Date of Award
Master of Science (MS)
Increasing the prediction accuracy and computational efficiency of turbulence models at high Reynolds number remains a challenging problem in Computational Fluid Dynamics (CFD). In this paper, several turbulence models are applied for numerical simulation of flow past a circular and a square cylinder at high Reynolds number. Wray-Agarwal (WA) turbulence model is a recently developed one-equation turbulence model derived from k-w closure. Comparisons are made among computational results from WA model, Spalart-Allmaras (SA) model, the shear stress transport SST k-w model and the standard Wilcox k-w model. For circular cylinder, the computations are performed for Reynolds numbers and and simulation for a square cylinder is performed at a Reynolds number .The computed results are assessed against previous simulations and experimental measurements. Both circular and square geometries produce vortex wakes and oscillating lift and drag. According to the results, the new WA model is competitive in accuracy with the two-equation models and has computational efficiency of a one-equation model. Another case of transitional flow past a circular arc is simulated in this thesis. For this case it has been found experimentally that a sharp and sudden increase in lift and decrease in drag occurs at a certain Reynolds number (called the lift and drag crisis). The flow is computed using the Transition SST model, Transition k-kl-ω model and SST k-ω model as well as a laminar flow model for Reynolds numbers slightly below and higher than at which the sharp and sudden increase in both lift and drag is observed. Computations show that the transition models provide results closer to the experimental data. When flow changes from laminar to turbulent close to the critical Reynolds number of , the laminar-turbulent transition is responsible for sudden rise in lift and drag.
David Peters Swami Karunamoorthy