• 대한기계학회논문집B
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• 제27권8호
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• pp.1122-1133
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• 2003

Numerical characteristics of implicit upwind schemes, such as upwind ADI, line Gauss-Seidel (LGS) and point Gauss-Seidel (LU) algorithms, for Navier-Stokes equations have been investigated. Time-derivative preconditioning method was applied for efficient convergence at low Mach/Reynolds number regime as well as at large grid aspect ratios. All the algorithms were expressed in approximate factorization form and von Neumann stability analysis was performed to identify stability characteristics of the above algorithms in the presence of high grid aspect ratios. Stability analysis showed that for high aspect ratio computations, the ADI and LGS algorithms showed efficient damping effect up to moderate aspect ratio if we adopt viscous preconditioning based on min-CFL/max-VNN time-step definition. The LU algorithm, on the other hand, showed serious deterioration in stability characteristics as the grid aspect ratio increases. Computations for several practical applications also verified these results.

• 대한기계학회논문집B
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• 제25권3호
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• pp.322-329
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• 2001

A study of the shock wave turbulent boundary layer interaction is presented. The focus of the study is the interactions of the shock waves with the turbulent boundary layer on the falt plate. Three examples are investigated. The computations are performed, using mixed explicit-implicit generalized Galerkin finite element method. The linear equations at each time step are solved by a preconditioned GMRES algorithm. Numerical results indicate that the implicit scheme converges to the asymptotic steady state much faster than the explicit counterpart. The computed surface pressures and skin friction coefficients display good agreement with experimental data. The flowfield manifests a complex shock wave system and a pair of counter-rotating vortices.