Improving low-frequency characteristics of recycling/rescaling inflow turbulence generation

For the study of turbulent flows with low-frequency dynamics (e.g. shock-wave/boundary-layer interactions), it is desirable that the inflow turbulence does not contaminate the solution with spurious spatiotemporal correlations introduced by the mechanism of inflow turbulence generation. To investigate the creation and mitigation of these adverse low-frequency effects, large-eddy simulation of a Mach 2.28 boundary layer over an adiabatic flat plate is carried out using a typical recycling/rescaling procedure. Spurious temporal autocorrelations and energy spectral peaks are observed associated with the recycling frequency and its harmonics. Comparisons are made with common "synthetic" turbulence-generation techniques, and improvements to the standard recycling/rescaling procedure are suggested to substantially reduce or eliminate the inherent low-frequency contamination. It is found that by applying a nonconstant reflection or translation operation to the recycled turbulence plane at randomly-distributed time intervals, one is able to maintain realistic turbulence without low-frequency contamination.