Investigation of fully dispersed shock wave in droplets-gas mixture

对激波在液滴-气体混合流动中的扩散进行了实验和数值研究。利用激波后Mie散射技术测量了液滴的大小和数量密度。实验中获得了试验场的二维图像，并用个人计算机对图像进行数字化分析。在离激波锋面不远的区域内，假设液滴尺寸不改变，则数密度的分布与入射光束强度的消光率成正比，由于液滴的密度比与速度比的倒数成正比，这是由质量守恒成立的，最后，我们可以从液滴的数密度分布得到液滴与气流之间的速度滑移比。根据这些结果确定了动量弛豫长度。实验结果表明，随着相对速度的减小，弛豫区增大。v…More值比理论上预测的要高得多。结果表明，对于人群粒子和非定常运动，阻力系数模型方程需要进行修正。另一方面，为了研究激波的弥散，对激波后压力分布进行了详细的测量，当入射激波马赫数为1.4时，激波后压力分布呈现部分不连续的分布。液滴与气流之间的粘滞效应在该区域起着重要的耗散作用。当Ms=1.4时，该区域的典型长度约为15mm。热松弛长度要长得多，是这个长度的10倍。这归因于动量松弛和热松弛是分散的。弱激波的压力分布与Young和Guha（1991）的预测接近。否则，数值预测在压力剖面上没有显示出这种分散。在计算中应考虑到粘滞效应，建立更有效的抗非线性波陡化物理模型。少

An experimental and numerical investigation was carried out for the dispersion of shock waves in droplet-gas mixture flows. The droplet size and number density were measured by means of Mie scattering technique behind the shock wave. Two-dimensional image of test field was obtained in the experiment and the image was analyzed in digital by personal computer. Under the assumption that the droplet size should not be changed in the region not far from the shock front, the distribution of number density is proportional to the extinction rate of incident light beam intensity, Since the density ratio of droplet is proportional to the reciprocal of velocity ratio which is valid from the mass conservation, finally, we can obtain the velocty slip ratio between the droplet and gas flow from number density distribution of droplet. The momentum relaxation length is determined from these results. Experimental result show that the relaxation region increases as the relative velocity decreases. The v … More alue is much higher than theoretically predicted one. It is concluded that the model equation of drag coefficient should be modified for the crowd particles and unsteady motion. On the other hand, the pressure distribution behind the shock wave was measured in detail in order to investigate the dispersion of shock wave, When the incident shock Mach number is 1.4, the pressure profile shows a partly discontinuous distribution just behind the shock front. Viscous effect between the droplets and gas flow plays a significant dissipation function in this region. The typical length of this region is about 15 mm for Ms=1.4. The thermal relaxation length is much more long and 10 times of this length. This is attributed that the momentum relaxation and thermal relaxation is dispersed. The pressure profile of weak shock wave is close to that predicted by Young and Guha(1991). Otherwise, the numerical prediction did not show such dispersion on the pressure profile. It is concluded that the viscous effect should be accounted in the calculation with more valid physical model against the nonlinear wave steepenning. Less