Wave Frequency Coupled Dynamic Responses Analysis Of TLP

The quality of the tension leg platform motion performances directly affects the platform design form and the use level of the steel, further more determines the economical efficiency of the platform ,so it is the key of the platform design .The responses of TLP can be divided into three scopes :Wave frequency responses, low frequency responses and high frequency responses. In those scopes, the coupled affection of the tendons is all very important. This article we begin with the easier wave frequency responses, and do some researchers to establish a suite of methods to calculate the coupled dynamics responses of the TLP.Firstly, according to 3D potential flow theory, formulation of 3D unsteady velocity potential in frequency without forward speed is given and source distributed boundary integral equation is used to get the numerical solution of the fluid potential. Subsequently, the hydrodynamic coefficients, wave forces, hydrostatic restoring coefficients and drag coefficients of large scale bodies are calculated. The linearlization of drag force is also performed. Therefore, Wave loads of the platform in wave frequency are determined.Secondly, after analyzing the internal state of stress at a point on the tendon, the governing equations for the dynamics tendon in water is obtained. To solve the equations, we discrete the tendon into 3D beam element, by applying the Galerkin's method to governing equation over the length of the element, we get the solution equations and give the physics means of each part. For the small amplitude motions, the equations is linearized and the frequency solving method is discussed.Finally, according to the match of the motions and forces at the points connecting the platform and the tendons, the coupled stiffness of the tendons is computed as linear springs and 3D beam element models. Then the coupled motion equations is obtained and the solving method is discussed.