Numerical Simulation Of Microbubble Drag Reduction And Mechanism Analysis

As we all know, energy, the basic driving force of the development of the world andeconomy, is the foundation of human survival. As the society developed, energy shortage,scramble for resources and environmental problems threaten human survival and develop,energy conservation and emissions reduction have been a focus of attention. Reducing thenavigation resistance can effectively reduce energy consumption. After a host ofexperiments and numerical simulation we have found out that the method of skin frictionreduction of solid wall by injecting microbubbles to boundary layer is a technique fordrag reduction, especially for slow-speed ship which friction drag is the major part of thetotal drag. There are broad prospects for development.Research shows that bubbles to reduce skin-friction they must in some way changethe turbulent momentum exchange in the boundary, and then reduce friction. There aremany factors that influence microbubble drag reduction. The relevant parameters include:free-stream velocity, gas velocity, downstream distance from the injector and so on. Thecenterpiece of the microbubble drag reduction study is the effect of the above relevantfactors on ship hull boundary layer flow.This article is based on Eulerian-Eulerian multiphase flow model and selects theturbulence model and drag model. This article studies gas velocity, direction of the gasand type of gas influence on friction resistance reduction. The streamwise velocitydeveloping tendency and bubbles distribution of boundary layer have been discussed. Gasvelocity and draft influence on air bubble distribution and friction resistance reduction ofa three-dimensional bulk carrier have been studied. Based on the flow of the ship hullboundary layer, this article studies about increasing a vent in the direction of ship lengthand adding dashboard in the direction of ship beam to preventing gasses from escaping.The results showed that when the gas velocity was increased, the friction resistancereduction increased; when the direction of gas velocity is vertical wall, the ratio ofreduced resistance is the most; type of gas had little influence upon result. The results ofthe measured drags of the bulk carrier model showed that when the gas velocity wasincreased, the friction resistance reduction increased; draft has little impact on dragreduction. Both increasing a vent in the direction of ship length and adding dashboard in the direction of ship beam can efficiently increase the ratio of reduced resistance. Thestudy result has the certain leading meaning to improve and control air bubbledistribution around hull, which increases drag reduction of ship.