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A comparison of three-dimensional nonequilibrium solution algorithms applied to hypersonic flows with stiff chemical source termsThree solution algorithms, explicit underrelaxation, point implicit, and lower upper symmetric Gauss-Seidel (LUSGS), are used to compute nonequilibrium flow around the Apollo 4 return capsule at 62 km altitude. By varying the Mach number, the efficiency and robustness of the solution algorithms were tested for different levels of chemical stiffness. The performance of the solution algorithms degraded as the Mach number and stiffness of the flow increased. At Mach 15, 23, and 30, the LUSGS method produces an eight order of magnitude drop in the L2 norm of the energy residual in 1/3 to 1/2 the Cray C-90 computer time as compared to the point implicit and explicit under-relaxation methods. The explicit under-relaxation algorithm experienced convergence difficulties at Mach 23 and above. At Mach 40 the performance of the LUSGS algorithm deteriorates to the point it is out-performed by the point implicit method. The effects of the viscous terms are investigated. Grid dependency questions are explored.
Document ID
19950028587
Document Type
Conference Paper
Authors
Palmer, Grant (NASA Ames Research Center Moffett Field, CA, United States)
Venkatapathy, Ethiraj (Eloret Corp. Palo Alto, CA, United States)
Date Acquired
August 16, 2013
Publication Date
July 6, 1993
Subject Category
AERODYNAMICS
Report/Patent Number
AIAA PAPER 93-2861
Distribution Limits
Public
Copyright
Other