Barrel shaped droplet movement at junctions of perpendicular fibers with different orientations to the air flow direction

• Liquid droplets at junctions of perpendicularly oriented fibers were exposed to the air flow.
• Angle of one fiber relative to the flow direction changes from 0 to 30 and 45 deg.
• Experimental data were fitted to a correlation to estimate the lowest Reynolds number that initiates the drop motion.

Droplet movements on surfaces are of significant interest in a wide range of practical applications. In contrast to the widely studied motion of droplets on rough and smooth surfaces in a flat configuration, knowledge of the motion across fiber junctions is sparse, despite its significance in filters. Crossed fibers at various angles to flow are a fundamental structure within a complex fibrous medium. This work presents the experimental results of a microscopic study of liquid droplet movement on crossed fibers when subjected to air flow. The crossed fibers were positioned to create different angles, within a plane, relative to the airflow direction. Crossed fibers at various angles to flow are a fundamental structure within a complex fibrous medium. The liquid droplets were placed on the intersection point using a previous method developed by the authors for single fibers. A comparison was made between different fiber layouts in terms of Reynolds number of the gas flow. A mathematical correlation for the minimum Reynolds number of gas at which the droplets began to move was developed. This correlation predicts the gas flow conditions required to start the movement of drops at the fiber junction.

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