Author(s)

M. M. Seraj & M. S. Gadala

Abstract

A circular turbulent long jet has been assessed numerically using the volume-of-fluid method to examine the hydrodynamics of a long jet before impingement and to inspect the flow structure of a radial thin layer spreading over a flat plate after impingement. Typical steel mill industrial parameters are used in the model. Comparative results are shown for laminar and turbulent jets with different turbulence models. Model results showed good agreement with the analytical solution available for global parameters and jet behaviour. The film thickness of the water layer over the plate, for more than 27 jet diameter, was measured by tracking free-surface. A hydraulic jump was detected and occurred within the radial zone in different shapes in laminar and turbulent modelling, respectively. Keywords: hydrodynamics, long jet, numerical simulation, hydraulic jump. 1 Introduction Jet impingement is one of the effective means in cooling and heating applications. Water jet impingement has a distinguished ability to dissipate a large amount of heat fluxes and has attracted many studies over the past few decades. Recent reviews may be found in [1–3]. In an axisymmetric jet, the jet thickness decreases as the liquid radially travels outward. The thickness of the liquid sheet initially decreases with the radius but, because viscous drag slows the liquid sheet, its thickness begins to increase at larger radii. The rapid thickness decrease brings the growing boundary layer into contact with the free-surface of the liquid layer. If the Reynolds number is large enough, a shift to a turbulent regime could be expected for the radially spreading thin laminar liquid film. Layer thickening after thinning marks the radius of transition [3, 4].

Keywords

hydrodynamics, long jet, numerical simulation, hydraulic jump.