Ahmed Body Drag Coefficient

This example problem demonstrates how to compute the drag coefficient (C_D) for flow over the Ahmed body as a function of Reynold’s number. The Ahmed body is a simplified, vehicle geometry and is a well-known CFD benchmark for vehicle external aerodynamics.¹ This example describes how to calculate the turbulent flow field over the Ahmed body for a range of flow velocities and shows the comparison between Discovery results and experimental data for the drag coefficient. The problem highlights the following features and capabilities:

• Use of an incompressible fluid with k-omega SST turbulence to model fluid flow
• Use of a velocity inlet and pressure outlet to specify a given free stream velocity
• Use of symmetry to reduce the size of the problem domain
• Use of local fidelity to refine the discretization near the Ahmed body and in the wake region
• Use of defined variations to compute drag force as a function of velocity