Rehab Al-Kaby will present her PhD Comprehensive Exam
- Thursday, November 9, 2017 at 3:00pm
- Roberts Hall, Room 113 - view map
Rheo-NMR of Transient and Steady State Shear-Banding in Wormlike Micelles
Understanding the correlation between the macroscopic flow field and the microscopic structure and dynamics of the non-Newtonian (complex) fluids is crucial on both fundamental and practical grounds. Among the variety of complex fluids, wormlike micelle (WLM) solutions have become a model system to study an unusual mechanical phenomenon known as shear banding. In its simplest form, shear banding is observed as the organization of the flow into two macroscopic bands, high and low shear band bearing different viscosities and local shear rates.
In this study, the shear banding of a wormlike micelle (WLM) solution was investigated under steady state and time dependent conditions. The system was a solution of 6 wt. % cetylpyridinium chloride (CPCl) and sodium salicylate (NaSal) in 0.5 M NaCl brine in a concentric cylinder Rheo-NMR shear cell. 1D velocity profiles across the 1 mm fluid gap were recorded every 1 s after shear start-up using Rheo-NMR velocimetry and used to evaluate shear rates in the low and high shear band as well as interface position. Transient and steady state shear banding was observed for a range of shear rates across the stress plateau and results compared for flow protocols with and without pre-shear. The evolution of the shear rate and interface position with time after start-up was used to evaluate changes in the kinetics of shear band formation as a function of shear rate and flow protocol.
- Department of Mechanical & Industrial Engineering