A dns study to investigate turbulence suppression in rotating pipe flows

Rotating and swirling turbulence comprises an important class of flows, not only due to the complex physics that occur, but also due to their relevance to many engineering applications, such as combustion, cyclone separation, mixing, etc. In these types of flows, rotation strongly affects the characteristics and structure of turbulence. However, the underlying turbulent flow phenomena are complex and currently not well understood. The axially rotating pipe is an exemplary prototypical model problem that exhibits these complex turbulent flow physics. By examining turbulent statistics, the physical mechanisms responsible for turbulence suppression are investigated. Direct numerical simulations are conducted at a bulk Reynolds number up to Re_D = 19,000 with rotation numbers ranging from N = 0 to 3. Within the chosen range of Reynolds numbers, some Reynolds number dependence on the results was observed. Turbulent kinetic energy budgets and Reynolds stresses were computed for these flows to quantify the effects of rotation on the turbulent flow. It is found that rotation causes a reduction in production near the wall and an increase in dissipation in inner-scaled dissipation. Additionally, a small region of increased turbulent production was found near the center of the pipe flow.