Effect of the channel geometries on flow regimes of a viscoelastic surfactant solution in a cavity

Viscoelastic surfactant solutions exhibit a characteristic flow behavior in the cavity of a flow channel. These flows are categorized as the flow regimes of the Barus effect, bulge structure, and separation flow. The former two flow regimes sweep into the cavity, which helps increase the heat transfer efficiency of a heat exchanger with a cavity to increase the heat transfer surface. Therefore, this study visualized and quantified these characteristic flow behaviors in channels with different geometries, based on inertia and elasticity, using Reynolds number, Re, and Weissenberg number, Wi. The flow regimes were affected by both inertia and elasticity; thus, viscoelastic Mach number, Ma, was also useful for characterizing the flow transition. The reattachment and separation lengths of the streamlines that sweep the bottom wall of the cavity were quantified using Re and Ma. These characteristic flow lengths were characterized and modeled by dimensionless numbers in the flow regime of the Barus effect but were not uniformly characterized in the flow regime of the bulge structure. The bulge structure was an entirely unique flow regime, but it significantly reduced the recirculating regions in the cavity, which is promising for increasing heat transfer efficiency.

Automated summary

This study visualized and quantified the characteristic flow behaviors of viscoelastic surfactant solutions in the cavity of a flow channel. The flow regimes were influenced by both inertia and elasticity, and the bulge structure was found to be a unique and promising flow regime for increasing heat transfer efficiency.