Water imbibition in paper towels
摘要
The rapid absorption of water by paper towels is driven by their porous structure, where capillary forces, viscous resistance, and gravitational effects govern wicking dynamics. This study investigates the influence of inter-layer interactions in multi-ply configurations and the role of gravity in wicking behavior. Experiments are conducted on four paper towel brands–Bounty®, Tuff®, Sparkle®, and Georgia-Pacific®–in both vertical and horizontal orientations, representing conditions with and without gravitational influence, respectively. Near-infrared imaging is used to track the wetting front and the spatio-temporal evolution of moisture content (MC). Analysis of capillary rise length as a function of time reveals two distinct wicking regimes: an initial transitional phase followed by a later stable phase. MC contour analysis shows a decrease in water volume with elevation in vertical wicking, whereas in horizontal wicking, MC remains nearly uniform. These behaviors are attributed to the heterogeneous pore structure of paper towels, composed of interconnected pores of varying sizes. Larger pores facilitate faster flow and predominantly supply water to smaller pores, shaping overall wicking dynamics. This hierarchical distribution of flow explains the transition between wicking regimes and underscores the role of pore size variation in capillary-driven absorption.