Numerical Study Of Turbulent Drag Reduction Over Riblet Surface

Turbulent boundary drag reduction over riblet surface is an effective method to reduce turbulent drag, and it had very long researching history. Compared with other methods, it is more advantaged: Firstly, it is economical; Secondly, it is simple to carry out , which is affixed or machining on the surface of exiting objects; Last but not least, it is not prone to be effected by surrounding environment and temperature, and there is not needing any assistant facility. Presently, it has been applied in many fields, such as spaceflight, aviation, pipe transportation, sports and so on. Specially, it supplies a new and effective approach for the study of shipping and underwater aircraft.In the paper, the researching development and actuality of drag reduction over riblet surface in the domestic and overseas, were summarized. Based on the mechanism of turbulence producing and the turbulent structure near wall, the mechanism of drag reduction over riblet surface was discussed from two aspects, "the Second Vortex" theory and Viscosity theory.The paper adopted the soft of Computational Fluid Dynamics, Fluent to simulate the turbulent boundary flow of riblet plate and underwater aircraft. Evaluate and deeply analyze the characteristic of drag reduction over riblet surface. The factors of influencing turbulent drag reduction were discussed by changing riblet shape, dimension and etc. Firstly, a lognitudinal V-riblet plate model was made with gambit then the principle of grid spacing and boundary condition were ascertained; Secondly, the resistance features of riblet and the characteristic of turbulent flow field near wall were calculated and analyzed with RSM turbulent model. Based on the simulative computation, Deeply discuss the characteristic from four aspects, including velocity field, vortex, shear stress and turbulent dissipation rate. In order to validate the accuracy of simulation, to make the friction resistance coefficient of smooth surface be compared with results calculated by Prandtl turbulent boundary Layer formula , and make comparison between the simulative drag reduction efficiency and experimental data of Bechert. From the results of comparing, it was found that the results was consistent, and the computation was much precise. Lastly, the factors of influcing turbulent drag reduction efficiency were studied by changing the shape and dimension of riblet.Based on the research above, the drag feature of underwater aircraft with riblet surface was also got simulated, and the equilateral V-riblet surface setted on aircraft was adopted to calculated and analyzed the characteristic of drag reduction with the changing of Re and the influence of riblet distribution on the aircraft. At last, the design of underwater aircraft was got optimization.All analysis on mechanism of turbulent boundary drag reduction over riblet surface and calculation about resistence feature in the paper, there will be important significance for the reference and direction to further study in the field of turbulent drag reduction.