Numerical and experimental investigations into the rheological behaviour of wet foam flowing under a fence.

Experimental and numerical investigations were carried out to describe the flow of a wet foam under a fence placed in the middle of a horizontal duct with a square crosssection. The aim was to characterize the foam’s flow behaviour and model it using computational fluid dynamics in complex geometrical situations such as those encountered in industrial systems as for the cleaning of food equipment. As fences affect foam structure, organization and flow dynamics, these were characterized for three different flow rate conditions. Measurements using pressure sensors, particle image velocimetry and a conductimetry technique show a reorganization of the foam downstream, with a thicker liquid film at the bottom, larger bubble sizes at the top, as well as a larger void fraction increasing from the bottom to the top. The foam revealed a viscoelastic character as would be the case for a non-Newtonian fluid when passing through the fence. Herschel–Bulkley and/or Bingham laws relating to the presence of an underlying liquid film at the bottom of the channel were selected as being appropriate for this description. After adjusting these parameters from experimental data, computational fluid dynamics analysis was carried out. Results shown a close agreement with experiments using the Herschel–Bulkley model for two very different flow regimes. [ABSTRACT FROM AUTHOR]