The liquid film behaviors created by an inclined jet impinging on a vertical wall

Abstract

Liquid films created by inclined jet-wall impingement are commonly seen in industrial applications. We investigated the liquid film behaviors created by an inclined jet impinging on a vertical glass wall using a brightness-based laser-induced fluorescence method. It was found that the typical liquid film by an inclined jet-wall impingement consists of the thin layer zone, the raised zone, the liquid node, and the trailing edge. The liquid film expands with higher impingement velocity but keeps the same elliptical shape. A normalized linear correlation is proposed to estimate the liquid film thickness. Based on the continuity equation and the empirical convection model, the Reynolds number distribution is deduced from the film thickness distribution. The Reynolds number in the thin layer zone is less than the critical Reynolds number. The surface waves in the thin layer zone are divided into the ripple waves and the disturbance waves. The disturbance waves have a larger wavelength and amplitude than the ripple waves. The quantitative measurement of the disturbance waves shows that the wavelength and amplitude increase linearly along the radial distance. The smaller impingement velocity does not change the growth rate of the wavelength but accelerates the development of the amplitude.