Numerical and Experimental Analysis of External Aerodynamic Forces on the Locally Manufactured Outer Body of an FSR Isuzu Bus: Towards Drag Reduction with Roof Fairing and Rear Tail Plate

Abstract

Automotive aerodynamics is a crucial field in the automotive industry, particularly in the design of road vehicles. Buses, which can carry up to 300 passengers, are heavy vehicles with high fuel consumption. Also, now a days fuel economy and emission control are the main problems in the global automotive industry. A way to address this issue involves designing aerodynamically efficient and less fuel-consuming bus are needed. FSR Isuzu truck is a commercial vehicle that is widely used in Ethiopia. It was modified to the FSR Isuzu passenger bus without changing of chassis here in Ethiopia. However, the bus's poor aerodynamic shape, which is rectangular and blunt, leads to increased fuel consumption. This thesis investigates the effect of aerodynamically modifying the exterior body shape by using roof fairing and a rear tail plate to reduce the aerodynamic drag force on the bus. The study involved modeling baseline and modified models using SOLDWORKS and ANSYS workbench 19.2, as well as using a 3D printer to validate numerical results experimentally. The flow behavior around the FSR Isuzu was evaluated and optimized by CFD simulation using of realizable k-ϵ turbulence model with the converted polyhedral mesh. A tail plate at an inclination angle ranging from 100 to 160 at a fixed length of 0.244 m and roof fairing using half of NACA 0012 airfoil at a chord length ranging from 0.5 to 2 m were investigated. The maximum percentage of drag coefficient reduction of 27.56%, 28.87%, and 29.16% at a speed of 60, 80, and 100kmph respectively, was achieved at 0.5 m chord length. As a result, the maximum fuel saved at this chord length was 2.05, 5.06, and 9.88 lit/hr, and carbon dioxide emission saved was 5.18, 12.8, and 25.005 ton/year, respectively. Similarly, the maximum percentage reduction of drag coefficient of 23.88%, 25.20%, and 25.46% at a speed of 60, 80, and 100 kmph respectively achieved at 160 of tail plate inclination. The results showed that the roof fairing using half of the NACA 0012 airfoil on the roof showed better aerodynamic performance than the rear tail plate. This suggests that the roof fairing has the potential to improve the bus's overall efficiency due to its increased ability to reduce drag. Finally, the experimental results showed good agreement with the numerical results.