Mass entrainment process visualised using vertical profiles of the mass fraction of the μ₁ fluid. Only the uppermost parts of the convective layer and part of the stable layer are shown. The dotted line shows the initial condition and the remaining three sets of lines correspond to averages over time windows τ_av  =  2τ_conv  =  160 wide and centred on times of (from left to right) 580, 1250, and 1920.