ASoftware Toolset for Synthetic Turbulence Generation at Zonal Hybrid RANS/LES Interfaces

At NASA, there is an increased interest in using Computational Fluid Dynamics (CFD) tools to evaluate different aircraft designs and analyze their performance. The commonly used hybrid approaches employing Reynolds Averaged Navier Stokes (RANS) in attached regions and Large Eddy Simulation (LES) in regions of flow unsteadiness and separation, suffers from many issues related to the generation of resolved turbulence at the RANS/LES interface degrading their predictive accuracy. CRAFT Tech proposes to develop an integrated, modular, well-validated software toolset for the generation of acoustically adapted synthetic turbulence to be used in conjunction with any zonal hybrid RANS/LES approaches. This software toolset is envisioned to be a collection of STG approaches that are suited for various CFD codes used by NASA. Due to the artificial nature of the generated turbulence, it may not be entirely possible to avoid propagation of artificial acoustic disturbances from the interface. To address this, the toolset would also include an optional acoustic module than can be used to filter out spurious pressure fluctuations arising from the RANS/LES interface due to the synthetic turbulence generation. Many of the required feature sets for development and testing of the proposed toolset such as hybrid RANS/LES and WMLES turbulence models are already present in CRAFT CFDreg; and CRUNCH CFDreg; multi-physics codes developed and maintained at CRAFT Tech. The modeling capability will provide NASA with the means to efficiently characterize the flow across a RANS/LES interface thus drastically improving the predictive capability of the hybrid method. The toolset will be capable of interfacing with major CFD codes used by NASA such as FUN3D, LAVA, and OpenNCC, among others.