Optimal convection cooling flows in general geometries

TL;DR

This paper extends a method for finding optimal convection cooling flows to various geometries using conformal coordinates, revealing vortex structures that optimize heat transfer under different constraints.

Contribution

It generalizes a recent approach to optimize convection cooling flows across diverse geometries using conformal mappings and analyzes flow structures under energy and enstrophy constraints.

Findings

Optimal flows are similar in conformal coordinates across geometries.

Vortices range from the size of the hot surface to a small cutoff length.

Flow structures depend on the constraint of fixed kinetic energy or enstrophy.

Abstract

We generalize a recent method for computing optimal 2D convection cooling flows in a horizontal layer to a wide range of geometries, including those relevant for technological applications. We write the problem in a conformal pair of coordinates which are the pure conduction temperature and its harmonic conjugate. We find optimal flows for cooling a cylinder in an annular domain, a hot plate embedded in a cold surface, and a channel with hot interior and cold exterior. With a constraint of fixed kinetic energy, the optimal flows are all essentially the same in the conformal coordinates. In the physical coordinates, they consist of vortices ranging in size from the length of the hot surface to a small cutoff length at the interface of the hot and cold surfaces. With the constraint of fixed enstrophy (or fixed rate of viscous dissipation), a geometry-dependent metric factor appears in the equations. The conformal coordinates are useful here because they map the problems to a rectangular domain, facilitating numerical solutions. With a small enstrophy budget, the optimal flows are dominated by vortices which have the same size as the flow domain.