The aerodynamic interaction between inverted multi-element wings & rotating wheels in ground effect - A comprehensive investigation

This thesis demonstrates the research conducted to investigate the aerodynamic interaction between an inverted wing of varying spans in ground effect and a rotating wheel in a straight-line, a cornering and a fixed yaw condition. Experimental methods such as Particle Image Velocimetry (PIV) and force-balance measurements were performed to validate the data obtained from Detached Eddy Simulations (DES) that formed the basis of the numerical simulations. During the validation, whilst the flow predictions by the DES k-ω SST and the DES Spalart-Allmaras (S-A) models correlated well with the experimental data for the wing geometry, only the flow prediction from the DES k-ω SST model correlated well for the wheel geometry, and significantly outperformed the DES S-A model.

After the analysis of the wing and wheel geometries in an isolated configuration, placing the two com- ponents together in the straight-line condition revealed a highly complex interaction that was strongly dependent on the wingspan. In all cases, the wing experienced a downforce and drag reduction relative to the isolated configuration, with the wing that fully overlapped the wheel experiencing the largest loss of 35% and 43%, respectively, due to the high pressure on the front face of the wheel impinging onto its surfaces. The modifications to the wheel’s wake topology were ascribed to the introduction of the wing’s endplate vortices and the wing-induced upwash and crossflows, particularly the interaction of these flow features with the wheel’s upper vortices.

The cornering condition led to little change to the wing’s downforce, whilst the drag increased by approximately 10% relative to the straight-line condition. The wake, however, was noticeably modified immediately behind the wheel, with two factors being responsible for this: the freestream crossflow over the wheel that influenced the strength and positioning of the upper wheel vortices, and the changes to the strengths and paths of the endplate vortices. Together with the trajectory of the freestream flow, the wake’s downstream evolution was notably different from a topological and a positional perspective.

The fixed yaw condition was derived from the cornering condition to investigate the validity of ap- proximating the effects of cornering in a wind tunnel environment. It was found that the wing generated very similar downforce and drag levels to the cornering condition, although topological and positional differences in the wheel wake occurred. These were due to the difference in the crossflow over the wheels that led to the different strengths and positioning of the upper wheel vortices, together with the differences in the strengths of the endplate vortices and the trajectory of the freestream flow.