Comment on "Tank-treading and tumbling frequencies of capsules and red blood cells".

In a recent computational investigation, Yazdani et al. [Phys. Rev. E 83, 046305 (2011)] reported an exponential (logarithmic) dependence of the tank-treading frequency F(tt) with the viscosity ratio λ at low (moderate) viscosity ratios for erythrocytes in shear flows. We argue that the authors misinterpreted the inverse linear dependence on λ of the tank-treading frequency F(tt), as found by Wodson and Dimitrakopoulos [Biophys. J. 99, 2906 (2010)], owing to the fact that Yazdani et al. plotted their frequency-versus-λ results in a log-log plot.