Resumo

LARRAINZAR-SOLIS, Edgar Fernando et al. Evaluation of a vertical downward water film thickness using visualization and image recognition techniques. Ing. invest. y tecnol. [online]. 2020, vol.21, n.1, e00003.  Epub 03-Ago-2020. ISSN 2594-0732.  https://doi.org/10.22201/fi.25940732e.2020.21n1.003.

The present work is focused on the experimental study of a vertical downward annular flow to determine the thickness and stability of a falling film water flow. For this purpose, it was designed and implemented an experimental set up to generate the annular two-phase flow pattern, provided with an injection head with a special geometry to induce a liquid film inside a cylinder. Due to the small dimensions, the film was visualized using a pulsated laser to illuminate the region and the pictures were taken with a high-speed camera. This technique allowed the determination of the falling film thickness by means of an algorithm to recognize image contours. In some of the studied cases, a concurrent air flow was injected in the center of the cylinder in order to evaluate its influence on the interfacial hydrodynamics of the liquid film. Average film thickness were obtained for different Reynolds numbers in different axial observation points, and it was observed that the liquid film annular area and the shape of the header to inject the water, are important factors for the surface characteristic and thickness of the film, and its stability as well. The experimental results show that the standard deviation increases in proportion to the average film thickness, especially in the turbulent regime.

Palavras-chave : Hydrodynamics; annular flow; falling water film flow; film thickness; stability; image recognition.

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