Deflection of a two-dimensional natural convection wake due to the presence of a vertical surface in close proximity

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Abstract
The interaction between a freely rising thermal plume and an unheated vertical surface in its neighbourhood has been investigated. The underlying transport mechanisms are of interest from a fundamental standpoint, as well as in a variety of practical problems, such as the cooling of electronic equipment and room fires. A detailed numerical and experimental study of the flow is carried out. The temperature and velocity gradients are expected to be large, particularly near the thermal source. Also, any constraints imposed on the entrainment into the flow in the vicinity of the source are expected to significantly affect the nature of the flow and the interaction. These considerations make it imperative to solve the full governing equations in the interaction region. These equations are solved numerically by finite-difference methods, employing the vorticity-stream function formulation. The important physical variables in the problem are the total thermal energy input by the source, the size of the source, and the distance of the source from the vertical wall which is taken as adiabatic or isothermal in the computation. The flow is found to be strongly deflected towards the vertical surface for the parametric ranges considered. As expected, the diffusion effects in the main flow direction are found to decay downstream and the flow to gradually approach the characteristics of a wall plume resulting from a concentrated line heat source with the same total heat input. Thus, the axial diffusion terms may be neglected far downstream, allowing the flow there to be approximated as a boundary, layer, with the full equations being solved in the interaction region. Finally, an experimental investigation is carried out to characterize the nature of the interaction. The flow is visualized by means of a shadowgraph and the temperature field is measured in the interaction region, downstream of the source. Numerical predictions agree with the experimental results, lending support to the numerical model for this interaction.

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