地面效应对汽车模型气动阻力的影响  

Influence of ground effect on air drag of car model

作　　者：黄志祥[1] 金华[1] 胡兴军[2] 王靖宇[2] 陈立[1] 

机构地区：[1]中国空气动力研究与发展中心空气动力学国家重点试验室,四川绵阳621000 [2]吉林大学汽车仿真与控制国家重点实验室,吉林长春130025

出　　处：《交通运输工程学报》2017年第4期106-112,共7页Journal of Traffic and Transportation Engineering

基　　金：国家自然科学基金项目(11102070);空气动力学国家重点实验室项目(JBKY14010204)

摘　　要：为了获得地面效应对汽车模型气动阻力的影响,在中国空气动力研究与发展中心Φ3.2m风洞对1∶3的MIRA汽车模型进行了风洞试验,采用移动带作为统一的研究平台,研究了地面静止与运动,车轮静止与旋转,以及车身不同离地间隙对气动阻力的影响;模拟了横摆角为0°的无侧风工况,固定试验风速为25m·s^(-1),变雷诺数试验风速为15~26m·s^(-1);仅对汽车模型进行气动力测量,主要关注气动阻力,试验结果以量纲为1的气动阻力系数表示。分析结果表明:当静止地面边界层厚度与车身底面离地间隙之比不大于0.32,且车轮下表面与车身底面离地间隙之比(定义为量纲为1的离地间隙)不大于0.37时,静止地面比运动地面的气动阻力略小,差异小于1.1%,因此,可以忽略地面状态对气动阻力的影响;车轮静止比车轮旋转下的气动阻力略小,差异小于2.1%,因此,在工程应用中,当不能模拟车轮旋转时,应考虑修正(增加)气动阻力,但修正量不宜大于2.1%;随着车轮下表面离地间隙的增加,气动阻力总体呈现逐渐减小的趋势,且在量纲为1的离地间隙为0.069~0.370时,气动阻力差异小于2.0%,因此,在采用移动带开展汽车模型风洞试验时,在确保车轮不与移动带带面接触的情况下,车轮下表面到带面间隙应尽可能小。In order to obtain the influence of ground effect on air drag of car model,for a 1∶3 scaled MIRA car model,a wind tunnel test was carried out inΦ3.2 m wind tunnel in China Aerodynamics Research and Development Center.A moving belt was taken as a unified research platform,and the influence of ground’s fixed and moving states,wheels’ motionless and rotating states,and different clearances of car body to ground plane on air drag was studied.The working condition of no cross wind that yaw angle is 0°was simulated,the fixed test wind velocity was25 m·s-1,and the changing Reynolds number’s test wind velocity was 15-26 m·s-1.The aerodynamic force of car model was only measured,air drag was mainly focused,and the test result was expressed by the dimensionless air drag coefficient.Analysis result shows that when the ratio of boundary layer thickness of fixed ground and the clearance of car bottom to ground is equal to or less than 0.32,the clearance ratio of wheel bottom and body bottom to ground is equalto or less than 0.37,the air drag for fixed ground is less than the value for moving ground,and the difference is less than 1.1%,so the impact of ground state on air drag can be ignored.The air drag for motionless wheel state is less than the value for rotation wheel,and the difference is less than 2.1%.So in the engineering application,when wheel rotation condition can’t be simulated,correcting（increasing）air drag should be considered,but the allowance should be no more than2.1%.With the increase of the clearance from wheel bottom to ground,air drag gradually decreases on the whole,and when the dimensionless clearance is 0.069-0.370,the difference of air drag is less than 2.0%.Thus in the wind tunnel test of car model using the moving belt,the clearance of wheel bottom to belt surface should be as small as possible under ensuring the contactless state of wheel bottom and moving belt surface.

关 键 词：汽车工程 地面效应 风洞试验 汽车模型 气动阻力 离地间隙 

分 类 号：U461.2[机械工程—车辆工程]