Mechanism of Vortices Appearance in the Taylor-Couette Flow System

This work is devoted to study the Taylor-Couette flow at the early structuring stages. It is aimed to gain insight on the Taylor and Ekman vortices genesis mechanism since the first hints of presence detected at Ta=10-4. Simulations are carried out using Ansys Fluent software package. The basic system geometry is characterized bya height H= 150mm, ratio of inner to outer cylinder radii η= 0.9, radial gap δ= 0.11 and an aspect ratio corresponding to system height reported togap length, Г= H/δ = 15. Ekman and Taylor cells are tackled since the Taylor number Ta=10-4to the first (TVF) and second (WVF) instabilities settlement at Tac1= 43.8 and Tac2= 54, respectively. It is sought to shed light on the underlying mechanism responsible for flow genesis and to identify all the intermediate successive steps from ex-nihilo when the system is at rest up to complete vortices formation. The obtained results show that presence of Ekman cells is already perceptible since a Taylor number as low as Ta= 10-4. In fact, localized overpressure zones are detected on system inner endcaps surfaces regularly distributed according to a π/2 phase lag. These overpressure zones azimuthally propagate to meet and cover the entire gap circumference when Ta~10-2 to10-1.