An appendage is a boat tail which is installed at the rear section of the passenger car. An inflatable appendage has been developed to reduce the aerodynamic drag experienced by passenger cars. It can be inflated when driving under high-speed conditions and deflated while parking. In this study, an appendage is designed to maintain the streamlined rear body configuration and reduce flow separation. The profile of this aerodynamic device is based on several mathematical curves such as kappa curve, lame curve, catenary curve and aerofoil curve. Four types of boat tailing devices with different lengths and profiles were installed, and computational fluid dynamics (CFD) analysis was performed under moving ground conditions. The primary objective of this study is to find an optimum shape for the appendage and explain the aerodynamic drag reduction mechanism. Comparisons between the base model and modified models were made on the basis of the coefficient of drag, pressure contours, velocity contours, velocity streamlines and pressure distribution plot. It is shown that significant drag reduction can be obtained with the proposed aerodynamic device. Improvement in fuel efficiency varies based on the profile of add-on device. It is shown numerically that the aerodynamic performance is improved by 18.8% compared to the base model. As a result, the fuel consumption of the modified sedan reduces by 4.5%.
Study of Shape Optimization for Aerodynamic Drag Reduction of High-speed train