Two-dimensional unsteady inertial flows of a yield stress fluid around a cylinder
Abstract
Two-dimensional unsteady inertial flows of a yield stress fluid around a cylinder were studied experimentally. Carbopol aqueous gels, well-known model yield stress fluids, are used. The influence of interface conditions on vortex shedding was studied in particular by modifying the roughness of the cylinder. When wall adherence was guaranteed, it was possible to observe alternate vortex shedding similar to the Von Karman street occurring in Newtonian fluids. In contrast, when the fluid was able to slip on the cylinder wall, a highly particular flow morphology was observed. The effects of the Reynolds and Oldroyd numbers and that of confinement on the critical Reynolds number for vortex shedding and on the Strouhal number were demonstrated. The experimental results were compared with the numerical predictions using a Herschel-Bulkley viscoplastic model.