Monday, 11 October 2004 - 1:50 PM

This presentation is part of : Rajagopal Symposium

Rheology of Complex Systems : Non linear Effects

Daniel De Kee, Department of Chemical and Biomolecular Engineering and Tulane Institute for Macromolecular Engineering and Science (TIMES), Department of Chemical and Biomolecular Engineering and Tulane Institute for Macromolecular Engineering and Science (TIMES), New Orleans, LA 70118

This presentation will outline research which has been carried out in the field of polymer rheology. A number of unexpected phenomena have been observed which are important in many fields of science and technology.

We shall look specifically at phenomena dealing with:

- yield stress measurements in multiphase systems. In particular, we shall discuss our new slotted plate technique to determine yield stress values as low as 10-4 Pa without extrapolation. That is: we achieve an improvement of several orders of magnitude over the vane technique, making our plate technique suitable for yield stress determinations of colloidal and nano suspensions.

- bubble dynamics in viscoelastic media. Here we shall discuss our contribution towards the solution of the velocity jump discontinuity observed occasionally ( since the late sixties) when plotting bubble velocity versus bubble volume. Gas-liquid systems are ubiquitous in industrial practice and understanding bubble behavior in complex fluids is rather important.

- stress jump. We will discuss modified network model predictions of the instantaneous gain or loss of stress on startup or cessation of flow.


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