2002/04/23 by R. S. Sutherland, Ralph S. Sutherland, D. K. Bisset +4
Engineering · Physics and Astronomy · #Astrophysics (astro-ph) #Computational Fluid Dynamics and Aerodynamics #FOS: Physical sciences #Fluid Dynamics and Turbulent Flows #Plasma and Flow Control in Aerodynamics #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0204373
20 pages, 6 figures, revised version submitted to ApJ Supplement Series
arxiv created 2002/04/23 · openalex publication_date 2002/04/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We address a numerical instability that arises in the directionally split computation of hydrodynamic flows when shock fronts are parallel to a grid plane. Transverse oscillations in pressure, density and temperature are produced that are exacerbated by thermal instability when cooling is present, forming post--shock `stripes'. These are orthogonal to the classic post--shock 'ringing' fluctuations. The resulting post--shock `striping' substantially modifies the flow. We discuss three different methods to resolve this problem. These include (1) a method based on artificial viscosity; (2) grid--jittering and (3) a new localized oscillation filter that acts on specific grid cells in the shock front. These methods are tested using a radiative wall shock problem with an embedded shear layer. The artificial viscosity method is unsatisfactory since, while it does reduce post--shock ringing, it does not eliminate the stripes and the excessive shock broadening renders the calculation of cooling inaccurate, resulting in an incorrect shock location. Grid--jittering effectively counteracts striping. However, elsewhere on the grid, the shear layer is unphysically diffused and this is highlighted in an extreme case. The oscillation filter method removes stripes and permits other high velocity gradient regions of the flow to evolve in a physically acceptable manner. It also has the advantage of only acting on a small fraction of the cells in a two or three dimensional simulation and does not significantly impair performance.