超高速弹丸斜侵彻水现象的试验研究

利用新型可调发射角立式二级轻气炮发射高超声速弹丸，基于光反射原理和光电二极管测量弹丸出口速度，采用脉冲火花光源和连续激光光源拍摄高速弹丸斜侵彻水流场的纹影和阴影图像。结果表明，对于锥柱（圆柱和圆锥组合体）弹丸，弹丸入水前，其头部产生斜激波，尾部羽流膨胀并产生斜激波系；弹丸入水时，其头部斜激波对气水界面几乎无影响；弹丸入水后，其头部和羽流斜激波在气水界面产生复杂反射，弹丸斜侵彻产生的水喷射和飞散非对称地分布在其轨迹两侧。圆柱弹丸受波阻较大且减速较快，发射管羽流越过弹丸并和气水界面率先作用，高温羽流也出现和弹丸侵彻类似的非对称水喷射和飞散。2种情况下，弹丸和水侵彻后均产生在水中传播的半球形激波，弹丸尾流出现空化区，较大的水阻力导致弹丸减速很快。弹丸羽流和气水界面产生的水激波较弱。

Experimental Research on Hypervelocity Projectile Intruding Water

Hypervelocity projectile intrudes water at an angle was experimentally studied in this paper.Two-stage gas gun installed vertically was used to launch the projectile and its speed was measured by laser diode laser based on beam re-flection.Also,schlieren and shadowgraph images were respectively obtained by the impulse spark and laser source.The re-sults indicated that attached oblique shock waves were generated by a conical cylinder projectile before its intruding water. The shock waves emanate on the plume surfaces which originate from projectile base flow.Although these shock waves don’t obviously disturb the gas water surface water,the fragmentation which is similar to debris but asymmetrically distrib-uted along the projectile trajectory was generated during the intruding.For a cylindrical or flat projectile,the large wave drag was produced and its speed was drastically decreased.Therefore,jet plume from the launch tube overrun the flat pro-jectile and interact to gas water interface earlier.In the both cases,semi-spherical water shock waters can be generated and cavitation regions appear and expand downstream the projectile in water.The shock waves generated by jet plume were weak in contrast with projectile intruding.