Direct Numerical Simulation of Turbulent Flow in a Circular Pipe Subjected to Radial System Rotation

Abstract

In this thesis, direct numerical simulations have been preformed with a high-order spectral element method computer code to investigate the Coriolis force effect on a fully-developed turbulent flow confined within a circular pipe subjected to radial system rotations. In order to study the radially rotating effects on the flow, a wide range of rotation numbers (Ro τ ) have been tested. In response to the system rotation imposed, large-scale secondary flows appear as streamwise counter-rotating vortices, which highly interact with the boundary layer and have a significant impact on the turbulent flow structures and dynamics. A quasi Taylor-Proudman region occurs at low rotation numbers, where the mean axial velocity is invariant along the rotating axis. As the rotation number increases, laminarization occurs near the bottom wall of the pipe, and the flow become fully laminarized when the rotation number approaches Ro τ = 1.0. The characteristics of the flow field are investigated in both physical and spectral spaces, which include the analyses of the first-and second-order statistical moments, pre-multiplied spectra of velocity fluctuations, budget balance of the transport equation of Reynolds stresses, and coherent flow structures. i Acknowledgements I would like to express my great gratitude to my supervisor Prof. Bing-Chen Wang for his encouragement, support and guidance, and also for his experience and suggestions in social communication which was very helpful to me on how to conduct myself during my M.Sc. study in Canada. I would also like to express my appreciation to Dr. Xing-Jun Fang for his generous help and guidance on my M.Sc. study and project during his PhD program.