Laboratory simulation of slowflows

Slowflows occur widely in both industrial settings and geophysical environments, with earthflows representing a slow, viscous downslope movement of water-saturated fine materials. This study presents novel laboratory simulations to model such flows using a highly viscous molten jaggery as a viscous analogue for natural earthflows. Although jaggery lacks granular and plastic constituents, its viscosity falls well within the range of certain natural earthflows, allowing it to represent essential aspects of viscous mass movements. Experiments were conducted on low to moderately inclined chutes, mimicking natural terrains. Flow dynamics, such as the evolution of flow velocity, depth, and deformation, are exclusively analyzed. Results reveal tongue-shaped, centrally thickened flows with a frontal bulge and rear depression. These behaviors are consistent with large-scale simulations of earthflows. Flow evolution displayed a kinematic transition: initial acceleration is driven by free-surface pressure gradients, followed by deceleration, leading to a near steady velocity. Flow geometry evolves rapidly with increasing slope. Velocity patterns are governed by the interplay among the gravitational, free-surface pressure gradient, and the viscous forces. The front motion is well-described by combining a power law with a hyperbolic tangent function. Overall, molten jaggery proves to be a simplified, yet, dynamically meaningful analogue of viscous earthflows. Experimental results of the molten jaggery may be utilized for the validation of existing earthflow models. Here, we only consider the viscous material, not including the plastic behavior. However, further extensions of the present study to real heterogeneous, visco-plastic natural materials are needed to widen the scope of the present study.