Grid generation criterions in hypersonic aeroheating computations

Three wall normal grid generation criterions in hypersonic aeroheating computations are analyzed, including mean free path (MFP), and cell Reynolds number based on freestream parameters and wall parameters respectively. A wall parameter prediction method is proposed to avoid trial computations when MFP and cell Reynolds number based on wall parameters criterions are used. The proposed method is utilized and combined with different grid generation criterions to generate several grids. A comparison with the experimental data is conducted to test if the wall normal mesh size determined by the grid criterions can satisfy the precision requirement of thermal environment simulation, and also to verify the wall parameter prediction method proposed. Numerical simulations of two-dimensional cylinder with perfect and real gas effects, and three-dimensional blunt bicone are carried out. It can be concluded that the wall parameter prediction method is reliable, the criterion of the cell Reynolds number based on freestream parameters would amplify the wall grid scale with the increase of the freestream temperature, both MFP and cell Reynolds number based on wall parameters are influenced by wall temperature rather than by freestream temperature, and the grid scale determined by these two criterions are consistent and can satisfy the precision requirements of hypersonic aeroheating computations.