Vortex formation in stirred draining vessels

Abstract

AbstractWhen water was rotated by means of a “horse‐shoe” stirrer in a vertical, cylindrical tank and a stream was withdrawn from the bottom through a central exit pipe, a pronounced filament‐like vortex was formed under certain conditions. Experiments were performed to determine the factors which influenced the height of the vortex. The effects of vessel sue, stirrer geometry, rotational speed, exit flow rate and exit pipe diameter on vortex depth were studied. It was found that the vortex depth was highly dependent on the rotational speed, exit flow rate and exit pipe diameter. It was also found that under certain flow conditions the vortex penetrated the exit pipe. A relationship between the vortex depth and the pertinent variables was developed using dimensional analysis. The relationship resulting from a regression analysis of the dimensionless groups affecting the vortex depth was found to be: Motion picutes were taken showing the flow characteristics in the vicinity of the vortex by using a dye tracer technique. Ways of inhibiting vortex formation were also examined.