Analysis of the Performance of Different V2F Turbulence Models in a Stator Vane Passage Flow

Licentiatavhandling, 2003

When designing the cooling system of modern gas turbines it is important to be able to predict the heat transfer from the hot gas to the walls surrounding the gas path. One flow feature making this rather complicated is the presence of secondary, three-dimensional flow structures, often referred to as horse shoe vortices, which greatly enhance the rate of heat transfer to the endwall, especially in the leading edge region. During the last few years the V2F turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of ad hoc damping functions. The V2F model has also proved to be superior to other RANS methods in many fluid flows where complex flow features are present. In this study numerical simulations of a well documented stator vane passage flow have been performed using different versions of the V2F model. The main objective is to investigate the models' ability to predict the secondary fluid motion in the passage between two stator vanes. The predictions of vane passage flow field using the V2F model agree well with experiments. It is also shown that this model outperform several commonly used two-equation turbulence models. As the stator vane flow involves a large stagnation region controlling the stagnation point anomaly, a characteristic deficiency of eddy-viscosity based turbulence models, becomes very important. Therefore, the effect of the realizability constraint is investigated. It is shown that this constraint has a strong impact on the flow, especially in the stagnation region, and improves the predictions of the secondary flow field.