Experimental study on turbulence characteristics of a slot jet impingement on semi-circular surfaces

Abstract

实验研究了狭缝射流撞击圆柱表面后壁面射流区的平均流动和湍流特性.考察了雷诺数Re(6000-20000),喷口到受撞表面距离Y／W(5-13),喷口宽度W(6.25mm,9.38mm),受撞表面曲率(半圆柱体直径D=150 mm) 对流动和湍流结构的影响.通过分析X热线在壁面射流区的测量结果发现,在近壁区域,表面曲率、 Rew,Y／W 和 S／W 等参数对(u2)~1/2／Um的影响比对、(u2)~1/2／Um 强,并且切应力 uv／Uvn2 对表面曲率变化最敏感.当喷口与受撞击表面之间的距离 Y/W 在一定范围内增加时,沿圆柱表面流动的流向和横向的湍流强度增强. 用平板射流和圆柱体表面壁面射流的数据进行比较,从而得到表面曲率对壁面射流特性的影响.结果表明,曲率对壁面射流的影响较强,并随着 S／W 的增大而增强.随着雷诺数的增大,壁面曲率的影响也有强化的趋势. Detailed mean flow and turbulence measurements of a turbulent air slot jet impinging semi-circular convex surface were experimentally investigated. The effect of Reynolds number (6000-2000), impingement distance Y/W (5-13), slot jet width W (9.38mm) and impingement wall surface curvature (semi-cylinder diameter D = 150mm) on impingement wall jet flow and its turbulent structure are presented. The results of X-wire data show that, compared with transverse Reynolds normal stress, u2/Um2, the streamwise Reynolds normal stress, u2/Um2 is strongly affected by the examined dimensionless parameters of D/W, Y/W and S/W in the near wall region. It is also evidenced that the Reynolds shear stress, -uv/Um2 is much more sensitive to surface curvature, D/W. The streamwise and transverse turbulence intensity on the semi-cylinder surface increases with Y/W within range that we checked. To study curvature effects on turbulence characteristics, the experimental data of jet impingement on plate wall and semi-cylinder were compared with each other. The results show that effect of wall curvature on turbulence is distinct, and enhances with increase of S/W, Reynolds number based on jet exit width.