Observation of the Rayleigh-Benard convection cells in strongly coupled Yukawa liquids

Using first principles molecular dynamics simulation, we report for the first time the formation of Rayleigh-Benard convection cells (RBCC) in two-dimensional strongly coupled Yukawa liquids, characterized by coupling strength Gamma (ratio of average potential energy to kinetic energy per particle) and screening parameter kappa (ratio of average inter-particle distance to Debye length). For typical values of (Gamma, kappa), existence of a critical external temperature difference is demonstrated, beyond which RBCC are seen to set in. Beyond this critical external temperature difference, the strength of the maximum convective flow velocity is shown to exhibit a new, hitherto unsuspected linear relationship with external temperature difference and with a slope independent of (Gamma, kappa). The time taken for the transients to settle down tau(s)) to a steady state RBCC is found to be maximum close to the above said critical external temperature difference and is seen to reduce with increasing external temperature difference. For the range of values of (Gamma, kappa) considered here, tau(s) approximate to 10 000-20 000 omega(-1)(pd), where omega(pd) is dust plasma frequency. As Gamma is increased to very high values, due to strong coupling effects, cells are seen to be in a transient state without attaining a steady state for as long as 100 000 omega(-1)(pd), even for a very high external temperature difference. Role of system size, aspect ratio, and dust-neutral collisions has also been addressed. (C) 2015 AIP Publishing LLC