Effects of XG and PAM shear-thinning rheology on the hydrodynamic loads and wake dynamics of a NACA0012 hydrofoil

This study numerically investigates the hydrodynamic loads and wake dynamics of a NACA0012 hydrofoil in shear-thinning xanthan gum (XG) and polyacrylamide (PAM) solutions at a matched generalized Reynolds number of (Formula presented). A two-dimensional laminar power-law model is employed using experimentally fitted rheological parameters for polymer concentrations ranging from 0.01% to 0.05% and angles of attack from 0° to 20°. The results show that both polymers modify the hydrodynamic characteristics of the hydrofoil in a concentration-dependent manner. Specifically, 0.05% XG achieves a drag coefficient reaction or approximately 50% at low angles of attack; however, due to the adjusted inlet velocities required to maintain a matched-(Formula presented), this does not directly translate to an equivalent reduction in the absolute physical drag force. At higher angles of attack, both polymers exhibit non-monotonic effects on mean lift and force fluctuations. PAM shows a pronounced fluctuation peak near 0.04% under deep-stall conditions. Dynamic Mode Decomposition identifies polymer-dependent changes in modal amplitudes and frequency organization. Modes 2 and 3 remain harmonics of Mode 1 at (Formula presented), whereas selected deep-stall cases exhibit non-integer frequency ratios and a more complex multi-frequency response. These results link concentration-dependent rheology to hydrofoil loads and wake dynamics.