Investigating the effect of turbulence on hemolysis through cell-resolved fluid-structure interaction simulations

Abstract: Existing hemolysis algorithms are often constructed for laminar flows that expose red blood cells to a constant rate of shear. It remains an open question whether such models are applicable to turbulent flows, where there is a significant variation in shear rate along cell trajectories. To evaluate the effect of turbulence on hemolysis, we perform cell-resolved simulations of red blood cells in turbulent channel flow at $Re_\tau=180$ and 360 and compare them against the results obtained from laminar flow simulations at an equivalent wall shear stress. This comparison shows that, while the laminar flow generally induces greater stretch in the cell in a time-averaged sense, cells experience an overall larger deformation in turbulence. This difference is attributed to extreme events in turbulence that occasionally create bursts of high shear conditions, which, consequently, induce a large deformation in the cells. Associating damage with the most extreme deformation regimes, we observe that, in the worst case, the turbulent flow can produce deformation in the cell that is higher than the absolute maximum value in the analogous laminar case approximately 14\% of the time. Additionally, the $Re_\tau=180$ universally induced greater deformation in the cells than the $Re_\tau = 360$ case, suggesting that increasing the range of scales in the flow does not necessarily yield greater deformation when all other parameters are kept constant. A strong direct correlation ($R>0.8$) between shear rate and deformation metrics was observed in turbulence. The correlation against $Q$-criterion is inverse and weaker ($R\approx -0.26$), but once the shear contribution is subtracted, it improves in terms of areal dilatation ($R\approx -0.6$).