Numerical Simulation of Underwater Propulsion Using Compressible Multifluid Formulation

Underwater propulsion has various applications and is of great interest. Pressurized gaseous jet flows through a nozzle into water at various depths. The flow structure and processes are unsteady and involve multiple phases. There are various phenomena taking place when gaseous jet is injected into water, namely expansion, bulging, necking/breaking and back attack. Wave travel and information travel in gas and water medium are significantly different. Hence, compressible multifluid formulation which takes into account that all the information travel through the stiffened gas equation of state is used for numerical simulation. Finite volume method is used for spatial discretization and explicit four-stage Runge–Kutta scheme for time integration. For validation of the code developed, air–water shock tube case is carried out. As an application, an integrated unsteady simulation of nozzle and plume flow field of a convergent-divergent nozzle at sea level underwater is simulated. Unsteady flow features and their effect on thrust are computed. Nozzle wall pressure is integrated at various instances to get the thrust and the unsteady thrust has been related to flow features.