Behavior in strong transverse shear flows

Behavior in strong transverse shear flows 

Since the relaxation times t are very long, it is relatively easy to realize shear rates (.r) larger than 1 /t( and to measure the resulting properties. It is convenient to work in situations of permanent ( ), where the molecules reach a steady state with finite distortions. This can be achieved only in transverse shears. For dilute solutions (Chapter VII) we discarded the transverse shear situations because they led to small (and thus complex) effects. For concentrated solutions, the distortions become strong even in transverse shear flows, and we can restrict our attention to this more common case. 

For example, in simple shear (n, = sy Uy = w = 0) performed at finites we may still define an effective viscosity The literature in this area is vast and diffuse. However, there seems to be a convergence toward the following results. - The viscosity 7f s) appears to follow a universal scaling law 

The relaxation time is much more difficult to measure, but it is plausible to assume that it follows a similar scaling relationship  

If correct, eq. (VIII.30) represents an essential simplification for hydro-dynamic studies. It implies that STt s) is a function only of T((0), and thus that a single dimensionless parameter OT((0) is required to characterize non-newtonian effects in the flow. At large x we find/ CAr) x r with values which are of order 0.8. 

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Vlll.3.3. Behavior in strong transverse shear flows... 

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