On The Flow Process Of The Damaged Ship Based On The CFD Simulation

Shipping accidents seriously affect the safety of human lives and the cargo.Then in ship design and salvage, researchers should study on damaged ship, among which, the research for the damage stability is significant. At the same time, in the process of the ship breaking, it is necessary to pay attention to the phenomenon of fluid motion, the liquid level change, the free surface fluctuation and so on.Based on the computational fluid dynamics(CFD) software Fluent,this paper makes a time domain simulation study on the whole process of the flooding of more complex three-dimensional compartments of hull, spilling of a real-scale oil tanker in the case of multiple damaged hull, and also simulation study on the flow characteristics of damaged orifice.First of all, this paper sets up the numerical simulation method, meshing in Gambit platforms. For different meshes, the optimal convergence time step is calculated and the convergence analysis is carried out, and according to the actual situation, sets up the software parameters, selects the appropriate flow model, to establish a complete research method.This paper use the above methods to research the box type ship (many cabins) and the rectangular tank, flowing simulation of the fixed and free floating state of damaged ship,among them,using the VOF method to deal with water-air free surface,using six degrees of freedom(Six-DOF) solver and dynamic grid technology to deal with the trim and heave motion of the hull. The results of the study are compared with the existing results, and the degree of fit is high. In the process of simulation, the change of liquid level in the tank and the floating state of the ship hull, and the instantaneous phenomena of the water column injection can be observed. The study of the water inlet of the free floating state box shows that a larger extent degree of freedom is selected to simulate,other five degrees of freedom are limited have less effect on liquid level and float state of hull structure.In this paper, numerical simulation method can be used to estimate the discharge coefficient more comparatively accurately, and simulation calculation process can reflect more real flow. Discharge coefficient is an important factor in the assessment of damage.Because of the complicated flow of fluid dynamics software is limited by computational speed, the discharge coefficient can be used to improve the accuracy of the flow in the process of rapid simplified calculation.The Fluent software can be used in this paper for damaged orifice flow simulation,compared with experiment results to choose the good computational method,to deal with the simulation results, the discharge coefficient can be obtained. And in the different situation of orifice the research of discharge coefficients are analyzed.Finally, in this paper, based on the numerical simulation method, the simulation of gas-water-oil three phase flow is verified, and simulation analysis about the spilling and flooding of the damaged tanker has carried on. The results show that the design of the side cabin limits the leakage of oil to a certain extent. In the initial stage, the partial discharge of oil is injected directly from the oil tank, so that the width of the side chamber may be helpful to reduce the leakage of oil. In the simulation results,the roll and heave amplitude of the tanker is relatively small,compared with the motion state, fixed state of the tanker have more spills,less water inflow.