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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Effect of simulated hyperemia on the flow field in a mildly atherosclerotic coronary artery casting of man

Changes in an arterial flow field due to mild atherosclerosis were determined using a main coronary artery casting with a maximum obstruction of about 50 percent by area. Local pressure changes were measured using six pressure tap holes along the wall of the casting. The test-fluid was a 33 percent sugar-water solution of approximately the same viscosity as human blood. Flow visualization results were obtained by injecting blue-dye through the pressure tap holes. Measurement of local pressure demonstrated a significant Reynolds number effect. At Reynolds numbers of 80-710, a local pressure rise was observed downstream of the mild atherosclerotic constriction due to momentum changes. The Reynolds number necessary for flow separation in the divergent region of the coronary casting was about 330. The experimental results can be used to obtain a quantitative relation between coronary morphology and the fluid dynamic consequences of mild diffuse disease under conditions of maximum cardiac demand i.e., higher coronary flow rates and Reynolds numbers associated with space and atmospheric flight.

Cho, Y. I.↗
NASA NTRS2002

3-D Flow Field Diagnostics and Validation Studies using Stereoscopic Tracking Velocimetry

The measurement of 3-D three-component velocity fields is of great importance in both ground and space experiments for understanding materials processing and fluid physics. Here, we present the investigation results of stereoscopic tracking velocimetry (STV) for measuring 3-D velocity fields. The effort includes diagnostic technology development, experimental velocity measurement, and comparison with analytical and numerical computation. The advantages of STV stems from the system simplicity for building compact hardware and in software efficiency for continual near-real-time process monitoring. It also has illumination flexibility for observing volumetric flow fields from arbitrary directions. STV is based on stereoscopic CCD observations of particles seeded in a flow. Neural networks are used for data analysis. The developed diagnostic tool is tested with a simple directional solidification apparatus using Succinonitrile. The 3-D velocity field in the liquid phase is measured and compared with results from detailed numerical computations. Our theoretical, numerical, and experimental effort has shown STV to be a viable candidate for reliably quantifying the 3-D flow field in materials processing and fluids experiments.

Cha, Soyoung Stephen↗
NASA NTRS1994

Doppler global velocimetry: Development of a flight research instrumentation system for application to non-intrusive measurements of the flow field

Doppler Global Velocimetry (DGV) is a new diagnostic tool that offers potential for flow field measurements in flight by acquiring three-component velocity data in near real-time during flight maneuvers. The feasibility of implementation of a flight DGV system aboard NASA's High-Angle-of-Attack Research Vehicle (HARV) was addressed in this work by identifying the essential characteristics of a flight measurement system and by performing calibration and error tests. Results from this work were: an outline that establishes a preliminary basis for system configurations by analyzing measurement errors, installation issues, and operating requirements; measurement of the accuracy of the DGV technique using a laboratory breadboard DGV system based on a frequency-doubled Nd: YAG laser and iodine Absorption Line Filter (ALF), which showed excellent agreement between the DGV data and pilot measurements on a laminar flow jet with velocities of up to 150 m/sec; a survey of DGV system components and technologies that are relevant to the design of a flight measurement system, including a survey of cameras for the next generation DGV receivers; an assessment of the candidate lasers and absorption line filters for the flight system, resulting in a near-term recommendation of Nd: host lasers and an iodine ALF for both flight and wind tunnel applications.

Komine, Hiroshi↗
NASA NTRS1990

Flow field analysis for a class of waverider configurations

A package of computer codes for analysis of flow fields for waverider configurations is described. The package consists of a surface/volume grid generator and a finite-volume flow solver. The grid generator defines body geometries and computational grids by an algebraic homotopy procedure. The algebraic procedure is versatile in its application and can readily generate configurations in the class of blended wing-body geometries. This code has the ability to produce a wide variety of geometries in the given class with varying geometrical attributes. The flow solver employs a finite-volume formation and solves the explicit, Runge-Kutta integration technique. The method or flow simulation incorporates several techniques for acceleration of the convergence of the interaction process and an entropy corrected enthalpy damping procedure for efficient computation of high Mach number flows.

Moitra, Anutosh↗
NASA NTRS1979

The applicability of Brillouin scattering to flow field diagnostics

To fill the void between turbulence theory and experiment; particularly in the flow fields consisting of monatomic gases, for example in wind tunnels, means of measuring fluctuating quantities are needed. In the area of density fluctuation measurement, the optical method of Brillouin scattering was suggested. This was based on the theory, that the Brillouin scattered intensity is proportional to a function of density. In this investigation the potential of this method as a diagnostic tool was studied. Here the density fluctuations in gases were sought. Continuous wave lasers and interferometers were used as the primary illuminating source and scattered light filters respectively.

Laiosa, J.↗
NASA NTRS1986

Radiative coupled nonequilibrium flow fields associated with aeroassisted orbital transfer

Development of an algorithm which will allow nonequilibrium flow field codes to be coupled to radiative transfer codes (currently limited to equilibrium applications) was initiated. The algorithm consists of an equation for the prediction of electronic state population fractions (electronic state temperature) and equations for the computation of spectral absorption coefficients and source functions. These expressions represent a thorough treatment in the context of the bandless model which in the past has proven adequate for equilibrium radiative transfer predictions. Perhaps the approach is more than adequate as the current algorithm requires four temperatures for each transition. Clearly, a more sophisticated model can be developed; however, it would require more information, such as rotational temperatures of the electronic levels.

Horton, T. E.↗
NASA NTRS1988

Measurements of droplet drag coefficients in a polydispersed turbulent flow field

Measurements of drag coefficient versus Reynolds number were obtained in a polydispersed turbulent flow field for three turbulence velocities and for freestream turbulence intensities between 3 and 12 percent. Results are presented for a single nozzle with low number density and a twin nozzle with higher number density. The results for drops smaller than 30 microns showed strong differences from existing low turbulence results. The drag relation was found to be weakly affected by the freestream velocity and to be strongly affected by the velocity fluctuation levels of individual size classes. A drag effect with the drop-drop interaction may also be possible.

Rudoff, R. C.↗
NASA NTRS1987

LDA measurement of the passage flow field in an annular airfoil cascade

Models to predict the complex three-dimensional flow through turbomachine blade rows are being developed. To verify these models and direct necessary refinements, it is necessary that predictions be correlated with data obtained in experiments which model the fundamental three-dimensional blade row flow phenomena. This paper describes a series of experiments performed in a large scale, subsonic, annular cascade facility specifically designed to provide such data. In particular, the effect of incidence angle on the three-dimensional passage flow field through an annular cascade of cambered airfoils is investigated and quantified, accomplished by obtaining detailed and expensive LDA data. These data demonstrate and quantify the development of the passage vortices through the airfoil passage and their strong interaction with the endwall boundary layers.

Stauter, R. C.↗
NASA NTRS1990

Wind-Tunnel Survey of an Oscillating Flow Field for Application to Model Helicopter Rotor Testing

A survey was conducted of the flow field produced by the Airstream Oscillator System (AOS) in the Langley Transonic Dynamics Tunnel (TDT). The magnitude of a simulated gust field was measured at 15 locations in the plane of a typical model helicopter rotor when tested in the TDT using the Aeroelastic Rotor Experimental System (ARES) model. These measurements were made over a range of tunnel dynamic pressures typical of those used for an ARES test. The data indicate that the gust field produced by the AOS is non-uniform across the tunnel test section, but should be sufficient to excite a model rotor.

Mirick, Paul H.↗
NASA NTRS1987

Low thrust viscous nozzle flow fields prediction

An existing Navier-Stokes code (PARC2D) was used to compute the nozzle flow field. Grids were generated by the interactive grid generator codes TBGG and GENIE. All computations were made on the NASA/MSFC CRAY X-MP computer. Comparisons were made between the computations and MSFC in-house wall pressure measurements for CO2 flow through a conical nozzle having an area ratio of 40. Satisfactory agreements exist between the computations and measurements for different stagnation pressures of 29.4, 14.7, and 7.4 psia, at stagnation temperature of 1060 R. However, agreements did not match precisely near the nozzle exit. Several reasons for the lack of agreement are possible. The computational code assumes a constant gas gamma, whereas the gamma i.e. the specific heat ratio for CO2 varied from 1.22 in the plenum chamber to 1.38 at the nozzle exit. The computations also assumes adiabatic and no-slip walls. Both assumptions may not be correct. Finally, it is possible that condensation occurs during the nozzle expansion at the low stagnation pressure. The next phase of the work will incorporate variable gamma and slip wall boundary conditions in the computational code and develop a more accurate computer code.

Liaw, Goang-Shin↗
NASA NTRS1989

Computation of hypersonic flow fields

The present discussion of the theory, solution methods, and development status of chemically reactive flow CFD codes pertaining to the flow field around a hypersonic vehicle encompasses the formulation of multicomponent viscous equations, grid-generation techniques, and finite-difference algorithms. The Navier-Stokes equations presented focus on such particularities of high speed vehicles as their aerodynamic configuration, lee and wake flow, bow shock, and chemistry and low density effects. Issues for which further development is desirable encompass boundary treatments, grid quality, shock capturing, and the decoupling of chemistry from flow variables.

Li, Chien-Peng↗