Abstract Summary (Max 250 words)
Lamellar gel networks (LGN) are multiphase structures found in a range of personal care products including hair conditioners. Evolving fluid rheology and changing fill level during manufacture present significant mixing challenges in production and in scale-down for discovery of new formulations. This work explores the potential of a high throughput testing device for the investigation of new formulations, employing a helical ribbon in a 34 mm diameter cup filled to a height of 36 mm (100%). Since flow characteristics at this scale are not normally representative of those at pilot and production scale, this work aims at linking the scales through characterisation of the fluid dynamics and mixing. Dynamic torque measurements employing Newtonian and shear-thinning model fluids has shown that power draw in the laminar regime is generally linear with respect to rotational speed at fill levels of 25, 62.5 and 100%. In the laminar regime, inverse proportionality of the power number to the Reynolds number is found (3 < Re < 24), as expected. Comparison with OpenFOAM CFD simulations using the SIMPLE algorithm at low rotational speeds, where the free surface is modelled as flat, are in good agreement. However, as the rotational speed increases, vortexing and deformation of the free surface occurs in the experiments leading to an overprediction of torque, and consequently power draw. Volume of fluid (VOF) simulations allowing for free surface deformation give improved predictions, further validated by 2-D Particle Image Velocimetry (PIV) data obtained in both horizontal and vertical planes.
