CFD INVESTIGATION OF THE ONSET OF TIME-INDEPENDENT TAYLOR VORTEX FLOW IN A CYLINDRICAL ANNULUS FOR DIFFERENT WORKING FLUIDS

Fluid flowing in an annular gap between two coaxial cylinders, well known as Taylor-Couette flow, is one of the fundamental problems in fluid mechanics for the study of instabilities and the transition to turbulence. This flow system is typically a closed environment, where the working fluid is confined axially by endplates, and radially between the cylinders. In this work we investigate, via CFD simulation, the influence of the working fluids confined inside an infinite aspect ratio Taylor-Couette system on the onset of cellular pattern. The inner cylinder rotates freely about a vertical axis through its center while the outer one, the upper and the bottom endcaps are held at rest. The basic system is characterized by a height H = 150 mm, an annular gap d = 5 mm, a ratio of the inner to the outer cylinders radii eta = 0.909, an aspect ratio corresponding to the cylinders height reported to the gap length Gamma = 30 and a ratio of the gap to the radius of the inner cylinder delta = 0.1. The flow behaviour and the time-independent formation of axisymmetric vortices is investigated under steady state condition. The main goal of this work is to show how the change in cellular pattern operates when changing the working fluid by simulating and comparing four different liquids: hydrogen, helium, lithium and water. Particular attention is given to the onset of Taylor vortices in the vicinity of the threshold of transition, i.e., from the laminar Couette flow to the occurrence of Taylor vortex flow. In addition, the flow patterns are presented in terms of distributions of wall shear stress, skin friction coefficient and streamlines.