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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Development of a metal-clad advanced composite shear web design concept

An advanced composite web concept was developed for potential application to the Space Shuttle Orbiter main engine thrust structure. The program consisted of design synthesis, analysis, detail design, element testing, and large scale component testing. A concept was sought that offered significant weight saving by the use of Boron/Epoxy (B/E) reinforced titanium plate structure. The desired concept was one that was practical and that utilized metal to efficiently improve structural reliability. The resulting development of a unique titanium-clad B/E shear web design concept is described. Three large scale components were fabricated and tested to demonstrate the performance of the concept: a titanium-clad plus or minus 45 deg B/E web laminate stiffened with vertical B/E reinforced aluminum stiffeners.

Laakso, J. H.↗
NASA NTRS1973

Study of exothermic processes in shock ignited gases by the use of laser shear interferometry

Report on measurements of maximum exothermic power pulses attainable from a given chemical system. Experimental tests involved the use of a shock tube technique whereby the exothermic process of combustion was controlled by reflected shock, so that it occurred under virtually inviscid flow conditions, while the measurements were performed at a resolution commensurate with the actual rate of chemical reaction. Experimental observations were made by means of a novel method of laser shear interferometry - a cross-breed between holography and the conventional means for measuring refractive index fields, in that, on one hand, it was based on the exploitation of the phase coherence of the laser light beam, recording first a diffraction image of the wave fronts which, for the desired final result, had to be optically reconstructed, and, on the other, it yielded eventually either two-dimensional interferograms or schlieren photographs of the observed phenomena.

Meyer, J. W.↗
NASA NTRS1974

Prediction of turbulent shear layers in turbomachines

The characteristics of turbulent shear layers in turbomachines are compared with the turbulent boundary layers on airfoils. Seven different aspects are examined. The limits of boundary layer theory are investigated. Boundary layer prediction methods are applied to analysis of the flow in turbomachines.

Bradshaw, P.↗
NASA NTRS1974

A Study of the Effect of Adhesive and Matrix Stiffnesses on the Axial, Normal, and Shear Stress Distributions of a Boron-epoxy Reinforced Composite Joint

The mechanical properties of a symmetrical, eight-step, titanium-boron-epoxy joint are discussed. A study of the effect of adhesive and matrix stiffnesses on the axial, normal, and shear stress distributions was made using the finite element method. The NASA Structural Analysis Program (NASTRAN) was used for the analysis. The elastic modulus of the adhesive was varied from 345 MPa to 3100 MPa with the nominal value of 1030 MPa as a standard. The nominal values were used to analyze the stability of the joint. The elastic moduli were varied to determine their effect on the stresses in the joint.

Howell, W. E.↗
NASA NTRS1975

Spinning mode sound propagation in ducts with acoustic treatment and sheared flow

The propagation of spinning mode sound was considered for a cylindrical duct with sheared steady flow. Calculations concentrated on the determination of the wall optimum acoustic impedance and the maximum possible attenuation. Both the least attenuated and higher radial modes for spinning lobe patterns were considered. A parametric study was conducted over a wide range of Mach numbers, spinning lobe numbers, sound frequency, and boundary layer thickness. A correlation equation was developed from theoretical considerations starting with the thin boundary layer approximation of Eversman. This correlation agrees well with the more exact calculations for inlets and provides a single boundary layer refraction parameter which determines the change in optimum wall impedance due to refraction effects.

Rice, E. J.↗
NASA NTRS1974

Traction of elastohydrodynamic contacts with thermal shearing flow

The formulation and solution for the shear stress and temperature in heavily loaded sliding elastohydrodynamic contacts is presented. The solutions are presented in dimensionless design charts. Integration over the contact area will yield the traction. Accuracy is expected to be very good over the nearly flat part of the contact area where the majority of the sliding traction is generated. The procedure presented is not appropriate for thick film lubrication, for the inlet region, or for the rolling friction of elastohydrodynamic contacts.

Jakobsen, J.↗
NASA NTRS1974

On the passage of radiation through inhomogeneous, moving media. VIII - Ray paths and fluxes in a plane differentially sheared medium

We give a detailed discussion of the group-velocity ray paths in a plane differentially sheared medium with constant index of refraction as measured by a local inertial observer. For a given velocity profile the numerical ray paths are presented graphically for several representative cases. Assuming that the medium has a volume emissivity and that a given flux of radiation is incident at the base of the medium, the flux of radiation leaving the slab as a function of exit angle is calculated and presented in the same representative cases. Peaks and discontinuities in the flux generally appear at given exit angles, but their locations and the half-widths of the peaks depend sensitively on the index of refraction.

Lee, M. A.↗
NASA NTRS1974

Steady simple shear flow past a circular cylinder at moderate Reynolds numbers - A numerical solution

The two-dimensional steady flow of an incompressible viscous fluid past a circular cylinder, placed symmetrically in a simple shear field, has been studied for both the stationary and the freely rotating case by solving numerically the Navier-Stokes equations for values of the Reynolds number R in the range from 0.047 to 70. At R = 0.047, the results obtained are in substantial agreement with the analytic small-R perturbation solution given by Robertson and Acrivos (1970). Inertia effects were found, however, to play a significant role even at R = 1, and hence the calculated flow pattern for R greater than or equal to 1 differs significantly from that of the creeping-flow solution. Specifically, for the freely rotating case, the region of closed streamlines decreases rapidly in extent with increasing R, two symmetrically placed wakes are formed on either side of the cylinder, and the dimensionless rotational speed of the freely suspended cylinder decreases as the reciprocal of the square root of R.

Kossack, C. A.↗
NASA NTRS1975

Spinning mode sound propagation in ducts with acoustic treatment and sheared flow

The propagation of spinning mode sound was considered for a cylindrical duct with sheared steady flow. The calculations concentrated on the determination of the wall optimum acoustic impedance and the maximum possible attenuation. Both the least attenuated and higher radial modes for spinning lobe patterns were considered. A parametric study was conducted over a wide range of Mach numbers, spinning lobe numbers, sound frequency, and boundary layer thickness. A correlation equation was developed from theoretical considerations starting with the thin boundary layer approximation of Eversman. This correlation agrees well with the more exact calculations for inlets and provides a single boundary layer refraction parameter which determines the change in optimum wall impedance due to refraction effects.

Rice, E. J.↗
NASA NTRS1975

Dual shear plate power processor packaging design

The use of solar electric propulsion (SEP) for spacecraft primary propulsion imposes an extreme range of operational and environmental design requirements associated with the diversity of missions for which solar electric primary propulsion is advantageous. One SEP element which is particularly sensitive to these environmental extremes is the power processor unit (PPU) which powers and controls the electric ion thruster. An improved power processor thermal-mechanical packaging approach, referred to as dual shear plate packaging, has been designed to accommodate these different requirements with minimum change to the power processor design. Details of this packaging design are presented together with test results obtained from thermal-vacuum and structural-vibration tests conducted with prototype hardware.

Franzon, A. O.↗
NASA NTRS1975

Finite element computation of a viscous compressible free shear flow governed by the time dependent Navier-Stokes equations

A finite element algorithm for solution of fluid flow problems characterized by the two-dimensional compressible Navier-Stokes equations was developed. The program is intended for viscous compressible high speed flow; hence, primitive variables are utilized. The physical solution was approximated by trial functions which at a fixed time are piecewise cubic on triangular elements. The Galerkin technique was employed to determine the finite-element model equations. A leapfrog time integration is used for marching asymptotically from initial to steady state, with iterated integrals evaluated by numerical quadratures. The nonsymmetric linear systems of equations governing time transition from step-to-step are solved using a rather economical block iterative triangular decomposition scheme. The concept was applied to the numerical computation of a free shear flow. Numerical results of the finite-element method are in excellent agreement with those obtained from a finite difference solution of the same problem.

Cooke, C. H.↗
NASA NTRS1976

A study of some effects of vertical shear on thunderstorms

Evidence is presented for the existence of vortices and vortex pairs in thunderstorms. A preliminary parameterized model of the nonthermal generation of thunderstorm vortices derived from field observations of storms and laboratory observations of a jet in crossflow is reported, together with an explanation of how such a model might be used to guide analysis of mesoscale rawinsonde, radar, and satellite data toward an improved capability for prediction of thunderstorm motion and growth. Preliminary analyses of radar and satellite data from Atmospheric Variability Experiment IV are used with available rawinsonde data to develop a correlation between wind shears, instability, and thunderstorm motion and development. Specific studies are recommended for best development of concepts and utilization of data from Atmospheric Variability and Atmospheric Variability Severe Storms Experiments.

Connell, J.↗
NASA NTRS1976

Shear layer structure of a low speed jet

A series of measurements of near field pressures and turbulent velocity fluctuations were made in a low speed jet with a Reynolds number near 50,000 in order to investigate more quantitatively the character and behavior of the large scale structures and their interactions with each other. The near field measurements were modelled according to the vortex pairing hypothesis to deduce the distribution of pairings along the jet axis and the variances about the mean locations. The hodograph plane description of turbulence was explored in some detail, and a complex correlation quantity was synthesized which has useful properties for turbulence in the presence of mean shear.

Petersen, R. A.↗
NASA NTRS1976

Diffusivity in turbulent fluid containing two dominant scales, and compressible shear layer according to a kinetic theory

The solution of the two nonequilibrium-degree kinetic equation was first determined for the effective length scale and turbulence energy for a spatially homogeneous turbulence field with two characteristic length scales, where the source for one family of eddies exists. This solution was applied to the evaluation of the eddy diffusivity in the combustion chamber of an internal combustion engine. The result was compared with another existing solution. This was carried out to demonstrate the feasibility of obtaining an effective length-scale equation within the context of the kinetic theory. A formulation and partial solution of the compressible plane shear layer are also presented.

Chung, P. M.↗
NASA NTRS1975

Lunar shear velocity structure at Apollo sites 12, 14, and 15

Spectral amplitude ratios of horizontal-to-vertical motion produced on seismograms of meteoroid impacts at the Apollo 12, 14, and 15 sites, the Apollo 14 and 15 lunar-module impacts, and the Apollo 15 S4B impact show consistent differences among the recording sites. On the assumption that the motion represents predominantly fundamental-mode Reyleigh waves and that the compressional-wave velocity structure is similar to that derived in other investigations involving the Apollo seismic experiments, estimates are made of the shear-wave velocity structure under the three sites. Near-surface velocities are about 35 m/s at the three sites. The results for site 14 indicate an increase to about 100 m/s near the 8-m depth and to 200 m/s at the 38-m depth. Results for sites 12 and 15 show a smoother gradient and generally a greater velocity at a given depth than that indicated at site 14, reaching velocities of about 400 m/s near the 120-m depth. If the assumed P velocity structures are correct and if changes in S velocity coincide with changes in P velocity, then the ratio of these velocities decreases from 2.9 to 2.0 in the upper 19 meters at site 12, in the upper 38 meters at site 14, and in the upper 21 meters at site 15.

Mark, N.↗
NASA NTRS1976

Turbulence measurements in a transonic boundary layer and free-shear flow using laser velocimetry and hot-wire anemometry techniques

Quantitative measurements of the turbulence fluctuations in velocity and mass flux have been obtained in Mach 0.6 and 0.8 turbulent boundary layer and free-shear layer flows by laser velocimetry and hot-wire anemometry techniques. To evaluate the effects of compressibility, these transonic data are compared to available incompressible and supersonic results. Based on some simplifying assumptions, estimates of the rms density fluctuations are made for which error bounds are given. In addition to these fluctuation data, the compressible mean velocity data obtained with the laser velocimeter are presented and compared to pitot tube results. The investigation was conducted in the Ames 6- by 6-Foot Supersonic Wind Tunnel at free-stream Mach numbers of 0.6 and 0.8 for a unit Reynolds number of about 10,000,000 per meter.

Johnson, D. A.↗
NASA NTRS1976

Noise measurements in a free-jet, flight simulation facility - Shear layer refraction and facility-to-flight corrections

The conversion of free-jet facility into equivalent flyover results is discussed. The essential problem is to 'calibrate out' the acoustic influence of the outer free-jet shear layer on the measurement, since this is absent in the flight case. Results are presented which illustrate the differences between current simplified models (vortex-sheet and geometric acoustics), and a more complete model based on the Lilley equation. Finally, the use of geometric acoustics for facility-to-flight data conversion is discussed.

Morfey, C. L.↗