Study On Coalescence Characteristics Of Pressure- Equalizing Exhaust Bubbles On The Surface Of Underwater Vehicles

The underwater launching of high-speed vehicles is an extremely complex process,involving liquid-gas-solid three-phase coupling.The vehicles’ underwater channel is unstable when the load on the vehicles is uneven.It is proved the pressure-equaling exhaust technology can effectively stabilize the channel,which is opening gas seam and gas holes structures on the surface of the vehicles and active exhaust when the vehicles begin to move,forming attached bubbles to stabilize the pressure of body surface.There are formation,development,coalescence and collapse of bubbles during the process.The coalescence of bubbles plays a key role in the stable operation environment of the vehicles.We design and carry out experiments and numerical calculations for the coalescence characteristics of pressure-equalizing exhausted bubbles in the process of vehicles underwater launching,the effects of three kinds of structures,such as single-row gas holes,double-row gas holes and the joint form of holes and seam on bubbles coalescence characteristics were discussed,providing reference for the design of exhaust structures.Firstly,we carry out experiments and numerical calculations of the pressure-equalizing exhaust process of single-row gas holes.we summary the morphological changes’ regular of exhaust bubbles,and the flow pattern partitions of exhaust bubbles are given.We analyses the phenomenon of bubbles coalescence under the structural,then the influences of parameters such as the number of holes,Froude number and exhaust flow rate on bubbles coalescence are given.Secondly,on the basis of single-row gas holes form,we carry out experiments and numerical calculations of the pressure-equalizing exhaust process of double-row gas holes,the results show that the bubble flow pattern partitions is similar to the single one.We study the rule of bubbles coalescence under the structural,in addition of the horizontal coalescence,and there are also vertical mixing and coalescence between two row structure bubbles.We contrast the experiment results and give the differences of bubbles coalescence characteristics in the form of single and double structures,we believe that double row holes has a certain effect on bubbles coalescence.The influences of parameters such as longitudinal hole distance,the number of holes,Froude number and exhaust flow rate on bubbles coalescence are given.Finally,we study on the morphological changes’ regular of exhaust bubbles under the joint form of holes and seam,which the flow pattern partitions is different from the previous and the regular of coalescence is also very different.It is found that under the joint form of holes and seam,the horizontal and vertical bubbles coalescence surely can take place under proper flow parameters,and the promoting effect on bubbles coalescence of this form is better than the previous two.At last,the influences of parameters such as Froude number and exhaust flow rate on bubbles coalescence are given.