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Tire aerodynamics has long been viewed as a critical area in the ongoing research on vehicle drag reduction as it is a significant contributor to the overall automotive parasitic drag. Previous wind-tunnel experiments have revealed that the flow over a rotating wheel is a very complex phenomenon. This complexity arises from the tire-ground contact patch, various points of flow separation due to the wheel geometry, and the effects of wheel rotation. These aspects make the numerical simulation of this type of flow rather challenging. Existing literature shows a number of ways, like sliding mesh, by which to simulate the flow over an isolated wheel, but the problem of finding an accurate yet cost-effective solution still remains elusive. The current paper attempts to investigate the different methodologies to emulate the wheel motion. In addition, the paper will address the influence of mesh parameters and solver setting dependency of the solution.

Faster turn-around times and cost-effectiveness make the Reynolds Averaged Navier-Stokes (RANS) simulation approach still a widely utilized tool in racecar aerodynamic development, an industry where a large volume of simulations and short development cycles are constantly demanded. However, a well-known flaw of the RANS methodology is its inability to properly characterize the separated and wake flow associated with complex automotive geometries using the existing turbulence models. Experience suggests that this limitation cannot be overcome by simply refining the meshing schemes alone. Some earlier researches have shown that the closure coefficients involved in the RANS turbulence modeling transport equations most times influence the simulation prediction results.

The aerodynamic design optimization of a ground vehicle highly depends on the wake region behind it. Vehicle's wake and its instability have a major contribution to the drag, lift, and side forces experienced by the vehicle. In this paper, we investigate numerically the dynamic characteristics of the wake downstream of a realistic generic car model, DrivAer Fastback, at a Reynolds number of 4.8 million based on the free stream velocity and wheel-base as the characteristic velocity and length scales, respectively. Two methods, Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) are applied to symmetric the 2D plane, taken at the centerline of the geometry, to decompose the unsteady wake to its major dynamic modes. We simulated the flow field using a validated IDDES approach and then applied POD and DMD on the streamwise velocity field.