The determination of effect of windshield ınclination angle on drag coefficient of a bus model by CFD method

Abstract

This paper focuses on determining of windshield inclination angle to aerodynamic drag coefficient for a 1/64 scaled bus model by Computational Fluid Dynamics (CFD) method. The bus models were designed by using SolidWorks program in 4 different windshield inclination angle (α=0˚, α=15˚, α=30˚, α=45˚). Flow analysis were performed at 15 m/s, 20 m/s, 25 m/s and 30 m/s free flow velocities and between the range of 173000-346000 Reynolds numbers in Fluent® program. To provide geometric similarity 1/64 scaled licensed model bus was used in order to obtain drawing datas. The blockage rate was 3.39% for the kinematic similarity. Reynolds number independence was used to ensure dynamic similarity in study. The effect of windshield inclination angle to drag coefficient was determined by CFD method. The aerodynamic drag coefficients (CD) of the bus models were determined as 0.759 for model 1, 0.731 for model 2, 0.683 for model 3 and 0.623 for model 4. There are 17.92%, 14.84% and 8.76% drag reduction in model 4 which has α=45˚ windshield inclination angle when compared model 1 (α=0˚), model 2 (α=15˚) and model 3 (α=30˚) respectively. 0.4% drag reduction was obtained by increasing every 1 degree of windshield angle. The windshield inclination angle considerably affects drag forces on buses. The distribution of total drag was determined as pressure-friction based. The flow visualizations were obtained and flow structure around of bus models was detected.