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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Hypervelocity atmospheric flight: Real gas flow fields

Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that have been reduced to a relatively compact set of equations in a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-average behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equations a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. Hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates chemical nonequilibrium is considered, and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

Howe, John T.↗
NASA NTRS1990

Hypervelocity atmospheric flight: Real gas flow fields

Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that were reduced to a relatively compact set of equations of a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-averaged behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equation a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. For hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates, chemical nonequilibrium is considered and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

Howe, John T.↗
NASA NTRS1986

Chemical and Thermal Nonequilibrium Heat-Transfer Analysis for Hypervelocity, Low Reynolds Number Flow

Chemical and thermal nonequilibrium phenomena are studied in the stagnation region of a hypervelocity blunt body. This investigation is motivated by the need to predict the heat-transfer rate to the leading edge of aeromaneuvering orbital transfer vehicles. Flight speeds of approximately 10 km/s at altitudes of approximately 80 km are considered for body radii of 1-50 cm. The analysis is based on continuum theory and is applicable to the viscous and incipient merged layer regimes of rarefied flow. A two-species, two-temperature gas model is assumed. Comparisons are made with previous theories, experimental data, and results based on the thermodynamic equilibrium assumption. The equation accounting for vibrational nonequilibrium is presented and its effects on flow properties are discussed. Parameters requiring further investigation are identified. Preliminary results indicate that the inclusion of vibrational relaxation has little effect on the heat-transfer rate for a fully catalytic surface. However, vibrational nonequilibrium may increase the heat-transfer rate to a noncatalytic surface, depending on the degree of nonequilibrium.

Brown, Kevin G.↗
NASA NTRS1985

Chemical and thermal nonequilibrium heat transfer analysis for hypervelocity, low Reynolds number flow

Chemical and thermal nonequilibrium phenomena are studied in the stagnation region of a hypervelocity blunt body. This investigation is motivated by the need to predict the heat transfer rate to the leading edge of Aeromaneuvering Orbital Transfer Vehicles. Flight speeds of approximately 10 km/s at altitudes of approximately 80 km are considered for body radii of 1 to 50 cm. The analysis is based on continuum theory and is applicable to the viscous-layer and incipient-merged-layer rarefied-flow regimes. A two-species, two-temperature gas model is assumed. Comparisons are made with previous theories, experimental data, and results based on the thermodynamic equilibrium assumption. The equation accounting for vibrational nonequilibrium is presented and its effects on flow properties are discussed. Parameters which require further investigation are identified. Preliminary results indicate that the inclusion of vibrational relaxation has little effect on heat transfer rate for a catalytic surface. However, vibrational nonequilibrium may increase the heat transfer rate to a noncatalytic surface, depending on the degree of nonequilibrium.

Brown, K. G.↗
NASA NTRS1983

Heat-transfer distributions on biconics at incidence in hypersonic-hypervelocity He, N2, air, and CO2 flows

Laminar heat transfer rates were measured on spherically blunted, 13 deg/7 deg on axis and bent biconics (fore cone bent 7 deg upward relative to aft cone) at hypersonic hypervelocity flow conditions in the Langley Expansion Tube. Freestream velocities from 4.5 to 6.9 km/sec and Mach numbers from 6 to 9 were generated using helium, nitrogen, air, and carbon dioxide test gases, resulting in normal shock density ratios from 4 to 19. Angle of attack, referenced to the axis of the aft cone, was varied from 0 to 20 deg in 4 deg increments. The effect of nose bend, angle of attack, and real gas phenomena on heating distributions are presented along with comparisons of measurement to prediction from a code which solves the three dimensional parabolized Navier-Stokes equations.

Miller, C. G.↗
NASA NTRS1983

Heat-transfer distributions on biconics at incidence in hypersonic-hypervelocity He, N2, air, and CO2 flows

Laminar heat-transfer rates were measured on spherically blunted, 13 degrees/F degrees on-axis and bent biconics (fore cone bent 7 degrees upward relative to aft cone) at hypersonic-hypervelocity flow conditions in the Langley Expansion Tube. Freestream velocities from 4.5 to 6.9 km/sec and Mach numbers from 6 to 9 were generated using helium, nitrogen, air, and carbon dioxide test gases, resulting in normal shock density ratios from 4 to 19. Angle of attack, referenced to the axis of the aft cone, was varied from zero to 20 degrees in 4 degree increments. The effect of nose bend, angle of attack, and real-gas phenomena on heating distributions are presented along with comparisons of measurement to prediction from a code which solves the three-dimensional 'parabolized Navier-Stokes' equations.

Miller, C. G.↗
NASA NTRS1984

Heat-transfer distributions for biconics at incidence in hypersonic-hypervelocity real-gas flows

Laminar heat-transfer distributions were measured on spherically blunted, 13/7 deg straight and bent biconics at freestream velocities from 4.5 to 6.9 km/s and Mach numbers from 6 to 9. The flows were generated in the NASA's Langley Expansion Tube using helium, nitrogen, air, and carbon dioxide; angle of attack, referenced to the axis of the aft cone, was varied from zero to 20 deg. The penalty in windward heating to the fore cone due to the 7-deg nose bend diminished rapidly with increasing angle of attack and was only 10 to 20 percent at the design trim angle of attack of 20 deg. Leeward heating initially decreased, then increased, with increasing angle of attack. Windward heating rates predicted with a computer code that solves the parabolized Navier-Stokes equations were in good agreement with measurements for helium and air. The study used a 1.9-percent scale model of the proposed generic planetary vehicle and is directly applicable to the orbital transfer vehicle, which incorporates a spherically blunted biconic.

Miller, C. G.↗
NASA NTRS1971

Laminar or turbulent boundary-layer flows of perfect gases or reacting gas mixtures in chemical equilibrium

Turbulent boundary layer flows of non-reacting gases are predicted for both interal (nozzle) and external flows. Effects of favorable pressure gradients on two eddy viscosity models were studied in rocket and hypervelocity wind tunnel flows. Nozzle flows of equilibrium air with stagnation temperatures up to 10,000 K were computed. Predictions of equilibrium nitrogen flows through hypervelocity nozzles were compared with experimental data. A slender spherically blunted cone was studied at 70,000 ft altitude and 19,000 ft/sec. in the earth's atmosphere. Comparisons with available experimental data showed good agreement. A computer program was developed and fully documented during this investigation for use by interested individuals.

Anderson, E. C.↗
NASA NTRS1973

Non-reacting and equilibrium chemically reacting turbulent boundary-layer flows.

Turbulent boundary-layer flows of nonreacting gases are predicted for both internal (nozzle) and external flows. Effects of favorable pressure gradients on two eddy viscosity models were studied in rocket and hypervelocity wind tunnel flows. Nozzle flows of equilibrium air with stagnation temperatures up to 10,000 K were computed. Predictions of equilibrium nitrogen flows through hypervelocity nozzles were compared with experimental data. A slender spherically blunted cone was studied at 70,000 ft altitude and 19,000 ft/sec in the earth's atmosphere. Comparisons with available experimental data showed good agreement. A computer program was developed and fully documented during this investigation for use by interested individuals.

Anderson, E. C.↗
NASA NTRS1986

Commentary on the 1985 NASA/Vanderbilt Symposium on Future Hypervelocity Flight Requirements

The discussion, started in Semiannual Status Report Number 1, on aerothermal problems of hypervelocity flight and experiments that may lead to significant improvements in analytical/computational predictive methods, continues. The commentary is based on presentations made by speakers at a symposium on this subject held in December 1985. Symposium participants focused on the serious deficiencies that exist in knowledge of real-gas, nonequilibrium thermochemical-kinetic processes, catalytic processes, surface and shock slip, gas/surface interaction, boundary layer transition, and vortical leeside flows under hypervelocity conditions. Programs of laboratory research and computations leading toward in-flight experiments were recommended. Feasibility of appropriate measurement techniques for the flight environment was assessed and problems for study in that area identified. A synopsis of the oral presentations is given.

Potter, J. L.↗
NASA NTRS1986

Thermophysical aspects of re-entry flows

The present conference discusses low density aerothermodynamics, the drag of bodies in rarefied hypersonic flow, transitional hypervelocity aerodynamic simulation and scaling, high temperature kinetics and transport properties, electron-nitrogen molecule collisions in high temperature nonequilibrium air, theoretical studies of dissociative recombination, the transport properties of some atom/ion interactions in air, and the interaction energies, dipole transition moments, and transport cross sections of N(+)-N and O(+)-O. Also discussed are the results of studies of potential fluid mechanisms for enhanced stagnation heating, vortex-induced leeward heating on a biconic at Mach 6 and 10, the effects of surface discontinuities on convective heat transfer in hypersonic flow, computational convergence in chemical reacting flows, and three-dimensional viscous shock layer applications for the Space Shuttle Orbiter.

Moss, J. N.↗