Simulations of flow around a simplified train model with a drag reducing device

Partially Averaged Navier Stokes is used to simulate the flow around a simple train model. The train model has previously been studied in wind tunnel experiments and has a length to height/width ratio of 7:1. The Reynolds number based on the height of the train model is 0.37 x 10^6. For this Reynolds number, the flow separates from the curved leading edges on the front then attaches again on the roof and sides forming a boundary layer there before separating in the wake. The first case is of the natural flow around the train model where direct comparison to experimental data of drag coefficient and pressure coefficient are made. In the second case an open cavity is placed on the base of the train model with the aim of reducing the overall drag on the model. The results show that the drag for model with the cavity is reduced by some 10% compared to the drag of the natural case. The agreement to experimental data for the natural case is not perfect but the general features in the flow field are simulated correctly.

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