基于Ramp-VG阵列的超声速混合层流动控制实验研究

Experimental Research on Supersonic Mixing Layer Flow Control Based on Ramp-VG Array

利用基于纳米示踪的平面激光散射(nano-tracer-based planar laser scattering,NPLS)技术研究了Ramp-VG阵列对超声速混合层流场的控制效果.对流Mach数Ma_(c)=0.17.通过比较无控和控制状态下的混合层NPLS图像,发现控制状态下混合层流动速度提高了5%~15%,K-H不稳定涡的平均波长减小了5%~30%,y_(1/2)处(ramp尖端)的层流段长度增加了12.8%.结合分形理论,分析了超声速混合层中的流动发展过程,发现引入控制后混合层的分形维数数值明显改变,y_(0)处(ramp凹槽)的分形维数幅值增加,y_(1/2)处的分形维数幅值减小.实验结果证明Ramp-VG阵列能够改善超声速混合层的能量分布,达到延迟转捩、改变掺混强度、提高流动速度和减小涡结构各向异性等目的.

The flow control effect of Ramp-VG array(ramp vortex generator array,RVGA)on the supersonic mixing layer was studied via the nano-tracer-based planar laser scattering(NPLS)technique at a convective Mach number of 0.17.By comparing the NPLS images of the supersonic mixing layer without control and with RVGA control,it is found that the flow velocity in the mixing layer increases by 5%~15%under the control state,and the mean wavelength of K-H instability vortices decreases by 5%~30%,while the length of laminar flow increases by 12.8%at location y_(1/2)(the tip of the ramp).The flow development process in the supersonic mixing layer was studied combined with the fractal theory.It is found that the value of fractal dimension obviously changes with RVGA control,namely that the value increases at location y_(0)(the tip of the RVGA′s notch)and decreases at location y_(1/2).The experimental results prove that the RVGA can improve the energy distribution in the supersonic mixing layer,which thereby achieves the goals of delaying transition,altering mixing intensity,increasing flow velocity and decreasing anisotropy of vortices.