The Research Of Water Entry Trajectory For Supercavity Rocket Depth Bomb

As the pressure of minimum point on surface reach or close to the saturated vapor pressure for movement of objects in the water,the bubbles of dissolved in water will re-escape,then they successive form to cavitation bubble that full of water and water vapor.The length of cavitation bubble approach or exceed the length of objects is known as supercavity.Exploit drag reduction principle of supercavity,which have great significance for achieve underwater weapons' speed breakthrough.This paper analyze fluid-structure interaction phenomenon of enter water for rocket depth bomb use the method of theoretical analysis and numerical simulation combination,and analyze every phenomenon of four phase according to trait of the depth charge entry water and summarize the characteristics of each phase.The model of water entry trajectory is set up.Then, current field is simulated by using the FLUENT software and LS-DYNA software. Several conclusions of natural cavitation can be get for this type depth bomb, and following are main points.At standard presureσ= 0.107 is critical cavitation factor for this type depth bomb.Cavitation bubble separation point fixed at circle position 5～7.5cm later projectile nose,and this position is fixed,not with the cavitation factor change.The size of cavitation bubble is different owing to speed and environment pressure are different for the same cavitation factor.With the decrease in cavitation factor,the length of supercavity is gradually increasing,total resistance coefficient obvious reduce.Skin friction can be reduced 52.3%～86.5% for the this type nose shape.The valve of impingerment pressure for projectile water-entry is relative with velocity,it increase in direct proportion to speed. Impingerment pressure operation on the duration of 200 microseconds In fifferent water-entry speed.The tail of this type of depth bomb makes ballistic instability in the water-entry early.