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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

PAN AIR analysis of the NASA/MCAIR 279-3: An advanced supersonic V/STOL fighter/attack aircraft

PAN AIR is a computer program for predicting subsonic or supersonic linear potential flow about arbitrary configurations. The program was applied to a highly complex single-engine-cruise V/STOL fighter/attack aircraft. Complexities include a close-coupled canard/wing, large inlets, and four exhaust nozzles mounted directly under the wing and against the fuselage. Modeling uncertainties involving canard wake location and flow-through approximation through the inlet and the exhaust nozzles were investigated. The recently added streamline capability of the program was utilized to evaluate visually the predicted flow over the model. PAN AIR results for Mach numbers of 0.6, 0.9, and angles of attack of 0, 5, and 10 deg. were compared with data obtained in the Ames 11- by 11-Foot Transonic Wind tunnel, at a Reynolds number of 3.69 x 10 to the 6th power based on c bar.

Madson, Michael D.↗
NASA NTRS1991

Latitudinal dynamics of steady solar wind flows

In many previous studies, it has been assumed that the streamlines of the solar wind are in a purely radial direction beyond a few solar radii. Therefore, the nonradial modulations by the magnetic force and gas pressure is neglected at large heliocentric distances. The work reported in this paper includes a two-dimensional magnetohydrodynamic (MHD) study of the latitudinal structure of solar wind flows. The dynamical effects of the interplanetary magnetic field (IMF) are investigated by MHD solutions and by comparing them with both one-dimensional and two-dimensional hydrodynamic (HD) solutions. The corotational effect of the sun and the influence of transient events in the solar atmosphere are neglected. With such a simplification, the latitudinal structure of the steady solar wind is controlled by the dynamic balance of the magnetic force and the gas pressure. Several different patterns of the evolution of the solar wind latitudinal structure are exhibited in the calculation. The results indicate the existence of a proton number density maximum at the magnetic neutral line, whether or not there is a density maximum or minimum at the inner boundary. The drift motion of magnetic field lines toward the magnetic neutral line enhances the magnetic field strength around the neutral sheet, which may provide a possible explanation of the discrepancy between the measured IMF at 1 AU and that extrapolated from the photospheric magnetic field by the current source-surface modeling.

Yang, W.-H.↗
DOE OSTI2025

Numerical simulation of flow and mixing in fracture intersections

Fluid transport through fractured geological formations is strongly influenced by the redistribution of solutes at fracture intersections. In this study, we perform detailed numerical simulations of flow and scalar transport within the intersection of two smooth, planar fractures. The analysis focuses on the mixing ratio, the proportion of solute flux exiting along the outlet branch aligned with the primary inlet flow direction, relative to the total solute flux at the outlets. We systematically investigate how the mixing ratio varies with four key parameters: Peclet number, Reynolds number, flow rate ratio between outlet branches, and fracture intersection angle. Results show that the mixing ratio decreases with increasing Peclet number and outlet flow rate ratio, consistent with reduced diffusive spreading and enhanced streamline routing. While low Reynolds numbers have minimal impact, inertial effects at higher Reynolds numbers significantly increase the mixing ratio. Additionally, acute and obtuse intersection angles alter flow partitioning and modify the solute distribution at the outlets. These findings provide a quantitative basis for incorporating physically realistic mixing behavior—intermediate between complete mixing and streamline-following assumptions—into network-scale transport models. The results have direct relevance to subsurface energy systems, including geothermal energy production, carbon sequestration, and contaminant remediation.

58 GEOSCIENCES↗
NASA NTRS1983

Aerothermal modeling program, phase 1

The combustor performance submodels for complex flows are evaluated. The benchmark test cases for complex nonswirling flows are identified and analyzed. The introduction of swirl into the flow creates much faster mixing, caused by radial pressure gradients and increase in turbulence generation. These phenomena are more difficult to predict than the effects due to geometrical streamline curvatures, like the curved duct, and sudden expansion. Flow fields with swirl, both confined and unconfined are studied. The role of the dilution zone to achieve the turbine inlet radial profile plays an important part, therefore temperature field measurements were made in several idealized dilution zone configurations.

Srinivasan, R.↗
DOE OSTI2020

Viscous Dissipation and Apparent Permeability of Gas Flow in Nanoporous Media

The nanopore confinement effect can increase the mobility for gas flow in shale rocks, and the apparent permeability is usually adopted to account for this effect. However, most of the apparent permeability calculation models are derived based on straight channels (capillaries) and neglect the influence of end effect. The end effect is caused by the bending of streamlines which yields more viscous dissipation and additional flow resistance for gas flow in nanoporous media. Here, for the first time the viscous dissipation for gas flow in nanoporous media is analyzed. In addition, an improved apparent permeability calculation model is proposed based on the Beskok-Karniadakis (B-K) model by introducing the influence of end effect, which is characterized by the ratio of the length to the width of a short channel (L/H). The accuracy of this model is validated by lattice Boltzmann simulations of gas flow in three different geometries: an infinite-length straight channel, a finite-length straight channel, and nanoporous media. For the infinite-length straight channel, there is no end effect therefore both the B-K model and the improved model can well predict the apparent permeability. However, for the finite-length straight channel and nanoporous media, the original B-K model overestimates the gas apparent permeability as it neglects the influence of end effect, while the improved model can still well predict the gas apparent permeability. In summary, the improved apparent permeability calculation model is more reasonable in predicting gas mobility in nanoporous media.

58 GEOSCIENCES↗
NASA NTRS2015

Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and with four different versions of the TIC nozzle model geometry, each of which was created with a different simplification to the test article geometry.

Braman, Kalen↗
NASA NTRS2015

Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated using RANS and URANS for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and for four approximations of the supersonic film injection geometry, each of which was created with a different simplification of the test article geometry. The results show that although a reasonable match to experiment can be obtained with varying levels of geometric fidelity, the modeling choices made do not fully represent the physics of flow separation in a TIC nozzle with film cooling.

Braman, K. E.↗
NASA NTRS2003

Upward And Downward Flame Spreading And Extinction In Partial Gravity Environments

The premise of this research effort has been to begin exploring the gap in the literature between studies of material flammability and flame spread phenomena in normal-gravity and those conducted in the microgravity environment, with or without forced flows. From a fundamental point of view, flame spreading in upward (concurrent) buoyant flow is considerably different from concurrent forced flow. The flow accelerates throughout the length of the buoyant flame bringing the streamlines and the flame closer to the fuel surface and strengthening the interaction between the flame and fuel. Forced flows are diverted around the flame and away from the fuel surface, except where the flow might be constrained by a finite duct. The differences may be most clearly felt as the atmospheric conditions, viz. pressure or oxygen content, approach the flammability limit. From a more practical point of view, flame spreading and material flammability behavior have not been studied under the partial gravity conditions that are the natural state in space exploration destinations such as the Moon and Mars. This effort constitutes the beginning of the research needed to engineer fire safety provisions for such future missions. In this program we have performed partial-gravity experiments (from 0.1 to 1 g/g(sub Earth)) considering both upward and downward flame spread over thin solid fuels aboard the NASA KC-135 aircraft. In those tests, the atmospheric pressure and the fuel sample width were varied. Steady flame spread rates and approximate extinction boundaries were determined. Flame images were recorded using video cameras and two-dimensional fuel surface temperature distributions were determined using an IR camera. These results are available, and complement our earlier work in downward spread in partial gravity varying oxygen content. In conjunction with the experiment, three-dimensional models of flame spreading in buoyant flow have been developed. Some of the computed results on upward spreading have been presented. A derivative three-dimensional model of downward spreading has been developed. It is currently being used to evaluate the standard limiting oxygen index (LOI) measuring device and its potential performance in different gravity levels.

Sacksteder, Kurt R.↗
NASA NTRS1975

FORTRAN program for predicting off-design performance of radial-inflow turbines

The FORTRAN IV program uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. The program inputs needed are the design-point requirements and turbine geometry. The output includes performance and velocity-diagram parameters over a range of speed and pressure ratio. Computed performance is compared with the experimental data from two radial-inflow turbines and with the performance calculated by a previous computer program. The flow equations, program listing, and input and output for a sample problem are given.

Wasserbauer, C. A.↗
NASA NTRS1982

Solutions to the equations for corotating magnetospheric convection

The equations of centrifugally driven convection appropriate to a treatment of the transport of Io plasma in Jupiter's magnetosphere are solved for two special cases of the source distribution. The results show that, in the corotating frame of Jupiter, the mass flows outward from the source, forming spirallike streamlines. It is found that the pitch of a spiral depends on the amount of resident mass and the ionospheric conductivity and that the outflow speed depends on the size of the source region, the resident mass, and the source strength of new ions. An example of a wide source and slow outflow is presented. It is noted that, in the limit of a narrow source, the outflow is rapid and the streamlines are nearly radial.

Summers, D.↗
NASA NTRS1984

A two-dimensional analysis of laser heat addition in converging nozzles

The two-dimensional equations of motion describing the interaction between a laser beam and a flowing gas are considered. An implicit numerical scheme is used to solve these equations for unchoked flow through a converging-diverging nozzle. Separate grids are used for the fluid dynamics and the radiation equations. The effects of beam focusing and cross-beam intensity profiles are included. The calculations are based upon real gas properties for all quantities except the gas absorptivity, which is taken as a constant. The solutions contain the expected hot central core region with cool gas near the walls. This results in steep temperature gradients in both the streamwise and cross-stream directions. The absorption zone acts as a blockage in the nozzle causing a nonuniform velocity profile at the inlet and an overall decrease in mass flow. The absorption region also forces the streamlines to move away from the axis of symmetry, although this effect is not strong.

Molvik, G. A.↗
NASA NTRS1984

Finite-analytic numerical method for unsteady two-dimensional Navier-Stokes equations

A finite analytic (FA) numerical solution is developed for unsteady two-dimensional Navier-Stokes equations. The FA method utilizes the analytic solution in a small local element to formulate the algebraic representation of partial differential equations. The combination of linear and exponential functions that satisfy the governing equation is adopted as the boundary function, thereby improving the accuracy of the finite analytic solution. Two flows, one a starting cavity flow and the other a vortex shedding flow behind a rectangular block, are solved by the FA method. The starting square cavity flow is solved for Reynolds number of 400, 1000, and 2000 to show the accuracy and stability of the FA solution. The FA solution for flow over a rectangular block (H x H/4) predicts the Strouhal number for Reynolds numbers of 100 and 500 to be 0.156 and 0.125. Details of the flow patterns are given. In addition to streamlines and vorticity distribution, rest-streamlines are given to illustrate the vortex motion downstream of the block.

Chen, C.-J.↗
NASA NTRS1987

Vortex breakdown simulation based on a nonlinear inviscid model

It is shown that the inviscid equations governing steady axisymmetric flow with swirl, admit solutions with closed streamlines. Results are obtained using two different numerical algorithms. The first is based on a multigrid method for nonlinear eigenvalue problems, while the second is based on a least squares formulation.

Hafez, M. M.↗
NASA NTRS1990

The stability of a three-dimensional laminar boundary layer on a swept flat plate

The linear stability of the laminar boundary layer on a swept flat plate with an imposed favorable pressure gradient was studied utilizing a linear stability model which accounts for streamline curvature for three-dimensional incompressible flows. Calculations were performed for an effective leading-edge sweep angle of 42.5 degrees and freestream velocity of 19 m/s. Computed disturbance amplification rates for the spectrum of amplified frequencies and wavelengths for stationary crossflow vortices were compared with experimental results.

Collier, F. S., Jr.↗
NASA NTRS1990

The stability of a three dimensional laminar boundary layer over a swept flat plate

The linear stability of the laminar boundary layer on a swept flat plate with an imposed favorable pressure gradient was studied utilizing a linear stability model which accounts for streamline curvature for three-dimensional incompressible flows. Calculations were performed for a leading-edge sweep angle of 45 degrees and freestream valocity of 19 m/s. Computed disturbance amplification rates and wavelengths for stationary crossflow vortices were compared with available experimental results.

Mueller, B.↗
NASA NTRS1991

Channeling episodes of Kasei Valles, Mars, and the nature of ridged plains material

The geologic mapping compiled at 1:500,000 scale of the northern Kasei Valles area of Mars (MTMs 25062 and 25067) indicates (1) at least three periods of Kasei Valles channeling, (2) the development of Sacra Fossae (linear depressions on Tempe Terra and Lunae Planum) in relation to Kasei channeling episodes, and (3) the nature of ridged plains material dissected by Kasei Valles on northern Lunae Planum. (The three channeling periods consists of two flood events and a later, sapping related event). These findings suggest hydrologic conditions and processes that formed Kasei Valles and associated features and terrains. It is concluded that an early period of flooding, whose source is perhaps buried beneath lava flows of Tharsis Montes, may have eroded streamlined features in northern Lunae Planum. Also, later floods originating from Echus Chasma formed after the initial flooding and the mesas adjacent to the plateau. The Sacra Fossae formed after the initial flooding and during the second flooding by sapping, outbreak, scarp retreat, and collapse along joints and fractures in ridged plains materials.

Chapman, Mary G.↗
NASA NTRS1994

Turbulent Flow In A Circular-To-Rectangular Transition Duct

NASA technical memorandum describes experiments and analysis of experimental data pertaining to subsonic, turbulent flow of air in duct that includes gradual transition from circular cross section at inlet to rectangular cross section at outlet. Study intended to support further research on physics of flow, by providing comprehensive set of data for calibration and verification of computer codes for simulation of transition-duct flows and mathematical models of turbulence in flows in which effects of curvature of streamlines important.

Davis, David O.↗
NASA NTRS2006

A Landing Gear Noise Reduction Study Based on Computational Simulations

Landing gear is one of the more prominent airframe noise sources. Techniques that diminish gear noise and suppress its radiation to the ground are highly desirable. Using a hybrid computational approach, this paper investigates the noise reduction potential of devices added to a simplified main landing gear model without small scale geometric details. The Ffowcs Williams and Hawkings equation is used to predict the noise at far-field observer locations from surface pressure data provided by unsteady CFD calculations. Because of the simplified nature of the model, most of the flow unsteadiness is restricted to low frequencies. The wheels, gear boxes, and oleo appear to be the primary sources of unsteadiness at these frequencies. The addition of fairings around the gear boxes and wheels, and the attachment of a splitter plate on the downstream side of the oleo significantly reduces the noise over a wide range of frequencies, but a dramatic increase in noise is observed at one frequency. The increased flow velocities, a consequence of the more streamlined bodies, appear to generate extra unsteadiness around other parts giving rise to the additional noise. Nonetheless, the calculations demonstrate the capability of the devices to improve overall landing gear noise.

Khorrami, Mehdi R.↗