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Numerical Caculation of Wave Resistance and Hull Lines Optimization

Author: LanLiang
Tutor: HuangSheng
School: Harbin Engineering University
Course: Design and manufacture of ships and marine structures
Keywords: wave resistance Michell integral Noblesse’s new slender ship theory Dawson method geneticalgorithm ship form optimization
CLC: U661.311
Type: Master's thesis
Year: 2012
Downloads: 248
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Abstract

It is the difficulty and hot that looking for the ship form with the best resistanceperformance of ship type in academia and engineering. The deeply systematic research on theship wave resistance calculation and the ship lines optimization based on the geneticalgorithm are the main contents in this paper.This paper systematically expounded the development of the ship wave resistance theoryand summed up the current situation and the developing trend on the aspects of the lineartheory and the nonlinear theory in china and abroad. It also expounded the application anddevelopment prospect of the wave resistance numerical calculation method in the way of theship form optimization.The procedure of the wave resistance numerical prediction and the calculation on thewave resistance of the different ship forms were succeed with the theory of the linear waveresistance. Detailedly, the tent function was used for the approximation of hull surface shapebased on the theory of Michell integral thin ship theory. A new numerical calculation methodwas adopted, and Kochin free amplitude function was calculated, and the integrand functionwas expended by using special function based on the theory of Noblesse’s new slender ship,meanwhile, the integral term of the freedom volatility function was analyzed, and the infinitedomain, where the integral originally was calculated in, was changed into the limited domain,and the wave-steepness limitation of elementary was used to revise the calculation results inorder to reduce the roller-coaster in the integral. The results show that the new numericalcalculation method can predict the performance of wave resistance partly, but the accuracy offorecasting depends on the ship type. The revisionary results by the theory of Noblesse’s newslender ship are more close to the experimental values. The the influence of the calculationresults by waterline integral items to the wave resistance in the method of Noblesse newslender ship has analyzed, and the important role of the wateline integral term is proved.Based on the potential flow theory, the no lift streaming problem of any3D objects wasanalyzed, and the streaming calculation procedure of any3D objects in static water wascompiled according to the Hess-Smith face element method. The calculation results have agood agreement with the experimental value by the numerical simulation for the streamingproblem of the simple3D objects (such as sphere, ellipsoid) to verify the reliability of the program text. And then, the hull double-model streaming was calculated to get the hullsurface velocity distribution and the stress distribution.The free surface grid was drawn by the methods of thinking streamline as horizontal gridline, double-model streaming as basic flow and using four-point Runge-Kutta Method totrack streamlines. The weak nonlinear wave resistance forecast program was compiled basedon the Dawson method with the wave disturbance affects in a free surface. In the process ofcomputation, the four-point upstream finite difference was used on the derivative through thefree surface streamline, and the two points difference was used on the boundary around thefree surface grid. The different ship form wave resistance was calculated, and the results werecompared with the results of the linear theory and the test dates. So the Dawson method is afast and accurate wave resistance calculation method. It also can predict the height andwaveform of the wave on the side of the ship, and the ship form doesn’t restrain the method’sapplicable range.The ship lines ware optimized to make the wave resistance as the objective. The use ofthe genetic algorithms in the optimization of ship forms was studied preliminarily. Accordingto the genetic algorithm toolbox of the University of Sheffield in British, compiled therelevant optimization program. Optimization results show that the wave resistanceperformance of the optimization ship forms has improved better than that of the mother shipforms.

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