Skinny currents, tremor and dambreaks

Dr. Neil Balmforth
RESEARCH INTERESTS

Skinny currents, tremor and dambreaks:

Gravity currents occasionally develop solid skins. For example, cooling freezes the surface of lava flows to create a surface crust that can oppose the flow of the underlying fluid. We have been exploring models of such currents with a view towards understanding the wrinkling and buckling of the surface skin. As part of this, we have also looked into some solid mechanics problems of buckling sheets without a fluid.
Volcanic tremor has been suggested to arise from the interaction between the magma flowing through a sub-surface conduit, and the surrounding, deformable rock walls. We have elabourated on this mechanism, due to Bruce Julian, to explore whether it can indeed provide a plausible mechanism.
Certain sudden and hazardous floods have been hypothesized to result from the failure of moraine-dammed glacial lakes. A popular explanation of this failure is that an ice or rock fall into the lake generates a wave that overtops the dams and incises a small channel through which lake water can flow. The flow causes erosion, which deepens the channel, allowing more flow and more erosion. The resulting runaway cuts a deep incision into the dam and empties a good fraction of the lake in a matter of hours. We have built fluid models (both experimental and theoretical) of the process.

Click to enlarge

An elastic-plated gravity current
(experiment performed by Anja Slim in the CRS Lab at WHOI showing a current of corn syrip flowing beneath a wrinkled "elastic skin" of clingfilm)

Solution of a model of volcanic tremor

(shown is a space-time plot of the thickness of a periodic conduit containing flowing viscous fluid and bounded by elastic walls)

Dambreak experiment

(a rectangular tank holds a reservoir dammed by a mixture of sand and grit; a wave is generated that sets up a seiche in the reservoir which repeatedly washes over the dam, eventually cutting a channel that instigates a catastrophic incision)

Shear-induced buckling
Buckling atop a channel flow
Elastic-plated gravity currents

Instability in flow down elastic conduits and volcanic tremor
More volcanic tremor Interfacial instability

Dambreaking
More Dambreaking
Thixotropic gravity currents

Dr. Neil Balmforth RESEARCH INTERESTS Skinny currents, tremor and dambreaks: Gravity currents occasionally develop solid skins. For example, cooling freezes the surface of lava flows to create a surface crust that can oppose the flow of the underlying fluid. We have been exploring models of such currents with a view towards understanding the wrinkling and buckling of the surface skin. As part of this, we have also looked into some solid mechanics problems of buckling sheets without a fluid. Volcanic tremor has been suggested to arise from the interaction between the magma flowing through a sub-surface conduit, and the surrounding, deformable rock walls. We have elabourated on this mechanism, due to Bruce Julian, to explore whether it can indeed provide a plausible mechanism. Certain sudden and hazardous floods have been hypothesized to result from the failure of moraine-dammed glacial lakes. A popular explanation of this failure is that an ice or rock fall into the lake generates a wave that overtops the dams and incises a small channel through which lake water can flow. The flow causes erosion, which deepens the channel, allowing more flow and more erosion. The resulting runaway cuts a deep incision into the dam and empties a good fraction of the lake in a matter of hours. We have built fluid models (both experimental and theoretical) of the process.
Click to enlarge

An elastic-plated gravity current (experiment performed by Anja Slim in the CRS Lab at WHOI showing a current of corn syrip flowing beneath a wrinkled "elastic skin" of clingfilm)	Solution of a model of volcanic tremor (shown is a space-time plot of the thickness of a periodic conduit containing flowing viscous fluid and bounded by elastic walls)	Dambreak experiment (a rectangular tank holds a reservoir dammed by a mixture of sand and grit; a wave is generated that sets up a seiche in the reservoir which repeatedly washes over the dam, eventually cutting a channel that instigates a catastrophic incision)
Shear-induced buckling Buckling atop a channel flow Elastic-plated gravity currents	Instability in flow down elastic conduits and volcanic tremor More volcanic tremor Interfacial instability	Dambreaking More Dambreaking Thixotropic gravity currents