Aerodynamic analysis of vehicle wheel-housings
Creators: name: Mavuri, Satya
Publisher: name: RMIT University
Year: 2024

description: Aerodynamics has a strong influence on the design of a vehicle. Over half the fuel used by modern passenger is wasted in overcoming aerodynamic drag. Despite intense research into the flow around the upper part of the vehicle, the drag coefficient has plateaued at about 0.3 and further drag reductions will come from the under body including the wheels and associated areas.<br><br>In general, vehicle must operate in the presence of the flow disturbances generated by the rotating wheels inside the wheel-housings. However, research into the effect of wheel-wells on the aerodynamic forces acting on automobiles has been sparse due to the considerable technical difficulties associated with wheels rotating in contact with moving ground plane and experimental complexity involved. Computational Fluid Dynamics (CFD) has not yet reached the level of reliability and confidence where it could be used exclusively as a design tool without performing validating experiments on scale or full-scale models. <br><br>In this work, CFD techniques were used for the parametric study and analysis of wheel-housing geometry of a generic test vehicle due to its potential economic and time saving capabilities. However, to get benchmarking parameters and flow structures in the RMIT Industrial Wind-Tunnel, (which does not have a moving ground or facilities to work with conventional rotating wheels), a simple cost effective double-symmetry method was developed based on the conventional single symmetry wind-tunnel testing technique. Initially the concept was investigated via wind-tunnel experiments and CFD on the Ahmed body. Computed values of aerodynamic drag coefficients were in the range of the experimental values and also showed the same base pattern for tested case. <br><br>Whilst a full car simulation was desirable, a relatively simple two wheeled RMIT body was developed to reproduce front and rear wheel effects and aerodynamics of a normal four wheeled passenger car. A grid optimised CFD model was able to simulate the flow parameters accurately. It was concluded that the double-symmetry concept could provide a solution for some vehicle rotating wheel and moving ground problems with somewhat simple measurement mechanisms in any normal wind-tunnel. However, It was noted that the draw backs include the transient traverse flow across the symmetric plane, the influence of ground boundary layer, sealing the gap around the body and the ground and splitting the test vehicle. <br><br>From the benchmarking flow visualisation on the base body, the complexity of flows involved around the wheel area for both front and rear wheel portions was confirmed. Parametric tests revealed that front wheel-housing is directly affected by the flow impinging onto the wheel and wheel-housing where as the rear wheel-housing is mainly sensitive to the changes in wheel-housing geometry. The results indicate that the structure of wheel-housing aerodynamic flows is more complex than previously thought. Flow structures of the wheel, wheel-housing and the total vehicles show that both front and rear wheel-housing shapes have a significant influence on the aerodynamics of the total vehicle. Thus it can have significant impact on vehicle fuel economy and improved road safety<br>