Numerical Study On Trimaran Heave And Pitching Hydrodynamics Based On Panel Method

The main hull of the trimaran is a slender body,the left and right sides hull is generally symmetrical distribution.As a new type of ship,it shows better hydrodynamic performance than the conventional mono-hull ship.Research on the trimaran has become the hot topic.With the development and application of the potential flow theory,the research on the motion of trimaran on wave is becoming more and more important,one of which is the numerical calculation of hydrodynamic coefficients.Panel method is one of the commonest numerical methods to solve the potential flow problem.In this paper,the panel method,combined with Green function based on Rankine source,is used to solve the hydrodynamic coefficients of trimaran under swaying motion of micro-amplitude.Firstly,the definite conditions of the steady-state wave-making problem of trimaran in the infinite open water is established;Then the boundary elements are partitioned on each boundary surface,sources and sinks is distributed on boundary elements,and the potential function of each field point can be expressed by Green’s function;According to the boundary conditions,the equation systems can be concatenated to obtain source density of each singular point and potential function;Finally,the hydrodynamic coefficients of the ship are obtained by the Bernoulli equation and the integral equation.On solving radiation problem,often taking into account the ship’s unsteady motion,that is,the unsteady velocity potential is included in the total velocity potential.Then the unsteady radiation problem is established in the frequency domain to solve the ship hydrodynamic coefficients.In addition,coupling effects of steady motion and unsteady motion are considered on the boundary condition,that is m-term,so that the hydrodynamic coefficients of the trimaran can be expressed and calculated more effectively.In order to verify the reliability and accuracy of this program,Firstly,the numerical results of the additional mass of the ellipsoid of different scale ratio in the unbounded flow are compared with the theoretical value.Then calculating a certain depth of the ellipsoid and Wigley wave resistance,and the program exists reliability and certain accuracy by comparing result with the experimental data.Finally,the partial hydrodynamic coefficients of the Wigley and trimaran under under swaying motion of micro-amplitude are calculated,that is the additional mass and damping coefficient values under heave,pitch motion and coupled motion,the results of the single Wigley calculations are compared with those of other authors.At the end,the influence of different speed and side-body layout on the additional mass and damping coefficient of trimaran was analyzed to study the trimaran’s heave and pitch motion,and draw the final conclusion of this paper.