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In modern Computational Fluid Dynamics (CFD), Direct numerical Simulation (DNS) and Large-Eddy Simulation (LES) are still too computationally expensive for the vast majority of engineering problems. As a result, the combination of low-cost Reynold's Averaged Navier-Stokes (RANS) and LES modeling is at the forefront of modern research. In this thesis, both LES and RANS/LES hybrids were implemented and validated in the codes U2NCLE and Overflow using benchmark problems. The LES models include the Smagorinsky and Wall-Adaptive Local Eddy Viscosity (WALE) models. Validation was performed using the canonical Taylor-Green Vortex (TGV) and Decaying Homogenous Isotropic Turbulence (DHIT) cases where the models were tuned and both the dissipation and wavenumber spectra were analyzed. Upon validation of LES, LES was coupled with the Spalart-Allmaras (SA) and Shear-Stress Transport (SST) RANS models using a series of different functions to blend RANS and LES. These blending functions were calibrated and verified using two common scenarios, namely a zero pressure gradient flat plate and subsonic flow around a cylinder to establish a basis for the future modeling of more complex engineering problems. |
