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5.2 Simulation for the sailing performance in North Pacific Seaways
 
 We investigate the sailing performance of the sail-assisted ship equipped with the underwater fin in actual sea condition. We think that the route of this sail-assisted ship is the round trip of north pacific seaways. At first stage, we simulate the sailing performance for the quasi-steady condition in this seaway. This means that north pacific seaway is divided into some blocks and the wind condition at each block is used the averaged data for one year. The wind velocity and direction is constant in each block. The statistics data of North Pacific is used from the wave database. The route and wind condition used in simulation is shown in Fig. 11. We evaluate the sailing performance in each block when the rotation velocity of propeller is constant. The evaluation of propulsive performance is used the fuel consumption. The fuel consumption is decided that integrated BHP for navigation time is multiplied by the coefficient of fuel consumption for engine.
 However, in this study, the characteristic of engine is unknown. We substitute the DHP into the BHP. We can understand the qualitative change of the fuel consumption. The coefficient of fuel consumption on engine is constant in this study. We estimate the fuel consumption in north pacific seaways for each fin configurations. Moreover, the navigation time is important for delivery service. We estimate navigation time in north pacific seaways for each fin configurations. The fuel consumption and navigation time is shown in Fig. 12. The estimation of the fuel consumption and navigation time is the ratio of the estimation value of each fin configuration to the estimation value of the original hull.
 
Fig. 11 The seaway and average wind condition in north pacific
 
Fig. 12 
The evaluation of sailing performance when propeller rotation velocity is constant
 
a) 
The change of the fuel consumption for fin configurations
 
b) 
The change of navigation time for fin configurations
 
 For the fuel consumption, Case 3 is the best efficiency. This result becomes same as the results of the steady condition simulation. The fuel consumption of Case 3 can decrease in 5.3% compared with that of original. We have found that the effect of the resistance due to the appendage resistance and rudder deflection is large. The decreased ratio for the averaged DHP for wind direction when fin is installed is different from the decreased ratio for the fuel consumption when fin is installed, since the wind direction in this seaway is assumed to be one direction.
 For the navigation time, the minimum of navigation time is Case 3. We think that the case of the fuel consumption is same. The navigation time of Case 3 decreases in about 3.9% compared with that of original. The economy of ship can be improved due to the shortening of the navigation time, since the underwater fin is installed.
 These under water fin configuration can improve the propulsive performance in actual seaways. But the fin configuration should be investigated in detail for propulsive performance in the future. Also we use fixed route in north pacific in this study, the optimum route should be investigate in order to improve the fuel consumption and navigation time in actual seaway.
 
6. CONCLUSIONS
 This paper concerns the underwater fin arrangements of the sail-assisted ship. So we have constructed the simulation tool for the sail-assisted ship. We investigate the differences of the underwater fin configurations by using this simulation tool. We have obtained the following conclusions from results of simulations.
 
(1) The DHP' of the ship equipped with the sail and fin is decreased in about 8% compared with the original in steady wind condition in this study. We have understood that the sail-assisted ship improves the propulsive performance.
 
(2) We have found that the sail area is restricted greatly due to the rudder deflection angle. The rudder deflection has the tendency to become large in sailing condition since the target ship is novel merchant ship.
 
(3) The most efficient underwater fin arrangement in steady wind condition is Case 3 that is center board type, placed in backside of ship. However, the area of fin in Case 3 is small than the other case installed the fin, the resistance of Case 3 is smallest due to small fine area and small rudder deflection.
 
(4) We investigate about the fuel consumption and navigation time for sailing in North Pacific Seaways to estimate the sailing performance in actual seas. Case 3 is the most efficiency for both fuel consumption and navigation time in other case as same as simulation for steady wind condition. The fuel consumption of the Case 3 is decreased in 5.3% compared with the original. The navigation time of the Case 3 is decreased in 3.9% compared with the original.
 
 Simulation results show the improvement of propulsive performance by sailing. Moreover, One case of the underwater fin configurations can improve compared with the original hull equipped with only sail, since the under water fin can improve the attitude of ship and rudder deflection, It is will be a possibility to investigate the fin configuration in detail which can improve the propulsive performance. In this study, we use the fixed route in north pacific. Next target is to investigate the optimum route in actual seaway and the control method for the propeller and engine. Also, we would like to research the total design combined hull form, rudder and underwater fin in order to improve the sailing performances in the future
 
REFERENCES
[1] Minami, Y, Nimura, T, Fujiwara, T, Ueno, M, (2003), "Investigation into Underwater Fin Arrangement Effect on Steady Sailing Characteristics of a Sail Assisted Ship", The Proceedings of the 13th International Offshore and Polar Engineering Conference
 
[2] Hirano, M ,Takai, T, Matsumoto N "The application of Manoevrablity model for ship design Proceedings of The 3 rd Symposium on Ship Manoevrablity, the Society of Naval Architects of Japan, pp.101-136,1981
 
[3] Fujiwara, T, Ueno, M, and Nimura, T, (1998), "Estimation of Wind Forces and Moments acting on Ships", Vol. 183, J. of the society of Naval Architects of Japan.pp. 57-69
 
[4] Fujiwara, T, Ueno, M, and Nimura, T, (2003), "On aerodynamics characteristics of a hybirid-sail with square soft sail", The Proceedings of the 13th International Offshore and Polar Engineering Conference
 
AUTHOR' S BIOGRAPHY
 Yosimasa Mimami was graduated from the Naval Architect Department of Kyushu University in 1993. I worked in National Maritime Institute. I mainly research about the hull design in actual sea.







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