Numerical prediction of turbulent flow and aerodynamic loading on bluff bodies

Abstract

The effort described in this dissertation led to the development and implementation in a computer code of a hybrid Two-Layer/Large Eddy Simulation (hybrid TL/LES) turbulence model suitable for prediction of flow past and the aerodynamic loading on bluff bodies. The hybrid TL/LES model is based on the Reynolds Averaged Navier-Stokes equation (RANS) in the near wall region and on the Large Eddy Simulation (LES) in the outer region. In the near-wall region, a two-layer model was adopted to allow for a reduction in the number of computational grid points (in the direction normal to the wall) without scarifying the accuracy of the computational results. One-equation model was used to solve for the turbulent kinetic energy. To combine the two-layer model with the LES model, the position of the switching line was automatically established during computations. The hybrid TL/LES model was employed in the unsteady three-dimensional calculations of turbulent flow past a square cylinder, a surface-mounted cube, and the Texas Tech University test building. Overall, a good agreement was found between the hybrid TL/LES predictions and the corresponding experimental data. A comparison of the hybrid TL/LES and the LES results showed that the same level of accuracy could be accomplished with a significantly smaller number of computational (normal to the wall) grid points when the LES model was replaced by the hybrid TL/LES model. Further studies are needed to fully explore potential of the hybrid TL/LES model in practical applications involving separated turbulent flows.