EUROFLEETS2-D11.3-Guidelines and recommendations for ship design on bubble sweep down avoidance

The object of the report is to provide guidelines and recommendations on bubble-sweep down avoidance for regional research vessels (RRVs). The indications for design solutions in order to mitigate the bubble sweep-down phenomenon are given on the basis of the simulation-based design analyses and optimization performed on two vessels' hull shapes one with bulb and one without bulb. The problem has been addressed using a multilevel optimization approach including two single-objective optimizations and a multi-objective optimization. Specifically, the following objectives have been evaluated: 1) the mean downwards velocity component of the flow, which is correlated to the average angle of streamlines, evaluated in a prescribed region of the hull for assigned environmental (sea- state) and operating (speed) conditions; 2) the root mean square (RMS) of the vertical acceleration evaluated in a prescribed point at the bow for assigned environmental (sea-state) and operating condition (speed).