Drag reduction of a bus model by passive flow canal

Abstract

In this study, the drag force of 1/33 scale bus model was improved by passive flow control method. The effect of passive air canal application to drag coefficient was experimentally and numerically investigated on a bus model. Experiments were carried out in the range of 3.8x105 - 7.9x105 Reynolds numbers. The similarity conditions were provided in experimental studies with the exception of the moving road. To provide the geometric similarity condition, the model bus was produced in 3D printer by scanning 3 dimensions. Reynolds number independence was used for dynamic similarity condition. The rate of blockage is 6.81% for kinematic similarity, which is lower than the rate of blockage accepted in the literature. Respectively 4.21%, 7.48% and 12.19% aerodynamic improvement achieved with 1, 3, and 5 passive air canals whose diameter 6 mm. Flow analysis was performed in Fluent® program of the model 3 bus to view the flow structure around the bus. The numerical results support to wind tunnel results. In this study the effect of obtained aerodynamic improvements by applied passive flow control method can decrease fuel consumption about 2-6% at high vehicle speeds.