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EPSRC Centre for Doctoral Training in Fluid Dynamics

Kinematics and fluid dynamics of settling flocculated dispersions

Lead Academic Supervisor

Tim Hunter (School of Chemical and Process Engineering)

Lead Industrial Supervisor

Geoff Randall, Sellafield Ltd and Andrew Manning, HR Wallingford

Co-Supervisor(s)

Jeff Peakall (School of Earth and Environment), Rob Dorrell (School of Earth and Environment) and Anthony Stickland (University of Melbourne)

Theme(s)

Environmental FlowsParticulate Flows, Sediments and Rheology

Summary

Particles present in liquid dispersions may agglomerate to form larger fractal structures under various conditions. Such ‘flocs’ are ubiquitous in many industries and the natural environment, where their fluid properties can be altered dramatically in respects to discrete particles. In particular, the kinematics and associated fluid dynamics of settling, flocculated suspensions are poorly understood, where associations with entrained gases create further complexities. Of increasing importance, is the use of polymeric flocculants to enhance aggregation and separation; however, there is requirement for a significant advancement in our understanding of how the particle-polymer-particle interaction forces alter fluid hydrodynamics and phase separation, especially in settling environments of variable shear. This project will seek to develop the first theoretical and experimental models to predict the sedimentation dynamics of such flocculating, sediment systems with and without entrained gas, using state-of-the-art instrumentation for experimental validation. Results will be able to be used to predict particle and fluid dynamics of diverse natural and engineering systems, from sediment formation in estuarine mud-fats to water treatment and minerals processing operations.

Two figures are shown across page illustrating complex floc formation and settling behaviour. 

Fig. 1: PVM images and ParticleTrack trends measuring four stages of flocculation and dispersion. (Pandey, A., Smith, B., Redman, T., (2014) Best Practice for Water/Particle Separation. Engineering & Mining Journal.)

 

Fig 2: Left - agglomerated magnesium hydroxide wastes of various aggregate sizes, captured with SEM, Sysmex and PVM imaging techniques. Right – influence of particle concentration on mass flux of a settling suspension of the same system. Edited From; Johnson, Peakall, Hunter et al. I&EC Res, 2016 (DOI:10.1021/acs.iecr.6b02383)