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.
Liquid film cooling by jet–wall impingement on the combustor wall is commonly used in small rocket engines. The heat transfer mechanism inside the liquid film is closely related to the film flow. Therefore, we establish a comprehensive analytical model with reasonable assumptions for the liquid film flow by inclined jet–wall impingement, and we validate it through a series of experiments. It is found that the predicted liquid film dimensions agree well with the experimental results. As the impingement angle increases from 30 to 60 deg, the shape of the liquid film turns from an oval to a circle. With the increase of the impingement velocity from 7.8 to [Formula: see text], the width, length, and area of the liquid film increase. The wall roughness [Formula: see text] ranges from 6.3 to [Formula: see text], which shows negligible effects on the liquid film dimensions. As the surface tension increases from 36.03 to 67.13 mN/m and the viscosity increases from 1 to [Formula: see text], the dimensions of the liquid film decrease. The effect of viscosity is more significant than surface tension within the scope of this experiment. Finally, an empirical correlation for the three investigated film dimensional parameters is proposed.
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