Similarity criterion for a confined swirling jet system

Abstract

A similarity criterion is proposed for a confined, isothermal, axisymmetric swirling jet system. This criterion has been derived in essentially two different manners, firstly by integrating the differential equations of motion under certain assumptions and secondly by considering the overall changes in the system. The criterion indicates that two dimensionless parameters, a Swirl Number and the Craya-Curtet number for confined swirling jets, characterize the system completely. Experimental investigations on such a confined, swirling jet system are also presented. The data indicate that essential features of the jet such as entrainment, radial profiles of axial velocity and decay of centre-line velocity exhibit uniform behaviour with variations in the value of the two parameters. Also, the static pressure variation along the wall of the confining duct is in qualitative agreement with the criterion. The experimental data are consistent with the theoretically derived similarity criterion for confined swirling turbulent jets.