Flow Characteristics Based on The With and Without of Spoilers for Passenger Cars Using CFD and Wind Tunnel Experiments

This study was conducted to improve the aerodynamic characteristics of passenger cars, which are essential for enhancing fuel efficiency and driving stability.The research analyses the flow characteristics around a vehicle with and without a spoiler.A CFD(Computational Fluid Dynamics) analysis and a scaled-down wind tunnel experimental setup were designed and utilized to achieve this.The models used in this study were commercialized "A" vehicles from manufacturer H, with and without spoilers.The simulations used Star-CCM+, employing the SST - turbulence model.The CFD analysis results revealed that the spoiler significantly affected the airflow's separation point and flow direction passing over the vehicle's upper body.For the base model (without a spoiler), the flow was directed towards the ground at 13.5 .However, The angle of the N model (with a spoiler) was reduced to 3.5 .This change led to increased airflow velocity under the vehicle and a corresponding rise in downforce.Compared to the base model, the CFD analysis showed that the spoiler model exhibited a 0.2% increase in drag coefficient and a 10.1% increase in lift coefficient.The pitch moment was also reduced by 14.4%, indicating improved vehicle stability.The results from the scaled-down wind tunnel experiments, although differing in magnitude, showed trends consistent with the CFD simulations.Specifically, the lift coefficient( ) increase was more pronounced than the drag coefficient( ) increase in both cases.By operating the wind tunnel at dynamically scaled speeds, the flow pattern changes observed in the experiments were similar to those in the CFD analysis.This study demonstrates that spoilers can significantly enhance downforce and vehicle stability without substantially increasing aerodynamic resistance.The findings can serve as fundamental data for product design and analysis in the automotive tuning market and for simplified wind tunnel testing.