Abstract
A Taylor vortex flow (TVF) is one of the key technology for process intensification in the flow field with applications for particle classification or synthesis, micro mixing, separation and solvent extraction. Flow measurement is also important with these technologies and in this study, spatio-temporal velocity field in the TVF with a short annulus was investigated by using Ultrasonic Doppler velocity Profiler (UVP) and Ultrasonic Time Domain Correlation method (UTDC). These methods have significant advantages over conventional methods since they can obtain the instantaneous spatio-temporal information as a function of space and time even in the opaque liquid like slurry. The UTDC method is comparatively a new technique and expected to have a same accuracy as UVP in measuring the mean velocity profile. 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=0.375 are measured in both UVP and UTDC. Velocity profiles obtained from the UTDC are compared with ones from the UVP to confirm the accuracy. Instantaneous velocity profiles with oscillation in higher Reynolds region (Re=1,500) 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 the previous regular flow behaviors as seen in a larger radius ratio like η=0.667.
