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Effect of wetness patchiness on evaporation dynamics from drying porous surfaces
Author(s) -
Lehmann Peter,
Or Dani
Publication year - 2013
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 - 10.1002/2013wr013737
Subject(s) - evaporation , materials science , porosity , transpiration , porous medium , flux (metallurgy) , boundary layer , cluster (spacecraft) , mechanics , chemical physics , thermodynamics , composite material , chemistry , physics , biochemistry , photosynthesis , computer science , metallurgy , programming language
An important aspect of evaporative fluxes from porous surfaces is vapor emission through discrete pores giving rise to nonlinear dependency on surface water content (i.e., the flux is not proportional to surface water content). This nonlinearity is attributed to interactions among pore sizes and spacing, and the thickness of air boundary layer. The study examines effects of pore clustering on evaporation rates, addressing the question: do pore clusters behave like effective large pores? To answer this question, evaporation fluxes from surfaces with distributed or clustered pores (similar pore numbers and sizes) for various boundary layer thicknesses were computed numerically and analytically. Results show consistent suppression of clustered surface evaporation rates (relative to distributed pores configuration) with increasing cluster size. For cluster sizes of the order of boundary layer thickness (∼10 −2 m) the relative evaporation rate becomes proportional to the fraction of cluster surface area resulting in maximum evaporation suppression. An analytical expression for evaporative fluxes from patterned surfaces was derived based on superposition of diffusive fluxes from individual pores accounting for enhanced flux along cluster perimeter. Results may assist design of engineered porous surfaces for efficient evaporation suppression, and for interpretation of effects of coordinated stomatal clustering on transpiration fluxes from plant leaves.