Determination of the macroscopic optical properties of snow based on exact morphology and direct pore‐level heat transfer modeling

Haussener, Sophia; Gergely, Mathias; Schneebeli, Martin; Steinfeld, Aldo

doi:10.1029/2012jf002332

Cited by 31 publications

(30 citation statements)

References 71 publications

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“…Morphological parameters such as porosity (ε) and specific surface area (SSA) were then calculated. The opening size distribution with spherical structuring elements on the micro-CT scans was used to estimate the mean pore size (d p ) (Haussener et al, 2012). The effective permeability was calculated using the finite volume technique CFD (computational fluid dynamics simulation software from ANSYS; ANSYS, 2010) by solving the continuity and Navier-Stokes equations (Zermatten et al, 2011(Zermatten et al, , 2014 for laminar flow…”

Section: Namevmentioning

confidence: 99%

Tomography-based monitoring of isothermal snow metamorphism under advective conditions

Ebner

Schneebeli²,

Steinfeld

2015

The Cryosphere

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Abstract. Time-lapse X-ray microtomography was used to investigate the structural dynamics of isothermal snow metamorphism exposed to an advective airflow. The effect of diffusion and advection across the snow pores on the snow microstructure were analysed in controlled laboratory experiments and possible effects on natural snowpacks discussed. The 3-D digital geometry obtained by tomographic scans was used in direct pore-level numerical simulations to determine the effective permeability. The results showed that isothermal advection with saturated air have no influence on the coarsening rate that is typical for isothermal snow metamorphism. Isothermal snow metamorphism is driven by sublimation deposition caused by the Kelvin effect and is the limiting factor independently of the transport regime in the pores.

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Section: Namevmentioning

confidence: 99%

Tomography-based monitoring of isothermal snow metamorphism under advective conditions

Ebner

Schneebeli²,

Steinfeld

2015

The Cryosphere

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“…Note that this scattering behavior is a known characteristic of two-phase media in the geometric optic limit and with irregular phase boundaries (e.g. in [7] ). Fig.…”

Section: Materials Parametersmentioning

confidence: 99%

“…The collision-based Monte Carlo ray-tracing method (MCRT) is used in combination with radiative distribution functions for semitransparent media [7,14,17,36] . A large number of stochastic rays N distributed within REV of the fibrous samples are emitted.…”

Section: Multi-rte Approachmentioning

confidence: 99%

“…This approach has the ability to incorporate realistic and morphologically complex media. As an example, this approach was used by Haussener et al [7] for the determination of the macroscopic properties of different types of snow, a dispersed ice medium semitransparent in the visible wavelength range. In this previous study, a direct comparison between multi-RTE approaches and single-RTE approaches had been conducted, indicating that [19][20][21][22][23][24][25] , they are interesting materials for other applications such as combustion support in burners [26] , solar fuel production [27] , and thermal protection systems [28,29] among others.…”

Section: Introductionmentioning

confidence: 99%

“…The determination of the apparent radiative properties of dispersed media based on media morphology and composition becomes crucial to the accuracy of this approach. This topic has continuously attracted interest from the radiative transfer community due to its large variety of applications such as solar energy conversion [3][4][5] , nuclear technologies [6] , snow physics [7] , and medical applications [8] . The reviews of Viskanta and Mengüç [9] , Baillis and Sacadura [10] , and Bail-lis et al [11] present the theoretical approaches and experimental methodologies for the characterization of spectral, directional apparent radiative properties of particulate and realistic disperse media, such as foams, fibrous materials, various ceramics, polymer coatings containing microspheres, and aerogel super-insulations.…”

Section: Introductionmentioning

confidence: 99%

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Radiative characterization of random fibrous media with long cylindrical fibers: Comparison of single- and multi-RTE approaches

Randrianalisoa

Haussener

Baillis

et al. 2017

Journal of Quantitative Spectroscopy and Radiative Transfer

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a b s t r a c tRadiative heat transfer is analyzed in participating media consisting of long cylindrical fibers with a diameter in the limit of geometrical optics. The absorption and scattering coefficients and the scattering phase function of the medium are determined based on the discrete-level medium geometry and optical properties of individual fibers. The fibers are assumed to be randomly oriented and positioned inside the medium. Two approaches are employed: a volume-averaged two-intensity approach referred to as multi-RTE approach and a homogenized single-intensity approach referred to as the single-RTE approach . Both approaches require effective properties, determined using direct Monte Carlo ray tracing techniques. The macroscopic radiative transfer equations (for single intensity or two volume-averaged intensities) with the corresponding effective properties are solved using Monte Carlo techniques and allow for the determination of the radiative flux distribution as well as overall transmittance and reflectance of the medium. The results are compared against predictions by the direct Monte Carlo simulation on the exact morphology. The effects of fiber volume fraction and optical properties on the effective radiative properties and the overall slab radiative characteristics are investigated. The single-RTE approach gives accurate predictions for high porosity fibrous media (porosity about 95%). The multi-RTE approach is recommended for isotropic fibrous media with porosity in the range of 79 −95%.

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Tomography-based characterization of ice-air interface dynamics of temperature gradient snow metamorphism under advective conditions

Ebner

Andreoli

Schneebeli³

et al. 2015

J. Geophys. Res. Earth Surf.

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Snow at or close to the surface commonly undergoes temperature gradient metamorphism under advective flow, which alters its microstructure and physical properties. A functional understanding of this process is essential for many disciplines, from modeling the effects of snow on regional and global climate to assessing avalanche formation. Time-lapse X-ray microtomography was applied to investigate the structural dynamics of temperature gradient snow metamorphism exposed to an advective airflow in controlled laboratory conditions. Experiments specifically analyzed sublimation and deposition of water vapor on the ice structure. In addition, an analysis of the ice-air interface dynamics was carried out using a macroscopic equivalent model of heat and water vapor transport through a snow layer. The results indicate that sublimation of the ice matrix dominated for flow rates < 10 À6 m 3 s À1 while during increased mass flow rates the water vapor deposition supplied by the advective flow counteracted sublimation. A flow rate dependence of water vapor deposition at the ice interface was observed, asymptotically approaching an average estimated maximum deposition rate on the whole sample of 1.05 · 10 À4 kg m À3 s À1 . The growth of microsized whisker-like crystals on larger ice crystals was detected on microscope photographs, leading to an increase of the specific surface area and thus suggest a change of the physical and optical properties of the snow. The estimated values of the curvature effect of the ice crystals and the interface kinetic coefficient are in good agreement with previously published values.The growth of ice particles in dry seasonal snow is caused by vapor diffusion among particles due to temperature gradients imposed on the snow cover [Colbeck, 1983]. The whole ice matrix is continuously recrystallizing EBNER ET AL.TEMPERATURE GRADIENT SNOW METAMORPHISM 2437

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Determination of the macroscopic optical properties of snow based on exact morphology and direct pore‐level heat transfer modeling

Cited by 31 publications

References 71 publications

Tomography-based monitoring of isothermal snow metamorphism under advective conditions

Tomography-based monitoring of isothermal snow metamorphism under advective conditions

Radiative characterization of random fibrous media with long cylindrical fibers: Comparison of single- and multi-RTE approaches

Tomography-based characterization of ice-air interface dynamics of temperature gradient snow metamorphism under advective conditions

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