两并列矩形柱绕流的PIV试验研究

PIV experimental study on flow around two parallelized rectangular columns

利用PIV流速测量技术,在一定的流量下,通过改变两并列矩形柱的间距比D/B,对矩形柱的绕流特性进行了试验研究。结果表明:D/B在1.3~1.4之间存在一个临界值,大于和小于该临界值时两矩形柱开缝下方所形成的漩涡个数、形态及紊动强度等都有较大的差异;随着D/B的增大,两矩形柱间开缝出口断面和矩形柱与水槽边壁之间的断面流速变化较复杂,但两断面的单深流量呈线性关系,并且相关系数接近于1;当D/B≤1.4,雷诺切应力随D/B的增大而增大,当D/B>1.4,雷诺切应力随D/B的增大而减小,但最大雷诺切应力对应点的流速随D/B的增大而增大。研究成果有助于进一步理解矩形钝体绕流的流动特性,对提高水工建筑物的稳定性具有实际指导意义。

Using PIV technical methods for measuring velocity, the flow characteristics around two parallel rectangular columns are studied by changing the spacing ratios(D/B) between two parallel rectangular columns under a certain flow. Experimental results show that:(1) there is a critical value of D/B between 1.3~1.4, i.e., the number and shape of vortices and turbulent intensity downstream of two rectangular columns are totally different for D/B larger than and less than the critical value;(2) with the increase of D/B, the velocity variations in both outlet section of the gap between two rectangular columns and the sections between rectangular column and flume wall are quit complex, however, there is a linear relationship for discharge per unit depth of two sections with a correlation coefficient near 1;(3) when D/B≤1.4, Reynolds shear stress increases with the increase of D/B, however, when D/B>1.4, with the increase of D/B, Reynolds shear stress decreases while the velocity at the maximum Reynolds shear stress increases. The results are helpful for understanding the flow characteristics around the rectangular bluff body and have practical guiding significance to improve the stability of hydraulic structures.