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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1957

Thin airfoil theory based on approximate solution of the transonic flow equation

A method is presented for the approximate solution of the nonlinear equations transonic flow theory. Solutions are found for two-dimensional flows at a Mach number of 1 and for purely subsonic and purely supersonic flows. Results are obtained in closed analytic form for a large and significant class of nonlifting airfoils. At a Mach number of 1 general expressions are given for the pressure distribution on an airfoil of specified geometry and for the shape of an airfoil having a prescribed pressure distribution. Extensive comparisons are made with available data, particularly for a Mach number of 1, and with existing solutions.

WING-SECTION THEORY↗
NASA NTRS1958

Thin airfoil theory based on approximate solution of the transonic flow equation

A method is presented for the approximate solution of the nonlinear equations of transonic flow theory. Solutions are found for two-dimensional flows at a Mach number of 1 and for purely subsonic and purely supersonic flows. Results are obtained in closed analytic form for a large and significant class of nonlifting airfoils. At a Mach number of 1 general expressions are given for the pressure distribution on an airfoil of specified geometry and for the shape of an airfoil having a prescribed pressure distribution. Extensive comparisons are made with available data, particularly for a Mach number of 1, and with existing solutions.

Spreiter, John R↗
NASA NTRS1989

Rarefied gas flow through two-dimensional nozzles

A kinetic theory analysis is made of the flow of a rarefied gas from one reservoir to another through two-dimensional nozzles with arbitrary curvature. The Boltzmann equation simplified by a model collision integral is solved by means of finite-difference approximations with the discrete ordinate method. The physical space is transformed by a general grid generation technique and the velocity space is transformed to a polar coordinate system. A numerical code is developed which can be applied to any two-dimensional passage of complicated geometry for the flow regimes from free-molecular to slip. Numerical values of flow quantities can be calculated for the entire physical space including both inside the nozzle and in the outside plume. Predictions are made for the case of parallel slots and compared with existing literature data. Also, results for the cases of convergent or divergent slots and two-dimensional nozzles with arbitrary curvature at arbitrary knudsen number are presented.

De Witt, Kenneth J.↗
NASA NTRS1986

A smoke-wire study of low Reynolds number flow over a NASA LRN(1) - 1007 airfoil section

Smoke-filament visualization photographs are presented for two-dimensional flow over a NASA LRN(1) - 1007 airfoil section designed specifically for high-efficiency operation at low chord Reynolds numbers. Results are included for chord Reynolds numbers of 60,000, 100,000, and 220,000 and for angles of attack ranging from 0 to 16 degrees. Two kinds of laminar separation bubble are found to develop in the flow over the airfoil. The sites and characteristics of formation of these bubbles are described, and their dimensional properties are estimated. The transition-to-turbulence Reynolds numbers, surface pressure coefficient distributions, and lift coefficients deduced from the measured coefficients are compared with those obtained by other authors.

Fisher, S. S.↗
NASA NTRS1983

Effect of particle presence on the incompressible inviscid flow through a two dimensional compressor cascade

A computational model for calculating the flow field, in the presence of solid particles, through a two dimensional compressor cascade is presented. The method treats the particle phase in the Lagrangian system and the fluid phase in the Eulerian system. The equations of momentum of the fluid phase are modified to account for the momentum exchange between the two phases. The resulting modified momentum and continuity equations are reduced to the conventional stream function-vorticity formulation. The analysis yields the change in the blade surface pressure distribution, the total pressure and velocity in the flow field. Based on this, it is possible to predict the decrease in compressor performance under the presence of particles.

Balan, C.↗
NASA NTRS1975

Nozzle Free Jet Flows Within the Strong Curved Shock Regime

A study based on inviscid analysis was conducted to examine the flow field produced from a convergent-divergent nozzle when a strong curved shock occurs. It was found that a certain constraint is imposed on the flow solution of the problem which is the unique feature of the flow within this flow regime, and provides the reason why the inverse method of calculation cannot be employed for these problems. An approximate method was developed to calculate the flow field, and results were obtained for two-dimensional flows. Analysis and calculations were performed for flows with axial symmetry. It is shown that under certain conditions, the vorticity generated at the jet boundary may become infinite and the viscous effect becomes important. Under other conditions, the asymptotic free jet height as well as the corresponding shock geometry were determined.

Shih, Tso-Shin↗
NASA NTRS1978

Velocity, temperature, and electrical conductivity profiles in hydrogen-oxygen MHD duct flows

Two-dimensional duct flow computations for radial distributions of velocity, temperature, and electrical conductivity are reported. Calculations were carried out for the flow conditions representative of a hydrogen-oxygen combustion driven MHD duct. Results are presented for: profiles of developing flow in a smooth duct, and for profiles of fully developed pipe flow with a specified streamwise shear stress distribution. The predicted temperature and electrical conductivity profiles for the developing flows compare well with available experimental data.

Greywall, M. S.↗
NASA NTRS1982

Turbulent transport modelling of separating and reattaching shear flows

The improvement of capabilities for computer simulation of turbulent recirculating flows was investigated. Attention has been limited to two dimensional flows and principally to statistically stationary motion. Improvement of turbulence modeling explored the treatment of the near wall sublayer and of the exterior fully turbulent region, working within the framework of turbulence closures requiring the solution of transport equations for the turbulence energy and its dissipation rate. The work on the numerical procedure, based on the Gosman-Pun program TEACH, addressed the problems of incorporating the turbulence model as well as the extension to time dependent flows, the incorporation of a third order approximation of convective transport, and the treatment of non-orthogonal boundaries.

Launder, B. E.↗
NASA NTRS1942

The stability of laminar flow past a sphere

As a contribution to the problem of turbulence on a surface of rotation, the method of small oscillation is applied to the flow past a sphere. It was found that the method developed for two-dimensional flow is applicable without modifications. The frictional layer in the vicinity of the stagnation point of a surface of rotation is less stable against small two-dimensional disturbances than in the stagnation point itself, as proved from an analysis of the velocity distribution made by Homann.

Pretsch, J↗
NASA NTRS1994

Computing Incompressible Flows With Free Surfaces

RIPPLE computer program models transient, two-dimensional flows of incompressible fluids with surface tension on free surfaces of general shape. Surface tension modeled as volume force derived from continuum-surface-force model, giving RIPPLE both robustness and accuracy in modeling surface-tension effects at free surface. Also models wall adhesion effects. Written in FORTRAN 77.

Kothe, D.↗
NASA NTRS1994

Laser interferometer skin-friction measurements of crossing-shock-wave/turbulent-boundary-layer interactions

Wall shear stress measurements beneath crossing-shock-wave/turbulent boundary-layer interactions have been made for three interactions of different strengths. The interactions are generated by two sharp fins at symetric angles of attack mounted on a flat plate. The shear stress measurements were made for fin angles of 7 and 11 deg at Mach 3 and 15 deg at Mach 3.85. The measurements were made using a laser interferometer skin-friction meter, a device that determines the wall shear by optically measuring the time rate of thinning of an oil film placed on the test model surface. Results of the measurements reveal high skin-friction coefficients in the vicinity of the fin/plate junction and the presence of quasi-two-dimensional flow separation on the interaction center line. Additionally, two Navier-Stokes computations, one using a Baldwin-Lomax turbulence model and one using a k-epsilon model, are compared with the experimental results for the Mach 3.85, 15-deg interaction case. Although the k-epsilon model did a reasonable job of predicting the overall trend in portions of the skin-friction distribution, neither computation fully captured the physics of the near-surface flow in this complex interaction.

Garrison, T. J.↗
NASA NTRS1987

Experimental validation of a two-dimensional shear-flow model for determining acoustic impedance

Tests were conducted to validate a two-dimensional shear-flow analytical model for determining the acoustic impedance of a liner test specimen in a grazing-incidence, grazing-flow environment. The tests were limited to a test specimen chosen to exhibit minimal effects of grazing flow so that the results obtained by using the shear-flow analytical model would be expected to match those obtained from normal-incidence impedance measurements. Impedances for both downstream and upstream sound propagation were generally consistent with those from normal-incidence measurements. However, sensitivity of the grazing-incidence impedance to small measurement or systematic errors in propagation constant varied dramatically over the range of test frequencies.

Parrott, Tony L.↗
NASA NTRS1980

An interaction algorithm for prediction of mean and fluctuating velocities in two-dimensional aerodynamic wake flows

A theoretical analysis is presented yielding sets of partial differential equations for determination of turbulent aerodynamic flowfields in the vicinity of an airfoil trailing edge. A four phase interaction algorithm is derived to complete the analysis. Following input, the first computational phase is an elementary viscous corrected two dimensional potential flow solution yielding an estimate of the inviscid-flow induced pressure distribution. Phase C involves solution of the turbulent two dimensional boundary layer equations over the trailing edge, with transition to a two dimensional parabolic Navier-Stokes equation system describing the near-wake merging of the upper and lower surface boundary layers. An iteration provides refinement of the potential flow induced pressure coupling to the viscous flow solutions. The final phase is a complete two dimensional Navier-Stokes analysis of the wake flow in the vicinity of a blunt-bases airfoil. A finite element numerical algorithm is presented which is applicable to solution of all partial differential equation sets of inviscid-viscous aerodynamic interaction algorithm. Numerical results are discussed.

Baker, A. J.↗
NASA NTRS1982

A variational principle for compressible fluid mechanics: Discussion of the multi-dimensional theory

The variational principle for compressible fluid mechanics previously introduced is extended to two dimensional flow. The analysis is stable, exactly conservative, adaptable to coarse or fine grids, and very fast. Solutions for two dimensional problems are included. The excellent behavior and results lend further credence to the variational concept and its applicability to the numerical analysis of complex flow fields.

Prozan, R. J.↗
NASA NTRS1992

Nonequilibrium algebraic turbulence modeling considerations for transonic airfoils and wings

The nonequilibrium algebraic turbulence model of Johnson and King has been applied successfully to both airfoils and wings. However, in wing applications a different expression for the outer 'equilibrium' eddy viscosity has been used because of apparent difficulties in determining the boundary-layer thickness. It is shown in this paper, that this expression does not give eddy viscosity levels for two-dimensional flows that are consistent with Clauser's correlation for equilibrium turbulent boundary layers. And as a consequence, results in inferior predictions when used in airfoil calculations. The objective of this paper is to develop a formulation applicable to wing flows which reduces to the proper form in the two-dimensional case. This necessitates, in part, finding a better way of estimating the boundary-layer thickness from the computed flowfield.

Johnson, D. A.↗
NASA NTRS1986

Three-Dimensional Grids for Flow-Field Calculations

New procedure generates boundary-conforming three-dimensional grids suitable for calculating flow fields around bodies with complex shapes. Extension of earlier methods limited to mapping two-dimensional flow regions onto rectangular grids in transformed planes. Technique also useful in solving thermodynamic and electrostatic fields near complex surfaces.

Thomas, P. D.↗
NASA NTRS1990

Time-accurate Navier-Stokes computations of classical two-dimensional edge tone flow fields

Time-accurate Navier-Stokes computations were performed to study a Class II (acoustic) whistle, the edge tone, and gain knowledge of the vortex-acoustic coupling mechanisms driving production of these tones. Results were obtained by solving the full Navier-Stokes equations for laminar compressible air flow of a two-dimensional jet issuing from a slit interacting with a wedge. Cases considered were determined by varying the distance from the slit to the edge. Flow speed was kept constant at 1750 cm/sec as was the slit thickness of 0.1 cm, corresponding to conditions in the experiments of Brown. Excellent agreement was obtained in all four edge tone stage cases between the present computational results and the experimentally obtained results of Brown. Specific edge tone generated phenomena and further confirmation of certain theories concerning these phenomena were brought to light in this analytical simulation of edge tones.

Liu, B. L.↗