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At least 307 records · Page 17

All sources NASA NTRS DOE OSTI

NASA NTRS1972

Impact probe displacement in a supersonic turbulent boundary layer.

The experiment was performed on the test section sidewall in a supersonic pressure tunnel. The boundary layer at the test station was surveyed in turn by each of 8 impact probes ranging in size from about 1.3 to 48 mm. The impact pressures measured by these probes were combined with the test section static pressure to calculate Mach numbers. Probe displacement effects were evaluated in terms of these Mach number values.

Allen, J. M.↗

NASA NTRS1972

Longitudinal curvature and displacement speed effects on incompressible laminar boundary layers.

The title problem is considered for the case of flow past a circular cylinder placed normal to a uniform mainstream with Reynolds numbers from 40 to 200. Implicit finite difference numerical solutions are obtained for a set of boundary-layer equations that account for the second order effects associated with surface curvature and displacement speed. It was found that both of these contributors have a significant influence on the internal structure of the viscous region and that an accurate estimate of the surface pressure distribution is essential for estimating the surface shear stress.

Werle, M. J.↗

NASA NTRS1973

Three-dimensional elastic stress and displacement analysis of tensile fracture specimens containing cracks

A seminumerical method is presented for three-dimensional elastic analysis of finite geometry solids with traction-free cracks. Stress and displacement distributions are calculated for two rectangular bars which are loaded by a uniform surface stress distribution. The first bar contains a through-thickness central crack while the second bar has double-edge cracks. Stress intensity factors K sub I for both configurations are presented.

Gyekenyesi, J. P.↗

NASA NTRS1973

Three-dimensional elastic stress and displacement analysis of finite circular geometry solids containing cracks

A seminumerical method is presented for solving a set of coupled partial differential equations subject to mixed and coupled boundary conditions. The use of this method is illustrated by obtaining solutions for two circular geometry and mixed boundary value problems in three-dimensional elasticity. Stress and displacement distributions are calculated in an axisymmetric, circular bar of finite dimensions containing a penny-shaped crack. Approximate results for an annular plate containing internal surface cracks are also presented.

Gyekenyesi, J. P.↗

NASA NTRS1973

Measurement of gas quantities by liquid displacement.

Derivation of equations relating the different variables involved in gas quantity measurements by liquid displacement from a Mariotte flask. The results are used to elucidate design criteria and operational procedures required for the realization of various degrees of desired accuracy down to 0.01%.

Christian, J. D.↗

NASA NTRS1974

Three-dimensional elastic stress and displacement analysis of finite geometry solids containing cracks

The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement distributions in various bodies containing cracks. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. When decoupling the equations and their boundary conditions is not possible, the use of a successive approximation procedure permits the analytical solution of the resulting ordinary differential equations. The results obtained show a considerable potential for using this method in the three-dimensional analysis of finite geometry solids and suggest a possible extension of this technique to nonlinear material behavior.

Gyekenyesi, J. P.↗

NASA NTRS1974

Rotating and positive-displacement pumps for low-thrust rocket engines. Volume 1: Pump Evaluation and design

Rotating and positive displacement pumps of various types were studied for pumping liquid fluorine for low-thrust, high-performance rocket engines. Included in the analysis were: centrifugal, pitot, Barske, Tesla, drag, gear, vane, axial piston, radial piston, diaphragm, and helirotor pump concepts. The centrifugal pump and the gear pump were selected and these were carried through detailed design and fabrication. Mechanical difficulties were encountered with the gear pump during the preliminary tests in Freon-12. Further testing and development was therefore limited to the centrifugal pump. Tests on the centrifugal pump were conducted in Freon-12 to determine the hydrodynamic performance and in liquid fluorine to demonstrate chemical compatibility.

Macgregor, C.↗

NASA NTRS1974

Rotating and positive-displacement pumps for low-thrust rocket engines. Volume 2: Fabrication and testing

Rotating and positive displacement pumps of various types were studied for pumping liquid fluorine for low thrust high performance rocket engines. Included in the analysis were: centrifugal, pitot, Barske, Tesla, drag, gear, vane, axial piston, radial piston, diaphragm and helirotor pump concepts. The centrifugal and gear pumps were carried through detail design and fabrication. After preliminary testing in Freon 12, the centrifugal pump was selected for further testing and development. It was tested in Freon 12 to obtain the hydrodynamic performance. Tests were also conducted in liquid fluorine to demonstrate chemical compatibility.

Csomor, A.↗

NASA NTRS1974

Examples of oil cavitation erosion in positive displacement pumps

The effects of cavitation flow on piston type, positive displacement, hydraulic pumps are discussed. The operating principles of the pump and the components which are most subject to erosion effects are described. The mechanisms of cavitation phenomena are identified from photographic records. Curves are developed to show the solubility of air in water, oil-water emulsion, and industrial hydraulic oil.

Halat, J. A.↗

NASA NTRS1974

Boundary-layer transition and displacement thickness effects on zero-lift drag of a series of power-law bodies at Mach 6

Wave and skin-friction drag have been numerically calculated for a series of power-law bodies at a Mach number of 6 and Reynolds numbers, based on body length, from 1.5 million to 9.5 million. Pressure distributions were computed on the nose by the inverse method and on the body by the method of characteristics. These pressure distributions and the measured locations of boundary-layer transition were used in a nonsimilar-boundary-layer program to determine viscous effects. A coupled iterative approach between the boundary-layer and pressure-distribution programs was used to account for boundary-layer displacement-thickness effects. The calculated-drag coefficients compared well with previously obtained experimental data.

Ashby, G. C., Jr.↗

NASA NTRS1974

A simple two-fiber optical displacement sensor

An optical displacement sensor is described in which only a pair of large-diameter fibers is used rather than a branched bundle of many small-diameter fibers. The basic idea of the two-fiber sensor is that the axes of the fibers are at an angle to one another at the sensor face, rather than parallel as is the case for the many-fiber configuration. The sensitivity of this two-fiber sensor is approximately the same as the most sensitive configuration of the many-fiber sensor.-

Powell, J. A.↗

NASA NTRS1974

A wire/extensometer method for measuring small displacements

A method has been developed for making precise point-to-point displacement measurements on critical structures under structural, thermal, or gravity loading. The technique consists of attaching the gauge to the structure at one point, and connecting it to a second point on the structure by a thin (0.25 mm) tungsten wire. The wire provides a dual function: in addition to physically connecting the gauge to a remote point, it provides a calibrating function. Tests have demonstrated that measurements can be made within a micron over a length of a meter or two, even in the presence of severe thermal shock, such as exposure to a sun gun or to a refrigerant spray.

Wilson, M. W.↗

NASA NTRS1974

Bimetallic fluid displacement apparatus

Stirring and heating stored gases and liquids is accomplished by using the deformation of a bimetallic structure which deforms significantly when heated. The deformation is used to effect gradual or impulsive motion of a piston, vane, wire, or diaphram for displacement of the fluid. The heated bimetallic is also employed for heating the stored fluid.

Canning, T. N.↗

NASA NTRS1974

Inclusion of transverse shear deformation in finite element displacement formulations

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.

Narayanaswami, R.↗

NASA NTRS1975

Analytical displacements and vibrations of cantilevered unsymmetric fiber composite laminates

A fiber composite flat cantilever plate that has symmetric and nonsymmetric laminate configurations is theoretically investigated to determine its static and dynamic structural response. The finite element analysis method used includes a unique triangular finite element developed at Lewis for the analysis of fiber composite airfoils. The various responses investigated include tip displacements, natural frequencies, and fundamental mode shapes. The results show that laminate configurations may be selected for a cantilever such that when the tip at the leading edge is loaded normal to the plane of the plate, the tip at the trailing edge can (1) deflect in the opposite direction, (2) deflect about the same, or (3) deflect more than the tip at the leading edge. This variation in response can be utilized to provide built-in structural damping to resist flutter.

Minich, M. D.↗

NASA NTRS1975

Three-dimensional elastic stress and displacement analysis of finite geometry solids containing cracks

Gyekenyesi, J. P.↗

NASA NTRS1975

Influence of probe geometry on pitot-probe displacement in supersonic turbulent flow

An experiment was conducted to determine the varying effects of six different probe-tip and support-shaft configurations on pitot tube displacement. The study was stimulated by discrepancies between supersonic wind-tunnel tests conducted by Wilson and Young (1949) and Allen (1972). Wilson (1973) had concluded that these discrepancies were caused by differences in probe geometry. It is shown that in fact, no major differences in profiles of streamwise velocity over streamwise velocity at boundary-layer edge vs normal coordinate over boundary-layer total thickness result from geometry. The true cause of the discrepancies, however, remains to be discovered.

Allen, J. M.↗

NASA NTRS1976

On the response of superpressure balloons to displacements from equilibrium density level

The response of a superpressure balloon to an initial displacement from its constant-density floating level is examined. An approximate solution is obtained to the governing vertical equation of motion for constant-density superpressure balloons. This solution is used to filter out neutrally buoyant oscillations in balloon records despite the nonlinear behavior of the balloon. The graph depicting the pressure data after deconvolution between the raw pressure data and the normalized balloon wavelet shows clearly the strong filtering-out of the neutral buoyancy oscillations.

Levanon, N.↗