Resistance Simulation Of Ship Appendages Based On Dynamic Grid

Installing appendage is the most efficient way to improve the surrounding fluid field for ships,without changing the main ship hull form.With a relatively small scale and convenient installation,ship appendage has tremendous influence on the ship rapidity and its manoeuvrability in many good ways,which is essential to those high performance vessels.With the development of the grid generation method,especially the dynamic grid generation technology,lots of dynamic boundary problems have been solved.The dynamic boundary related problems of ship appendages for the CFD simulation within shipping field are carried out,in this paper,using two dynamic gridding methods,the deforming grid and the overlapping grid.For the fixed appendages,the related hydrodynamic values under different appendage geometry parameters should be calculated aiming at the specific ship hull,which is called the optimal selection design.The traditional calculation philosophy is to modify the geometry model,re-grid and re-calculate from the initialized fluid field after one geometry parameter case has been done,which means,one appendage geometry parameter,one calculation case.A deforming grid method is brought up to realize the optimal selection design,in this paper.The new philosophy is to transform the related geometry parameter directly using the deforming grid,under the circumstance of the now-existing fluid field,which has been obtained while calculating under the original geometry parameter.This means one calculation case covers all the geometry parameters under the same sailing speed.Firstly,three basic deformations have been brought up,in this work,which are the stretching deformation,the slope deformation,and the rotation deformation,aiming at the common characteristic parameters of those widely used ship appendage.Secondly,the cases on two specific ship appendages,the interceptor and the stern wedge,are calculated,making the above deformations into use,to verify this new calculation philosophy in the optimal selection design for ship appendages.Due to the obtained fluid field while calculating under the original geometry parameter,the convergence will be faster after the deforming process takes place,which is a giant advantage for the optimal selection design.For the active controlled appendages,a real-time adjustment to the active motion of the appendages should take place while sailing.A deforming grid method is used to simulate this active motion,in this paper,by calculating the hydrodynamic values of an active controlled hydrofoil as an example.What’s more,the 6-DOF motion of the ship while the hydrofoil is rotating has been simulated using overlapping grid method,in this paper,which could mean a lot to the research on the active controlled appendages.