Effect Of Gas Exhausting On Hydrodynamic Characteristic Of Underwater Vehicle Considering Wave

By changing the fluid medium of surface of the underwater vehicle, gas exhaustingchanges the pressure distribution, lowers the hydrodynamic and loads during theunderwater navigation stage and water-exit course, and reduces the angular deflection,to meet the requirement of taking off. However, people have not yet formedcomprehensive understanding of the theory that the evolution process of bubbles on thesurface of the underwater vehicle and it’s correcting mechanism on the angulardeflection. Therefore, it is of great engineering significance to take a numerical study inthe fluid dynamic problem of inhibition of the cavitation head type underwater vehiclewith gas exhausting.By analyzing physical characteristic of the launching process of the underwatervehicle, the simplified computational model with submarine speed of multi degree offreedom motion was established. The mathematical model was numerically solved byMixture and VOF multi-phase model, standard k-ε turbulence model, dynamic meshtechnology and user defined function. Considering the interaction between fluid flowand underwater vehicle motion during the process of calculation, dynamic simulation ofthe underwater launching process was realized by one-way and two-way couplingmethod. Research was conducted on the effect of gas exhausting, water-exit phase andcross flow on hydrodynamic characteristic of the underwater vehicle.The vertical launching of the underwater vehicle at different water-exit phase wassimulated, which didn’t consider the influence of gas exhausting. The influence ofwater-exit phase on multiphase flow and hydrodynamic characteristic of underwatervehicle were gained. The results show that the wave-exit phase has a significantinfluence on the hydrodynamic of the underwater vehicle, and it also changes its motioncharacteristic. When water-exit course is being on the wave trough, the deflection angleis evidently less than on the wave crest and the deflection of centroid trajectory is alsoreduced.Study was conducted on the launching of the underwater vehicle under thecondition of hydrostatic, which considered gas exhausting or not. The evolution of thebubbles and its correcting mechanism of angular deflection were acquired. By changingthe fluid medium of the surface of the underwater vehicle, gas exhausting changes theform of surface pressure distribution and lowers the pitching moment during theunderwater navigation stage, and reduces the deflection of angle and centroid trajectory.On the basis of above research, the simulation was conducted on the multi degreeof freedom motion of the underwater vehicle, which considered many factors such as water-exit phase, cross flow and gas exhausting. The flow characteristic of exhaust slot,motion and hydrodynamic characteristic of underwater vehicle were obtained in variouslaunching condition. Water-exit phase and cross flow both have a significant influenceon the hydrodynamic characteristic of the underwater vehicle on the condition of gasexhausting. When water-exit course is being on the wave trough, the deflection of angleand centroid trajectory is evidently less than on the wave crest. The influence of crossflow makes the angular deflection increases.