Manipulating Coherent Structures by Heat in a Boussinesq Jet

Abstract

Entrainment and mixing are problems of major concern in many fluid-dynamical applications, especially in the presence of heat release (e.g. combustion, clouds). A simple but interesting idealization here is to use the Boussinesq approximation, which is not directly applicable to most combustion problems, but happens to be quite realistic in many geophysical applications. With this objective in view, Basu & Narasimha [1] have performed a series of simulations using a pseudospectral method to compute the temporal evolution of a jet-like flow with volumetric heat injection over some region well away from the origin of the flow. Furthermore, recent experimental work on such flows [2-4] provides a basis for mutual validation and enhanced understanding. The experimental studies show that off-source heating accelerates the flow and arrests jet growth; absolute values of turbulence intensity increase but not as rapidly as the mean velocities, so normalized turbulence intensities are lower. It is gratifying that strong qualitative similarities with the experiments have been observed in the numerical simulations. This gives us considerable confidence in the results we shall present in this paper, where we describe a new study on how off-source volumetric heat injection can alter and manipulate the coherent vortical structure and entrainment characteristics of a jet.