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

Partially Averaged Navier Stokes is used tosimulate the flow around a simple train model.The train model has previously been studied inwind tunnel experiments and has a length toheight/width ratio of 7:1. The Reynolds numberbased on the height of the train model is 0.37 x 10^6.For this Reynolds number, the flow separates fromthe curved leading edges on the front then attachesagain on the roof and sides forming a boundarylayer there before separating in the wake. The firstcase is of the natural flow around the train modelwhere direct comparison to experimental data of dragcoefficient and pressure coefficient are made. In thesecond case an open cavity is placed on the baseof the train model with the aim of reducing theoverall drag on the model. The results show that thedrag for model with the cavity is reduced by some10% compared to the drag of the natural case. Theagreement to experimental data for the natural caseis not perfect but the general features in the flow fieldare simulated correctly