Article
Glover, H.W., Brass, T., Bhagat, R.K., Davidson, J.F., Pratt, L., Wilson, D.I.
2016J. Food Engineering17895-109
Scale1e-6 to 1e-3 m
/ 1e-3 to 1 s, 1 to 60 s
Non-expert summaryThis paper describes an experimental study of the removal of thin (less than or equal to 1 mm) layers of (i) dried polyvinyl alcohol, PVA, and (ii) petroleum jelly (a viscoplastic fluid) from vertical glass or polymethyl methacrylate (PMMA) surfaces by the normal impingement of a turbulent coherent water jet (passing through air). The PVA experiments feature a static nozzle and surface so a circular region of cleared material grows steadily over time: the petroleum jelly also features experiments where the surface moves relative to the the nozzle, replicating a moving jet. In the latter case, the jet generates a rounded cleaning front upstream of the impingement point.
The viscoplasticity of the petroleum jelly limits the extent of the cleaned area. A quantitative model is presented where the cleaning rate is related to the flow of momentum per unit length in the liquid film, modified for yield stress behaviour. This model is able to describe the results obtained for static and moving configurations. An expression is obtained for the momentum flow rate associated with viscoplastic behaviour.
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