Analysis of a Synthetic Turbulence Generation Method for Periodic Configurations

With increasingly available computational resources, scale-resolving simulations are beginning to become affordable for industrially relevant flows in turbomachinery. While full Large Eddy Simulations (LES) may still be out of reach, the combination of Reynolds-Averaged Navier-Stokes (RANS) and LES methods is a promising approach. Both LES and zonal RANS-LES methods require the prescription of resolved velocity fluctuations at the inflow or the RANS-LES interfaces. To save computational resources, the flow in a turbomachinery configuration is usually assumed to be periodic in the spanwise or blade-to-blade directions. Synthetic turbulence generators based on Fourier reconstruction of the fluctuating velocity field using random wave number vectors are, by definition, not periodic in a given direction. This leads to a violation of continuity at periodic boundaries of the computational domain and can, in turn, result in abnormal turbulence statistics downstream. Motivated by this deficiency, a simple correction, which restores periodicity, is proposed and its performance with respect to statistical properties of turbulence such as Reynolds stresses, two-point correlations and energy spectra is evaluated.