Congratulations to Eirik Flekkøy, Knut Jørgen Måløy, James Campbell, Jon Alm Eriksen and their collaborators from the Universities of Swansea and Oxford ! Their article entitled “Frictional fluid instabilities shaped by viscous forces” has been published under Nature Communication on May 26th, 2023.
Nature Communications | (2023) 14:3044
Multiphase flows involving granular materials are complex and prone to pattern formation caused by competing mechanical and hydrodynamic interactions. Here we study the interplay between granular bulldozing and the stabilising effect of viscous pressure gradients in the invading fluid. Injection of aqueous solutions into layers of dry, hydrophobic grains represent a viscously stable scenario where we observe a transition from growth of a single frictional finger to simultaneous growth of multiple fingers as viscous forces are increased. The pattern is made more compact by the internal viscous pressure gradient, ultimately resulting in a fully stabilised front of frictional fingers advancing as a radial spoke pattern.