(186i) Study on Taylor Vortex Formation in a Liquid Gap with Significant Boundary Effects

Taylor vortex flow is a classical topic in fluid mechanics and it has found increasing application to processes such as reaction, filtration and extraction. Usually, Taylor vortices are studied in devices that have narrow gaps and high aspect ratios in order to avoid end effects. However, it is also known that Taylor vortices formed in short, wide gap devices exhibit novel features. These include, for example, a much higher critical Reynolds number for transition from Taylor vortex flow to wavy vortex flow (Edwards, Beane and Varma, 1991). A quantitative characterization of the flow in such a system is still largely unavailable. Here we present a study on the Taylor vortices formed in a mineral oil (with a density of 860kg/m3 and a viscosity of 29.67cp) between a rotating inner cylinder and a stationary outer cylinder. The radius and aspect ratios are 0.613 and 5.17, respectively. Rotation speeds of the inner cylinder range from 20 to 800rpm. We use a two-dimensional particle image velocimetry (PIV) system to determine the position, shape and velocity distribution of the vortices. Silver-coated hollow glass beads (16ìm in diameter) serve as the tracer particles. We also use computational fluid dynamics (Fluent 6.1) to simulate the Taylor vortex flow. This provides us with the ability to explore operating conditions not covered in the experiments and to probe possible explanations for the experimental observations. The effects of various boundary conditions on the Taylor vortex flow are also investigated. For a short column, both ends play an important role in shaping the vortices in the annulus. Their influences are examined by varying the height of liquid layers above and below the gap. Additionally, the wide gap makes it possible to introduce thin baffles on the outer cylinder wall. The horizontally placed baffles limit the space in which the flow develops and, as a result, the shape and location of the vortices are different from those observed without baffles. All of the above work combines to provide a better understanding of the Taylor vortex flow in the presence of strong boundary effects.

Reference: Edwards W. S., Beane S. R. and Varma S. Onset of wavy vortices in the finite-length Couette-Taylor problem. Phys. Fluids A 3(6):1510-1518, 1991