Multi-block large-eddy simulations of turbulent boundary layers

Time-developing turbulent boundary layers over an isothermal flat plate at freestream Mach numbers of 0.3 and 0.7 are computed using an explicit finit e-difference method on structured multi-block grids. The size of each block is adjusted depending on the dimension of the largest structures present l ocally in the flow. This alleviates the cost of calculations in which the w all layer is resolved, and may result in substantial savings of memory and CPU time, if several layers are used. In the calculations presented the nea r-wall region is computed using a domain with a spanwise length L-o(+) = 82 0, which is sufficient to contain several streaks. This grid block is repea ted periodically in the spanwise direction. The outer layer, which contains larger structures, is computed using a domain that is twice as wide (L-o() = 1640). Although the flow at the interface between the blocks has a peri odicity length determined by the inner-layer block, within a few grid point s longer wavelengths are generated. The velocity statistics and rms intensi ties compare well with single-block calculations that use substantially mor e grid points. (C) 2000 Academic Press.