Study On The Scale Effect And Energy Saving Efficiency Of Wake Equalizing Duct Based On Numerical Simulation Method

The ship energy-saving problem is increasingly prominent nowadays,so the energy-saving devices(ESDs)are becoming more and more popular.But for a long time,the prediction method of energy saving efficiency of ESDs beset the scholars around the world.The ship model experiment can only meet the Froude number similarity,and the Reynolds number is different between model scale and full scale.So it has the problem of scale effect.At the same time,the existing extrapolation method is not applicable to model with ESDs.Therefore it is difficult to forecast energy saving efficiency of ESDs.This article applies the complete similarity theory,and presents a prediction method of energy saving efficiency of ESDs based on the CFD commercial software.This paper studies on 75000 DWT bulk carrier with wake equalizing duct.The hydrodynamic performance of bare hull is calculated with normal simulation.Normal simulation results are compared with the experimental value to validate the accuracy of numerical simulation method.Three different scale models of bare hull are calculated with complete similarity theory simulation(CSTS).The resistance and the flow field are made a comparison,and the results show the validity of CSTS method.Self-propulsion experiments of bare hull and model with wake equalizing duct are performed in normal simulation and complete-similarity theory simulation(CSTS)methods.The differences of the flow field between normal simulation and CSTS show the existence of scale effect.And the CSTS method can eliminate scale effect.Meanwhile,this paper takes a brief introduction on the basic theory of CFD.The governing equation and CSTS method are deduced.The discrete method and the SST k-co turbulence model is introduced and the VOF method is used to track free surface.The regional movements are carried out to simulate propeller rotation.