Investigation of fully dispersed shock wave in droplets-gas mixture

对液滴-气体混合流中激波的扩散进行了实验和数值研究。利用Mie散射技术测量了冲击波后的液滴尺寸和数密度。实验中获得了试验场的二维图像，并用PC机对图像进行了数字化分析。在离激波锋面不远区域内液滴尺寸不变的假设下，液滴密度比与速度比的倒数成正比，液滴密度比与速度比的倒数成正比，从液滴数密度分布可以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，相对速度越小，弛豫区越大。The v…更多的价值比理论上预测的要高得多。结果表明，对于群流颗粒和非定常运动，应对阻力系数模型方程进行修正。另一方面，为了研究激波的弥散，对激波后的压力分布进行了详细的测量，当入射激波马赫数为1.4时，激波前缘的压力分布呈现部分不连续的分布。液滴与气流之间的粘性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15 mm。热弛豫长度要长得多，是这个长度的10倍。这归因于动量弛豫和热弛豫是弥散的。弱激波的压力分布与Young和Guha(1991)的预测结果接近。否则，数值预报不会在压力分布上显示这样的弥散。因此，在计算中应考虑粘性的影响，采用更有效的物理模型来对抗非线性波浪的陡化。较少

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