Numerical Study Of Slip-flow Drag Reduction Over Bionic Superhydrophobic Surface

Energy conservation and emission reduction have always been the goals for humans to pursue, So nowadays scientists start to devote more and more efforts to the effective utilization and protection of energy. Unite our major, to find out a method of reducing resistance effectively is a worthy goal to strive for in the field of marine and offshore engineering. So aimed at this goal, we expecting to promote the development of drag reduction technology of ship based on the theory of ―Lotus Effect‖. Therefore, the drag reduction over bionic superhydrophobic surface will also become a new field of study with broad perspective.In this thesis, the computational fluid dynamics is used to investigate the slip flow drag reduction over bionic superhydrophobic surfaces. Turbulent flow over three different superhydrophobic surfaces are simulated, flow velocity and wall shear stress under different Reynolds numbers are calculated; Simulation results are analyzed and d iscussed in detail in several ways, including by drag reduction performance, the mechanism of drag reduction and flow field characteristics; At last, the research results of three different superhydrophobic surfaces are applied to ship resistance performance, further explore how slip flow over superhydrophobic surface affect ship resistance performance.We have found that superhydrophobic surfaces from the perspective of bionics have better drag-reducing performance than smooth surfaces. O ne of the important reasons that drag is decreasing is because of the existance of no shear gas- liquid interface on the fluid-solid interface. From the perspective of hydrodynamics, the no shear gas- liquid interface corresponds to the slip velocity boundary condition, there fore, certain simplification can be made on the air layer physical model of the superhydrophobic surface slip flow, slip velocity boundary condition is used to the corresponding interface. In combination with ship resistance performance, it is found that superhydrophobic surface applied to hull surface has certain drag-reduction effects on the ship resistance performance at current scientific development level. As for Wigley form with simple shape and thin, the maximal reduction rate is about 27.688%; Superhydrophobic surface with the same area is placed for the best drag reduction effect on midship, then bow, at last is stern.