Deformation of Shock Wave in Supersonic Plasma Jet Caused by Applied Magnetic Field

对欠膨胀等离子体射流进行了实验研究，揭示了外加磁场对法向激波即马赫盘周围流动行为的影响。流动的照片是用数码单反相机拍摄的。从图像的未压缩RAW文件中提取光强度。根据光强的梯度确定了反射激波起始点的炮管和反射激波与水流方向的夹角。反射冲击波的角度随磁场强度的增大而增大。另一方面，身管激波波角随场强的增大而减小。与无磁场相比，马赫盘下游区域的光强等值线图随着外加磁场的变化而发生显著变化。利用光强研究了磁场对超音速锥形探头周围斜激波的影响。从斜激波角度用Taylor-Maccoll方程计算得到的射流中的局部马赫数随场强的增大而增大。

An experimental study of underexpanded plasma jet was carried out to reveal the effects of applied magnetic field on flow behavior around the normal shock wave, that is, Mach disk. Photographic images of the flow were taken with a digital single-lens reflex camera. The light intensity is extracted from uncompressed RAW files of the images. Angles of barrel and reflected shock wave to the flow direction at the reflected shock starting point were determined from the gradient of the light intensity. The angle of reflected shock wave increases with magnetic field intensity. On the other hand, the angle of barrel shock wave tends to decrease with increases in the field strength. Contour plots of the light intensity in downstream region from Mach disk significantly changes with applied magnetic field compared to those without the field. The effects of magnetic field on oblique shock wave around a conical probe in supersonic region of the jet were also studied using the light intensity . The local Mach number in the jet, evaluated from the oblique shock angle using Taylor-Maccoll equation, shows a tendency to increase with the field strength.