Fracture patterns in viscoplastic gravity currents

Constant-flux gravity currents of viscoplastic fluid remain axisymmetric when extruded onto a dry horizontal plane. However, if the plane is coated with shallow layer water, current suffers dramatic non-axisymmetric instability in which localized $v$ -shaped cuts appear outer edge where contact water. These ‘fractures’ lengthen and guide subsequent radial outflow, leading to distinctive flower-like patterns. This pattern formation process illustrated for two materials, an aqueous suspension Carbopol, mixture water joint compound (a kaolin-based, commercially available product). The fracturing spreads over entire upper surface deeper baths are used, complicating extrusion can be removed entirely ambient replaced by immiscible liquid comparable viscosity, indicating that presence at key process. We conjecture underlying mechanism fracture under tension material, exacerbated