Hydrodynamic Optimization for Pod Propulsion System using Real-coded Genetic Algorism

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In the present study, calculation methods for optimizing propeller and pod-strut system in hydrodynamic aspect were developed. Real-coded genetic algorism was used as an optimization technique.At first, completely original parallel computing system was developed in order to reduce the computing time for optimization.Improvement to reduce the cavitating area to half on an original propeller was attempted using presented calculation method for propeller optimization. Experiments were conducted to confirm the optimization results. The cavitating area did not reduce remarkably and the propeller efficiency declined. The main reason of this failure may be caused by the strict restriction for cavitation.Experiments to confirm the accuracy of the calculation method for hydrodynamic forces acting on the pod propeller were conducted. Hydrodynamic forces on five different pods were measured. Calculated results agreed well with the experimental data. In order to reduce the lateral force on the pod propeller, the effect of the attachment angles of the strut to the pod was investigated by experiment. It was found that there was an optimum attachment angle to make the lateral force nearly zero. Calculated results about lateral force had the similar tendency to the experimental results.As the preliminary experiments for the further development of the present study, the effect of small fin mounted under the pod was investigated. There is the possibility to make the lateral force nearly zero and also to prevent the increment of the force acting on the pod propeller in the advancing direction. If we choose size and shape of the fin, optimum number of the fin and optimum position of attachment appropriately, we can create a new type pod propeller which has excellent hydrodynamic performance.