Experimental Study of Bubble Evolution Produced by Pyrotechnic Composition Underwater Combustion

In order to investigate the acoustic radiation mechanism for pyrotechnic composition underwater combustion,the whole evolution process of bubble produced by the underwater combustion was experimentally studied based on the means of high speed photography and video due to its instantaneity.It is found that this combustion process can be obviously divided into four stages,i.e.bubble formation,bubble floating upward,bubble swarm formation of the breaking bubble and spout or splash on the water surface.The bubble evolution becomes more intense and bubble incorporation appears along with the increase of combustion velocity,meanwhile the radiation noise is also increased.In the whole rising process,bubble does not present a perfect sphericity and rises curvilinearly due to its volume change that results in uneven pressure acted on it.