Downslope evolution of an adhered elastic-plated gravity current

The downslope spreading of viscous fluid beneath an adhered elastic sheet is controlled by a balance between elastic deformation of the sheet, viscous dissipation of the fluid advected downslope, and the adhesion between the sheet and the substrate. We describe a series of constant flux experiments carried out using clear, PDMS elastic sheets adhered to an inclined glass table. The method of dye attenuation allows the full evolution of an elastic-plated gravity current travelling downslope to be captured. Initially, pressure gradients are dominated by elasticity and the evolution reduces to that of a horizontal, adhered elastic-plated gravity current. When the downslope flux due to gravity becomes comparable to the axisymmetric flux due to the flexure of the plate, the current transitions into a second, quasi-two-dimensional regime where a downslope channel forms with a pronounced nose whose structure is dominated by elastic effects. We describe a simple theoretical scaling for the width of the channel, consistent with our experimental results, and experimentally characterise the transient behaviour near the injection hole point and at the nose. The prominent static channel formed has applications to the formation of lava channels and horizontally propagating dykes.