| In the past twenty years, with sustained and rapid development China’s economic, Marine shipping industry got huge growth and Marine energy consumption increased year by year. Besides all above, the world energy demand is growing tension, so new energy-saving way is widespread concerned by all countries. The micro-bubble drag reduction is a very promising energy-saving way.The micro-bubble drag reduction mode improve the boundary layer structure with micro-bubbles and thus to reduce the frictional resistance of the ship. Extensive literature reported that micro-bubble drag reduction is effective. Japanese scholars have got the absolute drag reduction rate of5.44%in an experiment of ship which is7800t. Scholars from various countries have made some achievements in the field of ship micro-bubble drag reduction, but most results still remain at the laboratory stage except a small number of application examples of the real ship and part of the experimental nature of the real ship.There is a very important reason to constraint micro-bubble drag reduction technology applied in the real ship. The reason is that friction reduction effect dependent on many factors. Especially, similar relations between ship mode and the real ship have not been solved.Similar relations of ship mode and real ship have been discussed preliminarily in the "The bubble ship types research report ". But the similarity relation is not perfect. I will find out the numerical relations of jet parameters of different model with numerical simulation of series of simplified model. And then it may provide the theory basis for real ship forecast.The research object of this paper has4models, respectively,2m,4m,6m8m four scales. I will make numerical simulation for each scale mode and each jet parameters which can be clearly found that the jet parameters on the effect of ship resistance. Free surface effects are ignored in numerical calculation. There are three jet parameters in the paper, which are Jet flow, Jet slit size and the vertical distance from Jet slit to the ship bottom. By numerical simulation, and the results of calculation, this paper draws the following conclusions:1) When the model scale and the flow velocity is constant, the drag reduction rate increases with the jet flow increasing, when the jet flow saturated, then increases the jet flow, the drag reduction rate changes little.2) This paper calculates the four model in saturated air jet flow, friction drag reduction rate reached more than10%, the absolute drag reduction rates were all above10%, thus, micro-bubble drag reduction effect and application is prospect.3) Micro bubble not only reduces the friction resistance of ships, will also affect the pressure distribution of hull surface to reduce bow and stern pressure difference, thereby reducing the pressure resistance of ships.4)When the flow velocity is constant, jet speed has little effect on the velocity of the micro-bubbles in the bottom. When micro-bubbles move a very short distance away from the jet slit, its speed will be reduced consistent with the flow speed.5) When the scale model, the flow velocity and jet flow is determined, the jet parameters h and b has little effect on ship resistance, so it is not necessary to converse the h and b.6) When the model scale and the flow velocity is determined, the jet flow have great effect on ship resistance before saturation. When the Fr of ship model is similar, saturated air jet flow conversion relation as follows:... |
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