A relationship between Reynolds stresses and viscous dissipation: implications to red cell damage.

Viscous shearing is examined as a mechanism by which turbulent flows can cause cellular damage. The use of Reynolds stress as an indicator of hemolysis is considered, and an alternative measure based on viscous dissipation is proposed. It is shown that under simple flow conditions the Reynolds stresses can be related to viscous dissipation. Data from the literature show that the instantaneous viscous shear stress at which hemolysis occurs is similar to the shear stress thresholds obtained from laminar flow studies. Also, the Kolmogorov length scales for most of the turbulent hemolysis studies are similar to the size of a red blood cell. These observations indicate that, for the jet and couette experiments examined, viscous shearing is an important mechanism in the destruction of erythrocytes by turbulence. However, pressure fluctuations may also contribute to damage for these cells and for cells of similar or larger size.