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

超音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在SCRAM喷气发动机上进行混合强化。此外，它还可以应用于热喷涂、喷漆等。在这种混合中的一个问题是，在超音速通过过程中，混合的程度和速度如何，这意味着没有时间进行混合。本项目的理想是基于我们的超音速混合专利，旨在将激波用于超音速主流和弯曲激波。然后，将超音速流过的风道壁面修改为下面附设空腔的多孔壁，以使超音速主流混合良好。结果表明，通过光学观测、二维压力分布测量和簇状流显示等手段，可以较好地阐明喷嘴的流动特性。实验结果与三维Navier-Stokes可压缩数值计算结果的比较表明，计算结果是合理的，并为我们提供了射流和杆子的布置、起始激波的位移等重要参数。空腔内的流动还受到射流和棒状物的影响，这一点在簇流显示中得到了证实。设备的一个重要因素是压力损失。实验和计算还表明，杆和射流垂直于主超音速流动的布置方式获得了最大的压力损失，在设计这类装置时必须考虑这一点。根据上述结果，证实了空腔和主风道之间的再循环，这表明在超音速流动中存在混合增强的可能性。

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.