Multi-degree-of-freedom Coupled Ship Model Considering Coordinate System Position Transients And Analysis Of Parametric Rolling Motion

The safety of the ship in the wave has been the forefront of the ship engineering field,and the parameter rolling in the ship is the key and key problem encountered in the second generation of the ship stability specification.This paper studies the analysis method of ship parameter roll and reveals the mechanism of ship parameter rolling,which has important theoretical and engineering significance.The aim of this paper is to establish the model of parametric roll analysis considering the ship's actual navigational condition,and to analyze the analysis method of ship parameter roll,reveal the condition and mechanism of ship roll.The main contents and conclusions are as follows:A new multi-degree-of-freedom coupled motion equation is established for the ship under the instantaneous equivalent rotational motion system by using the new non-Euler dynamics system considering the position transients of ship-borne coordinate system.In this system,the second order coupling term is introduced to the transient of the coordinate system.The second order coupling term has a certain influence on the nonlinear roll motion of the ship.According to the theory of potential flow,the calculation method of the incident force and the radiant force of the ship in the wave considering the instantaneous wet surface and the complex motion of the ship is established.The wave force calculation program and the time domain motion calculation program are compiled.The calculation of the regular wave,random longitudinal waves and random oblique waves in the multi-degree of freedom coupling movement,thus to analyze the ship in the wave motion characteristics.The effects of natural frequency,wave frequency and sailing frequency on ship motion are analyzed and analyzed.The results show that the main frequency of ship rolling motion will occur when rolling motion is large.Migration and chaos in the process of motion and other complex nonlinear characteristics.Based on the probabilistic method,the random behavior of ship rolling in random wave is analyzed.The method of multidimensional distribution fitting function is established,and the ship roll angle and probability of occurrence under random wave are estimated.In addition,the uncertainty of ship random roll motion is analyzed by using the 4-D relational graph.The innovation of this paper is to establish ship motion model based on instantaneous rotation matrix.The model can take into account the simultaneous motion of multi-axis rotation and the influence of the second-order coupling term,which can improve the accuracy of large ship motion prediction.The results show that the instantaneous wet surface change of the ship is the main reason causing the parametric roll,and different frequencies including the natural frequency and the encounter frequency have important influence on the parameter roll.