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NASA NTRS1985

Experimental aerodynamic coefficients on a Shuttle-like vehicle at Mach 6 and 10 and comparison to prediction

Aerodynamic coefficients measured for an Orbiter-like configuration are presented for a range of angle of attack from 15 deg to 45 deg at Mach 6 and 10. The low-gamma aspect of a real gas on aerodynamic characteristics and shock detachment distance were simulated by testing this configuration in Mach 6 air (freestream gamma equal to 1.4) and Mach 6 CF4 (freestream gamma equal to 1.17). The effects of Mach number, Reynolds number, and gamma on these measurements are examined and comparisons made to an inviscid flowfield computer code known as HALIS. Pitching-moment coefficients measured in CF4 revealed a nose-up increment when compared with measurements in perfect air, indicative of real-gas effects. In general, the HALIS code accurately predicted the measured aerodynamic coefficients in air and CF4.

Micol, J. R.↗

NASA NTRS1986

Numerical simulation of hypersonic, axisymmetric flowfields

Flow conditions corresponding to those of three previously conducted hypersonic axisymmetric flow experiments are presently treated by numerical solutions of the axisymmetric, thin layer Navier-Stokes equations with the Chemistry and Gasdynamic Implicit computer code's Version 2. While simulation and experimental results agree for ideal gas flows, the simulation for the case of a real gas flow reveals that the particular coupling of the gasdynamics and the chemistry used in the code degrades the convergence level obtainable, by comparison with ideal gas cases. The computed stagnation point heating is 60 percent lower than for the experiment.

Green, M. J.↗

NASA NTRS1987

Peacekeeper tank slosh model

Information on a tank slosh model for Peacekeeper missiles is given in viewgraph form. Allowable vehicle errors for nose cone ejection clearance, vehicle maneuver sloshing problems, slosh/moment prediction, slosh surface specification, code validation, experimental model-computational model comparison and the propellant storage assembly are covered.

Schwartz, Sidney H.↗

NASA NTRS1990

Relative efficiency and accuracy of two Navier-Stokes codes for simulating attached transonic flow over wings

In the present study, two codes which solve the three-dimensional Thin-Layer Navier-Stokes (TLNS) equations are used to compute the steady-state flow for two test cases representing typical finite wings at transonic conditions. Several grids of C-O topology and varying point densities are used. After a description of each code and test case, standards for determining code efficiency and accuracy are defined and applied to determine the relative performance of the two codes in predicting turbulent transonic wing flows. Comparisons of computed surface pressure distributions with experimental data are made.

Bonhaus, Daryl L.↗

NASA NTRS1991

Relative efficiency and accuracy of two Navier-Stokes codes for simulating attached transonic flow over wings

Two codes which solve the 3-D Thin Layer Navier-Stokes (TLNS) equations are used to compute the steady state flow for two test cases representing typical finite wings at transonic conditions. Several grids of C-O topology and varying point densities are used to determine the effects of grid refinement. After a description of each code and test case, standards for determining code efficiency and accuracy are defined and applied to determine the relative performance of the two codes in predicting turbulent transonic wing flows. Comparisons of computed surface pressure distributions with experimental data are made.

Bonhaus, Daryl L.↗

NASA NTRS1991

Flowfield computations and comparison with Shuttle aerodynamic data

An in-house developed flow solver, E3D, has been applied to investigate the flow field around the Shuttle Orbiter over an angle-of-attack range of 0 deg to 60 deg at Mach 3.5 and 10.0. The 3D Euler equations are integrated by means of a time-marching finite-volume shock-capturing method, based on cell-centered and upwind evaluation of the cell face fluxes with van Leer or Roe's flux-splitting techniques. A comparison of CFD, wind tunnel, and aeronautical data base is presented. Solutions are in very good agreement with available experimental data. Through the comparisons, it is demonstrated that the E3D code is capable of evaluating total aerodynamic performance.

Ma, E. C.↗

NASA NTRS1992

Computation of H2/air reacting flowfields in drag-reduction external combustion

Numerical simulation and analysis of the solution are presented for a laminar reacting flowfield of air and hydrogen in the case of an external combustion employed to reduce base drag in hypersonic vehicles operating at transonic speeds. The flowfield consists of a transonic air stream at a Mach number of 1.26, and a sonic transverse hydrogen injection along a row of 26 orifices. Self-sustained combustion is computed over an expansion ramp downstream of the injection and a flameholder, using the recently developed RPLUS code. Measured data is available only for surface pressure distributions, and is used for validation of the code in practical 3D reacting flowfields. Pressure comparison shows generally good agreements and the main effects of combustion are also qualitatively consistent with experiment.

Lai, H. T.↗

NASA NTRS1992

Computation of H2/air reacting flowfields in drag-reduction external combustion

Numerical simulation and analysis of the solution are presented for a laminar reacting flowfield of air and hydrogen in the case of external combustion employed to reduce base drag in hypersonic vehicles operating at transonic speeds. The flowfield consists of a transonic air stream at a Mach number of 1.26 and a sonic transverse hydrogen injection along a row of 26 orifices. Self-sustained combustion is computed over an expansion ramp downstream of the injection and a flameholder, using the recently developed RPLUS code. Measured data is available only for surface pressure distributions and is used for validation of the code in practical 3D reacting flowfields. Pressure comparison shows generally good agreements, and the main effects of combustion are also qualitatively consistent with experiment.

Lai, H. T.↗

NASA NTRS1993

LinAir: A multi-element discrete vortex Weissinger aerodynamic prediction method

LinAir is a vortex lattice aerodynamic prediction method similar to Weissinger's extended lifting-line theory, except that the circulation around a wing is represented by discrete horseshoe vortices, not a continuous distribution of vorticity. The program calculates subsonic longitudinal and lateral/directional aerodynamic forces and moments for arbitrary aircraft geometries. It was originally written by Dr. Ilan Kroo of Stanford University, and subsequently modified by the author to simplify modeling of complex configurations. The Polhamus leading-edge suction analogy was added by the author to extend the range of applicability of LinAir to low aspect ratio (i.e., fighter-type) configurations. A brief discussion of the theory of LinAir is presented, and details on how to run the program are given along with some comparisons with experimental data to validate the code. Example input and output files are given in the appendices to aid in understanding the program and its use. This version of LinAir runs in the VAX/VMS, Cray UNICOS, and Silicon Graphics Iris workstation environments at the time of this writing.

Durston, Donald A.↗

NASA NTRS1993

Solution of mixed convection heat transfer from isothermal in-line fins

Transient and steady state combined natural and forced convective flows over two in-line finite thickness fins (louvers) in a vertical channel are numerically solved using two methods. The first method of solution is based on the 'Simple Arbitrary Lagrangian Eulerian' (SALE) technique which incorporates mainly two computational phases: (1) a Lagrangian phase in which the velocity field is updated by the effects of all forces, and (2) an Eulerian phase that executes all advective fluxes of mass, momentum and energy. The second method of solution uses the finite element code entitled FIDAP. In the first part, comparison of the results by FIDAP, SALE, and available experimental work were done and discussed for steady state forced convection over louvered fins. Good agreements were deduced between the three sets of results especially for the flow over a single fin. In the second part and in the absence of experimental literature, the numerical predictions were extended to the transient transports and to the opposing flow where pressure drop is reversed. Results are presented and discussed for heat transfer and pressure drop in assisting and opposing mixed convection flows.

Khalilollahi, Amir↗

NASA NTRS1994

Navier-Stokes and potential theory solutions for ahelicopter fuselage and comparison with experiment

A thin-layer Navier-Stokes code and a panel method code are used to predict the flow over a generic helicopter fuselage. The computational results are compared with pressure data at four experimental conditions. Both methods produce results that agree with the experimental pressure data. However, separation patterns and other viscous flow features from the Navier-Stokes code solution are shown that cannot be easily modeled with the panel method.

Chaffin, Mark S.↗

NASA NTRS1995

Advanced high area ratio nozzles

The objective is to develop computational techniques for the design of high-area-ratio nozzles and to validate these models by comparison with experiments and computations using other codes. Progress was made in two areas during the past year. First, performance computations were added to the PARC2D code and the performance of the SSME nozzle was computed for inviscid, laminar and turbulent flow assuming a perfect gas with gamma = 1.2. Second, the PARC2D code was modified in a non-CASP project to compute equilibrium flow about hypersonic blunt bodies. Progress has been made toward modifying this code to compute equilibrium H2/O2 flow through the SSME and related nozzles.

Raiszadeh, Farhad↗

NASA NTRS1989

Advanced high area ratio nozzles

The objective is to develop computational techniques for the design of high-area-ratio nozzles and to validate these models by comparison with experiments and computations using other codes. Performance computations were added to the PARC2D code and the performance of the space shuttle main engine (SSME) nozzle was computed for inviscid, laminar and turbulent flow assuming a perfect gas with gamma = 1.2. The PARC2D code was modified in a non-CASP (Center for Advanced Space Propulsion) project to compute equilibrium flow about hypersonic blunt bodies. Progress has been made toward modifying this code to compute equilibrium H2/O2 flow through the SSME and related nozzles.

Raiszadeh, Farhad↗

NASA NTRS2001

Numerical Investigation of Radiative Heat Transfer in Laser Induced Air Plasmas

Radiative heat transfer is one of the most important phenomena in the laser induced plasmas. This study is intended to develop accurate and efficient methods for predicting laser radiation absorption and plasma radiative heat transfer, and investigate the plasma radiation effects in laser propelled vehicles. To model laser radiation absorption, a ray tracing method along with the Beer's law is adopted. To solve the radiative transfer equation in the air plasmas, the discrete transfer method (DTM) is selected and explained. The air plasma radiative properties are predicted by the LORAN code. To validate the present nonequilibrium radiation model, several benchmark problems are examined and the present results are found to match the available solutions. To investigate the effects of plasma radiation in laser propelled vehicles, the present radiation code is coupled into a plasma aerodynamics code and a selected problem is considered. Comparisons of results at different cases show that plasma radiation plays a role of cooling plasma and it lowers the plasma temperature by about 10%. This change in temperature also results in a reduction of the coupling coefficient by about 10-20%. The present study indicates that plasma radiation modeling is very important for accurate modeling of aerodynamics in a laser propelled vehicle.

Liu, J.↗

NASA NTRS2001

Simulation of Supersonic Jet Noise with the Adaptation of Overflow CFD Code and Kirchhoff Surface Integral

An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow field are modeled with the aid of Spalart-Allmaras one-equation turbulence model. Appropriate acoustic and outflow boundary conditions were implemented to compute time-dependent acoustic pressure in the nonlinear source-field. Based on the specification of acoustic pressure, its temporal and normal derivatives on the Kirchhoff surface, the near-field and the far-field sound pressure levels are computed via Kirchhoff surface integral, with the Kirchhoff surface chosen to enclose the nonlinear sound source region described by the CFD code. The methods are validated by a comparison of the predictions of sound pressure levels with the available data for an axisymmetric turbulent supersonic (Mach 2) perfectly expanded jet.

Kandula, Max↗

NASA NTRS2002

Simulation of Jet Noise with OVERFLOW CFD Code and Kirchhoff Surface Integral

Kandula, M.↗

NASA NTRS1995

A Green's function method for heavy ion beam transport

The use of Green's function has played a fundamental role in transport calculations for high-charge high-energy (HZE) ions. Two recent developments have greatly advanced the practical aspects of implementation of these methods. The first was the formulation of a closed-form solution as a multiple fragmentation perturbation series. The second was the effective summation of the closed-form solution through nonperturbative techniques. The nonperturbative methods have been recently extended to an inhomogeneous, two-layer transport media to simulate the lead scattering foil present in the Lawrence Berkeley Laboratories (LBL) biomedical beam line used for cancer therapy. Such inhomogeneous codes are necessary for astronaut shielding in space. The transport codes utilize the Langley Research Center atomic and nuclear database. Transport code and database evaluation are performed by comparison with experiments performed at the LBL Bevalac facility using 670 A MeV 20Ne and 600 A MeV 56Fe ion beams. The comparison with a time-of-flight and delta E detector measurement for the 20Ne beam and the plastic nuclear track detectors for 56Fe show agreement up to 35%-40% in water and aluminium targets, respectively.

NASA Discipline Radiation Health↗

NASA NTRS2008

Rotorcraft Technology for HALE Aeroelastic Analysis

Much of technology needed for analysis of HALE nonlinear aeroelastic problems is available from rotorcraft methodologies. Consequence of similarities in operating environment and aerodynamic surface configuration. Technology available - theory developed, validated by comparison with test data, incorporated into rotorcraft codes. High subsonic to transonic rotor speed, low to moderate Reynolds number. Structural and aerodynamic models for high aspect-ratio wings and propeller blades. Dynamic and aerodynamic interaction of wing/airframe and propellers. Large deflections, arbitrary planform. Steady state flight, maneuvers and response to turbulence. Linearized state space models. This technology has not been extensively applied to HALE configurations. Correlation with measured HALE performance and behavior required before can rely on tools.

Young, Larry↗