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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Discrete models for the numerical analysis of time-dependent multidimensional gas dynamics

A possible technique is explored for extending to multidimensional flows some of the upwind-differencing methods that are highly successful in the one-dimensional case. Emphasis is on the two-dimensional case, and the flow domain is assumed to be divided into polygonal computational elements. Inside each element, the flow is represented by a local superposition of elementary solutions consisting of plane waves not necessarily aligned with the element boundaries.

Roe, P. L.↗
NASA NTRS1986

A numerical analysis applied to high angle of attack three-dimensional inlets

The three-dimensional analytical methods used to analyze subsonic high angle of attack inlets are described. The methods are shown to be in good agreement with experimental results for various three-dimensional high angle of attack inlets. The methods are used to predict aerodynamic characteristics of scarf and slotted-lip inlets.

Hwang, D. P.↗
NASA NTRS1987

Numerical analysis of a NACA0012 airfoil with leading edge ice accretions

Analysis of a NACA0012 airfoil with leading edge ice has been performed using a Navier-Stokes code coupled with a grid generation code. The computed results were compared to experimental information obtained for an airfoil with a well defined artificial ice shape. The computations were performed at angles of attack ranging from zero to ten degrees. This range is sufficient to show the development of the separation bubble aft of the ice shape on both the upper and lower surfaces. Velocity profile plots in the separation bubble are examined in order to determine if recirculation patterns are predicted properly and if separation and reattachment points are found within the resolution of the experimental information. Also, the massive separation near the point of stall is examined in order to more accurately evaluate the lift coefficient curve in that region. Lift, drag, and moment coefficients are computed and compared to experiment.

Potapczuk, Mark G.↗
NASA NTRS1987

Numerical analysis of flow through scramjet engine inlets

A set of computer programs has been developed to analyze flow through supersonic combustion ramjet (scramjet) inlets. These programs solve either the two- or three-dimensional Euler/Navier-Stokes equations in full conservation form by MacCormack's explicit or explicit-implicit method. An algebraic two-layer eddy viscosity model is used for turbulent flow calculations. The programs are operational on Control Data CYBER-200 series vector-processing computer system and have been optimized to take maximum advantage of the vector processing capability of the system. Since their development, the programs have been extensively verified and used to analyze a number of very complex inlet configurations. In this paper, results are presented from two-dimensional, quasi-three-dimensional, and three-dimensional analyses of the inlet flow field to illustrate the use of the programs.

Kumar, Ajay↗
NASA NTRS1987

A multidomain and multidimensional numerical analysis of flow in fuelside preburner, high pressure turbine, hot gas manifold and main injector assembly of the Space Shuttle main engine

The Space Shuttle Main Engine (SSME) consists of a large number of critical components each serving a special purpose. Any design change in one of these components not only alters its performance but also the performance of the ones in the upstream and in the downstream. To evaluate the effects of such a design change on the flow fields and on SSME's overall performance a multidomain and multidimensional analytical procedure has been developed and applied here to the series of components on the fuel side of the SSME. The results obtained from the multidomain analysis and their comparison with the single-domain solution when the SSME is operating at Full Power Load indicates that the multidomain model shows greater realism. It is concluded that this modeling technique would assist the designer significantly to achieve still higher performance levels of the SSME.

Mukerjee, T.↗
NASA NTRS1988

Numerical Analysis Of Interlaminar-Fracture Toughness

Finite-element analysis applied in conjunction with strain-energy and micromechanical concepts. Computational procedure involves local, local-crack-closure, and/or the "unique" local-crack-closure method developed at NASA Lewis Research Center, for mathematical modeling of ENF and MMF. Methods based on three-dimensional finite-element analysis in conjunction with concept of strain-energy-release rate and with micromechanics of composite materials. Assists in interpretation of ENF and MMF fracture tests performed to obtain fracture-toughness parameters, by enabling evaluation of states of stress likely to induce interlaminar fractures.

Chamis, C. C.↗
NASA NTRS1987

Numerical analysis of flow through scramjet engine inlets

A set of computer programs was developed to analyze flow through supersonic combustion ramjet (scramjet) inlets. These programs solve either the two or three dimensional Euler/Navier-Stokes equations in full conservation form by MacCormack's explicit or explicit-implicit method. An algebraic two-layer eddy viscosity model is used for turbulent flow calculations. The programs are operational in Control Data CYBER-200 series vector-processing computer system and were optimized to take maximum advantage of the vector processing capability of the system. Since their development, the programs were extensively verified and used to analyze a number of very complex inlet configurations. Results are presented from two-dimensional, quasi-three-dimensional, and three-dimensional analyses of the inlet flow field to illustrate the use of the program.

Kumar, Ajay↗
NASA NTRS1988

Numerical analysis of three-dimensional viscous internal flows

A 3-D Navier-Stokes code has been developed for analysis of turbomachinery blade rows and other internal flows. The Navier-Stokes equations are written in a Cartesian coordinate system rotating about the x-axis, and then mapped to a general body-fitted coordinate system. Streamwise viscous terms are neglected using the thin-layer assumption, and turbulence effects are modeled using the Baldwin-Lomax turbulence model. The equations are discretized using finite differences on stacked C-type grids and are solved using a multistage Runge-Kutta algorithm with a spatially-varying time step and implicit residual smoothing. Calculations have been made of a horseshoe vortex formed in front of a flat plate with a round leading edge standing in a turbulent endwall boundary layer. Comparisons are made with experimental data taken by Eckerle and Langston for a circular cylinder under similar conditions. Computer and measured results are compared in terms of endwall flow visualization pictures and total pressure loss contours and vector plots on the symmetry plane. Calculated details of the primary vortex show excellent agreement with the experimental data. The calculations also show a small secondary vortex not seen experimentally.

Chima, Rodrick V.↗
NASA NTRS1988

Numerical analysis of pulse facility transient flow through a supersonic combustion model

The supersonic high enthalpy flow from a shock tunnel facility flowing through a two-dimensional duct simulating a combustor has been computed for two test conditions for both steady and transient inflow. The nominal test conditions had stagnation enthalpies of 4.3 and 12.1 MJ/kg, with corresponding flight Mach numbers of 9 and 16, respectively. A full Navier-Stokes code (SPARK) was used to compute the flow development and the mixing of a hydrogen jet injected from the base of a central strut. Results of the calculations are presented and compared with wall pressure data. Additional comparisons of the transient and steady inflow results are presented to assess the effect of transient flow on the data. This paper presents a status of the progress in applying CFD codes to analyze the transient flow from a pulse facility.

Rogers, R. Clayton↗
NASA NTRS1988

Numerical analysis of three-dimensional viscous internal flows

A 3-D Navier-Stokes code has been developed for analysis of turbomachinery blade rows and other internal flows. The Navier-Stokes equations are written in a Cartesian coordinate system rotating about the x-axis, and then mapped to a general body-fitted coordinate system. Streamwise viscous terms are neglected using the thin-layer assumption, and turbulence effects are modeled using the Baldwin-Lomax turbulence model. The equations are discretized using finite differences on stacked C-type grids and are solved using a multistage Runge-Kutta algorithm with a spatially-varying time step and implicit residual smoothing. Calculations have been made of a horseshoe vortex formed in front of a flat plate with a round leading edge standing in a turbulent endwall boundary layer. Comparisons are made with experimental data taken by Eckerle and Langston for a circular cylinder under similar conditions. Computer and measured results are compared in terms of endwall flow visualization pictures and total pressure loss contours and vector plots on the symmetry plane. Calculated details of the primary vortex show excellent agreement with the experimental data. The calculations also show a small secondary vortex not seen experimentally.

Chima, Rodrick V.↗
NASA NTRS1989

Numerical analysis of flow about a total temperature sensor

The unsteady flowfield about an airfoil-shaped inlet temperature sensor has been investigated using the thin-layer and full Navier-Stokes equations. A finite-volume formulation of the governing equations was used in conjunction with a Runge-Kutta time stepping scheme to analyze the flow about the sensor. Flow characteristics for this configuration were established at Mach numbers of 0.5 and 0.8 for different Reynolds numbers. The results were obtained for configurations of increasing complexity; important physical phenomena such as shock formation, boundary-layer separation, and unsteady wake formation were noted. Based on the computational results, recommendations for further study and refinement of the inlet temperature sensor were made.

Von Lavante, Ernst↗
NASA NTRS1989

A numerical analysis of the effects of conjugate heat transfer, vapor compressibility, and viscous dissipation in heat pipes

The effects of conjugate heat transfer, vapor compressibility, and viscous dissipation in heat pipes are discussed. The accuracy of the partially parabolic versus the elliptic presentation of the governing equations is also examined. The results show that the axial wall conduction has a tendency to make the temperature distribution more uniform for heat pipes with large ratios of pipe wall to effective liquid-wick thermal conductivity. The compressible and incompressible models show very close agreement for the total pressure drop, while the local pressure variations along the heat pipe are quite different for these two models when the radial Reynolds number at the interface is high.

Faghri, Amir↗
NASA NTRS1991

Numerical analysis of ignition transients in solid rocket motors

A model to analyze the unstready multidimensional turbulent flow in the head-end, star slot section of a solid rocket motor during the ignition transient is developed. The present paper examines the fluid dynamic aspects of the starting transient. A finite-difference solution of the unsteady, compressible, full Navier-Stokes equations, together with a two-equation k-epsilon turbulence model, is obtained utilizing the MacCormack explicit, predictor-corrector technique. Computed results for the flow in the slot are compared with experimental data obtained in cold flow tests of a scaled model of the Space Shuttle SRM head-end, star grain section. The agreement between the calculated flowfield and existing experimental data is very good.

Ciucci, A.↗
NASA NTRS1991

Numerical analysis and simulation of an assured crew return vehicle flow field

A lifting body was proposed as a candidate for the Assured Crew Return Vehicle (ACRV) which will serve as a crew rescue vehicle for the Space Station Freedom. The focus is on body surface definition, both surface and volume grid definition, and the computation of inviscid flow fields about the vehicle at wind tunnel conditions. Very good agreement is shown between the computed aerodynamic characteristics of the vehicle at M(sub infinity) = 10 and those measured in wind tunnel tests at high Reynolds numbers.

Weilmuenster, K. James↗
NASA NTRS1992

Numerical analysis of the Iosipescu specimen for composite materials

A finite element analysis of the Iosipescu shear tests for unidirectional and cross-ply composites is presented. It is shown that an iterative analysis procedure must be used to model the fixture-specimen kinematics. The correction factors which are needed to compensate for the nonuniformity of stress distribution in calculating shear modulus are shown to be dependent on the material orthotropic ratio and the finite element loading models. Test section strain distributions representative of typical graphite-epoxy specimens are also presented.

Ho, H.↗