Strategy Research On Active Flow Control Of Ahmed Model To Reduce Aerodynamic Drag With Steady Jet

With the continuous development of the automotive technology of our country, coupled with the improvement of the people environmental protection consciousness, our country issued new vehicle fuel consumption national standards of mandatory. When gas flows through the vehicle body, will produce flow separation in the tail of the body.Then will produce a negative pressure area in the tail. Thus result in a larger aerodynamic drag. By means of analyzing the tail vortex structures, the reason of the pressure drag can be known, and the corresponding control measures can be used to reduce the aerodynamic drag. Currently, the most widely used flow control technologies are mainly passive control and active control. Usually the passive control are relatively simple, and the cost is low. Its control measures once selected is generally constant, so it is also called the fixed control. Such as the spoiler and the flow guiding cover. The active control is just opposite with the passive control, its control is dynamic, and can change in real-time, can change with the change of the flow state, achieve the ideal control effect. Usually including synthetic jet technology, steady jet technology, suction, blowdown and other ways.The development of computer technology provides convenience for the study. At the present stage, the numerical simulation technology has become the mainstream and can effectively study the change of the external flow field. It has a short calculation period and cost low. Comparing with the wind tunnel test, there are many conveniences.This paper mainly uses CFD simulation software STAR-CCM+, carry on the simulation research on the tail flow field of the Ahmed model. Firstly, studying the accuracy of the simulation. Then, discussing the drag reduction measures of jet drag reduction. Simulating the tail flow field of the 25°Ahmed model with the method of steady jet and SST k-w turbulence model. Studying the position of each possible drag reduction and finding the best drag reduction conditions at each location, then analyzing the change of the vortex. By controlling the separation vortex of the tail,we can change the body’s pressure. Thereby reducing the pressure resistance of the model, achieve the purpose of reducing resistance.After analyzing each effective location in the tail of the 25°Ahmed model, select the optimal reduction resistance condition of the five effective reducing resistance positions to research on the jet hole shape, increase the discontinuous slot and winglets. Through simulation and calculation, found that the resistance reduction effect applying the continuous slot is best. Mainly because the jet range of the continuous slot is bigger, this can change model tail flow structure to a greater extent. Then the optimal parameters of the five drag reduction conditions are combined, simulate and calculate the combination scheme, found that the combination of test conditions have better drag reduction effect than the single jet slot. So the orthogonal test design method is used to find the optimal drag reduction condition of the combined working conditions, realize the maximum drag reduction of the 25° Ahmed model under the current conditions, and also analyze the structure characteristics and drag reduction mechanism of the optimal drag reduction condition. Through the analysis of 25° Ahmed model, summary the rule of jet drag reduction, provide a certain basis for the drag reduction research of the next 35° Ahmed model.At last, we research the jet drag reduction simulation of 35°Ahmed. the tail flow structure of 35° Ahmed model and 25°Ahmed model is completely different. After the airflow flows through 35° Ahmed model, separate directly the obliquity of the tail. It’s difficult to achieve the drag reduction.Referring to the research on the 25° Ahmed model, select jet slot setting scheme at all possible effective position. By expanding the jet slot distance and jet velocity values, carry on drag reduction analysis on 35° Ahmed model applying stepwise optimization method of drag reduction, found that can achieve better drag reduction, reach more than 6% of the resistance reduction results. Analyzing the structure characteristics and drag reduction mechanism of the optimal drag reduction condition, have more in-depth understanding of the drag reduction method for the active control of jet drag reduction.