The effect of jet length and wall curvature on the flow patterns generated by an impinging water jet were quantified and the effect on cleaning investigated in a brief study. The length of time taken to establish steady flow was characterised. Jet impingement on a flat vertical wall was investigated for jets of diameter 2-4 mm for lengths, L, up to 1 m. The amount of liquid lost to splatter was measured and found to be insensitive to L for short L (< 300 mm for these nozzles) and strongly related to L for longer values. The shape of the radial flow zone on flat walls agreed with existing models once the fraction of liquid lost to splatter was accounted for. Tests on horizontal and vertical cylinders with curvatures in the range 6.9 to 20 m-1 showed that the curvature of the impinged wall did not affect the shape of the radial flow zone until higher flow rates (> 1.5 dm 3 min-1). The cleaning of two viscoplastic model food soils was studied briefly: a hydrophobic petroleum jelly and Carbopol ® , a water-soluble gel. The splatter correction was not able to account for all the differences observed in cleaning at different jet lengths. There was no appreciable effect of curvature on cleaning behaviour. Soaking of the Carbopol ® increased its cleaning rate.

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