Computational Fluid Dynamics (CFD) Analysis on Aerodynamics of Vehicle

Kwan, Soon Leong (2024) Computational Fluid Dynamics (CFD) Analysis on Aerodynamics of Vehicle. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

In the past, when the availability of fuel was less of an issue, cars were made with a focus on speed and style rather than on aerodynamic stability and fuel efficiency. However, the experts have shifted their attention to designing cars aerodynamically in order to cut fuel consumption as well as minimise pollution due to the crisis in gasoline prices and environmental impacts from exhaust emissions. The poor aerodynamic design produces excessive drag, which raises fuel consumption rates. In this research project, the aerodynamic drag produced at the rear windowsurface of a sedan is studied. Several experiments prove that the occurrence of flow separation at the roof end due to the low velocity of airflow in the boundary layer which will cause a low-pressure region to drag the car backwards. In order to counter this drag issue, the vortex generators at the roof end of the sedan are utilised by Mitsubishi and Honda. However, this approach only reduces minimum drag because the streamwise vortices already produce drag by themselves with turbulence flow. In this research project, the roof ducts idea is created with the theory of slotted flaps used in aircraft. The roof duct is utilised to energise the airflow so that the airflow can stay attached to the rear window or delay the occurrence of flow separation which creates drag. The inlet size of the roof duct, different angles of the inlet side walls of the roof duct and different positions of the roof duct inlet are studied to obtain the best possible results. All the results are obtained and studied numerically by using ANSYS Fluent. Design 2 has the greatest improvement (33.42%) in drag coefficient at the rear window area only of a sedan with optimum inlet size of the roof duct, diverged inlet side walls of the roof duct and optimum positions of the roof duct inlet. In conclusion, these designs are hoped to provide some alternative way for car manufacturers to design more aerodynamic efficient cars and also reduce fuel or energy consumption of vehicles which emit CO2 to the surrounding by reducing aerodynamic drag.