of pertinent aerodynamic terms that normally are excluded in the classical treatment. Applied to the large-amplitude, slowly varying, nonplanar motion of a body, the formulation suggests that the aerodynamic moment can be compounded of the moments acting on the body in four basic motions: steady angle of attack, pitch oscillations, either roll or yaw oscillations, and coning motion. Coning, where the nose of the body describes a circle around the velocity vector, characterizes the nonplanar nature of the general motion.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TR-R-421 , A-5057
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  • 70
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    Transonic single-mode flutter and buffet of a low aspect ratio wing having a subsonic airfoil shape (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Transonic flutter and buffet results obtained from wind-tunnel tests of a low aspect ratio semispan wing model are presented. The tests were conducted to investigate potential transonic aeroelastic problems of vehicles having subsonic airfoil sections. The model employed NACA 00XX-64 airfoil sections in the streamwise direction and had a 14 deg leading edge sweep angle. Aspect ratio, and average thickness were 4.0, 0.35, and 8 percent, respectively. The model was tested at Mach numbers from 0.6 to 0.95 at angles of attack from 0 deg to 15 deg. Two zero lift flutter conditions were found that involved essentially single normal mode vibrations. With boundary layer trips on the model, flutter occurred in a narrow Mach number range centered at about Mach 0.90. The frequency and motion of this flutter were like that of the first normal mode vibration. With the trips removed flutter occurred at a slightly high Mach number but in a mode strongly resembling that of the second normal mode.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TN-D-7346 , A-4966
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  • 71
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    Simple methods for determining the virtual origin of turbulent boundary layers in hypersonic flow on sharp-edged flat plates (1974)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Two methods for determining the virtual origin of turbulent boundary layers in hypersonic flow are evaluated. The results of the analyses are restricted to wind-tunnel models having sharp-edged surfaces with zero or small pressure gradients. Virtual origin and skin friction estimates from these two methods are compared with values from a base method for which the virtual origin is calculated from the measured momentum thickness at a station downstream of boundary layer transition.
    Schlagwort(e): AERODYNAMICS
    Materialart: ASME PAPER 74-APM-V
    Format: text
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  • 72
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    Transverse vibrations of non-uniform beams (1974)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The free vibrations of elastic beams with nonuniform characteristics are investigated theoretically by a new method. The new method is seen to combine the advantages of a finite element approach and of a Rayleigh-Ritz analysis. Comparison with the known analytical results for uniform beams shows good convergence of the method for natural frequencies and modes. For internal shear forces and bending moments, the rate of convergence is less rapid. Results from experiments conducted with a cantilevered helicopter blade with strong nonuniformities and also from alternative theoretical methods, indicate that the theory adequately predicts natural frequencies and mode shapes. General guidelines for efficient use of the method are presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Sound and Vibration; 37; Dec. 22
    Format: text
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  • 73
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    Forward slanted slot throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60 percent internal contraction (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The results of an experimental investigation to increase the stable airflow operating range of a supersonic mixed-compression inlet are presented. Two forward-slanted slot stability-bypass entrance configurations were tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of 18.5 percent was obtained with the superior configuration if a constant pressure was maintained in the bypass plenum. Limited unstart angle-of-attack data are presented.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-2973 , E-7706
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  • 74
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    Effect of screen-induced total-pressure distortion on axial-flow compressor stability (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: An experimental investigation was made to determine the effects of screen-induced total-pressure distortions on two J85-GE-13 turbojet engines. Results were compared to those from a previous program run with a third engine. All compressors were found to be sensitive to a critical angle of circumferential distortion equal to 60 deg., and they all adhered closely to the parallel compressor model. The sensitivity of compressor exit pressure to virtually any type of distortion pattern can be determined by defining stall lines for undistorted, hub radial distorted, and tip radial distorted inflows. The effect of multiple sectors of circumferential distortion is defined.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-3017 , E-7792
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  • 75
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    Non-linear behavior of fiber composite laminates (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The non-linear behavior of fiber composite laminates which results from lamina non-linear characteristics was examined. The analysis uses a Ramberg-Osgood representation of the lamina transverse and shear stress strain curves in conjunction with deformation theory to describe the resultant laminate non-linear behavior. A laminate having an arbitrary number of oriented layers and subjected to a general state of membrane stress was treated. Parametric results and comparison with experimental data and prior theoretical results are presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-2313 , TFR/7309
    Format: application/pdf
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  • 76
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    Failure criteria for viscoelastic materials (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Research projects concerned with developing a theory of fracture of materials are discussed. The effects of the geometry of the structure and the loads acting on the structure as they influence the failure process are analyzed. The effects of the viscoelastic deformation characteristics of the bulk elastomer on failure behavior are examined. Additional material parameters which control the fracture process are identified.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-138125 , GALCIT-120
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  • 77
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    Advance development of a technique for characterizing the thermomechanical properties of thermally stable polymers (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The torsional braid experiment has been interfaced with a centralized hierarchical computing system for data acquisition and data processing. Such a system, when matched by the appropriate upgrading of the monitoring techniques, provides high resolution thermomechanical spectra of rigidity and damping, and their derivatives with respect to temperature.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-138123
    Format: application/pdf
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  • 78
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    Combined Quadrupole-dipole Model for Inlet Flow Distortion Noise from a Subsonic Fan (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A combined quadrupole-dipole model has been developed for the noise generated by inlet flow distortion in a subsonic fan. A formula is derived for the total upstream-radiated acoustic power in each tone as a function of the design parameters of the fan and the properties of the inlet flow distortion. Numerical results are obtained for values of the parameters corresponding to various quiet fans. The analysis is compared with noise measurements taken on a 51-cm (20-in.) diameter research fan as well as with those taken on a number of full-scale fan stages. Fairly good agreement was obtained. It should therefore be possible to use this model to study the noise-reduction potential of the various fan design parameters.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TN-D-7676 , E-7881
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  • 79
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    Low speed aerodynamic characteristics of NACA 6716 and NACA 4416 airfoils with 35 percent-chord single-slotted flaps (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: An investigation was conducted in a low-turbulence pressure tunnel to determine the two-dimensional lift and pitching-moment characteristics of an NACA 6716 and an NACA 4416 airfoil with 35-percent-chord single-slotted flaps. Both models were tested with flaps deflected from 0 deg to 45 deg, at angles of attack from minus 6 deg to several degrees past stall, at Reynolds numbers from 3.0 million to 13.8 million, and primarily at a Mach number of 0.23. Tests were also made to determine the effect of several slot entry shapes on performance.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-2623 , L-8410
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  • 80
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    Flight Reynolds number effects on a contoured boattail nozzle at subsonic speeds (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A contoured boattail nozzle typical of those used on a twin-engine fighter was tested on an underwing nacelle mounted on an F-106B aircraft. The gas generator was a J85-GE-13 turbojet engine. The effects of Reynolds number, Mach number, and angle of attack on boattail drag and boattail pressure profiles were investigated. Increasing Reynolds number caused a slight reduction in boattail drag at both Mach 0.7 and 0.9. The nozzle had relatively low boattail drag even though the flow was separated over a large portion of the boattail.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-3053 , E-7818
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  • 81
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    An Analytical Investigation of Wing-Jet Interaction (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The aerodynamic interaction between the wing and an inviscid jet with Mach number nonuniformity is formulated by using a two-vortex-sheet model for the jet. One of the vortex sheets accounts for the induced jet flow and the other the induced outer flow. No additional source distribution is needed for the jet at an angle of attack. The above problem is solved by satisfying the jet and wing tangency and the jet pressure-continuity conditions and using a quasi vortex lattice method for computing the induced flow field. The latter method is derived through theoretical consideration by properly accounting for singularities present in the equations and possesses the same simplicity and generality as the conventional vortex lattice method but has a better rate of numerical convergence. The resulting system of algebraic equations is solved by Purcell's vector method. The numerical formulation is first applied to the wing-slipstream interaction problem. Results for one centered-jet configuration are compared with those predicted by some existing theories.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-CR-138140 , CRINC-FRL-74-001
    Format: application/pdf
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  • 82
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    Analysis of laminated, composite, circular cylindrical shells with general boundary conditions (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: This report develops: (1) a refined approximate theory for the static and dynamic analyses of finite, laminated, composite, circular cylindrical shells with general boundary conditions; (2) an exact three-dimensional analysis of simply supported, laminated, composite, circular cylindrical shells, and (3) a thin-shell theory for laminated, composite, circular cylindrical shells. In the refined approximate theory the displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and transverse normal stress are included. A variational approach is followed to obtain the governing differential equations and boundary conditions. A general solution of the governing differential equations is also presented. The results obtained by using the refined approximate theory and the thin-shell theory are compared with the exact results for the case of free vibrations of simply supported, laminated, composite, circular cylindrical shells. The refined approximate theory is very accurate, even for thick shells with short nodal distances, whereas thin-shell theory is reasonably accurate only for thin shells at moderate nodal distances and wave number less than 2.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TR-R-412 , L-8828
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  • 83
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    Flutter suppression and gust alleviation using active controls (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The effects of active controls on the suppression of flutter and gust alleviation of two different types of subsonic aircraft (the Arava, twin turboprop STOL transport, and the Westwind twin-jet business transport) are investigated. The active controls are introduced in pairs which include, in any chosen wing strip, a leading-edge (LE) control and a trailing-edge (TE) control. Each control surface is allowed to be driven by a combined linear-rotational sensor system, located on the activated strip. The control law, which translates the sensor signals into control surface rotations, is based on the concept of aerodynamic energy. The results indicate the extreme effectiveness of the active systems in controlling flutter. A single system spanning 10% of the wing semispan made the Arava flutter-free, and a similar active system, for the Westwind aircraft, yielded a reduction of 75% in the maximum bending moment of the wing and a reduction of 90% in the acceleration of the cg of the aircraft. Results for simultaneous activation of several LE - TE systems are presented. Further work needed to bring the investigation to completion is also discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-CR-138658 , TAE-198
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  • 84
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    The passage of an infinite swept airfoil through an oblique gust (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: An approximate solution is reported for the unsteady aerodynamic response of an infinite swept wing encountering a vertical oblique gust in a compressible stream. The approximate expressions are of closed form and do not require excessive computer storage or computation time, and further, they are in good agreement with the results of exact theory. This analysis is used to predict the unsteady aerodynamic response of a helicopter rotor blade encountering the trailing vortex from a previous blade. Significant effects of three dimensionality and compressibility are evident in the results obtained. In addition, an approximate solution for the unsteady aerodynamic forces associated with the pitching or plunging motion of a two dimensional airfoil in a subsonic stream is presented. The mathematical form of this solution approaches the incompressible solution as the Mach number vanishes, the linear transonic solution as the Mach number approaches one, and the solution predicted by piston theory as the reduced frequency becomes large.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-CR-2395
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  • 85
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    Holographic nondestructive tests performed on composite samples of ceramic-epoxy-fiberglass sandwich structure (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: When a hologram storing more than one wave is illuminated with coherent light, the reconstructed wave fronts interfere with each other or with any other phase-related wave front derived from the illuminating source. This multiple wave front comparison is called holographic interferometry, and its application is called holographic nondestructive testing (HNDT). The theoretical aspects of HNDT techniques and the sensitivity of the holographic system to the geometrical placement of the optical components are briefly discussed. A unique HNDT system which is mobile and possesses variable sensitivity to stress amplitude is discribed, the experimental evidence of the application of this system to the testing of the hidden debonds in a ceramic-epoxy-fiberglass structure used for sample testing of the radome of the Pershing missile system is presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TR-R-430 , M-461
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  • 86
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    Procedures for experimental measurement and theoretical analysis of large plastic deformations (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Theoretical equations are derived and analytical procedures are presented for the interpretation of experimental measurements of large plastic strains in the surface of a plate. Orthogonal gage lengths established on the metal surface are measured before and after deformation. The change in orthogonality after deformation is also measured. Equations yield the principal strains, deviatoric stresses in the absence of surface friction forces, true stresses if the stress normal to the surface is known, and the orientation angle between the deformed gage line and the principal stress-strain axes. Errors in the measurement of nominal strains greater than 3 percent are within engineering accuracy. Applications suggested for this strain measurement system include the large-strain-stress analysis of impact test models, burst tests of spherical or cylindrical pressure vessels, and to augment small-strain instrumentation tests where large strains are anticipated.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TM-X-3027 , E-7661
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  • 87
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    Wind tunnel blockage and support interference effects on winged-body models at Mach numbers from 0.6 to 1.0 (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Three sting-mounted winged-body models with tunnel blockages of 0.1, 1.0, and 2.0 percent were tested in the Lewis Research Center's 8- by 6- Foot Supersonic Wind Tunnel. Fuselage pressures were obtained over a Mach number range of 0.6 to 1.0 at angles of attack from 0 deg to 4 deg. Two other types of model support were investigated, which included simulated wing-tip and fuselage support-strut mountings. The effects of tunnel porosity and sidewall geometry were also investigated. Model blockage effects were small up to M sub 0 = 0.95. At higher speeds the major blockage effect observed was a displacement of the local transonic terminal shocks on the model. The effects of the wing-tip type of model support were small up to M sub 0 = 0.95, but disturbances were observed on the fuselage at higher speeds. Changes in local tunnel porosity were effective in reducing the disturbances up to M sub 0 = 0.975, but a change in sidewall geometry was not.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-3011 , E-7596
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  • 88
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    An experimental study of the validity of the heat-field concept for sonic-boom alleviation (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: An experimental program was carried out in the NASA-Langley 4 ft x 4 ft supersonic pressure tunnel to investigate the validity of the heat-field concept for sonic boom alleviation. The concept involves heating the flow about a supersonic aircraft in such a manner as to obtain an increase in effective aircraft length and yield an effective aircraft shape that will result in a shock-free pressure signature on the ground. First, a basic body-of-revolution representing an SST configuration with its lift equivalence in volume was tested to provide a baseline pressure signature. Second, a model having a 5/2-power area distribution which, according to theory, should yield a linear pressure rise with no front shock wave was tested. Third, the concept of providing the 5/2-power area distribution by using an off-axis slender fin below the basic body was investigated. Then a substantial portion (approximately 40 percent) of the solid fin was replaced by a heat field generated by passing heated nitrogen through the rear of the fin.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-CR-2381 , ATR-74(7218)-1
    Format: application/pdf
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  • 89
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    Analysis of three-point-bend test for materials with unequal tension and compression properties (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: An analysis capability is described for the three-point-bend test applicable to materials of linear but unequal tensile and compressive stress-strain relations. The capability consists of numerous equations of simple form and their graphical representation. Procedures are described to examine the local stress concentrations and failure modes initiation. Examples are given to illustrate the usefulness and ease of application of the capability. Comparisons are made with materials which have equal tensile and compressive properties. The results indicate possible underestimates for flexural modulus or strength ranging from 25 to 50 percent greater than values predicted when accounting for unequal properties. The capability can also be used to reduce test data from three-point-bending tests, extract material properties useful in design from these test data, select test specimen dimensions, and size structural members.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TN-D-7572 , E-7544
    Format: application/pdf
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  • 90
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    FORTRAN 4 programs for summarization and analysis of fracture trace and lineament patterns (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Systematic and detailed analysis of lineament and fracture trace patterns has long been neglected because of the large number of observations involved in such an analysis. Three FORTRAN 4 programs were written to facilitate this manipulation. TRANSFORM converts the initial fracture map data into a format compatible with AZMAP, whose options allow repetitive manipulation of the data for optimization of the analysis. ROSE creates rose diagrams of the fracture patterns suitable for map overlays and tectonic interpretation. Examples are given and further analysis techniques using output from these programs are discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TM-X-70596 , X-644-74-3
    Format: application/pdf
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  • 91
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    Estimation of deviation angle for axial-flow compressor blade sections using inviscid-flow solutions (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Development of a method of estimating deviation angles by analytical procedures was begun. Solutions for inviscid, irrotational flow in the blade-to-blade plane were obtained with a finite-difference calculation method. Deviation angles for a plane cascade with a rounded trailing edge were estimated by using the inviscid-flow solutions and three trailing-edge hypotheses. The estimated deviation angles were compared with existing experimental data over a range of incidence angles at inlet flow angles of 30 deg and 60 deg. The results indicate that deviation angles can be estimated accurately (within 1 deg) by using one of the three trailing-edge hypotheses, but only when pressure losses are low. A new trailing-edge hypotheses is presented which is suitable (for the cascade considered) for both low- and high-loss operating points.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TN-D-7549 , E-7453
    Format: application/pdf
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  • 92
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    Normal loads program for aerodynamic lifting surface theory (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A description of and users manual are presented for a U.S.A. FORTRAN 4 computer program which evaluates spanwise and chordwise loading distributions, lift coefficient, pitching moment coefficient, and other stability derivatives for thin wings in linearized, steady, subsonic flow. The program is based on a kernel function method lifting surface theory and is applicable to a large class of planforms including asymmetrical ones and ones with mixed straight and curved edges.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-62326
    Format: application/pdf
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  • 93
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    Cold-air study of the effect on turbine stator blade aerodynamic performance of coolant ejection from various trailing-edge slot geometries. 1: Experimental results (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Trailing-edge slot configurations were investigated in a two-dimensional cascade of turbine stator blades. The trailing-edge slots were incorporated into blades with round trailing edges. The five blade configurations investigated included blades with two different trailing-edge thicknesses and four different slot widths. The results of the investigation showed that there was, in general, a significant increase in primary-air efficiency due to the coolant flow, the increase varying with slot configuration. For the five configurations tested, the average percent change in primary-air efficiency per percent coolant flow varied almost linearly from zero to about 1.4 percent over a range of coolant- to primary-air exit-velocity ratios between 0 and 1.2. However, for different configurations there was considerable deviation from the average values in the lower range of exit velocity ratios.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-3000 , E-7743
    Format: application/pdf
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  • 94
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    Sensitivity analysis of torsional vibration characteristics of helicopter rotor blades. Part 2: Aerodynamics and sensitivity analysis (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A theoretical investigation of dynamic response characteristics of rotor blades was carried out with special emphasis on torsional degrees-of-freedom. Coupled equations of motion for flapwise bending and torsion were formulated at varying azimuth positions for rotor blades with noncollinear aerodynamic, elastic and mass axes. Both structural and aerodynamic mass, damping and stiffness coefficients were included. The variations of a sample blade at different flight conditions were investigated from these equations. The obtained numerical results were illustrated. The sensitivity of overall blade vibration characteristics to torsional oscillations was also investigated from the equations of motion for the sample blade. The illustrated results show the importance of torsional degrees-of-freedom in rotor blade analysis. Various possibilities of improving the overall response by tuning blade geometric, structural and aerodynamic characteristics are discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-2380
    Format: application/pdf
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  • 95
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    A rapid numerical solution to subsonic flow over planar and axisymmetric profiles at an angle of attack of 0 deg (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A numerical solution is presented for the incompressible flow over thin planar and axisymmetric profiles at an angle of attack of 0 degrees. The method uses a finite-difference field solution to the governing equation with a Gauss-Seidel successive overrelaxation scheme. However, the use of a simple Cartesian grid system restricts this method to slender profiles. Results are presented for a cambered airfoil, airfoil in wall effect (two-dimensional flowthrough inlet), body of revolution, and flowthrough nacelle. A computer program is presented which can be used for any of the previously mentioned cases with simple input changes. Results for compressible flow are available with the use of the appropriate two-dimensional or axisymmetric compressibility corrections. Computational time for a typical field calculation of 3000 grid points and 200 cycles through the field is less than 1 minute with less than 50,000 octal storage on the Control Data Corporation 6600 computing system.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TN-D-7410 , L-8904
    Format: application/pdf
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  • 96
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    Numerical calculations of velocity and pressure distribution around oscillating airfoils (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: An analytical procedure based on the Navier-Stokes equations was developed for analyzing and representing properties of unsteady viscous flow around oscillating obstacles. A variational formulation of the vorticity transport equation was discretized in finite element form and integrated numerically. At each time step of the numerical integration, the velocity field around the obstacle was determined for the instantaneous vorticity distribution from the finite element solution of Poisson's equation. The time-dependent boundary conditions around the oscillating obstacle were introduced as external constraints, using the Lagrangian Multiplier Technique, at each time step of the numerical integration. The procedure was then applied for determining pressures around obstacles oscillating in unsteady flow. The obtained results for a cylinder and an airfoil were illustrated in the form of streamlines and vorticity and pressure distributions.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-CR-2368
    Format: application/pdf
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  • 97
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    Equation solving program for aerodynamic lifting surface theory (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A description of and user's manual are presented for one of a group of FORTRAN programs which, together, can be used for the analysis and design of wings in steady, subsonic flow according to a kernel function method lifting surface theory. This particular program is the one which solves the sets of simultaneous, linear, algebraic equations arising from the thin wing analysis. This program has the capability of striking out rows and columns of the aerodynamic influence matrix and rows of the associated boundary condition vectors (right hand sides). This capability significantly enhances the effectiveness of the kernel function method of lifting surface theory because studies of the convergence of solutions with the number of control points can be done with the calculation of only a single influence matrix.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TM-X-62325
    Format: application/pdf
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  • 98
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    Research turbine for high temperature core engine application. 1: Cold-airoverall performance of solid scaled turbine (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A solid, half-scale model of a 50.8-cm (20-in) research turbine designed for a high temperature core engine application was investigated over a range of speeds and pressure ratios. The results of this test are presented. The effect of rotor blade twist was also investigated. At the design equivalent speed and specific work output, the total efficiency of the turbine with untwisted rotor blades was 87.1 percent; at the same pressure ratio the efficiency of the turbine with twisted rotor blades was 88.0 percent.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TN-D-7557 , E-7592
    Format: application/pdf
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  • 99
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    Fixed-base simulation study of decoupled controls during approach and landing of a STOL transport airplane (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A fixed-base visual simulation study has been conducted to evaluate the use of decoupled controls as a means for reducing pilot workload during approach and landing of an externally blown jet-flap short take-off and landing (STOL) transport. All six rigid-body degrees of freedom were employed with the aerodynamic characteristics based on wind-tunnel data. The primary piloting task was to use a flight director to capture and maintain a two-segment glide slope, with a closed-circuit television display of a STOL airport used during simulations of the flare and landing. The decoupled longitudinal controls used constant prefilter and feedback gains to provide steady-state decoupling of flight-path angle, pitch angle, and forward velocity. The pilots were enthusiastic about the decoupled longitudinal controls but believed the decoupled concept offered no significant advantage over conventional controls in the lateral mode.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-TN-D-7363 , L-8825
    Format: application/pdf
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  • 100
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    Assembly and analysis of fragmentation data for liquid propellant vessels (1974)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Fragmentation data was assembled and analyzed for exploding liquid propellant vessels. These data were to be retrieved from reports of tests and accidents, including measurements or estimates of blast yield, etc. A significant amount of data was retrieved from a series of tests conducted for measurement of blast and fireball effects of liquid propellant explosions (Project PYRO), a few well-documented accident reports, and a series of tests to determine auto-ignition properties of mixing liquid propellants. The data were reduced and fitted to various statistical functions. Comparisons were made with methods of prediction for blast yield, initial fragment velocities, and fragment range. Reasonably good correlation was achieved. Methods presented in the report allow prediction of fragment patterns, given type and quantity of propellant, type of accident, and time of propellant mixing.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-134538
    Format: application/pdf
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