Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 08, 2021 - November 10, 2021
We performed direct numerical simulation of subcritical transition in Taylor–Couette–Poiseuille flows (TCPf) with a high radius ratio of η = 0.883. TCPf is a combined-shear flow consist of the azimuthal rotating cylinders and the axial pressure gradient in a concentric annular pipe. Various wall-bounded shear flows were found to undergo spatiotemporal intermittency with localized-turbulent structures in the forms of spots or stripes. For instance, the turbulent spot and stripe seen in a counter-rotating Taylor–Couette flow (TCf) are known as intermittent turbulent spot (INT) and spiral turbulence. On the other hand, the turbulent stripe in an annular Poiseuille flow (aPf) exhibits helical turbulence with a high radius ratio of η ≥ 0.5. The control parameters are the Reynolds numbers Rein and Reout based on the cylinders’ rotating velocities and the axial pressure gradient function F(P). In this study, we chose the Reynolds numbers at which INT occurs for the pure TCf, and increased F(P) gradually until the Poiseuille component was dominant. The INT with interpenetrating spirals in the F(P) = 0 has changed to complete laminar flow via forming spiral turbulence. The flow fields exhibit turbulent stripes again in higher F(P) than the laminar conditions (Reτ,z ≳ 40). This turbulent stripe may be helical turbulence since the Poiseuille component is more dominant than the Couette component in this stage.
