Study Of Capsizing Probability Of The Damaged Warship Subjected To Underwater Explosion And Random Excitations

The survivability of the damaged warship has received the attention of researchers at home and abroad because of its important military significance .It is well known that the tremendous warship in battle subjected to such random excitations as wave and wind. The fixed heeling angle of the damaged warship caused by the weapons makes it be less survivable and the integral capsizing probability is larger than the probability of the lack of enough strength.The uncertain theory is used in this paper to study the problem of capsizing probability. Firstly, considering that the structural style of the large warship is special, unlike the traditional method ,the coefficient of wind pressure Cm is seenas a variable in order to take into the effect of the ship shape on the random wind excitation and the effect of the speed of the warship on the wind velocity is also considered so as to take into the relative effect of wind velocity. The calculating formula of the wind excitation applied on the large-scale warship and influenced by the factor named the speed of the warship is provided. Secondly, based on the linear wave model ,the theory of the random process is applied to describe the stochastic model of the wave ,the property of which is determined by the power spectral density function. At last ,the theory of the underwater explosion is applied to describe the weapon attack to the warship as determinate but irregular excitation. The three aspects referred as before are the basis of the following parts of this paper.At first, introducing two filters, the path integral method which is theoretically matured in the stochastic dynamics domain is generalized to obtain the capsizing probability of the tremendous warship subjected to the stochastic storm perturbation and the weapon attack, that is, the dimension of the stochastic differential equation is expanded to five. Secondly, the numerical method is used to solve the corresponding five dimensions FPK equation to obtain the probability density function of the rolling angle. Finally, the existing capsizing criterion is introduced to evaluate the capsizing probability. Because the coefficients of the FPK equation are related closely to wind and explosion, the expression for calculating the capsizing probability derived as above not only can evaluate the effect of random wave on the capsizing probability, but also the effects of wind and explosion on it ,which is helpful to evaluate rationally the survivability of the damaged warship in battle subjected to wind evidently.