Multi-Block Large-Eddy Simulations of Turbulent Boundary Layers

Abstract

Time-developing turbulent boundary layers over an isothermal flat plate at free-stream Mach numbers of 0.3 and 0.7 are computed using an explicit finite-difference method on structured multi-block grids. The size of each block is adjusted depending on the dimension of the largest structures present locally in the flow. This results in substantial savings of memory and CPU time, compared to standard single-block methods. The near-wall region is computed using a smaller domain, repeated periodically in the spanwise direction. The outer layer, which contains larger structures, is computed using a domain that is twice as wide. Although the flow at the interface between the blocks has a periodicity length determined by the inner-layer block, within a few grid points longer wavelengths are generated. The velocity statistics and rms intensities compare well with single-block calculations that use substantially more grid points.