Numerical Simulation Of Parametric Rolling Of The Tumblehome Hull And Research Of Using Tank To Prevent Parametric Rolling

In order to pursue good stealth performance,the tumblehome hull adopts inclination of bulwarks and superstructures on the waterline and the design of the bow of the wave,which causes the stability problems in the wave: due to the small area of the waterline,Resulting in insufficient recovery torque resulting in roll-off and loss of pure stability;in the swell wave,the inclination of the bulwarks and superstructures can easily lead to the difficulty of returning to the equilibrium position after the sway;in the head wave,the change in the relative position of the ship wave causes The restoring arm produces periodic changes and the parametric rolling occurs.The inward sloping bow,low freeboard and no bulwark ship design lead to extremely easy waves on the deck,which not only damages the superstructure and equipment on the deck,but also seriously affects the stability of the ship.The motion of the tumblehome hull is very nonlinear.In this paper,for the DTMB 5613 tumblehome hull,based on the sticky CFD software STAR-CCM +,the overlapping grid method is used to perform a numerical simulation analysis of the parametric rolling of the tumblehome hull and the deck wave phenomenon that is more likely to occur when the parametric rolling occurs Understand the external conditions of parametric rolling of the tumblehome hull and the influence of the waves on the deck caused by the unique ship form design of the inclination boat,and discuss the avoidance measures of the parameter roll.By simulating the parametric rolling of the tumblehome hull in the wave,the effects of initial disturbance,amplitude and wavelength conditions on the parametric rolling were studied.It is concluded that properly increasing the initial disturbance will significantly shorten the time of the parametric rolling,and will only affect the transition stage before stabilization.It will affect whether the parametric rolling occurs and the stable roll amplitude of the parametric rolling.No effect;parametric rolling occurs only when the pitching vessel meets a certain wavelength,wave height,and encounter frequency ratio range,and compared with other ship types such as container ships that have the potential for parametric rolling,the frequency of parametric roll encounter The interval is small,this is due to the relatively gentle change of the waterline surface of the tumblehome hull;the stable roll amplitude of the parametric rolling of the tumblehome hull is not positively correlated with the wave steepness,because the large wave steepness is accompanied by the parametric rolling,The tumblehome hull also has waves on the deck,and there is always a considerable volume of accumulated water on the deck.This part of the accumulated water increases the roll damping of the ship to a certain extent,changes the natural period of the ship’s roll,and keeps the tumblehome hull away.Parametric rolling interval.Based on the understanding of the Mathieu equation and the suppression effect of the waves on the deck on the parametric rolling,the possibility of using the existing water tank of the inclination boat to avoid the parametric rolling is discussed,and the anti-roll effect with the installed bilge keel model compared.The results show that increasing the bilge keel can delay the time of parametric rolling and reduce the stable roll amplitude,and can not completely avoid the occurrence of parametric rolling;by setting the amount of water in the water tank reasonably,the occurrence of parametric rolling can be completely avoided.The principle is to change the natural period of the ship’s roll,and to keep the inclination ship away from the frequency range where the parametric rolling occurs,which provides an effective way to suppress the parametric rolling.