Drag in visco-elastic fluids

From a theoretical standpoint, the creeping-flow steady translation motion of a sphere in a visco-elastic medium has been selected as one of the benchmark problems for the validation of procedures for numerical solutions [Walters and Tanner, 1992 Chhabra, 1993a], Unfortunately, the picture which emerges is not only incoherent but also inconclusive. Most simulation studies are 

On the other hand, the elfects of shear-thinning viscosity completely overshadow those of visco-elasticity, at least in the creeping flow region. Indeed, a correlation based on a viscosity model, with zero shear viscosity and/or a characteristic time constant, provides satisfactory representation of drag data when the liqmd exhibits both shear-thinning properties and visco-elasticity [Chhabra, 1993a]. 

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