In this paper, a numerical method for the design of the marine propellers is described. The lifting line model discretized with the vortex lattices and the variational calculus are used to determine the optimum circulation of the propeller blades under the design requirement. According to this optimum circulation distribution, the specified type of pressure distribution on the sections of the blade and the thickness of the blade section, the blade of propeller is designed by a numerical design method based on the sueface panel method. By Morino's surface panel method the performance of the designed propeller is analysed and the pitch of the designed propeller is modified to make its circulation distribution be consistent with the optimum circulation distribution. The propeller in the uniform flow and the wake adapted propeller in the circumferentially uniform axial wake are designed as examples by this method.

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The performance of screw propellers in unsteady flow and the stressdistribution and deflection of their blades are computed by surface panel method in combination with the thick shell finite element method, and compared with the experimental results. The characteristics of the surface flows on rigid and deflected blades are approximated by Taylor's series expasion and minimization of the perturbation velocities. A new method is applied to estimate the time derivatives of perturbation potential on the basis of a minimization of the change of its kinetic energy. The comparison between calculated and measured data for pressure distribution confirms the reliability of the estimation of unsteady characteristics at tip of the propeller.

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Recently various types of special vessel as like FPSO, shuttle tanker, and drill ship are come to fore and are ordered from the European ship owner, because of the necessity of multi-purpose vessel and deep sea drilling rig. Traditionally mooring line systems of offshore structures has been used to keep her position in shallow water but nowadays Dynamic Positioning System is being used to keep her position in deep sea. In this study, DP simulation program will be introduced. The program can predict the time varied motion of the ship with mooring and DP propulsion system in the horizontal plane. Motion equations used in this program considers the wind, waves, and current as the external forces and mooring line forces in addition to propulsion systems. To find the input variables of the positioning systems, PID and LQR processes are considered as the control system. Furthermore Kalman filter and digital filter are used to exclude the noise and high frequency components of motions in the calculation of input power. For the validation of this program, model test results of 125K shuttle tanker and 103K drill ship are used. The comparison between model tests results and simulation results showed good agreements.

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