| When liquid tanks are partially filled,there would be significant coupling effects between tank sloshing and ship motion of an LNG carrier. Thus, taking into account of tank sloshing effect is important for predicting hull motions and loads accurately. Currently the researches of the problem mainly focus on theoretical methods, and calculation and analysis of real ship is rarely inland.Thinking about the impact of tank sloshing on the hull motion, this article expands the 3-D linear frequency-domain wave loads calculation method to get hull motion responses; Take the tank movements as an incentive type, using CFD method to simulate fluid motions in the tank, and forecasting the pressure changes of the bulkheads. Thereby a set of applicable method suitable for ship motions and wave loads prediction about LNG ship was formed. The main contents are as follows:1. To consider the slight motions of the liquid in the tank, and based on liner potential theory, boundary element method and free surface Green function are used to get the additional hydrodynamic coefficient of six degrees of freedom due to tank sloshing;2. Consider the coupling between the tank and the hull, and add the additional hydrodynamic coefficients into the initial motion equations. New motion equations are formed and solved. The hull RAOs are compared with those don't consider the hull tank sloshing;3. Use CFD method to simulate tank sloshing motion. Establish N-S equations and disperse them with the finite volume method. Selecte the standard k ?εturbulence model, and use VOF method to track the free surface changes. The wall area will adopt the standard wall function method. Write the UDF and in combination with dynamic grid, to simulate tanks rolling movement and predict pressure changes of the tank. 4. An LNG ship's motions and the tank pressures are calculated by this method, and the results are compared with the values provided by the literatures, as a result to validate the method.
|
PDF Full Text Request