Evolution of the effective nozzle diameter in the buoyancy free development of turbulent jets with variable density

Abstract

 Decay laws in the initial, non buoyant region of round, turbulent, variable density jets can be derived from dimensional similarity considerations. This paper presents the concept of normalized effective diameter. In the case of turbulent jets issuing into a coflow air stream (initial density ratio varying from 0.07 to 1), this quantity is experimentally derived from measurements of mean density and velocity and is found to follow a unique exponential decay. Results are also presented in terms of global force of the nozzle fluid.