Drop movement along a fiber axis due to pressure driven air flow in a thin slit

The movements of liquid drops on fibers commonly occur in fabrics used in household and commercial applications. The fundamental mechanisms controlling the movement of drops on the fibers are basically the same as those for flat surfaces, but the differences in the geometries cause different kinematic behaviors. Drops on surfaces are widely discussed but fewer publications discuss drops on fibers. The results of pressure driven air flow experiments to move liquid drops along a fiber axis are presented here. Data from these new experiments are used to revise a drag coefficient correlation previously reported with data from a Couette flow device. The revised correlation combines the data sets from the Couette flow and the pressure driven flow experiments and significantly extends the range of the Reynolds number in the correlation. Also, a new correlation is obtained to predict the minimum Reynolds number of the gas flow necessary to initiate the movement of the drops on the fibers. The second correlation gives an estimate of the gas flow conditions necessary to start the movement of drops on fibers. The first correlation provides a drag coefficient to estimate the average speed of drops moving on the fibers. (C) 2014 Elsevier B.V. All rights reserved.