Numerical Simulation Of Viscous Flow Around High-speed Aircavity Craft

Originating from the national 863 projects investigation of "investigation of high speed air cavity form" , the project's work is that on the basis of the earlier stage of the project, some information of flow is found, by using Fluent software to simulate viscosity flow field numerically, such as the hull's friction resistance, distribution of micro bubble thickness at the ship bottom, distribution of micro bubble velocity and so on.Because of the impoverishing of the energy, exploiting ship form, which economizes on energy, becomes an inevitable topic. Reducing the drag and enhancing the speed of ship effectively are the main attack direction in optimizing the ship form. The air cavity is one type of the ships with fine resistance performance, and it is a kind of ship that adopts the technology of microbubble drag reduction, which is to lead air (or waste gas) into hull bottom ,and form mixing two phase flow of air and water at hull bottom surface , and that may reduce the vicinity fluid density at the hull bottom surface,change the flow structure within the boundary layer, thereby, reduce the friction drag at the hull bottom surface and then conserve energy. Since the 1960s, a lot of scholars at home and abroad have done lots of investigations about micro bubble drag reduction technology. Those experiments results indicated that the effect of drag reduction is very obvious by injecting of micro bubble.The object in this article is a high speed craft. The results of numerical simulating viscosity flow field in two cases, injecting or uninjecting of microbubble, are analyzed comparatively. And the effect of microbubble drag reduction for ship friction is discussed. In this paper, Euler's method of mixing two-phase model and standard k-εturbulence model is adopted for numerically simulation, and some related settings are maked, see session three of chapter IV for specific. To simplifying the model in the calculation, some related assumption are maked for the bubble - the water flow, see Chapter IV for specific.This paper adopts block grids. In order to facilitate the value of transferring and improve accuracy, regular net is used for transition between blocks. Because of the complexity of the ship hull surface, the boundary grids can not be created availability. In order to featuring the boundary layer fluxion well, nonstructural grid is adopted around the ship hull, notes is disposed in grads, and the notes was adjust gradually. In order to save calculation space and improve computing speed, structural grid is used in other blocks.Using numerical simulation, the distribution of micro bubble thickness at the ship bottom, and velocity vectors of micro bubble, under the conditions of different velocities and different jet amounts. Compareing the result of 16 states, such as assorted teams the model velocity V=2.281,2.566,2.851,3.136 m/s and jet amounts Q=15,18,21,24 m3/h, the effect of micro bubble drag resistance by velocity and jet amounts. Then, compareing the friction drag at the hull bottom of injet with that of jet, it get micro bubble reduction ratio to the friction drag, which is agree with the test result of flat experimentation by Madavan el at.