The flow of materials is studied in the science of rheology. When there are sudden changes in flow geometry, such as contraction or expansion, a complex mixture of shear and elongational flow occurs. The behaviour of a fluid in this complex flow depends on its viscoelastic properties. To optimise processing and product development analytical techniques are needed to determine these viscoelastic properties. In food industry textural properties e.g. creaminess, smoothness and foaming depend on the extensional rheological behaviour. Extensional characteristics are also important for polymer processing, the ease of swallowing and even affect cell mitosis. There are few measuring systems available for measuring these properties, especially for medium viscosity fluids.
The main objective of this project is to attain a better understanding of the complex behaviour of fluid flow through contractions and to utilise this knowledge to develop an experimental technique for determining the extensional properties of fluids. Numerical analysis of flows through different contractions and evaluation of different mathematical models are studied. This generates knowledge in how to optimise the experimental technique and how to optimize process and product development to achieve a product of high quality and desired properties.