Experiments on transient natural convection in a cavity

A laboratory experiment is used to study the transient flow in an initially isothermal cavity at temperature T 0 following the rapid change of the two vertical endwalls to temperatures T 0 ± Δ T respectively. Individual temperature records are taken and the transient flow in the entire cavity is visualized with the aid of a tracer technique. It is shown that an oscillatory approach to final steady-state conditions exists for certain flow regimes, although the form of the oscillatory response is different to that suggested by previous work. It is argued that this oscillatory behaviour is due to the inertia of the flow entering the interior of the cavity from the sidewall boundary layers, which may lead to a form of internal hydraulic jump if the Rayleigh number is sufficiently large.