Structure formation in moderately concentrated viscoelastic suspensions insimple shear flow

We report experimental results on the evolution of the particle microstruct ure for noncolloidal particles that are suspended in a viscoelastic medium. For dilute suspensions consisting of particles having a monodisperse parti cle size distribution subjected to steady and oscillatory shear flows, as w ell as suspensions having a bidisperse size distribution subjected to stead y shear, we verify previous results reported in the research literature. We also present new results of the particle microstructure for a dilute bidis perse system that was subjected to oscillatory shear. For moderately concen trated suspensions we report the formation of particle strings that corresp ond to a quantitative reduction in the simultaneously measured shear stress . (C) 2001 The Society of Rheology.