Fluid-structure interaction analysis of an elastic surface-piercing propellers

In high-speed planing craft, surface-piercing propellers (SPPs) operate semi-submerged in a two-phase air-water environment, facing stress and displacement from variable forces. In this paper, the fluid-structure interaction (FSI) of the SPP is investigated at immersion ratios of 30 %, 50 %, 70 % and 90 %, under low and high advance coefficients. A coupling of Reynolds-averaged Navier–Stokes equations (RANS) and elasticity theory are used to simulate fluid dynamics and the blade deformation with the multi-physics computational fluid dynamics software STAR-CCM+. The analysis is performed after several rotations of the SPPs at five different positions. The results show that at the advance coefficient of 0.4, a higher immersion ratio increases torque, thrust, efficiency, maximum stress, and maximum displacement. When the advance coefficient is equal to one, the efficiency, maximum stress, and maximum displacement remain constant for the immersion ratio above 50 %. The maximum displacement occurs at the blade tip, while maximum stress is at the trailing edge root. Most blade deformations happen where the blade enters the water, aligns perpendicularly with the water surface, and exits. The two-phase flow around the blade increases its displacement.