Two quasi-steady states observation in an asymmetrically heated vertical channel
Résumé
Passive cooling of photovoltaic double-skin facades can be modelled by considering natural convection in an open-ended vertical channel heated under isoflux conditions. Such a system is particularly challenging for numerical simulations, where turbulence may be observed for high Rayleigh numbers (Ra∗ > 10^5 , Ra∗ being the modified Rayleigh number based on channel width, aspect ratio, and wall heat flux). We present an experimental investigation of the flow along an asymmetrically-heated vertical channel with a modified Rayleigh of Ra∗ = 3.3 × 10^7 . The flow behaviour is studied through wall temperatures and velocities measurements in the channel. The main result is the observation of two quasi-steady states that occur successively without any external trigger on the flow. The states are said to be quasi-steady as their durations being much longer than the time needed to switch. The shift between these states may correspond to the existence of flow reversals.