Optimization of the Aerodynamic Shape and Aero-Acoustic Analysis of a Modified Ground Vehicle Mounted Vortex Generators and Underbody Diffuser Using CFD Simulation

Ground vehicle studies usually aim to reduce fuel consumption by applying special airflow control methods or modifications. The main aim of this project is to improve airflow around, especially the rear region of the body, and apply optimization to drag reduction. This work is relatively unique since the vortex generator (VG) is used as a passive control device by mounting on the slant surface of the body and the rear underbody diffuser is applied with rounded rear edges of the body and optimization is applied by using the genetic algorithm (GA) for all parameters of control devices. The aero-acoustic analysis is also performed using broadband noise source model and acoustic improvement is indicated by comparing baseline and optimized bodies. Few studies investigate all these analyses together in the literature. In this study, an analysis is performed using Computational Fluid Dynamics (CFD) simulation in the Fluent software, and validation is achieved by comparing experimental data reported in the literature. After mounting VGs and making modifications, the CFD solution is repeated using the k–k_L–ω transition turbulence model at 1.39 × 10⁶ and 2.78 × 10⁶ Reynolds numbers. The optimization process is carried out using nine design parameters of the vortex generator and the diffuser. The Central Composite Design (CCD) is used and 147 design points are obtained for the Design of Experiment (DoE). The genetic algorithm is then applied to find optimum design variables for minimizing the drag under specified constraints and airflow conditions. Finally, the results of the investigation of the modified and optimized body revealed that a significant reduction in the drag is achieved at about 13.28 and 19.16% for 1.39 × 10⁶ and 2.78 × 10⁶ Reynolds numbers, respectively, when compared with the baseline body. The results show that the size of the vortex is reduced and its formation on the slant surface is eliminated. In addition, it can be stated that aerodynamic noise is significantly reduced when observing the acoustic power level contours for baseline and optimized bodies.