1998-08-26
10:15 at CAB D 28

The Dynamic Modelling of Microstructure Formation of Soft Solid Materials

Xue-Feng Yuan

University of Bristol

Complex fluids like polymer mixtures, lyotropic liquid crystals and microemulsions etc., exhibit very rich and striking similar phase behaviours including lamellar, haxagonal, spherical and bicontinuous phases. They are structured fluids and show non-Newtonian fluid behaviours due to their microstructures can be easily changed by flow. Recently, the interplay of morphology, kinetics of microstructure formation and rheology in complex fluids has attracted growing attention. Understanding the relationships is the only avenue to manipulate morphology and hence to control the macroscopic properties of materials. It has both scientific and technological significance. A general Lagrangian-Eulerian approach for modelling complex fluids is presented. The numerical technique can track the microstructure evolution of complex fluids under flows in a natural physical way. It is especially useful for modelling of complex fluid flows in which the characteristic time and length scales are usually several orders of magnitude higher than simple fluids. We preserve Voronoi cells as Lagrangian fluid elements in the scheme. The difficulty acknowledged in the previous formulation that arises from the mismatching between the number of equations and variables has been eliminated. The numerical scheme has been applied in dynamic modelling of spinodal decomposition in polymer solution. Recent results of shear-banding of viscoelastic fluids will be presented.