Steady Hydrodynamic Performance Research On Ship Motion Control Lifting Bodies

Seakeeping is one of the particularly important performances for a ship.Generally there are two major measures to improve the seakeeping performance;One is to design a more excellent seakeeping ship,focusing on the four elements:the principal dimensions of the ship,the bow cross-sectional shape,bulb shape and design of the bow freeboard;the other one is to install a variety of stabilizing devices on the ships,including early bilge keels,anti-rolling tank and kinds of new anti-rolling appendages.This thesis mainly studies the steady hydrodynamics performance of the lifting body under the background of the ship stabilizing efficiency research.Normally,the hydrofoil theories include the lifting-line theory,lifting-surface theory,the panel method based on the potential theory and the CFD technology based on the viscous flow.This article only uses the constant penal method to calculate the perturbance field of the hydrofoil.Boundary element method can satisfy the boundary condition on the real body surface,without the approximation of the body shape,and it has been able to calculate the fluid dynamic performance of the lift body accurately after so many years of development.In this paper,the main works are to calculate the steady hydrodynamic performance of marine lifting bodies based on surface element method,Firstly,according to the boundary condition of the hydrofoil,the paper constructs the boundary integration equations,and solves the equations using the Fortran language,then repeats the calculation process by the Newton-Raphson iteration method until the results satisfy the Kutta condition,which is that the pressure of the upper and lower surface near the trailing edge is equal.Secondly,the paper considers the interaction between the ship body surface,free surface and the hydrofoil under the assumption of the high and low velocity condition,and gives out of the curve line of the hydrodynamic varied with the distance near to the free surface of the hydrofoil.Thirdly,the paper introduces the Taylor Expansion Boundary Element Method to the calculation of the hydrodynamic of the lifting body,and compares the calculation accuracy with the traditional boundary element method.Fourthly,the paper considers curly tail vortex surface shape to improve the accuracy of the hydrofoil hydrodynamic performance,for the hydrofoil which the span-chord ratio is low,the paper considers the effect of the tip vortex,referred to the Bollay vortex model and Qin X.C's panel method model,and it is proved that the new model is more approximate to the experiment values.Finally,the paper calculates the steady hydrodynamic performance of a T-shaped hydrofoil using the aforementioned theories,and then analyzes the stabilizing efficiency of the T-shaped hydrofoil,which is of engineering significance.