Drying of porous building materials: hydraulic diffusivity and front propagation

Lockington, David; Parlange, Jean‐Yves; Barry, D. A.; Leech, C

doi:10.1007/bf02481524

Cited by 6 publications

(1 citation statement)

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“…However, when the data are fitted by a power law, the shrinking (drying) time varies as t d ¼ 96h a 1.5 min and the swelling (wetting) time varies as t d ¼ 29h a 1.3 min (where h a is in mm), quite different from the Washburn law. This large difference between drying and wetting is to be expected due to the different mechanisms responsible for these processes; liquid water is driven by capillary forces while wetting, while drying is dominated by the slow diffusion of vapour through pores at late stages, which leads to large variations in the effective diffusion coefficient in drying porous media (Pel et al 1996;Lockington et al 2003). The coupling of large strains (up to 20%) to water transport and localization of viscous dissipation at a bottleneck in the material may account for this discrepancy in the wetting stage; indeed, when a bottleneck of size l b dominates water transport, we expect t $ h a l b /D.…”

Section: Pine Conesmentioning

confidence: 99%

Hygromorphs: from pine cones to biomimetic bilayers

Reyssat

Mahadevan

2009

J. R. Soc. Interface.

415

360

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We consider natural and artificial hygromorphs, objects that respond to environmental humidity by changing their shape. Using the pine cone as an example that opens when dried and closes when wet, we quantify the geometry, mechanics and dynamics of closure and opening at the cell, tissue and organ levels, building on our prior structural knowledge. A simple scaling theory allows us to quantify the hysteretic dynamics of opening and closing. We also show how simple bilayer hygromorphs of paper and polymer show similar behaviour that can be quantified via a theory which couples fluid transport in a porous medium and evaporative flux to mechanics and geometry. Our work unifies varied observations of natural hygromorphs and suggests interesting biomimetic analogues, which we illustrate using an artificial flower with a controllable blooming and closing response.

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Section: Pine Conesmentioning

confidence: 99%

Hygromorphs: from pine cones to biomimetic bilayers

Reyssat

Mahadevan

2009

J. R. Soc. Interface.

415

360

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Revisiting Salvucci’s Semi-analytical Solution for Bare Soil Evaporation with New Consideration of Vapour Diffusion and Film Flow

et al. 2023

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Bare soil evaporation is controlled by a combination of capillary flow, vapour diffusion and film flow. Relevant analytical solutions mostly assume horizontal flow conditions and ignore gravitational effects. Salvucci (1997) provided a rare example of a semi-analytical solution for vertical bare soil evaporation. However, they did not explicitly represent vapour diffusion and film flow, which are likely to account for a significant proportion of total flow during vertical evaporation from soils. Vapour diffusion and film flow can be incorporated via Salvucci’s desorptivity parameter, which represents the proportionality constant relating Stage 2 cumulative evaporation to the square root of time under horizontal flow conditions. The objective of this article is to implement vapour diffusion and film flow within Salvucci’s semi-analytical solution and test its performance by comparison with isothermal numerical simulation and relevant experimental data. The following important conclusions are drawn. Analytical solutions that assume horizontal flow conditions are inadequate for understanding vertical evaporation problems because they overestimate evaporation rates and mostly predict vapour diffusion and film flow to be of negligible influence. Salvucci’s semi-analytical solution is effective at predicting the order-of-magnitude reduction in evaporation caused by gravitational effects. However, it is unable to identify the correct importance of vapour diffusion and film flow because these processes can only be represented through its desorptivity parameter.

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