Natural convection and ventilated solar envelopes

How air moves, on its own, behind a heated façade — and why the temperature of the outside air is not the boundary condition everyone assumes it is.

A ventilated solar façade works by letting heated air rise in the channel behind it. Predicting that flow rate is what decides whether the envelope cools the photovoltaic panels or traps heat against them.

This work, begun during a doctorate shared between the University of Lyon and UNSW Sydney, combined experiments and direct numerical simulation to study transitional natural convection in vertical heated channels. Two results run through it: the thermal stratification of the surrounding air changes the mass flow rate substantially, and must be represented in prediction models rather than replaced by a single outdoor temperature; and the transition to turbulence in these flows proceeds through identifiable coherent structures, which decomposition methods can extract and track.