Abstract
Interaction of liquid with ultra-hydrophobic surface is accompanied by creation of layer of air. The effect of the air film has a potential of use in industry in many applications. The quality of the surface is influenced by matrix roughness, the character of physical or chemical cover. There was developed a method for analysis of the liquid flow and the air film using the lighting in volume, visualization with CCD camera and long distance microscope, and optical filters. There were prepared four stainless steel samples of inner channel of dimensions (80 × 8 × 8) mm and initial surface roughness Ra 0.33, Ra 1.0, Ra 2.0, and Ra 2.2. The inner channel was treated with plasma and commercial hydrophobic coating Greblon (WEILBURGER Coatings GmbH). There was realized study focused on the liquid flow velocity profile close to the air film. There are present results for laminar, transient and turbulent flows. The study also estimated the air film thickness depending on the Re number. The knowledge of the air film behaviour helps applied suitable degree of processing and cover for the target application.
Highlights
The ultra-hydrophobic surfaces have the prospect of great importance in industry, both in applications demanding easy cleaning, and they are presumed to reduce loss when the active parts of hydraulic machines are treated
This properties lead to monolithic air layer presented as air film, or lead to plurality of bubbles of various sizes seated upon the surface
The study of the velocity profile close to the air film, and the wall was based on the visualization using lightening in volume and the CCD camera with regulated shutter and defined depth of field
Summary
The ultra-hydrophobic surfaces have the prospect of great importance in industry, both in applications demanding easy cleaning, and they are presumed to reduce loss when the active parts of hydraulic machines are treated. The quality of the surface is influenced by the matrix roughness, the character of physical or chemical cover This properties lead to monolithic air layer presented as air film, or lead to plurality of bubbles of various sizes seated upon the surface. There was already described in the previous publication, focusing on the initial identification of an air layer, that the dynamics of the air layer is dependent on the velocity of the flowing liquid. This speed is expressed as Reynolds number, which is taken as a hydraulic diameter of the duct without an air layer. This speed is expressed as Reynolds number, which is taken as a hydraulic diameter of the duct without an air layer. [1]
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