THE DEVELOPMENT OF THREE-DIMENSIONAL TURBULENT SURFACE JETS
Timothy J. Craft
Turbulence Mechanics Group, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, PO Box 88, Manchester M13 9PL, UK
Jasper W. Kidger
Mechanical Engineering Department, UMIST, PO Box 88, Manchester, UK
Brian E. Launder
School of Mechanical, Aerospace & Civil Engineering, The University of Manchester, PO Box 88, Manchester M60 1QD, UK
The paper explores the computation of a turbulent liquid jet discharged at the free surface of an expanse of the same fluid at rest. The turbulent stress field has been modelled by second-moment closure wherein transport equations are solved for each of the Reynolds stresses. The model of the pressure-strain correlation is especially influential on the flow's development. Two alternatives are explored: the basic return-to-isotropy model with free-surface reflection terms and the newer two-component-limit (TCL) model developed at UMIST over the past decade.
The computations show that the TCL model is indeed much more successful than the simpler alternative for this flow. Experimental data are limited to the near-field but our calculations suggest that to reach the asymptotic rates of spread requires well over 100 discharge diameters of development. The exceptional distance is due to the gradual growth of streamwise vorticity driven by the strongly anisotropic Reynolds stress field acting in the jet's cross-section.