The structure of anomalous entry flow patterns through a planar contraction

Role of the elasticity number in the entry flow of dilute polymer solutions in micro-fabricated contraction geometries

“…For shear-thinning elastic fluids in planar contraction geometries, elastic corner vortices grow with increasing Wi; however the extent of vortex growth within a planar geometry [7][8][9][10] is less than in the equivalent axisymmetric geometry [11]. Table 1 identifies cases in which numerical simulations have been able to reproduce either qualitatively or quantitatively the results of specific experimental studies.…”

“…Re 1) but non-zero. An example of this includes the presence of diverging streamlines, which have been observed experimentally in the entry flow of Boger fluids at Reynolds numbers less than 0.1 [25,26], and more commonly in shear-thinning elastic fluids [7][8][9][10][11]27,28]. In the latter case, inertia has always been present due to the shear-thinning nature of the fluids.…”

Direct measurements of viscoelastic flows of DNA in a 2:1 abrupt planar micro-contraction

“…The mechanism of vortex enhancement may involve the corner vortex, the lip vortex, or a combination of the two, depending on contraction ratio, inertia and fluid rheology, with the lip vortex playing a larger role and appearing at lower Wi for higher contraction ratios [28,31,32]. For very dilute shear-thinning fluids, however, Chiba et al [33] report that inertia results in suppression of the lip vortex, followed by unstable, three-dimensional flows at higher Wi.…”

The inertio-elastic planar entry flow of low-viscosity elastic fluids in micro-fabricated geometries

“…For an axisymmetric geometry, it has been found that lower elasticity solutions experience regimes consisting of diverging flow with unstable salient vortices, and regimes with Goertler-like and lip vortices, while for higher elasticity solutions, unstable regimes extend to asymmetric flow patterns, azimuthally varying salient vortices, and 'buckling' flow structures. The "Goertler-like" vortex regime is also common to 4:1 planar contractions of high aspect ratio, h/w c > 20 using the same low elasticity solutions [13,14]. …”