Experimental and Numerical Study of Spoiler Effect on Ship Stability: Effect of Spoiler Inclination Angle

Abstract

Ship stability is studied experimentally and numerically. The injection of air or exhaust gas stabilizes cavities behind spoilers. The spoiler system is tested experimentally to understand the parameters affecting the flow field and bubble formation around the spoiler. These parameters are the spoiler inclination angle, rise of floor angle and injected air position. The spoiler inclination angle effect is studied in this paper. The images of flow field variation and bubble formation are recorded with scientific video camera and compared with the computed flow field at different conditions and time sequence. The two-phase flow field around a ship spoiler with the free surface simulation in Piecewise Linear Interface Construction method is modeled numerically using a three-dimensional Navier-Stokes code. The bubbles shape, the three-dimensional flow field around the spoiler body and the pressure variation on the wake of the spoiler body are computed. The comparison between the numerical and experimental results shows a good matching of bubble formation and the difference may be attributed to the laminar flow computation without including turbulence effects. The moment around the 90° inclined spoiler fixation line is 1.651 times that around the 30° inclined spoiler and 1.1 times that around the 60° inclined spoiler after 1 second. Therefore, varying the spoiler inclination angle produces different bubble shapes and consequently different forces are introduced to control the roll, pitch motion and speed of the ship leading to ship stability.