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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Analysis of flow dynamics through small diameter gas sampling systems

The removal of gas material through a capillary opening in a surface is analyzed. The gas, from which the sample is removed, is moving past the surface at supersonic velocities. A variety of possible conditions of temperature, pressure and composition are discussed in an effort to emulate conditions that might be found at the surface of a vehicle traversing the altitude range 100-50 km, or might exist at the surface of a model in the stream of a high enthalpy wind tunnel. Aspects discussed include: (1) the throughput of the capillary for conditions of different lengths and different L/a (length/radius) ratios; (2) the total throughput when the surface in question contains many hundreds of these capillaries; (3) the effect of the capillaries upon the composition of the analyzed gas; (4) the effect of the capillary or capillaries upon the gas stream itself; and (5) the implications of the calculations upon the possible implementation of this type of device as an inlet for a mass spectrometer to be developed for analyzing the upper atmosphere.

Brown, K. G.↗
NASA NTRS1984

Dynamic flow quality measurements in the Langley Low Turbulence Pressure Tunnel

The results of tests to measure the disturbance levels across the cooler, screens, and nozzle in the test section of the rehabilitated Langley Research Center Low Turbulence Pressure Tunnel are reported and discussed. The velocity fluctuations measured upstream and downstream of the cooler were approximately equal and ranged from 5 to 15 percent. The attenuation of the measured velocity fluctuations across the screen agreed with predictions from Dryden's (1949) theory. Velocity fluctuations in the test section ranged from 0.025 percent at Mach 0.05 to 0.3 percent at Mach 0.2. Pressure fluctuations at the test section walls agreed with previous measurements made under a turbulent boundary. The autocorrelation functions indicated that there were large reductions in the integral scale of turbulence across the cooler and screens. The spectra measured upstream and downstream of the cooler were mostly broadband.

Stainback, P. C.↗
NASA NTRS1985

Optical diagnostics of gas-dynamic flows using advanced laser measurement techniques

Using laser-induced fluorescence to probe nitrogen flows seeded with small amounts of nitric oxide, simultaneous measurements of all three thermodynamic scalar quantities temperature, density, and pressure, were demonstrated in a supersonic turbulent boundary layer. Instrumental uncertainty is 1% for temperature and 2% for density and pressure, making the techniques suitable for measurements of turbulent fluctuations. This technology is currently being transferred to an experimental program designed to use these optical techniques in conjunction with traditional methods to make measurements in turbulent flowfields that were not possible before. A detailed descritpion of the research progress and pertinent results are presented.

Gross, K. P.↗
NASA NTRS1992

An alternative to unstructured grids for computing gas dynamic flows around arbitrarily complex two-dimensional bodies

In this paper we describe an approach for dealing with arbitrary complex, two dimensional geometries, the so-called cartesian boundary method. Conceptually, the cartesian boundary method is quite simple. Solid bodies blank out areas of a background, cartesian mesh, and the resultant cut cells are singled out for special attention. However, there are several obstacles that must be overcome in order to achieve a practical scheme. We present a general strategy that overcomes these obstacles, together with some details of our successful conversion of an adaptive mesh algorithm from a body-fitted code to a cartesian boundary code.

Quirk, James J.↗
NASA NTRS1992

Parallel implementation of a particle simulation for modeling rarefied gas dynamic flow

When the conditions of flow are rarefied and hypersonic, a more suitable alternative to the use of the Navier-Stokes equations for developing a numerical solution is the Direct Simulation Monte Carlo method (DSMC), a method of simulation which employs a large number of particles in modeling a rarefied gas. The performance of a parallel DSMC code developed for the Intel iPSC/860 Touchstone Gamma prototype computer is studied and the scaleup is found to be very nearly over the range of 16-128 processors.

Fallavollita, M. A.↗
NASA NTRS1993

Liquid rocket propulsion dynamic flow modeling using the ROCETS engineering modules in the EASY5x environment

A report on the progress of porting the ROCETS (ROCket Engine Transient Simulator) into the EASY5x simulation environment is presented. Brief descriptions of each of the software systems, information regarding the actual port process, and examples comparing the results of the two systems are given. It is shown that EASY5x is a suitable environment for utilization of the ROCETS engineering modules, and that, for the example systems shown, EASY5x actually seems to give more accurate solutions than the straight ROCETS code.

Follett, Randolph F.↗
NASA NTRS1999

Abel Inversion of Deflectometric Measurements in Dynamic Flows

We present an Abel-inversion algorithm to reconstruct mean and rms refractive-index profiles from spatially resolved statistical measurements of the beam-deflection angle in time-dependent, axisymmetric flows. An oscillating gas-jet diffusion flame was investigated as a test case for applying the algorithm. Experimental data were obtained across the whole field by a rainbow schlieren apparatus. Results show that simultaneous multipoint measurements are necessary to reconstruct the rms refractive index accurately.

Agrawal, Ajay K.↗
NASA NTRS1986

Statistical prediction of dynamic distortion of inlet flow using minimum dynamic measurement. An application to the Melick statistical method and inlet flow dynamic distortion prediction without RMS measurements

The Melick method of inlet flow dynamic distortion prediction by statistical means is outlined. A hypothetic vortex model is used as the basis for the mathematical formulations. The main variables are identified by matching the theoretical total pressure rms ratio with the measured total pressure rms ratio. Data comparisons, using the HiMAT inlet test data set, indicate satisfactory prediction of the dynamic peak distortion for cases with boundary layer control device vortex generators. A method for the dynamic probe selection was developed. Validity of the probe selection criteria is demonstrated by comparing the reduced-probe predictions with the 40-probe predictions. It is indicated that the the number of dynamic probes can be reduced to as few as two and still retain good accuracy.

Schweikhard, W. G.↗
NASA NTRS1980

Flow Induced Spring Coefficients of Labyrinth Seals for Application in Rotor Dynamics

Flow induced aerodynamic spring coefficients of labyrinth seals are discussed and the restoring force in the deflection plane of the rotor and the lateral force acting perpendicularly to it are also considered. The effects of operational conditions on the spring characteristics of these components are examined, such as differential pressure, speed, inlet flow conditions, and the geometry of the labyrinth seals. Estimation formulas for the lateral forces due to shaft rotation and inlet swirl, which are developed through experiments, are presented. The utilization of the investigations is explained and results of stability calculations, especially for high pressure centrifugal compressors, are added. Suggestions are made concerning the avoidance of exciting forces in labyrinths.

Benckert, H.↗