الفهرس 
INTRODUCTION AND AIM OF THE WORKOnly 14 pages are availabe for public view
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Abstract
Ship resistance is one of the main parameters that must be estimated earlier in the preliminary and concept design phases. One of the main requirements of the design for the owners and the shipping companies is the design speed, owners may refuse the ship if in sea trials it doesn’t achieve the design speed, in this case, it will be too late to make any modification in the design, and any other modification will be costlier in both initial cost and the operational cost as well, as the power required in this case will be increased to achieve the design speed. Another significant requirement for the ship is to achieve the design speed not only in a steady sea state but in different sea conditions during operation as well. This arises the significance of the study of ship resistance not only in still water but in waves as well. The resistance in both calm water and waves must be estimated earlier. One of the main aims of this study is to build a methodology to estimate the total resistance in calm water and waves to derive the added resistance in different sea conditions by varying the incoming wavelength. The tool used in this methodology deriving is CFD using STAR-CCM+, and the ship model used is KCS (KRISO container ship) in KRISO model scale, with constant Fr number at ship design speed with a value of 0.26 and constant wave steepness of 1/60. To estimate the added resistance the model is constrained to move in the longitudinal direction instead the water is advancing in the opposite direction with the constant current speed of 2.19699 m/s to achieve the Fn number of 0.26(the model is without a propeller). The conditions used in the presented study with different wavelength ratios of 0.85, 1.15, and 1.35 respectively. Each condition is studied in two simulations, one with a fixed ship without any motion and zero degrees of freedom, whereas the other is with free motion ship with two degrees of freedom for the heave and the pitch motion, these two cases aim to estimate the expected components of the added resistance, which are the component of the wave radiation from the ship motions, and the diffraction/reflection component of resistance which results from the changed wave shape caused by the ship hull, the second aim in this study is to investigate the grid convergence of the used mesh in the simulation, ITTC procedures are used in this grid convergence study to estimate the errors and the interpolated results between different grid sizes. Finally, a lot of comparisons are performed between the results of the presented work and results from the previous work, this comparison is used in the validation and to check the solution convergence of the CFD used setup. The future work is mentioned in our study, and it is to perform a lot of simulations with the same setup used in this study but with several waves, steepness differs from the used one of 1/60, by increasing wave steepness, it is expected that the added resistance is expected to be increased so that this is a point of our future investigations, another work needs to be estimated is to perform hull shape optimization to minimize the resistance and the power required for operational/ design speed and the cruising speed as well. Another important parameter that must be earlier determined in the design is the added power due to ship motion in waves, in the presented work not only the added resistance is analyzed but the added power as well. The same KCS model and the same converged numerical grid setup are used. This time a self-propelled KCS model with the same scale as the KRISO model scale. The propeller used in this simulation is KP505 with a scale ratio of 31.6. for the aim of validation and results analysis, the self-propulsion simulation of KCS is done using two vii different approaches. The first approach uses the actuator disk (virtual disk in STAR-CCM+) which applies the body force method (momentum theory). The second approach uses the discretized KP505 propeller. wave steepness of 1/60 and Fr number of 0.26 are kept constant in all simulations to keep the ship’s speed at 2.19699 m/s. To minimize computer efforts and simulation time, as a start several simulations using VD were done with different propeller rotation rates in still water and critical head waves of 𝐶2 = 𝜆/LBP=1.15 which causes heave and pitch motion resonance. Linear interpolation between results was used to determine the propeller rate that achieves the Fn number of 0.26 in both still water and waves. Another concept used to determine the rotation rate of the propeller is using the PID controller and the two concepts are compared finally. The propeller rotation rate results from the VD simulations are used in the discretized propeller simulations also, and another PID controller is used in the other discretized propeller simulations, finally, comparisons between the VD and the discretized propeller results are compared and analyzed, for example 𝑘𝑡 , 𝑘𝑄, J, 𝜂𝐻 and 𝑐𝑇 results. The wakefield description behind the propeller plane, in front of the propeller plane, and at the propeller plane are investigated in our work in both cases VD and DP. The advance speed and the wake fraction are analysed in the cases of still water and head waves as well. In the case of head waves, the wakefield is described in different phase angles between the ship and the wave. The results of the wake field in still water in the case of the virtual disk can be used in an optimization process for the KP505 propeller at full scale in future work. Several results are obtained and illustrated in the present work. The results of the towed model used to show the effect of the wavelength change on the added resistance in regular head waves. In this case results shows that the at wave frequency near the heave motion resonance frequency the added resistance is maximum as the pitch motion is difficult to be in resonance as the moment of inertia of the ship around the horizontal axis is very high, also the self-propelled model results used to illustrate and analyse the effect of the wave steepness on the added powering of the ship in regular head waves in this case the wave length kept constant 𝐶2 = 𝜆/LBP=1.15. results showed that the shaft power increased from 0.15 kw in still water to 0.92 kw in the case of the maximum steepness used of 𝐻/ 𝜆 =1/40. This shows that the power increased significantly with 5 times the calm water value, this is the main finding in the present study. Another investigation of the wakefield and the interaction between ship’s hull, waves, propeller, and rudder is obtained through the results, which show that the wakefield velocities is totally different with wave crest located mid ship than the wave trough located mid ship. Results show that the wake velocities are higher in the case of the wave trough at mid ship than the case that wave crest located mid ship. During ship motions in waves this frequency and fluctuation of the velocities around the propeller due to wave troughs and crests, this leads to losses in the energy given to the fluid by the propeller, this decreases the propeller efficiency. In the conclusion it can be said that propeller efficiency in waves decreases significantly, and this can be more significant with the increase of the wave steepness. Finally, Recommendations are mentioned. As the flow around the propeller can be improved to be homogenous by optimizing the shape of the ship’s stern and its lines and the shape of the propeller as well. Another recommendation about using motion damping devices to decrease the fluctuation of the wake velocities in the propeller plane. Modern power saving devices can be used as well such as the bulbed rudder or ducted propeller as another solution.