Setting Up the Mesh

To calculate the drag coefficient of the train as it is subjected to cross-winds at different angles accurately there must be enough cells near to the train, which requires a relatively fine mesh.

You can minimize the total number of cells in the mesh by generating a fine mesh around the train, and having a coarse mesh in the remainder of the fluid domain. Using different mesh densities is a good practice for mesh generation, promoting faster solution convergence, and effective use of processing power. In external aerodynamics cases, it is common to have a high mesh cell count (>1 million cells). However, the mesh generated in this tutorial is much lower to decrease the run-time.