An entrainment model for an axisymmetric buoyant swirling turbulent plume in a quiescent homogeneous density surrounding medium has been developed. The streamwise similarity of the mean axial velocity, swirl velocity, turbulent Reynolds stresses, and the density difference between the plume and the ambient fluid are assumed. Consistent with various integrated conservation equations, the entrainment is found to be a function of the Reynolds stress, the form of various similarity profiles, the local densimetric Froude number, and the swirl ratio of the swirling plume. While the swirl alone always increases the rate of entrainment across the boundaries of the plume, it also interacts with the buoyancy forces to cause a slight detrainment of the fluid from the plume. The numerical results for the decays of axial and swirling velocities and the spread of the jet agree reasonably well with the existing experimental investigations.

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