СТРУКТУРА КАНАЛА ПЛЮМА, ФОРМИРУЮЩЕГОСЯ В ПЛОСКОМ СЛОЕ (МОДЕЛИРОВАНИЕ ПЛЮМА В ЗОНЕ СУБДУКЦИИ)

Abstract

Experimental studies of a plume forming in a flat paraffin layer above a local heat source are presented. The experiments were performed on an installation with a transparent front wall. The flat payer is inclined two degrees with respect to the gravity vector. The thermal power transferred from the plume conduit under conditions of stationary thermal conduction is determined. The structure of the plume conduit and the structure of free-convective flows are determined for different plume thermal power values. Free-convection flows along the conduit height are cellular ones. The cellular structure occurs due to unstable stratification along the height of the plume conduit. The ascending flow in the plume conduit is a localized jet stream; the descending flow exists along the perimeter of the conduit. The cell boundaries correspond to narrowings of the plume conduit, formed due to cooling of the descending flow to a temperature close to the melting point. The cell parameters are determined for different values of relative thermal power (Ka criterion).The free-convection flow structure in the cells of the plume conduit is elucidated. The modes of reaching the surface for plumes forming in a flat layer are determined in relation to Ka criterion. When the relative power Ka exceeds 1.14, the model plume reaches the surface with the formation of a mushroom-shaped head. This case may correspond to plumes responsible for the formation of batholiths in the Andean subduction zone. Experiments have shown that the structure of the plume conduit in a flat layer corresponds to the plume structure formed in a solid massif above a local heat source. Distinctions in the thermal and hydrodynamic structure for a flat layer are observed due to the solid surfaces bounding the layer.