464839 Flow in the Thin Film Created By Normal and Oblique Turbulent Liquid Jets Impinging on a Vertical Wall: Application to Cleaning

Wednesday, November 16, 2016: 9:45 AM
Powell I (Parc 55 San Francisco)
Rajesh Kumar Bhagat, Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, United Kingdom and D. Ian Wilson, Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge, United Kingdom

Liquid jets are used for various applications including cleaning, heat transfer, and cutting. When a coherent liquid jet impinges on a vertical wall it forms a thin film, spreading radially away from the point of impingement, until a point where the outward momentum is balanced by surface tension. At this point, the liquid film changes its thickness abruptly giving a jump. A model for the jump location, based on Nusselt’s film theory, was presented by Wilson et al. (Chem. Eng. Sci, 2012, 68, 449-460). In this study, the flow field created by a turbulent liquid jet and the location of the film jump are studied and a new model is presented. The liquid film passes through three zones, namely the laminar boundary layer, the laminar film and the turbulent film zone. The location of the laminar to turbulent transition is described theoretically. In addition, the analysis explains why the location of film jump is observed to be insensitive to the nature of the substrate at high flow rates. The model is compared with new, as well as previously reported, data for the film jump location and film thickness when a jet impinges perpendicularly and at an oblique angle. The average velocity of the liquid was estimated from the initial growth of the film. Good agreement is obtained between the measurements and the model, which has no adjustable parameters. The results are then applied to the cleaning of two representative soil types; (1) Polyvinyl acetate layer which interacts with the liquid in the film, and (2) hydrophobic, non-interacting petroleum jelly.

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