The Flow Behavior of a Confined Viscoplastic Annular Jet

Abstract

Flow characteristics of a confined annular jet of a viscoplastic non-Newtonian fluid were investigated numerically within the steady laminar flow regime. A parametric study is implemented to investigate the influence of confinement ratio, CR, inner-to-outer annular nozzle diameter ratio, k, and yield number, Y, over the following range of parameters: CR = {5, 40}, k = {0, 0.5, 0.8}, and Y = {0, 0.5, 1}. Central and outer recirculation regions typically characterize the flow of a confined Newtonian annular jet. However, extent of the outer recirculation region and recirculation intensities of both the central and outer regions were found to substantially diminish with the yield number for all confinement and annular diameter ratios, resulting in the elimination of recirculation throughout the whole flow field at high yield numbers. The confinement ratio has a dramatic impact on the recirculation intensity of the outer region, and centerline velocity and jet momentum evolution, only in the case of Newtonian flows. Axial penetration of the submerged annular jet decreases with the inner-to-outer annular nozzle diameter ratio and the yield numbers for all confinement ratios.