Occurrence of coexisting dendrite morphologies: immiscible fluid displacement in an anisotropic radial hele-shaw cell under a high flow rate regime

Abstract

Viscous fingering morphologies during the displacement of a high viscosity fluid by a low viscosity immiscible fluid in a radial fourfold anisotropic Hele-Shaw cell are examined. By using the kerosene-glycerin system for which the µ/T ratio (µ being the relative viscosity and T the interfacial tension between the fluids) is about ten times higher than that for the commonly used air-glycerin system, we have been able to access the hitherto unexplored N_ca 1 regime (capillary number N_ca=U_µ/T, U being the advancing fingertip velocity). Within the anisotropy-dominated regime, and when flow rates are significantly high (capillary number well beyond N_ca=1), a new phase is seen to evolve wherein the dendrites grow simultaneously along the channels and along the directions making an angle of 45° with the channels, both being kinetically driven. This new phase resembles the one observed in a miscible fluid system at all flow rates of the displacing fluid.