Search NASA⌕ Search

SEARCH · Search NASA

Results for “Geometry”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

FASTER 3: A generalized-geometry Monte Carlo computer program for the transport of neutrons and gamma rays. Volume 1: Summary report

The theory used in FASTER-III, a Monte Carlo computer program for the transport of neutrons and gamma rays in complex geometries, is outlined. The program includes the treatment of geometric regions bounded by quadratic and quadric surfaces with multiple radiation sources which have specified space, angle, and energy dependence. The program calculates, using importance sampling, the resulting number and energy fluxes at specified point, surface, and volume detectors. It can also calculate minimum weight shield configuration meeting a specified dose rate constraint. Results are presented for sample problems involving primary neutron, and primary and secondary photon, transport in a spherical reactor shield configuration.

Jordan, T. M.↗
NASA NTRS1970

FASTER 3: A generalized-geometry Monte Carlo computer program for the transport of neutrons and gamma rays. Volume 2: Users manual

A description of the FASTER-III program for Monte Carlo Carlo calculation of photon and neutron transport in complex geometries is presented. Major revisions include the capability of calculating minimum weight shield configurations for primary and secondary radiation and optimal importance sampling parameters. The program description includes a users manual describing the preparation of input data cards, the printout from a sample problem including the data card images, definitions of Fortran variables, the program logic, and the control cards required to run on the IBM 7094, IBM 360, UNIVAC 1108 and CDC 6600 computers.

Jordan, T. M.↗
NASA NTRS1972

Analytical correlation of centrifugal compressor design geometry for maximum efficiency with specific speed

Centrifugal compressor performance was examined analytically to determine optimum geometry for various applications as characterized by specific speed. Seven specific losses were calculated for various combinations of inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, blade exit backsweep, and inlet-tip absolute tangential velocity for solid body prewhirl. The losses considered were inlet guide vane loss, blade loading loss, skin friction loss, recirculation loss, disk friction loss, vaneless diffuser loss, and vaned diffuser loss. Maximum total efficiencies ranged from 0.497 to 0.868 for a specific speed range of 0.257 to 1.346. Curves of rotor exit absolute flow angle, inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, head coefficient and blade exit backsweep are presented over a range of specific speeds for various inducer tip speeds to permit rapid selection of optimum compressor size and shape for a variety of applications.

Galvas, M. R.↗
NASA NTRS1972

A study to determine the flight characteristics and handling qualities of variable geometry spacecraft. Volume 2: Medium L/D concept with switch-blade wings

Flight characteristics and wing deployment transients for a variable geometry logistics spacecraft concept having a hypersonic lift-drag ratio near 2.0, and employing switch-blade wings for deployment at high subsonic speeds have been determined. These characteristics are based on detailed static wind tunnel results and estimated weight and inertial characteristics of a 9-man logistics lifting entry vehicle. In all instances, unpowered flight is assumed. The present volume is the second of a four volume series encompassing hypersonic lift-drag ratio vehicles from 1 to 3, and including several forms of deployable lifting surfaces. For Volumes 1 and 3, see N70-25699 and N72-15779 respectively.

Kuchta, B. J.↗
NASA NTRS1972

New circumferential seal design concept using self-acting lift geometries

Seal operating temperatures, leakage (pressurizing gas flow), torque, and wear of a conventional circumferential shaft seal were measured and compared to those of a conventional seal modified to have self-acting lift geometries. Both seal types had a 2.625-in diameter bore and were operated at a sliding velocity of 150 ft/sec with differential pressures ranging from 0 to 100 psi. Results of this investigation show that the self-acting seal operated at lower bulk carbon temperatures with half the torque and approximately one-tenth the wear of the conventional seal. Seal leakage of the self-acting seal was of order of 0.04 scfm for pressures above 60 psi which is well within the accepted range for gas turbine engine applications.

Hady, W. F.↗
NASA NTRS1972

Evaluation of range and distortion tolerance for high Mach number transonic fan stages. Task 2: Performance of a 1500-foot-per-second tip speed transonic fan stage with variable geometry inlet guide vanes and stator

A 0.5 hub/tip radius ratio compressor stage consisting of a 1500 ft/sec tip speed rotor, a variable camber inlet guide vane and a variable stagger stator was designed and tested with undistorted inlet flow, flow with tip radial distortion, and flow with 90 degrees, one-per-rev, circumferential distortion. At the design speed and design IGV and stator setting the design stage pressure ratio was achieved at a weight within 1% of the design flow. Analytical results on rotor tip shock structure, deviation angle and part-span shroud losses at different operating conditions are presented. The variable geometry blading enabled efficient operation with adequate stall margin at the design condition and at 70% speed. Closing the inlet guide vanes to 40 degrees changed the speed-versus-weight flow relationship along the stall line and thus provided the flexibility of operation at off-design conditions. Inlet flow distortion caused considerable losses in peak efficiency, efficiency on a constant throttle line through design pressure ratio at design speed, stall pressure ratio, and stall margin at the 0 degrees IGV setting and high rotative speeds. The use of the 40 degrees inlet guide vane setting enabled partial recovery of the stall margin over the standard constant throttle line.

Bilwakesh, K. R.↗
NASA NTRS1972

Flow conditions around the exit and downstream of certain stator blading with various trailing edge thicknesses and geometries

The blading investigated was curved back with thick profiles. The variations in flow conditions considered were flow angle and isentropic energy. Experimental data were obtained in a two-dimensional cascade from surveys with a combined angle, total-, and static-pressure probe and from an array of end-wall static pressure taps. Analytical results were obtained from ideal flow theory. The results showed large variations in flow conditions close to the plane of the trailing edge that were largely attenuated at a distance a little greater than one blade pitch downstream of the trailing edge in the direction of flow. The results were affected by the geometry and thickness of the trailing edge. The agreement between experimental and analytical results is generally fair to excellent.

Prust, H. W., Jr.↗
NASA NTRS1972

A shock surface geometry: The 15-16 February 1967 event

The flare-associated interplanetary shock observed by Explorer 33 and Pioneer 7 is analyzed to yield an estimation of the ecliptic plane geometry of the shock surface near 1 AU. These spacecraft were separated by 23 deg in the heliocentric longitude and Pioneer 7 was at a distance of 1.12 AU from the sun. Although a data gap occurred at the apparent time of passage of the disturbance at Pioneer 6, which was 85 deg in heliocentric longitude from Pioneer 7 and at 0.83 AU, the recovered data did suggest such a passage. A consistent picture of the shock propagation is given to explain the difference in arrival times at Pioneers 6, 7, and Explorer 33 and the difference of the shock normals observed by Pioneer 7 and Explorer 33. The average shock speed from the sun to each spacecraft and the local speed at Explorer 33 and their relations to the position of the initiating solar flare are obtained and discussed. In the region of space between the earth and Pioneer 7 the shock surface radius of curvature in the ecliptic plane was 0.4 AU or less.

Lepping, R. P.↗
NASA NTRS1973

Calculation of energy deposition distributions for simple geometries

When high-energy charged particles pass through a thin detector, the ionization energy loss in that detector is subject to fluctuations or straggling which must be considered in interpreting the data. Under many conditions, which depend upon the charge and energy of the incident particle and the detector geometry, the ionization energy lost by the particle is significantly different from the energy deposited in the detector. This problem divides naturally into a calculation of the energy loss that results in excitation and low-energy secondary electrons which do not travel far from their production points, and a calculation of energy loss that results in high-energy secondary electrons which can escape from the detector. The first calculation is performed using a modification of the Vavilov energy loss distribution. A cutoff energy is introduced above which all electrons are ignored and energy transferred to low energy particles is assumed to be equivalent to the energy deposited by them. For the second calculation, the trajectory of the primary particle is considered as a source of secondary high-energy electrons. The electrons from this source are transported using Monte Carlo techniques and multiple scattering theory, and the energy deposited by them in the detector is calculated. The results of the two calculations are then combined to predict the energy deposition distribution. The results of these calculations are used to predict the charge resolution of parallel-plate pulse ionization chambers that are being designed to measure the charge spectrum of heavy nuclei in the galactic cosmic-ray flux.

Watts, J. W., Jr.↗
NASA NTRS1973

The effect of nose geometry on the aerothermodynamic environment of shuttle entry configurations

The effect was studied of nose geometry on the transition criteria for the windward boundary layer, on the extent of separation, on the heat transfer perturbation due to the canopy, and on the surface pressure and the heat transfer in the separated region. The data for each of these problems is analyzed. A literature review that concentrates on separation and the leeward flow-field is presented.

Bertin, J. J.↗
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

Coaxial inverted geometry transistor having buried emitter

The invention relates to an inverted geometry transistor wherein the emitter is buried within the substrate. The transistor can be fabricated as a part of a monolithic integrated circuit and is particularly suited for use in applications where it is desired to employ low actuating voltages. The transistor may employ the same doping levels in the collector and emitter, so these connections can be reversed.

Hruby, R. J.↗
NASA NTRS1973

Effect of geometry on the nose-region flow-field of shuttle entry-configurations

In order to determine the convective heat-transfer distribution for the nose region of the space shuttle entry configurations, a three-dimensional flow-field is described which may include extensive regions of separated flow. Because of the complexity of the flow field for the nose region, experimental data are needed to define the relation between the nose geometry and the resultant flow field. According to theoretical solutions of the three-dimensional boundary layer, the boundary layer separates from the leeward generator of a blunted cone at an alpha equal to the cone half-angle. Separation results from the transverse pressure gradient, i.e., the velocity derivative due to crossflow. The boundary layer limiting streamlines converge toward the singular point of sep aration. The separated region is bounded by an ordinary line of separation.

Bertin, J. J.↗
NASA NTRS1973

A study of methods which predict supersonic flow fields from body geometry, distance, and Mach number

A study of seven methods for predicting flow-field pressure signatures from the parameters Mach number, body geometry, and field-path distance has been made. The methods included the method of characteristics, which served as a standard of comparison; a shock-capturing method; three Whitham theory methods; a modified characteristics method; and a bicharacteristics method. Results from each method were also compared with recently obtained wind-tunnel data for a cone-cylinder model at Mach numbers of 2.96 and 4.63 with ratios of radial distance to cone length of 2 and 5. The comparisons at a Mach number of 2.96 showed that signatures from all the methods correlated well with wind-tunnel data and with the signatures predicted by the method of characteristics. At a Mach number of 4.63, however, the agreement between the signatures obtained in the wind tunnel and those predicted by theory varied from good to poor, as did the agreement between the signatures obtained by the method of characteristics and the other six methods. It should be noted that these results and comparisons indicate pressure prediction capabilities only for the near-field flow about bodies of revolution.

Mack, R. J.↗
NASA NTRS1973

Geometry program for aerodynamic lifting surface theory

A computer program that provides the geometry and boundary conditions appropriate for an analysis of a lifting, thin wing with control surfaces in linearized, subsonic, steady flow is presented. The kernel function method lifting surface theory is applied. The data which is generated by the program is stored on disk files or tapes for later use by programs which calculate an influence matrix, plot the wing planform, and evaluate the loads on the wing. In addition to processing data for subsequent use in a lifting surface analysis, the program is useful for computing area and mean geometric chords of the wing and control surfaces.

Medan, R. T.↗
NASA NTRS1973

Effect of Subsonic Inlet Lip Geometry on Predicted Surface and Flow Mach Number Distributions

The effect of subsonic inlet lip geometry on predicted surface and flow Mach number distributions is illustrated. The theoretical results were obtained from incompressible potential flow calculations corrected for compressibility. The major emphasis of this investigation is on the low-speed (takeoff and landing) operating conditions. The low-speed results were obtained for a range of three geometric variables of interest: contraction ratio, defined as the ratio of highlight area to throat area; internal lip major - to minor-axis ratio; and internal lip shape. The low-speed results were obtained at both static conditions and a free-stream velocity of 42.6m/sec, with incidence angles ranging from 0 deg to 50 deg. The results indicate that of the three geometric variables considered, contraction ratio had the largest effect on the surface Mach number distributions. The effects of inlet diameter ratio and blunting of the external forebody on maximum external surface Mach numbers are illustrated at a cruise Mach number of 0.8.

Albers, J. A.↗