Development of software tool suite for the prediction of bubbly wake acoustic signature of waterjet propelled surface ships

Surface ship generated bubbles are a major signature contributor. For advanced ships such as the LCS, waterjet propulsion adds another source of air entrainment through the waterjet free surface interactions. In littoral warfare, such wakes provide an opportunity to wake homing torpedoes due to large acoustic cross-section of bubbles. While there is research on breaking waves bubbles, little is known about waterjet bubbly wakes. Therefore, it is imperative to develop computational tools capable of predictive analysis and design optimization for waterjet driven ships. DYNAFLOW / Penn State ARL team demonstrated in Phase I the feasibility of such a software tool suite. In Phase II, we will continue developing the software and validate it through laboratory testing at DYNAFLOW, model testing of FSF-1 in Option I, and full-scale testing of FSF-1 in Option II. Acoustic analysis to provide sound speed attenuation relevant to wake homing threats will assess the ship vulnerability in engagement simulations and experiments will validate and refine the models. We will employ our DF_UNCLE code and modify it to include volume of fluid and level set models to reproduce the wakes and add physical models of the waterjet free surface bubble entrainment mechanisms developed through experimental observations.