Studies Of CFD-based Resistance Performance For Mid-speed Fishery Administration Vessel

With the development of marine fishery to the deep sea,the sea fishery law enforcement environment which we are facing becomes more and more complex.The fishery law enforcement vessel should have the quick response ability,for which,the speed of the vessel has become more and more important.The speed will directly affect the fishery ship law enforcement ability and vitality.The most important factor affects the speed is ship resistance.Generally ship resistance should be forecasted and validated in the early stage of design.In the stage of ship line design,there are two ways to obtain the resistance,which are the ways by ship model experiment and numerical calculations.The model test need long time and high cost because of the model preparation.It is difficult to obtain the local flow stream line,pressure distribution of bow,stern and the appendages because of the limited test time.The Reynolds number and the Froude number can not be similar at the same time because of the scale effect.For the reasons above the test result and the ship voyaging in real sea still have some differences.The model test has great limitations.With the rapid progress of CFD theory and computer hardware,the numerical simulation has become an important method for ship resistance calculation.In this thesis,at first it briefly reviews numerical calculation of ship resistance development situation,analyses the typical ship resistance prediction method,introduces the main CFD drag prediction tools.Then calculating total resistance of the bare ship in ship and model scale by different analysis tools,and comparing results with the experiment to verify the accuracy of the results are done.At last,in the model size,calculating the resistances due to main appendages,such as bilge keel,spray strip and tail fin,analyzing the influence factors of various types of appendages on the hull resistance are conducted.Research shows that:(1)the CFD analysis tools such as fluent,Fine/Marine of such high-speed patrol boats can predict ship resistant with good results,which can meet the needs in the conceptual design of drag prediction and linear optimization;(2)for the same model under different Froude number of numerical simulation precision difference larger,so with the ship which has large variation range Speed,under different Froude number,the main resistance influence factors and the calculation model requirements might be different,it is difficult to using the same method in different Froude number to obtain reliable results;(3)in the Fine/marine by mesh refinement and increase the boundary layer,the numerical simulation can capture the bilge keel,spray strip sheet is attached to the body;(4)in the rational design,the bilge keel would not flow field around the hull produced great influence,mainly to increase friction resistance,near the design speed increase value is about 5%;(5)The spray strip is arranged on the tail can effectively reduce the total resistance of these ships,in this ship the drag reduction can reach about 5% at the design speed;(6)Total resistance caused by such a ship fin increases by about 6%,but along with the change of the Fourier number,increases the tendency of change in the proportion is more complex,actual ships sailing velocity should be given priority in design of caudal fin.In this thesis based on CFD tools on the resistance property of vessel of forecasting and research,for follow-up at the design stage of a fishery administration ship lines design provides a new method,and provides reference and reference for various types of attachment design.