The Slamming Response Of The Overhang Structure At Broadside Based On The Wet Mode-Superposition Method

With the need of ocean resources exploiting, various new type ships and ocean structures are coming fourth. Many problems came down to the coupling interaction of fluid and structure. Slamming is a transient highly nonlinear dynamic phenomenon because of the interaction between the moving ship and fluid; it involves the coupling among air, fluid and structure which is not settled completely till now. Due to the complexity, we introduce some simplification assumptions according to the features of the problem in the actual research, ignore some other secondary factors.In this paper on the basis of previous studies, uses the boundary element method to describe the interaction problem between the fluid and the ship, at the same time use the relevant theory of wet mode-superposition method to research the slamming response between the overhang structure of the broadside on the moving ship and the fluid.Base on the basic theory of BEM to divide element on the fluid-solid interface, meanwhile based on the basic theory of FEM, on the condition of uncoupling among the node freedoms to get the mass and stiffness matrix of plat shell element through the plane stress element and plate bending element, the structural damping use the Rayleigh damping. Base on the software of MATLAB to development the Finite Element Method program. Call the program to calculate the deflection and moment coefficient of plat on different aspect ratio, different boundary conditions under the uniform and concentrated force respectively, and coincide with the theoretical calculation result. While calculate the modal frequency and modal shape of plat and stiffened on different boundary conditions, and coincides with the result of theoretical calculation. Verify the correctness of the finite element method program through call this program.The Wet Mode-Superposition Method is a vibration modal research method which takes account of the dynamic influence between the ship and the fluid. Use the Hess-Smith method to discrete the integral equations of velocity potential at the source points, while use the Wet mode-superposition method turn the slamming force of ship into the added mass matrix and added damping matrix of fluid, and combine the Characteristic matrix of structure to research the response of fluid-solid coupling. Considering the Green function of 3-D pulsating source base on the software of MATLAB to development the boundary element method program, and combine the FEM program to compute the slamming response on the overhang structure of ship board at different selected design waves via the Wilson-θmethod. Obtain the time process curve of displacement, velocity and acceleration at different points and different slamming conditions during the slamming process. Apply the Fast Fourier Transformation to obtain the frequency response function of displacement response, thus draw the variation frequency of the structure at the influence of additional quality and additional damping during the slamming process.