风洞结构对试验段静压系数和静压梯度的影响

静压系数和静压梯度是评估汽车风洞试验段流场品质的重要参数.以数值仿真为主,风洞试验为辅的方法研究了风洞结构对试验段静压系数和静压梯度的影响.通过研究发现,使用包含2个拐角的计算模型进行静压系数和静压梯度仿真,可以得到真实的结果.无论是大喷口还是小喷口,收集口高度为270mm时,对应试验段静压系数和静压梯度最平缓,试验段可用长度最长,对试验测量影响最小.对于大喷口,随着收集口高度降低,收集口处静压系数和静压梯度不断下降;当收集口高度为240mm时,靠近收集口处的静压系数和静压梯度变为负值.对于小喷口,收集口面积远大于喷口面积,气流到达收集口的速度有所减少,当地静压系数和静压梯度均为正值.

Influence of Wind Tunnel Structure on Static Pressure Coefficient and Static Pressure Gradient of the Test Section

The static pressure coefficient and static pressure gradient are key parameters to estimate the flow quality of automotive wind tunnel test section. Numerical simulation was used along with wind tunnel test to study the influence of wind tunnel structure on static pressure coefficient and static pressure gradient of the test section. It is found that real results can be obtained by simulation of the static pressure coefficient and static pressure gradient using the computational model with two corners. No matter it is big or small nozzle, the static pressure coefficient and static pressure gradient corresponding to the collector height of 270 mm is the gentlest and the effective length of test section is the longest, which has the slightest impact on measurement. For the big nozzle, the static pressure coefficient and static pressure gradient at the position of collector is decreasing constantly with the reduction of the height of collector. When the height of collector is 240 mm, the static pressure coefficient and static pressure gradient close to the collector becomes negative. For the small nozzle, the area of the collector is much larger than that of the nozzle so that the velocity of airflow at the collector decreases, which contributes to a positive value of the local static pressure coefficient and static pressure gradient.