Engineering Commons^™

The Effect Of The Shear-Thickening Transition Of Model Colloidal Spheres On The Sign Of N1 And On The Radial Pressure Profile In Torsional Shear Flows, M. Lee, Mataz Alcoutlabi, J. J. Magda, C. Dibble, M. J. Solomon, X. Shi, G. B. Mckenna

Mechanical Engineering Faculty Publications and Presentations

A novel rheometer plate was used to measure radial pressure profiles during cone-and-plate and parallel-plate shearing flows of a concentrated colloidal dispersion of polymethyl methacryalate spheres suspended in dioctyl phthalate. There is a long history of using suspensions of this type as a model rheological system. The measured pressure profile can be used to calculate N1 and N2, and also provides a check on the flow field in the rheometer. At shear rates just below onset of shear thickening, our measurements show that N1 is positive as predicted by Stokesian dynamics simulations of model Brownian hard spheres, but we are …