Study On Aerodynamic Optimization Of Arc-shaped Sail And Interference Of Double Sails

With the global increasingly serious energy crisis and air pollution, Using the method of employing sail to assist the vessel is catching attention to the shipping and shipbuilding industry, because of its advantages such as sustainable development, low cost and green. Optimizing the aerodynamic characteristics of sail and improving the efficiency of wind energy utilization is one of the most important research of sail.This thesis is to adjust the structure of traditional arc-shaped sail,make it into double arc-shaped sail and optimize its aerodynamic performance. Related parameters of double arc-shaped sail which can influence its aerodynamic performance are studied based on computational fluid dynamics(CFD) by using control variable method and the final optimization model is chosen according to the principle of maximum thrust coefficient. At last, interferences of double sails of the optimized model are studied.Firstly, traditional arc-shaped sail is chosen as the optimization object by referencing to the relevant literatures and analyzing the advantages and disadvantages of different kinds of sails,the structure of traditional arc-shaped sail is adjusted and its structure parameters are defined. A bulk carrier is chosen as the target ship and the main scales of double arc-shaped sail are designed based on it.Secondly, Factors of the numerical modeling process, which affect the calculation results, such as turbulence model, wall function, boundary condition and discrete mode are compared, the appropriate parameter settings are selected in solver. By using control variable method, the ratios of outer and inner arch are respectively researched in the CFD software and their influence law to double arc-shaped sail are gotten. the final optimization model(double arc-shaped sail with outer arch ratio being 0.5 and inner arch ratio being 0.35) is chosen according to the principle of maximum thrust coefficient, its maximum lift coefficient is 50% larger than the traditional arc-shaped sail with arch ratio being 0.16 and its maximum thrust coefficient is 67% larger than the traditional arc-shaped sail of 0.16. The influences of angle of attack deviation and the ship roll are quantitatively calculated and the thrust deduction method is proposed.Finally, the interferences of flow direction and sails distance to double sails of the optimized model are studied. The results show that lateral reverse wind has a good influence on the double sails and lateral tailwind has a bad influence on them with the complete tailwind being worst. The results also show that the influences on double sails become small when their distance is larger than 3 times of their chord and good influences even appear at some lateral tailwind angles. Synchronous control characteristic curve of double sails are given when their distance are as 4 times as their chord. Quantitatively calculation of "Z-route optimization" are carried out and the results show that small range of yaw angle can improve the efficiency of wind energy utilization for double sails.