Clustering of Plumes in Turbulent Convection

Tubulent convection that leads to large-scale order by the clustering of convective plumes was investigated. Numerical simulations were performed for a fluid with a three-dimensional, solenoidal velocity field and a particular temperature field. The process occurred at a large aspect ratio with periodic boundary conditions in the horizontal directions. Clusters were formed as a result of the organization of the convective plumes and the clusters grew with time finally reaching the width of the computational domain. The sizes of the individual plumes remained on the scale of the boundary layer thickness whereas kinetic energy was transferred to low horizontal wave numbers.