Active Drag Reduction Of A Car Model For Low Drag Regime

Automobile industry in China has been in rapid development due to fast economic growth, which is seen in the increasing of vehicle population. By 2020, vehicle population in our country will beyond 270 million. However, we are still facing kinds of challenge while the industry keeps booming, such as using cost keeps increasing because of the oil’s upward price trend. Therefore, it is very important to work on energy-saving and emission reduction by using aerodynamics.The resistance of automobile includes aerodynamic resistance and rolling friction resistance. The aerodynamic resistance occupies at least 40% of the total resistance and up to 50% for high speed automobile. Saving energy and emission reduction by reducing the aerodynamic drag is a promising way.Blowing, as one of active control method, is an efficient way to reduce the drag of car model. Based on the study of researchers, blowing actuators are implemented to a 0.5 scale Ahmed car model. The effect of blowing actuation on drag coefficients of Ahmed car model is investigated through wind tunnel experiment. The car model that this paper focuses on the Ahmed car model with a rear slant angle of 35°.Firstly, the impact of Reynolds numbers on drag coefficients is studied. And the result is consistent with references. The main contents of this paper are listed as follows.The paper studied the drag coefficients of Ahmed car model under control of a single steady and unsteady blowing actuation with varying momentum coefficient. For each control approach, an optimal momentum coefficient and a maximum drag reduction of Ahmed car model is found. Based on the drag reduction results using a single blowing actuation, several steady and unsteady blowing actuations in different parts are combined together. The relationship between momentum coefficient of blowing actuations and drag coefficient is studied. An optimal control approach is found and drag reduction is up to 11.7%.In order to find the reasons of drag reduction using single blowing and the combine of steady and unsteady blowing, pressure scanning measurement on the rear slant and rear base of Ahmed car model is finished. According to the result of pressure scanning measurement, large pressure recovery both on the rear slant and rear base is found.