Scale of plume clustering in large-Prandtl-number convection

Clustering of plumes in turbulent Rayleigh-Bénard convection has been numerically observed in low-Prandtl number fluids. In this framework, turbulent plumes undergo a phase-separation process leading to large-scaleclusters and circulations, sometimes called plume superstructures and reminiscent of solar granulation andsupergranulation. On the other hand, the possible presence of large-scale plume aggregates has not been exploredin the case of large values of the Prandtl number, Pr, relevant to geological settings such as convection in planetaryinteriors. Here we address this problem and numerically explore the behavior of plume ensembles in turbulentconvection at very high Prandtl number values, including the case Pr -> infinity. The results indicate the presence ofplume clustering, albeit at smaller scale, also for large Pr number fluids, suggesting interesting consequences formantle convection processes.