Stirring-indueced vortical motion measured by ultrasound Doppler velocimetry; Initial 2D vector plots

Tokuhiro, Akira; Kobayashi, Jun 

An experimental investigation on stirring-induced vortical motion of a liquid was conducted in a cylindrical container measuring 280mm diameter 280mm height. The test medium was water and a magnetic stirrer located at the bottom on the container (centered) induced the flow. The motion can be generally described as rotationally induced vortex motion, which is of relevance to gas entrainment concerns, from the free surface of pool-type LMFBR. The objective of the investigation were two-fold: (1)to demonstrate that a two dimensional (2D) velocity field, using ultrasound Doppler velocimetry and a multiple number of ultrasound transducers (TDXs), could be measured and (2)to evaluate the content of the measured velocity information with respect to understanding the relevant vortex dynamics. Our results show that our first objective was fulfilled; that is, using 6 orthogonally situated TDXs to measure the V and V components of the flow field, a 2D vector field plot of a segment of the meridional plane was generated and shown to change with the rate of induced flow (rotation rate). However, because the number of TDXs used (6)were small, the coarse resolution of the velocity field limits the amount of velocity information. Therefore traditional data presentation methods to evaluate average and fluctuating quantities under steady and stepwise viewed transient conditions, are indispensible for data analysis. The measurement method holds promise as a useful tool in thermohydraulics as the number of TDXs is increased and therefore the spatial resolution. Some of these possibilities are described in this report.