Applied Math Seminar Announcement

A thixotropic generalization, proposed by Fredrickson AICHE J, 16 (1970), is applied to the Johnson-Segalman model. A nonmonotonic steady shear response can be realized as a result of both non-affine motion and a shear rate dependent destruction function in the fluidity evolution equation. Spurt dynamics are examined in the case where an added Newtonian viscosity is present. The time evolution is found to exhibit the same basic dynamical features as in the non-thixotropic case examined by Malkus et al. J. Comp. Phys. 87 (1990), even in the upper-convected limit. Also, for applied shaer rates in the unstable region, the shear stress does not approach a unique value in contrast to the case without added Newtonian viscosity addressed by Bautista et al. JNNFM 94 (2000). In addition, results for step strain and startup of steady shear flows for a variety of parameter regimes will be presented.