Study On The Relationship Between Structure Characteristics And Drag Reduction Performance Of V Shaped Groove Surface

With the increasing world energy crisis, energy conservation and emissions reduction gradually become the theme of the 21 st century and even the future. In real life, many problems of energy consumption are closely related to fluid flow. Therefore, the study of turbulent drag reduction technology has certain scientific research significance and practical value.From the perspective of bionics, V shaped groove surface models with horizontal and vertical distribution are established referring to the skin microstructure drag reduction characteristic of dolphins, sharks and other creatures. First, determine the groove sizes and computational domain sizes according to the empirical formulas of flat turbulence, and carry on meshing, setting conditions, verifying simulation and so on through fluent software package. Then, compare the drag reduction performance of transverse groove surfaces and longitudinal groove surfaces, adopting the method of both numerical simulation and experimental verification. And then put more emphasis on analysising the influence factors about drag reduction capability of transverse groove surfaces. In addition, simulation is carried out on the the transverse groove surfaces with different height distribution, and the drag reduction performance of them under different flow velocities is analyzed. Finally, analyse the drag reduction mechanism of groove surface by comparing the flow field structure of boundary layer in near wall region between smooth surface and groove surface.Results show:(1) Compared with smooth surfaces, both transverse groove surfaces and longitudinal groove surfaces have certain drag reduction effect. At lower speeds, longitudinal groove surfaces have better drag reduction capability. And with the increase of velocity, transverse groove surfaces show good stability of drag reduction. (2) Within the scope of the size and speed in this paper, longitudinal groove surfaces have the best drag reduction performance, up to 9.61%, at v=3m/s, h=s=12mm. And when v=12m/s and h=s=0.02mm, the drag reduction rate of transverse grooves can reach 5.94%. (3) The drag reduction performance of transverse groove surfaces is affected by the factors of flow velocitiy, groove size, groove number, distribution location, groove shape and so on. Among them, the influence of flow velocity, groove size, groove number and groove shape is greater. (4) The transverse groove surfaces with certain deformation law have better drag reduction performance, compared with groove surfaces with single dimension. And the drag reduction effect is obvious when the size of groove surfaces are from low to high distribution. (5) There are a large number of "Secondary vortexs" in the top of longitudinal groove surfaces, which increase the thickness of viscous sublayer in boundary laywer and reduce the wall shear stress, resulting in drag reduction. As for transverse groove surfaces, there is a Clockwise swirl at the bottom, which makes the sliding friction between incoming flow and wall converted to rolling friction between the fluids, resulting in drag reduction.