Mixed convection in a laminar axisymmetric water plume in a vertical coflowing stream at temperatures around the density extremum

Abstract

In all studies concerning mixed convection in round laminar plumes a linear relationship between fluid density and temperature has been used. However, it is known that the density-temperature relationship for water is nonlinear at low temperatures. In this study the problem of a round laminar water plume in a coflowing vertical free stream has been investigated in the temperature range between 20 °C and 0 °C taking into account the nonlinearity between density and temperature. The results are obtained with the numerical solution of the boundary-layer equations. The paper deals mainly with assisting mixed convection and with some special cases of opposing and assisting mixed convection at the same plume flow. For the assisting mixed convection it was found that the plume behavior depends on the temperature difference between the plume orifice and the ambient water due to the nonlinear relationship between water density and temperature. This dependence weakens and finally diminishes as the buoyancy parameter ξ increases and the mixed convection becomes pure forced convection.