Numerical Simulation Of The Effects Of Microbubble Drag Reduction Of Different Curves Of Area Of Transverse Section Of The Stern

Originating from the national 863 projects investigation of "investigation of high speed air cavity form", the main work of this paper is on the numerical simulation basis of the earlier stage of the project, and combinating with ship model tests,for a inland high-speed craft , under the condition of the unchanged displacement D and length L, alter its curve of area of transverse section of the stern, using the CFD commerce software FLUENT for modeling and simulating the viscous flow around the hull on the micro-bubbles, discuss the impact of resistance reduction on the micro-bubbles under the different transverse section of stern, to get the information such as the hull's viscous pressure resistance and friction resistance, distribution of micro bubble thickness at the ship bottom and so on.Reducing the drag and energy consumption is one of the main objects for ship design researchers. Optimizating hull lines to reduce the residual resistance is the primary means. For most surface and underwater navigation structures, friction resistiance accounts for a large proportion, so reduce friction resistance is expected to become a more effective means. The ship's friction resistance is determined by wet surface and the liquid around the ship. Generally, it is difficult to change the wet surface, so there are only two ways to reduce friction resistance: one is to minish the viscious coefficient of medium around the hull,the other is to change the flow around the hull,that is the turbulent boundary layer. And micro-bubbles may can achieve the purpose of drag reduction by the two ways.The form of curve of area of transverse section, especially the form of the stern, has an important effect on the performance of resistance,in general,the higher the speed,the fuller of the stern, the better of the performance of resistance. But the full stern can limite the diameter of propeller or there is a large longitudinal angle, To increase the the diameter of the propeller or minish the longitudinal angle, We can lift up the stern of the ship ,and use wave suppression plate to control the navigation state in order to obtain better performance of. For high-speed air cavities, because of the different curves of area of transverse section of the stem, the distribution of bubbles at the bottom is also different, and it can affect the effects of drag reduction. This thesis adopted Euler's method of mixing two-phase model and standard k-εturbulence model for numerically simulation in the three air-cavity crafts in two cases, injecting or uninjecting of microbubble, discussing the rules of micr-bubbles drag reduction under different curves of area of transverse section of the stem and if the favorableness influence of microbubbles drag reduction is the same as that without bubbles. Under the conditions without micr-bubbles, choosing standard k-εturbulence model and standard wall functions, taking into account of gravity. For air-jetting, adopting Euler's method of mixing two-phase model, and taking the flow of bubbles as the first phase, water as the second phase.Through numerical simulation, obtained the information about the impact of resistance of different forms of stem without micr-bubbles; under the condition of different velocities and different jet amounts, analyse the effects of resistance reduction,and the computed resultes of the prototype is accord with the test resultes. The results show: under the condition of the unchanged displacement and length, lift up the stem of the ship ,the distribution of micr-bubbles in the bottom of the hull is better, and it is favor for micr-bubbles drag reduction.