Effect of flow bifurcation transitions of shear-thinning fluids on hydrodynamic resistance of channels with sudden contraction and expansion

The aim of this work was to study the relationship between hydrodynamic resistance and flow instability of shear-thinning fluids in channels with sudden contraction and expansion. To this end, the critical conditions of bifurcation transitions from symmetric to asymmetric vortex flow depending on the channel geometry and rheological properties of Carreau model fluid were investigated. It was found that increasing the contraction ratio leads to decreasing the critical Reynold number as a power function, while variation in the length of the channel narrow part has almost no effect on the position of the bifurcation transition point, but changes the corner vortex lengths. It was found that the considered bifurcation transitions in shear-thinning fluids lead to a non-monotonic dependence of the hydrodynamic resistance of channels with sudden contraction and expansion on Reynolds number with a minimum located around the critical Reynolds number.