Study of Interaction between Jets normal to Supersonic Flow and Porous Cavity

超声速流场中的混合强化是一个重要的工业应用领域。超音速混合最有前途的应用是所谓的SCRAM喷气发动机中的混合增强。此外，它可以应用于热喷涂、涂漆等。这种混合的问题之一是在以超音速通过期间如何良好和快速地实现混合，这意味着没有时间混合。本课题的设计思想是基于我们的超音速混合专利，目的是利用激波对超音速主流和弓形激波的作用。然后，将超声速气流通过的通道壁面改造为多孔壁面，在壁面下方附加空腔，使超声速主流充分混合。结果表明，通过光学观测、二维压力分布测量和簇状流动显示，可以清楚地了解流动特性。通过与三维可压缩Navier-Stokes流场数值计算结果的比较，表明本文的计算是合理的，并提供了射流和杆的布置方式、起始激波的位移等重要参数。簇状流场显示证实了射流和杆对空腔内流动的影响。装置的重要因素之一是压力损失。实验和计算还表明，垂直于主流布置的杆和射流的压力损失最大，在设计这种装置时必须考虑这一点。根据以上结果，证实了凹腔与主通道之间的回流，表明了超声速流动中增强混合的可能性。

The mixing enhancement in a field of supersonic flow is an important and applicable to industrial fields. The most promising application of the supersonic mixing is, so called, mixing enhancement in SCRAM jet engines. Moreover, it could be applied to a thermal spray, painting etc. One of the problems in such mixing is how well and quickly the mixing is achieved during the passing at the supersonic velocity, which means that there is no time to mixing. The ideal of this project is based on our patent for the supersonic mixing aiming at the utilization of the shock wave to the supersonic main flow and the bow shock wave. Then, the wall of the duct in which the supersonic flow passes is modified to the porous wall attached with a cavity underneath in order to make the supersonic main flow mixed well. As the result, it is found that the flow characteristics are clarified by means of the optical observations, two dimensional pressure distribution measurements, and tuft flow visualization. Moreover, the comparison of the experimental results with the three dimensional Navier-Stokes compressible numerical calculations suggests that the calculation is reasonable and provide us with important parameters such as the arrangement of the jets and rods, the displacement of the starting shock wave. The flow in the cavity is also affected by the jets and the rods, which is confirmed by the tuft flow visualization. One of the important factors for the devices is a pressure loss. The experiments and the calculations also show that the arrangement of the rods and the jets normal to the main supersonic flow achieved the worst pressure loss, which must be taken into account in designing the kind of devices. According to above all results, recirculation between the cavity and the main duct has been confirmed suggesting the possibility of the mixing enhancements in a supersonic flow.