In this paper, terminal velocities of single wet fibers in water and staples in water and oil, which were assumed to be the model particles of fiber, were measured, and compared with those of dry fibers in air.
From the experimental results, by using the same effective diameter, circular equivalent diameter based on the projected area of the fiber and the staple, relationships between drag coefficients and Reynold's numder based on circular equivalent diameter were found to be the same for the staple and the fiber.
The drag coefficient thus obtained was from two to three times as the one for the spherical particle.

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