Ridged Surface Drag Reduction Characteristics And Structural Optimization Design Study

The technology of drag reduction of groove surface is rose lately. Compared with other technology of drag reduction, the technology of drag reduction of groove surface need not change the structure and figure, need not add accessory, the capability is stable, use extensively and cheap. So it is very valuable for military affairs and civil.The groove surface which perpendiculars to the flow is numerically computed and simulated. Drag-reduction characteristics of this groove are roundly studied on for the first time, at the same time, the groove under the different direction of flow is pilot studied. Started with the modeling, the discreteness of mathematical model and the gird build are researched on, analyzed and the mechanism of drag-reduction is deeply studied by comparing traveling wave surface with plate surface. First, foundation the equation of Navier-Stokes+Turbulent modeling. Use the low Reynolds of RNG k-ε model to dispose of the near wall region. In order to get the exact result, use the SIMPLEC to discrete the mathematic model. Use the triangular unstructured meshes to fill the groove, and increase more meshes in the near wall region, there is one mesh at the position of y~+ =1 at least. Second, based on the result of computation, analyzed and the mechanism of drag-reduction is deeply studied by comparing traveling wave surface with plate surface. The results show that, "second vortexes" are existent and the "viscous theory" is correct. Optimize the groove structure in term of size, shape, spacing, direction of flow and Reynolds.Optimize the groove structure in term of size, shape, spacing, direction of flow and Reynolds. The conclusions are as follows: the shape of u and v has better drag-reduction, the smaller the better, the best drag reduction is got when ,s~+=15. It is controversial about the best size of v , so commutate the size of h/s = 1, h/s = 0.5 and h/s = 2 of v, research on their drag-reduction characteristics, it is shows that, the best size is h/s = 1. The better drag-reduction characteristic is got at the low speed. When the spacing l~+ =22, the better drag-reduction characteristic is got, if l~+ >22, the drag increase obviously. At smaller Reynolds better drag-reduction characteristic is got. Preliminary study on the drag-reduction of groove for different flow direction, when the angle of flow direction and groove is 30° can get the better drag-reduction...