Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Multi Objective Optimization of Ship Hull Form Design by Response Surface Methodology
Multi Objective Optimization of Ship Hull Form Design by Response Surface Methodology
Pages 977-990
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From page 977... ...
as the optimization tool to search the global optimum for multi-objective functions. The RSM approximates the response surface by use of a polynomial function of design parameters, and the RSM can be evaluated without significant computational expense in the course of optimization process.
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From page 978... ...
OPTIMIZATION SCHEME FOR MULTI OBJECTIVE FUNCTION The optimizer in multi-objective design must search some candidate regions around the optimum point on each response surface widely. The genetic algorithm is commonly used to search a global optimum in wide region.
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From page 979... ...
Hence, the design parameters become five that is Lf ~La'Cf ,dcf ,dca For optimization of ship hull, it is important to rearrange grid system in every optimization step. In this study, we applied flexible grid method 173.
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From page 980... ...
As = (FP,—,—,—,1,1—, - - ,8—,9,9—,9—,9—, AP) 4 2 4 2 2 4 2 4 This module naturally provides the data for strip methods as the ship hull is modified in the course of optimization.
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From page 981... ...
These are evaluated independent of the hydrodynamic analysis. The wave excitation forces and moments are determined in accordance with the STF method, and nonzero term among there are ME ~ = M33 = pV M55 = It l C33 = Maw C35 = C53 = -,~AWXW C = ,~VBML J Here V is the displacement, IN the moment of inertia about the y-axis, Aw the water plane area, xwthe center of the water plane area, and BM, the longitudinal metacentric height.
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From page 982... ...
We have optimized a single objective function putting weighting factor on multi objective functions of resistance, added wave resistance and ship motion for Wigley model. The simulation condition is above.
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From page 983... ...
Multi objective functions are the resistance coefficient c`, the added wave resistance coeff~cientcr=,,, the nondimesional amplitude of heave motion z' and nondimensional amplitude of pitch motion B' . The principal dimensions of Series 60 model in this study are Length 7.0 m, Breadth 0.933m and draft 0.373m.
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From page 984... ...
We need to devise much more suitable modification method of ship hull form for multi-objective design in the future. In additions as the coefficient of RSM model increases to express complex configuration, we have to develop a design technique that approximate the response surface with quick response for change of design parameters.
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From page 985... ...
l Fig. 2 Modification system of ship hull form I Hull Surface/ K ~.
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1 If z O ARS 7 z Fig.7 Comparison of response surface of multi objective functions between forge RSNE and the ARS
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From page 987... ...
Optimization for the total performance Orignal Ct Craw v~ 1 1 i 1 i ~ 1 ~ 1 -F I I I I i 1 1 ~ r I I T T I 1 l ~ I I I I 1 1 -___~ 1 ~ 1 ~ i ~ 1 _1 1 1 1 I ~ 1 1 1 0.9 0.92 0.94 0.96 0.98 1 1.02 b) Optimizaiion for the Seakeeping performance Fig.11 Objective function for optimizes results as cor~pared to the value of original hull form (Series 60 model case)
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12 Comparison of body plan between for Me original hull forth and optimized hull form
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From page 989... ...
CFD tool can simulate a viscous flow in high accuracy and get information of flow field around hull for hull design or propeller design etc. On the other hand, ship motion can be estimated practically in normal wave condition by strip method excluding rough sea condition.
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From page 990... ...
For third question, the equation of general longitudinal motion is described in this thesis. But I'm sorry, I have not been describing clearly in this thesis that the influence of the surge motion is not considered in optimization process in order to simplify the calculation of ship motion.
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