Helical Ribbon Impellers for Rheometry of Complex Fluids 


Mr Gaspare Giancontieri    Dr Davide Lo Presti    Dr David Hargreaves

Background

A complex fluid is a particular mixture having a coexistence between two phases that does not follow the hydrodynamic law: polymers, gels, colloidal fluids, suspensions, emulsions, foams, etc. are categorised as complex fluids. 

Characterisation, modelling, formulation and processing of complex fluids are part of a challenging research area which would need to support the continuous development of new commercial products.

Several industry are involved with such materials: asphalt, plastic and rubber industries, ceramic, food, biochemical and pharmaceutical industries, cosmetic, detergent, paints, lubricants, inks, adhesives, construction industries, etc

The key focus of the area is the effect of the process on the resulting performance of the products and knowledge of their viscosity/rheological behaviour is paramount for their development and further successful application. However, the viscosity measurements of complex blends composed by suspended particles within fluids of different densities can be a challenge often leading to misleading viscosity results due to the phase separation of the component during the measurements process. 


Research approach

To overcome this problem, experimental studies conducted at the University of Nottingham are being carried out to evaluate the best impeller shape able to improve the degree of homogenisation of high viscous fluids with suspended particles. As a first result, a prototype of a Helical Ribbon Impeller (HRI) for a Brookfield Viscometer was designed and manufactured.

The mixing performance of complex fluids are being compared against those obtained with a standard impeller spindle, to establish which geometry allowed reaching the best level of homogenisation and the more realistic viscosity measurements. The HRI is being calibrated and then used for testing several materials in the field of pavement engineering.

The whole experimental programme will be then simulated by means of CFD analyses. At last a comparison between CFD particles volume fraction and experimental tests will be carried out to validate CFD simulations and to asses whether CFD modelling could represent a valid support to optimise design and manufacturing efforts of non-standard equipment for rheometry of complex fluids.  

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