Stability of a Submersible in Vertical Plane near Free Surface
HUANG Guo liang, LIU Tian wei, LU Jun, LOU Lian gen (School of Naval Architecture & Ocean Eng., Shanghai Jiaotong Univ., Shanghai 200030, China)
When a submersible runs near the free surface, the forces acting on it and its motion performances such as stability are different from those in the condition of deep submergence. A fourth order characteristic equation for a submersible running near the free surface which can analyse the dynamic stability in the vertical plane was derived. The calculations were conducted of the fourth order characteristic equation and the third order characteristic equation used for the stability analysis in the condition of deep submergence. The calculation results show that the submersible becomes worse in the dynamic stability or even unstable. The third order equation is unsuitable for the stability analysis of the submersible near the free surface. Besides, the dynamic stability in two initial equilibrium conditions (on even keel and in trim) were calculated and compared. Finally, the control stability was discussed and it was found out that trim angle control is a simple and effective method to make the submersible stable near the free surface.
【Fund】： 船舶工业国防科技应用基础研究基金! (96 J41.2 .1)