A study of swirling flow in hydraulic models

In this paper a study is made of vortex behaviour in axially asymmetrical hydraulic models. A brief review of the existing research on vortex models is given. Some of the existing theories have been extended to obtain theoretical descriptions of the vortices studied. The effects of model scale and geometry on vortices with well-developed air cores were investigated experimentally. Three model sizes having 2", 4" and 6" diameter sharp-edged orifices were tested and for each two reservoir configurations (rectangular and 'horsshoe chased) were used. An eccentric inflow produced a reasonably stable swirl. Similarity of swirl production, discharges and air cores has boon considered. It as found that vortex behaviour was sensitive to the irregularity of the model geometry. The vortices in the rectangular models were weaker ah stable than those in the horseshoe shaped models. A general dissimilarity was found between the swirls produced in the smallest model and those in the larger models. The highest swirl numbers 'ere observed in the smallest model. Apart from the above effect, a local scale effect was observed in the region of the air core; the swirl reduction in the region at the air core was greatest in the smallest model. A. theoretical explanation is given for this effect. Most of the experimental work was confined to steady flow at low submergence ratios ((flow depth)/(orifice diameter)