Numerical techniques for simulating groundwater flow in the presence of temperature gradients

Pestov, Irene

doi:10.21914/anziamj.v42i0.638

Cited by 5 publications

(2 citation statements)

References 19 publications

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“…Raleigh numbers during saturated measurements of soil thermal properties are in excess of the critical threshold, above which instability appears in the form of circulatory flow [cf. Pestov , 2000]. However, the effect of this circularly flow is unclear and further research is required to validate fully the DPHPS measurements under saturated conditions.…”

Section: Simulating Depth Dependency and The Relationship Between Thementioning

confidence: 99%

In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

Kettridge¹,

Baird²

2007

J. Geophys. Res.

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[1] Carbon uptake/release in peat soils (the latter especially in the form of methane) is strongly dependent on soil temperature. However, previous peatland temperature models have not represented soil temperatures accurately due to either errors in their parameterization or errors in the representation of heat transfer processes. Dual probe heat pulse sensors (DPHPS) and triple-probe heat pulse sensors (TPHPS) were used to provide detailed in situ measurements of the soil thermal properties of Sphagnum peat and the advective liquid heat flux resulting from percolating rainfall. The difficulties of applying the DPHPS approach within poorly decomposed Sphagnum peat are first considered. Our results suggest that measurement-induced advective vapor and liquid heat fluxes occurred when using the DPHPS. The analytical equations normally used to calculate the thermal diffusivity and volumetric heat capacity (C) from DPHPS measurements, therefore, cannot be applied within unsaturated Sphagnum peat. However, a numerical approach enabled the soil thermal properties to be estimated when an instrument-induced advective vapor flux was significant. When an instrument-induced advective liquid heat flux was significant, the relevant DPHPS data were identified and rejected. The measurements of the soil thermal properties were used to (1) develop an empirical model of the vertical variations in C through the unsaturated zone of poorly decomposed Sphagnum peat and (2) to develop an empirical relationship between the thermal conductivity (k) and C. The TPHPS measurements showed that the advective heat flux due to percolating rainfall occurred for a maximum of 24 hours after rainfall events. Its influence on soil temperatures may therefore be negligible. Citation: Kettridge, N., and A. Baird (2007), In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models,

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Section: Simulating Depth Dependency and The Relationship Between Thementioning

confidence: 99%

In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

Kettridge¹,

Baird²

2007

J. Geophys. Res.

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“…Our problem involves convection rolls up to a few metres. Convection in aquifers has been studied at much higher temperatures in geological formations (Pestov 2000) and in thermal energy storage in aquifers (Claesson et al 1985b).…”

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confidence: 99%

Seasonal groundwater turnover

Engström

Nordell²

2006

Hydrology Research

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Seasonal air temperature variations and corresponding changes in groundwater temperature cause convective movements in groundwater similar to the seasonal turnover in lakes. Numerical simulations were performed to investigate the natural conditions for thermally driven groundwater convection to take place. Thermally driven convection could be triggered by a horizontal groundwater flow. Convection then starts at a considerably lower Rayleigh number (Ra) than the general critical Rayleigh number (Ra c ) assuming that 108C groundwater is cooled to 48C, i.e. heated from below convection in porous media. This study supports the hypothesis that seasonal temperature variations, under certain conditions, initiate and drive thermal convection.

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Temperature-driven groundwater convection in cold climates

Engström

Nordell

2016

Hydrogeol J

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The aim was to study density-driven groundwater flow and analyse groundwater mixing because of seasonal changes in groundwater temperature. Here, density-driven convection in groundwater was studied by numerical simulations in a subarctic climate, i.e. where the water temperature was <4°C. The effects of soil permeability and groundwater temperature (i.e. viscosity and density) were determined. The influence of impermeable obstacles in otherwise homogeneous ground was also studied. An initial disturbance in the form of a horizontal groundwater flow was necessary to start the convection. Transient solutions describe the development of convective cells in the groundwater and it took 22 days before fully developed convection patterns were formed. The thermal convection reached a maximum depth of 1.0 m in soil of low permeability (2.71 · 10 −9 m 2 ). At groundwater temperature close to its density maximum (4°C), the physical size (in m) of the convection cells was reduced. Small stones or frost lenses in the ground slightly affect the convective flow, while larger obstacles change the size and shape of the convection cells. Performed simulations show that Bseasonal groundwater turnover^occurs. This knowledge may be useful in the prevention of nutrient leakage to underlying groundwater from soils, especially in agricultural areas where no natural vertical groundwater flow is evident. An application in northern Sweden is discussed.

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Numerical techniques for simulating groundwater flow in the presence of temperature gradients

Cited by 5 publications

References 19 publications

In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

Seasonal groundwater turnover

Temperature-driven groundwater convection in cold climates

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