Correlations of Wave Characteristics for a Liquid Film Falling Down Along a Vertical Wall

Abstract

The behavior of a liquid film that flows down countercurrently along the inner surface of a circular pipe was examined. In the experiments of the present study, silicone oils of 500 cS, 1000 cS, and 3000 cS, as well as water, were used as the liquid phase. The gas phase was air. The vertically oriented test section was a circular pipe of 30 mm in inner diameter and 5.4 m in length. The substrate thickness of the silicone films, the film Reynolds numbers of which were quite low, was close to the mean film thickness, while the water film substrate was much thinner than the mean film thickness. Waves were observed on the substrate. Waves of a certain amplitude were confirmed to exist, even on the silicone films near the flooding occurrence, where the film Reynolds number was quite low. The mean film thicknesses of the silicone films, as well as that of the water film, were well expressed by applying the universal velocity profile to the film flow. When the film Reynolds number was lower than 600, the wave velocity was well predicted as the velocity of small perturbation waves on a laminar film. As the film Reynolds number became large, the wave velocity became slower than the small perturbation wave velocity. The correlation for the wavelength was developed based on the present experimental results. Combining this correlation with the Nosoko correlations and modifying the constants and exponents of the parameters in the equations, new correlations for the wave velocity and maximum film thickness were proposed. These new correlations were used to predict the wave velocity and the maximum film thickness to an accuracy of within 15%.