An experimental study of the evolution characteristics of the air-mass-near-the-tube-carrying-type shoulder cavity and the attached tail cavity

The attached shoulder-tail cavities of an underwater vehicle are accompanied by complex flow phenomena and determine its motion and loading characteristics. The evolution of underwater vehicle-attached cavities is studied. The ability of the solid wall to carry the air mass near the tube is focused on. The evolutionary properties of cavity collapse and tailing surges are studied. The effects caused by the cavitation number and the Froude number are discussed. The study showed that the air mass near the tube-carrying-type shoulder cavity is prone to form disintegration before leaving the water when Frl ≤ 6.42. During vehicle traversing the free surface, the shattered shoulder cavity forms a splash jet impacting the tail cavity. As the Fr increased, the position of the disintegration point is progressively closer to the free surface, and the convex fluctuation point occurs near the leading edge of the cavity. The umbilical tailing surges gradually converge. Until Frl = 10.41, no significant disintegration of the cavity is observed. At low cavitation numbers, the ability to carry the air mass near the tube out of the tube is better than at high Fr. When Frl = 11.88, the maximum value of L¯1 is 0.5L. When Pdifference = 16.8, the maximum value of L¯1 is 0.72L. The high pressure ratio reduces the splashing effect of the jet. When the vehicle is completely above the free surface, L¯J−D8 = 6.28, L¯J−D9 = 4.75, and L¯J−D10 = 2.80. The tail cavity is pulled from the jet to form a tailing surge.