Stochastic and deterministic dynamics of free boundaries atop turbulent convection

A warm, upwelling flow is induced by a floating ``thermal blanket'', which locally cuts the heat loss from a fluid body that undergoes thermal convection. The interaction between the flows and the thermal blanket (a freely moving boundary) leads to rich behaviors, and each corresponds to a different potential landscape experienced by the free boundary. When the free boundary is small, it sees a bulged hill and tends to slide away. But when the free boundary is large enough, it is trapped in the middle of the fluid surface, as if it sits in a potential valley. The authors developed a method to reconstruct the potential landscapes through a simple model using their experimental data.