Numerical Study of Finite Element Method Based Solutions for Propagation of Wetting Fronts in Unsaturated Soil

Tan, Thiam‐Soon; Phoon, Kok‐Kwang; Chong, Pui-Chih

doi:10.1061/(asce)1090-0241(2004)130:3(254)

Cited by 21 publications

(7 citation statements)

References 11 publications

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“…Note that abrupt changes in the pressure head in the last layer are likely, especially due to the direct Gaussian solver of JULES. In order to reduce those numerical oscillations, a noniterative Picard method (Paniconi, Aldama, & Wood, 1991; Tan, Phoon, & Chong, 2004) is introduced between timesteps (Equation ).

R^{t + 1, l + 1} = \frac{R^{t + 1, l} + R^{t}}{2},

where t is the timestep and l is the number of iterations. One iteration is sufficient to remove the oscillations and to apply the new model explicitly.…”

Section: Methodsmentioning

confidence: 99%

Towards the representation of groundwater in the Joint UK Land Environment Simulator

Batelis

Rahman

Kollet

et al. 2020

Hydrological Processes

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Groundwater is an important component of the hydrological cycle with significant interactions with soil hydrological processes. Recent studies have demonstrated that incorporating groundwater hydrology in land surface models (LSMs) considerably improves the prediction of the partitioning of water components (e.g., runoff and evapotranspiration) at the land surface. However, the Joint UK Land Environment Simulator (JULES), an LSM developed in the United Kingdom, does not yet have an explicit representation of groundwater. We propose an implementation of a simplified groundwater flow boundary parameterization (JULES‐GFB), which replaces the original free drainage assumption in the default model (JULES‐FD). We tested the two approaches under a controlled environment for various soil types using two synthetic experiments: (1) single‐column and (2) tilted‐V catchment, using a three‐dimensional (3‐D) hydrological model (ParFlow) as a benchmark for JULES’ performance. In addition, we applied our new JULES‐GFB model to a regional domain in the UK, where groundwater is the key element for runoff generation. In the single‐column infiltration experiment, JULES‐GFB showed improved soil moisture dynamics in comparison with JULES‐FD, for almost all soil types (except coarse soils) under a variety of initial water table depths. In the tilted‐V catchment experiment, JULES‐GFB successfully represented the dynamics and the magnitude of saturated and unsaturated storage against the benchmark. The lateral water flow produced by JULES‐GFB was about 50% of what was produced by the benchmark, while JULES‐FD completely ignores this process. In the regional domain application, the Kling‐Gupta efficiency (KGE) for the total runoff simulation showed an average improvement from 0.25 for JULES‐FD to 0.75 for JULES‐GFB. The mean bias of actual evapotranspiration relative to the Global Land Evaporation Amsterdam Model (GLEAM) product was improved from −0.22 to −0.01 mm day−1. Our new JULES‐GFB implementation provides an opportunity to better understand the interactions between the subsurface and land surface processes that are dominated by groundwater hydrology.

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R^{t + 1, l + 1} = \frac{R^{t + 1, l} + R^{t}}{2},

where t is the timestep and l is the number of iterations. One iteration is sufficient to remove the oscillations and to apply the new model explicitly.…”

Section: Methodsmentioning

confidence: 99%

Towards the representation of groundwater in the Joint UK Land Environment Simulator

Batelis

Rahman

Kollet

et al. 2020

Hydrological Processes

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“…Computation of the two components Q S and Q L is more difficult because one needs to account for transient, variably-saturated subsurface flow. Stable numerical solutions of unsteady flow in unsaturated soils are difficult to obtain, especially for coarse materials with steep hydraulic functions (Tan et al 2004), and analytical solutions are only available for very special cases (Serrano 2004). One of these cases is represented by steady, fully-saturated, slope-parallel flow.…”

Section: Runoff Generation In the Debris-incised Channelmentioning

confidence: 99%

Experimental evidences and numerical modelling of debris flow initiated by channel runoff

2005

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Debris flow initiation by channel bed mobilization is a common process in high mountainous areas. Initiation is more likely to occur at the outlet of small, steeply sloping basins where concentrated overland flow feeds an ephemeral channel incised in slope deposits. Such geological conditions are typical of the Dolomite region (Italian Alps), which is characterized by widespread debris flow activity triggered by severe summer thunderstorms. Real-time data and field observations for one of these catchments (Acquabona catchment, Belluno, Italian Alps) were used to characterize the hydrological response of the initiation area to rainfalls of varying intensity and duration. The observed behaviour was then reproduced by means of a simple hydrological model, based on the kinematic wave assumption, to simulate the generation of channel runoff. The model is capable of predicting the observed hydrological response for a wide range of rainfall impulses, thus providing a physical basis for the understanding of the debris flow triggering threshold.

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“…The calculation of derivative terms in the Jacobian matrix makes the Newton scheme more costly and algebraically complex than the Picard scheme. As the slow convergence rate often occur in sharp wetting fronts with highly nonlinear soil hydraulic properties or initial dry conditions, various under-relaxation (or damping) techniques are developed to enhance convergence of a nonlinear iterative scheme (Paniconi and Putti, 1994;Tan et al, 2004). As the slow convergence rate often occur in sharp wetting fronts with highly nonlinear soil hydraulic properties or initial dry conditions, various under-relaxation (or damping) techniques are developed to enhance convergence of a nonlinear iterative scheme (Paniconi and Putti, 1994;Tan et al, 2004).…”

Section: ) Is An Iteration Index Fʹ() Is the Jacobian Matrixmentioning

confidence: 99%

“…As the slow convergence rate often occur in sharp wetting fronts with highly nonlinear soil hydraulic properties or initial dry conditions, various under-relaxation (or damping) techniques are developed to enhance convergence of a nonlinear iterative scheme (Paniconi and Putti, 1994;Tan et al, 2004). Brief review on different under-relaxation techniques and transformation methods can be found in Tan et al (2004) and Williams et al (2000). Transformation methods (Williams et al, 2000;Cheng et al, 2008) can reduce the nonlinearity of the solution profiles through the identification and application of an appropriate change of variable applied to the dependent variable in the governing equations.…”

Section: ) Is An Iteration Index Fʹ() Is the Jacobian Matrixmentioning

confidence: 99%

Infiltration and Seepage Analysis in Soil Slopes

2016

Rainfall-Induced Soil Slope Failure

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Numerical Study of Finite Element Method Based Solutions for Propagation of Wetting Fronts in Unsaturated Soil

Cited by 21 publications

References 11 publications

Towards the representation of groundwater in the Joint UK Land Environment Simulator

Towards the representation of groundwater in the Joint UK Land Environment Simulator

Experimental evidences and numerical modelling of debris flow initiated by channel runoff

Infiltration and Seepage Analysis in Soil Slopes

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