Flow distribution in the liquid film created by a coherent circular water jet impinging obliquely on a plane wall

Abstract

When a coherent liquid jet impinges normally on a flat wall, the liquid flows away from the point of impingement in a radial pattern. The effect of the angle of impingement on the distribution of the flow in the azimuthal direction on a vertical polymethylmethacrylate wall was studied for angles of impingement ranging from 35.3° to 144.7°. The flow distribution was calculated from measurements of the location of the hydraulic jump and the rate of growth of the area cleaned of a soft solid soil layer (moisturising cream), for water jets generated from a 2 mm circular nozzle with Reynolds numbers ranging from 10,600–31,800. Distributions based on the initial location of the jump (before a draining film was established) agreed well with those calculated from cleaning tests, and were compared with three models based on geometric constructions as well as the ideal case derived assuming no dissipation presented by Hasson and Peck (AIChE J, 1964, 10, 752). The latter consistently overpredicted the fraction of flow in the principal direction and underpredicted the flow in the backwards direction. The changing ellipse model (CEM) gave the best description of the experimental data presented here as well as some results reported by other workers, but not for others. The results indicate that a priori estimates of flow distribution require detailed numerical calculations: the CEM can be used in short-cut calculations following calibration.