Experimental Study on Three-Degree-of-Freedom Ventilated Cavities for Underwater Vehicles Considering the Air Mass near the Tube

A small-scale three-degree-of-freedom decompression launch experiment method is used to study the flow characteristics in a ventilated cavity at different transverse velocities. The study subjects are three typical head-shaped underwater vehicles: hemispherical, ellipsoidal, and conical. The evolution mechanism of the ventilated shoulder cavity in a vehicle under transverse velocity is investigated, and the effects of transverse velocity and vehicle head shape changes on the cavity are summarized. Research results show that the hemispherical-headed vehicle’s ventilated cavity is prone to cavity pre-positioning, thereby affecting the distribution of the confronted stream surface (CSS) cavity. As the transverse velocity increases, the cavity pre-positioning point disappears, and the degree of deflection in the vehicle’s trajectory increases. The difference between the opposing stream surface (OSS) and the CSS cavities decreases as the cavities shed. The drag effect of the shedding air mass causes a change in the cavity closure angle. At high transverse velocity (vt = 0.6 m/s), the cavity difference between the OSS and CSS of the ellipsoidal vehicle is the largest, and the amount of gas shed at the cavity’s end is the smallest. The initial angle of the closure angle at the cavity end is related to the ability of the air mass near the tube (AMNT) to be drawn in by the head shape of the vehicle. Under the influence of transverse velocity, the shedding cavity deflects toward the OSS. The interaction patterns between the shoulder and tail cavities on vehicles with different head shapes primarily include three modes.