Characteristic Of Heat Transfer And Flow Of Low-profile Concave Spherical Pits

In 1970s, after American NASA Langley Research Center found that the surface with low-profile riblets can lower down friction resistance effectively, the traditional idea that"the more the surface is smooth, the lower the resistance is"has been totally broken through. Since then, turbulent drag reduction techniques have been more and more applied in engineering equipment of convection heat transfer. But during heat transfer enhancement, as the incensement of heat transfer area and the influence of other disturbances, the flowage resistance of the fluid in the heat transfer equipment will increase greatly. Because of so, a comprehensive study of turbulent drag reduction and heat transfer enhancement begins to come onto stage.The thesis frames two types of low-profile concave spherical pits flats, staggered one and aligned one, by predigesting the epidermal configuration of high speed fish such as shark and Aclpenser Sinensis Grdy. The two models according to the turbulent boundary layer fundamental are to discuss about the influence of low-profile concave spherical pits on the convection heat transfer and friction resistance of flat forced convection heat transfer and the relationship between them.Non-low-profile concave spherical pits flat plate, the reference, is compared with the two low-profile concave spherical pits flats. Firstly, physical models have been established, and simple k-εmodel has also been used to analyze the mechanism of heat transfer enhancement and the efficiency of turbulent drag reduction. Secondly, the thesis has compared the comprehensive evaluation norms of reference flat and the two low-profile concave spherical pits flats which both consider heat transfer enhancement and turbulent drag reduction to select the best model. The result shows that the two low-profile concave spherical pits flats are optimum solution at Re=12000, and the staggered one is better than the aligned one.Finally, the thesis has carried out LES on the best model in the steady state, flat with staggered concave spherical pits at Re=12000 to study the feature of heat transfer and flow. The thesis has analyzed the parameter changing regularities of the velocity, temperature, pressure and vorticity, and generalizes the influence of low-profile concave spherical pits on the convection heat transfer and friction resistance, which paves the way for further studying the influence of low-profile concave spherical pits flats on flow field...