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Keller, J. D.

Publications and source records attributed to Keller, J. D..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Use of CYBER 203 and CYBER 205 computers for three-dimensional transonic flow calculations

Experiences are discussed for modifying two three-dimensional transonic flow computer programs (FLO 22 and FLO 27) for use on the CDC CYBER 203 computer system. Both programs were originally written for use on serial machines. Several methods were attempted to optimize the execution of the two programs on the vector machine: leaving the program in a scalar form (i.e., serial computation) with compiler software used to optimize and vectorize the program, vectorizing parts of the existing algorithm in the program, and incorporating a vectorizable algorithm (ZEBRA I or ZEBRA II) in the program. Comparison runs of the programs were made on CDC CYBER 175. CYBER 203, and two pipe CDC CYBER 205 computer systems.

Melson, N. D.↗
NASA NTRS1982

Experiences in using the CYBER 203 for three-dimensional transonic flow calculations

In this paper, the authors report on some of their experiences modifying two three-dimensional transonic flow programs (FLO22 and FLO27) for use on the NASA Langley Research Center CYBER 203. Both of the programs discussed were originally written for use on serial machines. Several methods were attempted to optimize the execution of the two programs on the vector machine, including: (1) leaving the program in a scalar form (i.e., serial computation) with compiler software used to optimize and vectorize the program, (2) vectorizing parts of the existing algorithm in the program, and (3) incorporating a new vectorizable algorithm (ZEBRA I or ZEBRA II) in the program.

Melson, N. D.↗
NASA NTRS1981

Inviscid transonic flow over axisymmetric bodies

Axisymmetric transonic flow is of interest not only because of its practical application to missile and launch vehicle aerodynamics but also because of its relation, in terms of area rule, to fully three dimensional flow. RAXBOD computer program analyzes steady, inviscid, irrotational, transonic flow over axisymmetric bodies in free air. RAXBOD uses finite-difference relaxation method to solve numerically exact formulation of disturbance velocity potential with exact surface boundary conditions. Agreement with available experimental results has been good in cases where viscous effects and wind-tunnel wall interference are not important.

South, J. C., Jr.↗
NASA NTRS1979

Vector processor algorithms for transonic flow calculations

This paper discusses a number of algorithms for solving the transonic full-potential equation in conservative form on a vector computer, such as the CDC STAR-100 or the CRAY-1. Recent research with the 'artificial density' method for transonics has led to development of some new iteration schemes which take advantage of vector-computer architecture without suffering significant loss of convergence rate. Several of these more promising schemes are described and 2-D and 3-D results are shown comparing the computational rates on the STAR and CRAY vector computers, and the CYBER-175 serial computer. Schemes included are: (1) Checkerboard SOR, (2) Checkerboard Leapfrog, (3) odd-even vertical line SOR, and (4) odd-even horizontal line SOR.

South, J. C., Jr.↗
NASA NTRS1978

Preliminary study of the use of the STAR-100 computer for transonic flow calculations

A description is presented for a new explicit algorithm for solving the transonic small-disturbance potential equation on the STAR-100 computer. The STAR computer has a 'pipeline' type of processor which is very efficient in doing arithmetic operations on long vectors. Unfortunately, the successive line over-relaxation method, which represents the best method for solving the considered equation, is not suitable for vector-arithmetic procedures. The described algorithm, however, can be vectorized to make an employment of the STAR-100 possible. It is found that a use of the new algorithm for solving the equation on the STAR-100 computer can almost halve the computer time required for this type of computation when compared to successive line over-relaxation on the CYBER 175 computer.

Keller, J. D.↗
NASA NTRS1977

Preliminary study of the use of the STAR-100 computer for transonic flow calculations

An explicit method for solving the transonic small-disturbance potential equation is presented. This algorithm, which is suitable for the new vector-processor computers such as the CDC STAR-100, is compared to successive line over-relaxation (SLOR) on a simple test problem. The convergence rate of the explicit scheme is slower than that of SLOR, however, the efficiency of the explicit scheme on the STAR-100 computer is sufficient to overcome the slower convergence rate and allow an overall speedup compared to SLOR on the CYBER 175 computer.

Keller, J. D.↗
NASA NTRS1976

RAXBOD: A FORTRAN program for inviscid transonic flow over axisymmetric bodies

A program called RAXBOD is presented for the analysis of steady, inviscid, irrotational, transonic flow over axisymmetric bodies in free air. The method solves the exact equation for the disturbance velocity potential function and applies the exact surface boundary condition. Instructions on program usage and listings of the program and sample cases are given.

Keller, J. D.↗
NASA NTRS1972

Numerical calculation of boundary-induced interference in slotted or perforated wind tunnels including viscous effects in slots

A numerical method is presented for calculating the incompressible boundary-induced interference in wind tunnels of rectangular cross section with slotted or perforated walls. The method includes a wall representation which is capable of satisfying a generalized homogeneous boundary condition including the effects of viscosity within the slots. The effects of viscosity in the slots are found to be very significant. The method allows for a variation in the boundary conditions along the tunnel walls. The model can be any configuration and can be located anywhere in the test section. The interference can be computed at any point in the test section.

Keller, J. D.↗
NASA NTRS1971

A numerical method of calculating the boundary-induced interference in slotted or perforated wind tunnels of rectangular cross section

A numerical method is presented for calculating the boundary-induced interference at subsonic speeds. The wind tunnel slot width or wall porosity can vary throughout the test section. The interference can be computed at any point in the test section. The model can be any configuration and can be located anywhere in the test section. Several examples are given, and comparison is made with other methods where available.

Keller, J. D.↗