Abstract
Flow measurement of spatio-temporal velocity field in a Taylor-Couette vortex flow (TVF) with a short annulus was investigated by using Ultrasonic Doppler velocity Profiler (UVP). These methods have significant advantages over conventional methods since it can obtain the instantaneous spatio-temporal information as a function of space and time even in the opaque liquid like solid-liquid multiphase fluids. Boundary effects with a short annulus of TVF called Ekman boundary layer are greatly related to the generation of the various modes in vortex structure. Parameters as an aspect ratio, Γ(=H/d) and radius ratio, η(=R1/R2) are important factors for flow bifurcation to these modes. Here, d is an annular gap width, H is a height of the test section, R1 and R2 are radii of the inner and outer cylinders respectively.
In the present study, mean velocity profiles of the TVF with Γ=3 and η=0.667 are measured with the UVP. Instantaneous velocity profiles with oscillation in higher Reynolds region (Re=1140) are also measured and analyzed by using the UVP and a spectrum method. The characteristics of wavy vortex flow in the normal 2 and 4 cell modes are much different from each other. Particle behavior in TVF is much complicated. The limit cycle orbit, which has previously only been confirmed numerically in the multi-phased TVF were found experimentally. In the limit cycle, solid particles are gathered in a very limited orbit line. While this phenomenon is unique and does not occur in the general flow region, it could be useful for analyzing the anti-plugging characteristics in industrial rotating filter devices or bioreactor.
