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. Author manuscript; available in PMC: 2015 Jun 22.
Published in final edited form as: Nat Commun. 2014 Jun 18;5:4120. doi: 10.1038/ncomms5120

Figure 4. Operating space of inertio-elastic focusing in straight microchannels.

Figure 4

The parameter spaces probed by these studies are conveniently located on a two-dimensional plot of the fluid elasticity and the fluid inertia, as characterized by the channel Weissenberg number (Wi) and the channel Reynolds number (Re), respectively. The slope of a line passing through this space represents the value of the channel elasticity number (El); which is controlled by variations in the fluid viscosity (η), the fluid relaxation time (λ) and the microchannel dimensions. A value of El > 1 indicates a primarily elastically dominated flow on the length scale of the channel, whereas a value of El < 1 indicates a primarily inertially dominated flow. The red bars correspond to the range of Wi and Re explored in this study. Note that the white shaded region (beginning at Re* ~ 2,500) within the red bar on the horizontal axis indicates the regime in which turbulent flow in the Newtonian fluid was observed. Also note that the studies of Di Carlo et al. and Ciftlik et al. are both in the Newtonian limit (that is, Wi = 0).