Two- and three-dimensional flows in nearly rectangular cavities driven by collinear motion of two facing walls |
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Authors: | Tanja Siegmann-Hegerfeld Stefan Albensoeder Hendrik C Kuhlmann |
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Institution: | (1) Institute of Fluid Mechanics and Heat Transfer, Vienna University of Technology, Vienna, Austria;(2) CeBeNetwork GmbH, Bremen, Germany |
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Abstract: | Two- and three-dimensional flows in nearly cuboidal cavities are investigated experimentally. A tight cavity is formed in
the gap between two long and parallel cylinders of large radii by adding rigid top, bottom, and end walls. The cross-section
perpendicular to the axes of the cylinders is nearly rectangular with aspect ratio Γ. The axial aspect ratio Λ > 10 is large
to suppress end-wall effects. The fluid motion is driven by independent and steady rotation of the cylinders about their axes
which defines two Reynolds numbers Re
1,2. Stability boundaries of the nearly two-dimensional steady flow have been determined as functions of Re
1,2 for Γ = 0.76 and Γ = 1. Up to six different three-dimensional supercritical modes have been identified. The critical thresholds
for the onset of most of the three-dimensional modes, three of which have been observed for the first time, agree well with
corresponding linear-stability calculations. Particular attention is paid to the flow for Γ = 1 under symmetric and parallel
wall motion. In that case the basic flow consists of two mirror symmetric counter-rotating parallel vortices. They become
modulated in span-wise direction as the driving increases. Detailed LDV measurements of the supercritical three-dimensional
velocity field and the bifurcation show an excellent agreement with numerical simulations.
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