Stagnation flows birefringence

Planar viscosities determined by measuring birefringence in unlubricated stagnation flow in both directions. The same polystyrene melt as Figure 7.4.4 was used in the same die. From Macosko et al. (1980). 

O. G. Harlen, E. J. Hinch, and J. M. Rallison, Birefringent pipes The steady flow of a dilute polymer solutions near a stagnation point, J. Non-Newt. Fluid Mech., 44, 229 (1992). 

Stagnation Large strain centre but non-homogeneous Birefringence Opposed nozzles low i] convenience of a wide range of e Wall effects (e.g. shear) Lubricant Stability of flow... 

Figure J. a. The opposed jets. The polymer solution is sucked into the jets along the symmetry axis, o represents the stagnation point in the center of the flow field, b. The flow field visualized by light scattered at 90° from tracer particles, c, A birefringent line between the jets for a 0.1% solution of atactic polystyrene (a-PS). d. The perturbed flow field during flare formation in a semiddute polyethylene oxide solution.

The peak in is known from birefringence, flow-field, and light-scattering observations to correspond to the highest e for which a stagnation... 

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