Numerical Prediction Of Hydrodynamic Derivatives And Maneuverability Of Ship In Brash Ice Region

When the ship is sailing in the brash ice region,the movement of the brash ice is affected by the hull and the flow field around the ship is disturbed by the movement.Its flow field characteristics are different from conventional waters.The impact of ice-water coupling need to be taken when calculating the hydrodynamic force and torque on the ship in the brash ice region.The main purpose of this article is to use the CFD software STAR-CCM + DEM particles to simulate brash ice.The momentum and energy exchange is performed to achieve the coupling effect between ice and water by turning on the two-way coupling mode under the DEM module.Ignore the effects of the free surface.Simulate PMM motion(oblique motion,sway motion)of a certain type of ship in the brash ice region and solves part of hydrodynamic derivatives under ice-water coupling.Establishe a prediction model for the Maneuverability of the brash ice region,compile the ship’s three-degree-of-freedom maneuvering motion program based on the MMG idea through computer language,then Carry out simple forecast of ship maneuverability in the brash ice region.It provides certain research ideas and technical means for the prediction of ship maneuverability under the influence of ice-water coupling in the brash ice region in the future.This article first introduces the ship ice-water coupling theory in detail from the governing equations of the incompressible fluid in CFD-DEM,the governing equations of the interaction between DEM particles and the SST wk-model.Three kinds of DEM brash ice particle contact theories,empirical formulas for ice resistance in brash ice region,and several models of hydrodynamic derivatives of ships under open water conditions are summarized.By comparing the static water resistance and the movement posture about bow and stern,s brash ice of 76000 DWT bulk carrier sailing experiment in brash ice region with those of using this paper,s grid and DEM setting in the numerical simulation,the accuracy of the grid setting and calculation method is verified;At the same time,the direct navigation resistance of a certain type of icebreaker in the brash ice region is compared with the Mellor and DUBROVIN formulas for error analysis to verify the rationality of the grid and calculation method again.Then,numerical simulations of the oblique and swaying motions of a certain type of icebreaker under open water and brash ice conditions were carried out,Calculate the lateral forces and turning moments of the ship under open water conditions and brash ice conditions,and then calculate the hydrodynamic derivative of a certain type of icebreaker in open water and coupled,Improve the calculation model of the bare hull hydrodynamics.Finally,based on the idea of MMG,the hydrodynamic derivative is randomly selected in the fluctuation interval of the coupled hydrodynamic derivative and applied to the corresponding hydrodynamic calculation model in the form of self-programming,which reflects the randomness of ice interference to water flow.Ignoring the influence of wind,waves and currents,a ship’s three-degree-of-freedom maneuvering motion equation based on the MMG idea is established,and the fourth-order Longge-Kutta method is used to solve the equation.Numerical simulation of a certrain type of icebreaker under open water and 30%brash ice region were carried out for direct navigation and full rotation.The simulation results are compared with references to verify the applicability of the simulation program for a certain type of icebreaker in the ice-breaking area.