Morphology, propagation dynamics and scaling characteristics of drying fronts in porous media

• Published in: Geophysical research letters 2012-05, Vol.39 (9), p.n/a
• Main Authors: Shokri, N., Sahimi, Muhammad, Or, D.
• Format: Article
• Language: English
• Subjects: Drying; Earth sciences; Earth, ocean, space; Evaporation; Evaporation rate; Exact sciences and technology; fractal dimension; Fractals; Geophysics; Hydrology; liquid phase distribution; Nonlinear systems; Porous media; Radiography; roughness of drying front; Sand; wettability effects
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2012GL051506

Effects of surface wettability on the dynamics and morphology of evaporation‐induced drying fronts (DF) receding into hydrophilic (HI) or hydrophobic (HO) sands were studied using highly‐resolved neutron radiography. A more pronounced pinning‐depinning motion (larger steps and longer waiting times) was observed for the DF in HI sand relative to HO, due to weaker capillary pinning forces in the latter. For length scalesl smaller than a correlation length ξ, quenched disorder dominates DF roughness expressed by a roughness exponent α = 0.77, whereas for l > ξ the fluctuations induced by the DF motion annealed the disorder and result in α= 0.44. Although wettability suppressed evaporation rates in HO relative to HI sand, differences in the evaporation dynamics and pinning behavior did not alter the DF morphology indicators‐the fractal dimension and roughness exponent‐which remained similar for the HI and HO sands. Key Points Hydrophobicity reduces velocity of DF displacement Wettability weakly affects the fractal dimension and roughness exponent of DF Lesser wettability limits the extent of film region and the evaporation rate