INHOMOGENEOUS FLOWS OF NON-NEWTONIAN FLUIDS - GENERATION OF SPATIAL CONCENTRATION GRADIENTS

The conformation of polymer molecules or of micelles is known to be changed when a stress or deformation-rate field is applied to a fluid. Thermo dynamic considerations suggest that the resulting entropy changes must lead to diffusion of the species effected toward regions of minimum stress level in any system in which the stress varies with position. That is to say, spatial stress gradients inevitably appear to give rise to spatial concentration gradients. Such flows differ intrinsically, therefore, from homogeneous flows in which the stress field, hence the fluid concentration levels and properties, are uniform throughout the continuum. Preliminary measurements of these concentration fields are reported and consequences of this phenomenon in several flow processes are considered. © 1979.