Education

• MS – 2005 Rensselaer Polytechnic Institute
• Bachelors – 1996 Rensselaer Polytechnic Institute

Matthew Armstrong
Ph.D. candidate
047 Colburn Laboratory
armstm@udel.edu
Tel: +1 302 831 2957

I am currently researching the rheology of complex fluids that have microstructure using numerical methods.  That is using several well-known thixotropic, rheological models to predict steady shear and Large Amplitude Oscillatory Shear flows (LAOS).  The first side of my research is applying efficient numerical methods to find globally optimized parameter values for thixotropic, complex fluids that are known to have a mircro-structure.  The numerical methods involve ODE solvers, parallel simulated annealing, minimization of least squares, etc.  Not only are we searching for globally optimum parameter values, but also the best thixotropic models to apply the numerical methods to ^[1,2,3,4].  We are able to compare the models with experimental data from other members of the group.  Ultimately we would like to combine as many good model features as possible into one model.

We have used our models and global parameter estimation on several published thixotropic systems including blood ^[5], an adhesive hard sphere system ^[6], and a model thixotropic system consisting of fumed silica in paraffin oil ^[7].  In addition we have recreated the model thixotropic system and gathered rheological data using an ARESG2 strain controlled rheometer.

The end state is a more accurate model that is able to predict flows in all flow fields, and is more thermodynamically consistent, as well as allows for a more three dimensional approach to the solution of the microstructure and rheological constitutive equation.

References

[1] Mujumbdar, A., Antony .N. Beris , Arthur B. Metzner. “Transient  phenomena in thixotropic systems.” J. Non-Newtonian Fluid Mech. 102, 157-178 (2002).

[2] De Souza Mendes, P. R. T. (2012). “A Unified Approach to Model Elasto-Viscoplastic Thixotropic yield-stress materials and apparent yield-stress fluids,” Rheol. Acta 52, 673 – 694 (2012).

[3] Mewis, J., Wagner, N. J. (2012). Colloidal Suspension Rheology. Cambridge University Press, New York, Cambridge University Press.

[4]. Dimitriou, C. J. (2013). The rhrological complexity of waxy crude oils: Yielding, thixotropy and shear heterogeneities. PhD, Massashusettes Institute of Technology.

[5] Bureau, M. e. al. “Rheological Hysteresis of Blood at Low Shear Rate,” Biorheology 17, 191-203 (1980).

[6] Kim, J. M. (2012). Effect of the Range of Attraction on the Rheology, Microstructure, and Thermodynamics of Thermoreversible Gels with Adhesive Hard Sphere Interactions. PhD, University of Delaware.

[7] Dullaert, K. a. J. M. (2005). “A model system for thixotropy studies,” Rheol. Acta 45, 23-32 (2005) 23 – 32.