Direct Numerical Simulation Of Turbulent Boundary Layer

As we know, turbulent boundary layer flow exists widely in the field of power engineering, chemical engineering etc.,which is seemingly chaotic movement. However in fact it contains coherent structures at multi-scales. So far, the definitions, generation mechanism, and interaction mechanism between the various scales and other basic problems have not yet been well-known. In recent years, with the improvement of the laboratory equipment and super-computers, studies of coherent structure and mechanism of the interaction between vortex are very active.Therefore, in this thesis, the development of a high resolution and high-order massively parallel direct numerical simulation code for Reynolds number flows has been developed. The numerical studies of simple flow with exact solution have proved the accuracy and reliability of algorithms developed in this paperMeanwhile, the thesis calculated the complex three-dimensional flow channel within the isothermal and non-isothermal turbulent channel flow to verify the accuracy of prediction of complex turbulent flows. Large-scale vortices inside the channel, and the generation and development of Q2and Q4events were analyzed and discussed in detail.Finally, direct numerical simulations of spatial development of isothermal and non-isothermal turbulent boundary layer were studied, which is a process from transition to a fully developed turbulent regime. Average and fluctuation statistics, characteristics of large-scale structure (streaks) and Q2and Q4events at different vertical height of the turbulent boundary layer were studied in details.The results of this paper can help assist the comprehension of the coherent structure and the mechanism of turbulent boundary layer development. And it provides a solid base for further study of gas-solid turbulent boundary layer characteristics and the effects of rough elements to the turbulent boundary layer.