The effects of Reynolds number, blockage and boundary layer in automotive wind tunnel tests are analyzed with some conclusions drawn. First, when scaled model is uased, the aerodynamic force measured will be affected by Reynolds number. Too low a Reynolds number will get a measured drag value 1% -2% larger than real one, and further lower Reynolds number may even change the patterns of local flow. Second, limited space of wind tunnel definitely produces blockage effects, which will affect the measurements of aerodynamic forces and ref-erence wind speed, yet can be corrected through suitable empirical methods and calibration procedure. Finally,boundary layer generated by the fixed floor of wind tunnel may disturb the flow characteristies especially under the vehicle and around the wheels. Without any control over boundary layer, the measured drag force will be smaller than the actual one, while the lift force will be larger. And the deviation will increase with the reduction in vehicle ground clearance. Thus, it is necessary to adopt reasonable control schemes to reduce the boundary layer effects on aerodynamic force measurements.%对汽车风洞试验中的雷诺数、阻塞和边界层效应进行了分析并得出若干结论:首先,采用缩比模型时,雷诺数将对气动力测量产生影响,雷诺数过低通常会使阻力系数测量值偏大约1%～2%,而更低的局部雷诺数甚至会改变局部气流特性;其次,有限的风洞尺寸必然产生阻塞效应,它影响气动力和试验参考风速的测量,但可以通过适当的经验方法和合理的标定程序进行修正;最后,风洞固定地板产生的边界层会干扰车辆底部和车轮附近的气流.如果没有任何边界层控制措施,气动阻力测量值会偏小,而升力测量值偏大;且底盘越低误差越大,因此须采取合理的控制方案以降低边界层对气动力测量的影响.
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