Rheology and Multiphase Flow

Projects for understanding the behavior of fluid flow fields.

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Novel Fabrication of Nanostructured Particles with an Arbitrary Shape

Convenient methods for the fabrication of complex nanostructures are emerging in the growing field of nanotechnology for novel optical, electrical, magnetic, and also biological functions. Recently we have developed a simple and effective method to produce various kinds of nanostructured particles like nanorice and nanospears (i.e., tapered nanorods) using alumina membrane as templates. The nanocylindrical pores of anodized alumina membranes are filled with spherical polymer nanoparticles by a solvent assisted nano-injection. Then the membranes are heated in an oven above the glass transition temperature of the polymer. Due to the non-uniform heating, non-equilibrium capillary forces, and the wetting property of the polymer nanospheres confined in the nanocylinders, the spherical nanoparticles coalesce to form both aspect ratio and end-shape controlled nanorods which are shaped in the forms of nanorice, nanospears or tapered nanorods. Other novel nanostructures include nanorods, nanograss, nanodisks, and broken nanodonuts using vaious nanomaterials such as polymers, metals, inorganic particles, and biomolecules.

Investigators (PI is linked): Ilsoon Lee
Categories: Rheology and Multiphase Flow, Colloid and Interface Science, Polymer Science and Engineering, Structural Materials, Nanomaterials

Extensional Viscosity of Elastomers and Thermoplastic Elastomers

The strain hardening of random copolymer elastomer melts is being investigated as a function of composition, strain rate and temperature. Sensitivity to detailed experimental procedures with two different instruments -- the RME and the rotary EVF fixture on the ARES-- has been investigated specifically for elastomers in this project.

Investigators (PI is linked): Krishnamurthy Jayaraman
Categories: Polymer Science and Engineering, Rheology and Multiphase Flow

Relaxation Models for Turbulent Mass Transfer Near Free and Rigid Interfaces

The relationship between the statistical coherent structures of turbulent flows near interfaces and turbulent transport phenomena is currently being investigated by using a novel statistical approach to the convective diffusion equation. A set of integro-differential equations relate the mean concentration field to the underlying space-time structure of the velocity field and a mean Green's function. Problems being studied using this methodology include: mass transfer at high Schmidt numbers near rigid and free interfaces; deposition of fine particles in filter beds; and physicochemical absorption.

Investigators (PI is linked): Charles A Petty
Categories: Rheology and Multiphase Flow

Drag Reduction by High Molecular Weight Polymers

Simple dimensional analysis anticipates difference in observable statistical properties of turbulent flows and viscous and viscoelastic fluids, but it does not explain the significant reduction in drag caused by a few parts per million of a high molecular weight polymer added to a fully developed turbulent flow of a Newtonian fluid. The phenomenon is being investigated in our laboratory both experimentally and theoretically. We have recently developed a statistical theory which shows many of the qualitative features characteristic of this phenomenon. Experiments are under way to verify these new findings.

Investigators (PI is linked): Charles A Petty
Categories: Rheology and Multiphase Flow

Extrusion and extensional flow of thermoplastic elastomers

Thermoplastic vulcanizates (TPVs) investigated here consist of micron-sized, crosslinked EPDM rubber particles dispersed at high volume fractions in a 0.8 MFR polypropylene matrix with a high-temperature paraffinic oil. The morphology and rheology of these suspensions is complicated by the presence of oil in both phases. One area of interest is in understanding the evolution of two-phase morphology with slip flow and boundary lubrication during extrusion of TPVs. Another is to develop procedures for using profile dies in estimating strain averaged extensional viscosity of TPV melts at higher strain rates.

Investigators (PI is linked): Krishnamurthy Jayaraman
Categories: Polymer Science and Engineering, Rheology and Multiphase Flow

Polymer nanocomposites and foams with nanoparticles

The goal of the project is to develop new cost-effective thermoplastic elastomer nanocomposite foam with a semi-crystalline polymer matrix such as polypropylene. Improving the melt strength of the polymer is essential for this task. Recent work by Pathak and Jayaraman (2007) shows evidence of improvements in melt strength of linear polypropylene by incorporation of anisotropic nanoparticles. Optimum foaming process conditions will be developed for both extrusion and injection molding of polymers and blends reinforced with nanofibers and nanolayers to control the cell size distribution in the foamed product.

Investigators (PI is linked): Krishnamurthy Jayaraman
Categories: Polymer Composites, Polymer Science and Engineering, Rheology and Multiphase Flow

Mixed-feed Direct Methanol Fuel Cells

The need for high energy density, lightweight power sources for demanding portable electronic applications gives incentive to the search for novel fuel cell concepts and approaches that could reduce size, weight, and system complexity. Such power sources could find applications in variety of portable medical devices, computer hardware, and military equipment. We are developing a direct methanol fuel cell (DMFC) system design approach where the fuel (methanol) and air are mixed and fed simultaneously to both the anodes and the cathodes of the fuel cell stack. This approach leads to substantial size and weight reductions by eliminating the need for bipolar flow-field/separator plates and cell seals and by simplifying fluid manifolds. The key issues are the need for selective electrocatalyis at both the anode and cathode and efficient mixing and separation systems upstream and downstream of the fuel cell stack, respectively.

Investigators (PI is linked): Scott Calabrese Barton
Categories: Sustainable Economy, Energy Production, Rheology and Multiphase Flow, Nanomaterials

Nanomixing or Nanodispersion of Nanomaterials

We have established a strategic partnership with the Primix Corporation to study the nanomixing, nanodispersion, and nanoparticulate processes. Due to the enhanced high shear forces, the dispersed nanomaterials have superior stability in solvents. We are currently studying why it helps the stability of the nanodispersion. The mixer, named T.K. Filmics, uses a multiphase swirling flow to achieve extremely high energy dissipation and achieve the dispersion. The mixer has a stationary outer cylinder, within which an inner cylinder rotates very rapidly. The two phases are introduced separately from the bottom and the particulates are dispersed by shear in the annular region between the two cylinders. The high shear force, thin film mixing system has been newly developed from the conventional mixers by the Primix Corporation located in Japan (http://www.primix.jp/en/index.html).

Investigators (PI is linked): Ilsoon Lee
http://www.primix.jp/en/index.html  Categories: Nanomaterials, Polymer Science and Engineering, Rheology and Multiphase Flow, Colloid and Interface Science

Fabrication of Large Diffractive Optical Element Solar Concentrator Panels by Extrusion

The low density of optically clear thermoplastics compared to inorganic glass makes them the materials of choice for making large area diffractive lenses with very low mass per unit area or areal density to be used as solar concentrators in space applications. Smaller optical components have been produced on a large scale by injection molding thermoplastic polymers; however optical elements in the present application will cover areas of up to 50 square meters. Hence the goal of this project is to achieve tight tolerances on thickness profiles over large areas of diffractive optical elements produced with an extrusion line from optical grade thermoplastic.

Investigators (PI is linked): Krishnamurthy Jayaraman
Categories: Structural Materials, Polymer Science and Engineering, Rheology and Multiphase Flow, Energy Production