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Evaporation Study Based on Micromodel Experiments: Comparison of Theory and Experiment
Author(s) -
Geistlinger Helmut,
Ding Yi,
Apelt Bernd,
Schlüter Steffen,
Küchler Matthias,
Reuter Danny,
Vorhauer Nicole,
Vogel HansJörg
Publication year - 2019
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2018wr024647
Subject(s) - contact angle , capillary action , wetting , mechanics , materials science , evaporation , porous medium , micromodel , drop (telecommunication) , thermodynamics , porosity , composite material , physics , engineering , mechanical engineering
Evaporation —a key process for water exchange between soil and atmosphere—is controlled by internal water fluxes and surface vapor fluxes. Recent studies demonstrated that the dynamics of the water flow in corners determine the time behavior of the evaporation rate. The internal water flux of the porous media is often described by capillary flow assuming complete wetting . Particularly, the crucial influence of partial wetting , that is, the nonlinear contact angle dependency of the capillary flow has been neglected so far. The focus of the paper is to demonstrate that SiO 2 ‐surfaces can exhibit contact angles of about 40°. This reduces the internal capillary flow by 1 order of magnitude compared to complete wetting. First, we derived the contact angle by inverse modeling. We conducted a series of evaporation experiments in a 2‐D square lattice microstructure connected by lognormal distributed throats. We used an explicit analytical power series solution of the single square capillary model. A contact angle of 38° ± 1° was derived. Second, we directly measured the contact angle of the Si‐SiO 2 wafer using the Drop Shape Analyzer Krüss 100 and obtained an averaged contact angle of 42° ± 2°. The results support the single square capillary model as an appropriate model for the description of the evaporation process in an ideal square capillary.