Numerical Investigation of Road Vehicle Aerodynamics Using the Immersed Boundary RANS Approach

This paper describes the computational results of the flow field around two vehicle geometries using the Immersed Boundary (IB) technique in conjunction with a steady RANS CFD solver. The IB approach allows the computation of the flow around objects without requiring the grid lines to be aligned with the body surfaces. In the IB approach instead of specifying body boundary conditions, a body force is introduced in the governing equations to model the effect of the presence of an object on the flow. This approach reduces the time necessary for meshing and allows utilization of more efficient and fast CFD solvers. The simulations are carried out for an SUV and a pickup truck models at a Reynolds number of 8×10⁵. Cartesian meshes (non-uniform) with local grid refinement are used to increase the resolution close to the boundaries. The simulation results are compared with the existing measurements in terms of surface pressures, velocity profiles, and drag coefficients. The comparisons between the simulation results and the time-averaged measurements revealed that the CFD calculations were able to track the flow trends very well. Furthermore, the CFD simulations predicted the drag coefficients for the SUV and the pickup truck models within 6% of the measured values.