Numerical and experimental network study of evaporation in capillary porous media. Drying rates

Laurindo, João Borges; Prat, Marc

doi:10.1016/s0009-2509(97)00348-5

Cited by 187 publications

(189 citation statements)

References 14 publications

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“…Nevertheless, this effect is not large and it is assumed that other effects have to contribute, especially as in 7.5 cm depth, the shapes of the profiles are significantly different. Further possible factors are (i) linearizing the p c -S l curve at very low water saturation leads to an overestimation of liquid water flow (e.g., Ciocca et al 2014;Mosthaf et al 2014), (ii) relative permeability functions affect the flow behavior and saturation distribution during the evaporation process, (iii) different hydraulic properties around the sensors or with depth may affect the saturation measurements (Assouline 2006), and (iv) film and corner flow also have an influence as highlighted in a study on evaporation from pore networks (Laurindo and Prat 1998).…”

Section: Porous-medium Quantitiesmentioning

confidence: 99%

“…The coupling between the free-flow and porous-medium flow is extremely relevant to evaporation processes from bare soil surfaces. Evaporation from soil surfaces is a vital research subject in the past few years and has been investigated at the pore scale, e.g., (Shahraeeni et al 2012;Assouline et al 2010;Yiotis et al 2007;Laurindo and Prat 1998;Suzuki and Maeda 1968), at the REV scale, e.g., (Trautz et al 2015;Zhang et al 2015;Mosthaf et al 2014 andSchneider-Zapp et al 2010), and at larger scales, e.g., (Vanderborght et al 2010;Shukla andMintz 1982 andPenman 1948).…”

Section: Introductionmentioning

confidence: 99%

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Effect of Turbulence and Roughness on Coupled Porous-Medium/Free-Flow Exchange Processes

2016

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The interactions between turbulent free flow and flow in a porous medium are of key interest in different fields, e.g., meteorology, agriculture, building physics, and aerospace engineering. Properly understanding the strongly coupled exchange processes between the two domains is crucial to describing these interactions. In (Mosthaf et al. in Water Resour Res 47(10):W10522, 2011. doi:10.1029/2011WR010685), a concept for coupling laminar compositional single-phase free flow to compositional two-phase porous-medium flow under non-isothermal conditions was presented. In this study, the existing coupling concept is first extended to turbulent free-flow conditions. This includes the interface conditions between a Reynolds-averaged Navier-Stokes free flow using algebraic turbulence models and a Darcy porous-medium flow. Second, eddy viscosity and boundary layer models for a rough interface are integrated into this model concept. Results from laboratory evaporation experiments are used for comparison of the developed model concept. A sensitivity analysis of the evaporation rate and porous-medium quantities on different model setups, boundary conditions, BeaversJoseph coefficients, and roughness lengths is performed. Results demonstrate how including turbulence, either with eddy viscosity or boundary layer models, affects the evaporation rate. The model concept is able to predict early stage-I and intermediate to later stage-II evaporation rates. Sand-grain roughness concepts are successfully included into the model and show the desired qualitative effect.

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Section: Porous-medium Quantitiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Turbulence and Roughness on Coupled Porous-Medium/Free-Flow Exchange Processes

2016

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“…In the presence of films, at any stage of drying, the pore space can be characterized by three kinds of pores (close-ups in Figure 7): pores L, fully occupied by liquid, pores G, fully occupied by gas, and pores F, occupied by gas but also containing liquid films. The existence of pores of type F is the distinguishing feature of this work, compared to previous (Prat, 1995;Laurindo and Prat, 1998;Prat and Bouleux, 1999;Tsimpanogiannis et al, 1999;Yiotis et al, 2001, Plourde andPrat, 2003). Our focus is on thick films, e.g.…”

Section: Problem Formulationmentioning

confidence: 49%

“…In the context of drying, past experimental work has emphasized the existence and speculated on the role of film flow (Shaw, 1987;Laurindo and Prat, 1998;Tsimpanogiannis et al, 1999). In a series of experiments Shaw (1987) found that, under comparable conditions, the drying front in a cell containing packed beads moved one order of magnitude faster than when the cell was empty.…”

Section: The Effect Of Liquid Filmsmentioning

confidence: 99%

“…Shaw attributed this "unorthodox" result to liquid counterflow through films which form along particle contacts, and argued that it is the dominant mechanism for the drying of porous materials. Laurindo and Prat (1998) performed drying experiments in twodimensional etched-glass micromodels and compared their results with predictions from a pore-network simulator, which did not contain films. The experimental rates were found to be about six times higher than the numerical.…”

Section: The Effect Of Liquid Filmsmentioning

confidence: 99%

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Pore-Network Modeling of Isothermal Drying in Porous Media

Yiotis

Stubos

Boudouvis

et al.

Upscaling Multiphase Flow in Porous Media

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Abstract. In this paper we present numerical results obtained with a pore-network model for the drying of porous media that accounts for various processes at the pore scale. These include mass transfer by advection and diffusion in the gas phase, viscous flow in the liquid and gas phases and capillary effects at the liquid-gas interface. We extend our work by studying the effect of capillarity-induced flow in macroscopic liquid films that form at the pore walls as the liquid-gas interface recedes. A mathematical model that accounts for the effect of films on the drying rates and phase distribution patterns is presented. It is shown that film flow is a major transport mechanism in the drying of porous materials, its effect being dominant when capillarity controls the process, which is the case in typical applications.

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Analysis of the impact of surface layer properties on evaporation from porous systems using column experiments and modified definition of characteristic length

et al. 2014

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The hydraulic properties of the layer at the vicinity of the soil surface have significant impact on evaporation and could be harnessed to reduce water losses. The effect of the properties of the upper layer on the evolution of phase distribution during the evaporation process is first illustrated from threedimensional pore network simulations. This effect is then studied from experiments carried out on soil columns under laboratory conditions. Comparisons between homogeneous columns packed with coarse (sand) and fine (sandy loam) materials and heterogeneous columns packed with layers of fine overlying coarse material and coarse overlying fine material of different thicknesses are performed to assess the impact of upper layer properties on evaporation. Experiments are analyzed using the classical approach based on the numerical solution of Richards equation and semianalytical theoretical predictions. The theoretical analysis is based on the clear distinction between two drying regimes, namely, the capillary regime and the gravity-capillary regime, which are the prevailing regimes in our experiments. Simple relationships enabling to estimate the duration of stage 1 evaporation (S1) for both regimes are proposed. In particular, this led to defining the characteristic length for the gravity-capillary regime from the consideration of viscous effects at low water content differently from available expressions. The duration of S1, during which most of the water losses occur, for both the homogeneous and two-layer columns is presented and discussed. Finally, the impact of liquid films and its consequences on the soil hydraulic conductivity function are briefly discussed.

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Numerical and experimental network study of evaporation in capillary porous media. Drying rates

Cited by 187 publications

References 14 publications

Effect of Turbulence and Roughness on Coupled Porous-Medium/Free-Flow Exchange Processes

Effect of Turbulence and Roughness on Coupled Porous-Medium/Free-Flow Exchange Processes

Pore-Network Modeling of Isothermal Drying in Porous Media

Analysis of the impact of surface layer properties on evaporation from porous systems using column experiments and modified definition of characteristic length

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