Robert C. Armstrong
Current Research

One of the most fertile research areas in chemical engineering today is the development of multiscale methods for linking molecular (or microstructural) behavior of chemical systems to process and product behavior. Non-Newtonian fluid mechanics, and the flow and processing of polymers in particular, offers a rich set of problems in which to develop these general methods. In our group we use theoretical, computational, and experimental methods to elucidate the rheology and fluid mechanics of non-Newtonian fluids. A wide variety of fluids are being studied including dilute polymer solutions, concentrated polymer solutions and melts, liquid crystalline polymers, biological polymers, concentrated suspensions, biodegradable polymers, and composites of rigid fillers and polymers. For many of these systems we are developing structural and molecular models which are of great importance for interrelating the microstructure with processing conditions, and in understanding the physics of these flows at interfaces.

We are also developing numerical methods for solving viscoelastic flow problems. These are among the most challenging numerical simulations facing scientists today. The finite element method is currently being used to solve confined and free surface flow problems for differential and integral viscoelastic fluid models, and for molecular and structural models for polymer solutions, liquid crystals, and suspensions. A particular area of interest is developing efficient methods for coupling the solution of molecular conformation evolution with the macroscopic flow problem. We are also interested in general methods for moving between fine-grain and coarse-grain descriptions of the molecules in a simulation. Efforts are also aimed at matching computational results with experimental results obtained by applying laser Doppler velocimetry, video imaging, birefringence, NMR, and standard rheometry to investigate model flows of these materials.

Our group has excellent facilities for carrying out non-Newtonian fluid studies. For numerical studies we have numerous workstations, and for large calculations, we have our own parallel cluster of Intel machines as well as easy access to other, very large parallel clusters. Experimental facilities include a six-beam, three-color laser Doppler velocimeter, a two-color laser birefringence apparatus, a Rheometrics Mechanical Spectrometer, an elongational flow viscometer, a biaxial extensional flow device, a high shear rate capillary viscometer, and numerous flow loops.

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