ABSTRACT
Swirling flow at intakes–leading, quite often, to the formation of air-entraining vortices–is the result of the complex interaction between the geometry of the intake chamber and the approach channel, the flow velocity and the liquid properties such as surface tension and viscosity. Design of intakes to be free of objectionable circulation is, therefore, based either on past experience and 'rules-of-thumb' or on physical-model studies. Circulation is dependent on the characteristics of the approach flow, the geometry of the intake chamber and the discharge. In the case of horizontal intakes, the reference circulation may need to be defined along some other curve, but it is immaterial what that curve is so long as the same curve is used consistently all the time. The role of the Weber number appears to be relatively less understood in spite of a few studies having been carried out to study its influence on vortex formation.
