Drag Reduction Of Vehicle Model Using Active Control

Cars consume a lot of fuel,and exhaust gas from cars pollutes the air.As people pay more and more attention to environmental protection and the automobile fuel price rises,how to reduce the fuel consumpthion of automobile becomes a research direction.When a car runs on the road,it consumes fuel because of aerodynamic drag.The pressure difference between the automobile front and back occupies 80% of the aerodynamic resistance.Therefore,it is a very effective method to reduce the fuel consumpthion of automobile by reducing the pressure resistance of automobile.Based on the angle of slant plane,the Ahmed car model can be divide d into low drag and high drag areas.This paper investigated on the 25 degree Ahmed car model and 35 degree Ahmed car model.This paper studied that how to reduce the drag of car by using active control and the mechanism of drag reduction.The main research contents of this paper are:Under the condithion of Reynolds number 1.67 × 10~5,this paper studied the tail flow structure of 35 degree Ahmed car model without control.By calculating the averaged,instantaneous velocity fileds sand vorticity fileds,we got the tail flow structure.Compared with that in other papers,the upper recirculation in this paper is bigger and plays a dominant role in the whole flow filed,and the lower recirculation acts a lesser role.Three actuators were installed in the 35 degree car model.This paper studied the tail flow structure with five control methods.The fisrt method used actuator S1 The second method used actuator S4.The third method used S5.The fourth method used combination of actuator S4 and S5.The fifth method used combination of actuator S1 and actuator S4 and S5.Based on the experimental data,the mechanism of drag reduction by using active control was found by analyzing the relation between changes of flow structure and the drag reduction.Under the condition that the Reynolds number is 1.67 × 10~5,we measured drag reduction of 25 degree Ahmed car model by using combined control of two steady jet actuators.By changing each actuator’s momentum coefficient,we measured maximum drag reduction 19%.And we measure pressure to verify the result of drag reduction.