Hydrodynamic characteristics of typical shear-thinning polymer flow past a cylinder

To illustrate the influence of shear-thinning polymer solution on hydrodynamic and flow structure of element assistance and its mechanism of action, this article conducted a numerical investigation for flow past a cylinder in typical shearing-thinning polymer solutions at Re = 60 based on the finite volume method (FVM). One flexible polymer (PEO) and two rigid polymers (XG, DG), whose rheological properties were experimental fitted using the Carreau-Yasuda model by other literature, were chosen to perform the numerical simulation. The vortex size and the back-flow region length both became smaller in polymer flows, and this inhibition effect was most significant in XG flow. On the contrary, except for the 50 ppm PEO flow, the shedding frequency was promoted in polymer flow. Meanwhile, the three polymers exhibited enhancement effects on the lift coefficient fluctuation, and inhibition effects on the drag coefficient; only XG flow significantly promoted the drag coefficient fluctuation. The dynamic model decomposition (DMD) analysis further indicated that the vortex intensity of each mode in polymer flow was stronger than that in water flow. New structures appeared in PEO, DG flows, while only quantitative difference was found in XG flow compared to water flow. The polymers also affected the mode growth rate and thus the flow stability. The rigid polymer only induced the dispersion degree of the growth rates, while flexible polymer may trigger positive values. In summary, the above hydrodynamic characteristics of shear-thinning polymer flow past a cylinder could provide theoretical support for further understanding the flow characteristics of non-Newtonian fluids.