References of "Delhez, Eric"
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See detailThree-dimensional modelling of the hydrodynamics of the Southern Bight of the North Sea: first results
Ivanov, Evgeny ULiege; Capet, Arthur ULiege; Barth, Alexander ULiege et al

Poster (2017, April 28)

In the frame of the Belgian research project FaCE-It (Functional biodiversity in a Changing sedimentary Environment: Implications for biogeochemistry and food webs in a managerial setting), the impact of ... [more ▼]

In the frame of the Belgian research project FaCE-It (Functional biodiversity in a Changing sedimentary Environment: Implications for biogeochemistry and food webs in a managerial setting), the impact of dredging activities andoffshorewindfarminstallationonthespatialdistributionofsedimentgrainsize,biodiversityandbiogeochemistry will be estimated in the Southern Bight of the North Sea (SBNS) with a focus on the Belgian Coastal Zone (BCZ). To reach this goal, the three-dimensional hydrodynamical model ROMS-COAWST is implemented in the SBNS in order to simulate the complex hydrodynamics and sediment transport. Two levels of nesting are used to reach a resolutionof250mintheBCZ.Themodelisforcedattheair-seainterfacebythe6-hourlyECMWFERA-interim atmospheric dataset and at the open boundaries by the coarse resolution model results available from CMEMS (Copernicus Marine Environment Monitoring Service), and also considers tides and 4 main rivers (Scheldt, Rhine with Maas, Thames and Seine). Two types of simulations have been performed: a 10-years climatological simulation and a simulation over 20032013toinvestigatetheinterannualdynamics.Themodelskillsareevaluatedbycomparingitsoutputstohistorical data (e.g. salinity, temperature and currents) from remote sensing and in-situ. The sediment transport module will then be implemented and its outputs compared to historical and newly collected (in the frame of FaCE-iT) observations on grain size distribution as well as with satellite Suspended Particulate Matter (SPM) images. This will allow assessing the impact of substrate modification due to offshore human activities at local and regional scales. [less ▲]

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See detailThree-dimensional modelling of the Southern Bight of the North Sea: first results and perspectives
Ivanov, Evgeny ULiege; Capet, Arthur ULiege; Barth, Alexander ULiege et al

Poster (2017, March 03)

The impact of offshore wind farm installation and dredging activities on the spatial distribution and dynamics of sediment grain size, biogeochemistry and biodiversity will be estimated in the Southern ... [more ▼]

The impact of offshore wind farm installation and dredging activities on the spatial distribution and dynamics of sediment grain size, biogeochemistry and biodiversity will be estimated in the Southern Bight of the North Sea (SBNS) with a focus on the Belgian Coastal Zone (BCZ) in the frame of the FaCE-It research project (Functional biodiversity in a Changing sedimentary Environment: Implications for biogeochemistry and food webs in a managerial setting). The three-dimensional hydrodynamical model ROMS-COAWST was implemented for simulation of the complex hydrodynamics of SBNS and sediment transport. The first level of nesting with the resolution of 1 km was used in the area of Belgian Economical Zone. In order to reach a fine resolution of 250 m in the BCZ, the second level of nesting will be used. Six-hourly ECMWF ERA-interim meteorological data was used to force the model at the sea-air boundary and the coarse resolution model results available from Copernicus Marine Environment Monitoring Service were used to force the model at the open boundaries. Tides and rivers were also considered. Next types of long-run simulations have been conducted: a 10-years climatological simulation and an interannual simulation over 2004-2013 in order to investigate the interannual dynamics. The model accuracy was evaluated through validation of its outputs against observed salinity, temperature and currents data (remote sensing and in-situ). Results validation of currents and temperature and salinity horizontal fields and vertical profiles against available satellite fields and in-situ data, i.e. from the project field campaign, is conducted and discussed. Application of the nested grid and its benefits for results accuracy is also presented. [less ▲]

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See detailDeveloping a hydrodynamical model of the Southern Bight of the North Sea for impact studies
Ivanov, Evgeny ULiege; Capet, Arthur ULiege; Barth, Alexander ULiege et al

Poster (2016, November 08)

In the frame of the Brain FaCE-It project (Functional biodiversity in a Changing sedimentary Environment: Implications for biogeochemistry and food webs in a managerial setting), the impact of fining and ... [more ▼]

In the frame of the Brain FaCE-It project (Functional biodiversity in a Changing sedimentary Environment: Implications for biogeochemistry and food webs in a managerial setting), the impact of fining and hardening resulting from dredging and wind farms installation on the sediment grain size distribution has to be assessed at the scale of the Southern Bight of the North Sea (SBNS) with a particular focus on the Belgian Coastal Zone (BCZ). With this aim, the ROMS-COAWST tri-dimensional (3D) hydrodynamic model is implemented to simulate the hydrodynamics in the SBNS. At its open boundaries with the Atlantic Ocean and the North Sea, the model is forced with the results of a coarse resolution model available from Mercator. A high resolution of 250 m is used in the area of the BCZ where the accuracy of model predictions needs to be refined. Model currents, tides, temperature and salinity fields will be described and first validation exercises with satellite and local data will be presented and discussed in regards with the objectives of FaCE-It. In a next step, the model will be coupled with a sediment transport in order to describe the dynamics of suspended particulate materials (SPM) and the distribution of the seafloor sediment grain size. When finalized the hydrodynamic model will be coupled with a diagenetic model and will provide environmental conditions for scaling up local foodweb studies that are performed in the frame of FaCE-iT. The final aim is to assess the impact of substrate modifications due to aggregate extraction and wind farms on the biogeochemistry, benthic functionality and food webs at local (around the wind farm) and regional scales (SBNS). [less ▲]

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See detailPartial ages: diagnosing transport processes by means of multiple clocks.
Mouchet, Anne ULiege; Cornaton, Fabien; Deleersnijder, Eric et al

in Ocean Dynamics (2016), 66

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See detailBenthic-Planktonic age biases: theoretical and modeling studies
Mouchet, Anne ULiege; Deleersnijder, Eric; Delhez, Eric ULiege et al

Conference (2015, June 25)

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See detailOptimizing Perfectly Matched Layers in Discrete Contexts
Modave, Axel ULiege; Delhez, Eric ULiege; Geuzaine, Christophe ULiege

in International Journal for Numerical Methods in Engineering (2014), 99(6), 410437

Perfectly Matched Layers (PMLs) are widely used for the numerical simulation of wave-like problems defined on large or infinite spatial domains. However, for both the time-dependent and the time-harmonic ... [more ▼]

Perfectly Matched Layers (PMLs) are widely used for the numerical simulation of wave-like problems defined on large or infinite spatial domains. However, for both the time-dependent and the time-harmonic cases, their performance critically depends on the so-called absorption function. This paper deals with the choice of this function when classical numerical methods are used (based on finite differences, finite volumes, continuous finite elements and discontinuous finite elements). After reviewing the properties of the PMLs at the continuous level, we analyse how they are altered by the different spatial discretizations. In the light of these results, different shapes of absorption function are optimized and compared by means of both one- and two-dimensional representative time-dependent cases. This study highlights the advantages of the so-called shifted hyperbolic function, which is efficient in all cases and does not require the tuning of a free parameter, by contrast with the widely used polynomial functions. [less ▲]

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See detailFactors influencing radiocarbon-based estimates of ocean ventilation: theory and models
Mouchet, Anne ULiege; Beckers, Jean-Marie ULiege; Deleersnijder, Eric et al

Conference (2014, May 29)

Detailed reference viewed: 30 (1 ULiège)
See detailThe concept of partial age, a generalisation of the notion of age: theory, idealised illustrations and realistic applications
Deleersnijder, Eric; Mouchet, Anne ULiege; Debrauwere, Anouk et al

Conference (2014, May 12)

Detailed reference viewed: 38 (1 ULiège)
See detailProcesses affecting radiocarbon estimates of ocean ventilation: theory and models
Mouchet, Anne ULiege; Deleersnijder, Eric; Delhez, Eric ULiege et al

Conference (2014, May 07)

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See detailResidence time vs influence time
Delhez, Eric ULiege; de Brye, Bejamin; de Brauwere, Anouk et al

in Journal of Marine Systems (2014), 132

The concepts of age, residence time, exposure time and influence time provide space and time dependent quantitative measures of the rate at which watermasses and pollutants enter and/or leave a control ... [more ▼]

The concepts of age, residence time, exposure time and influence time provide space and time dependent quantitative measures of the rate at which watermasses and pollutants enter and/or leave a control domain. To help avoid confusion between these concepts, this paper provides clear definitions of the residence time and the influence time. The similarities and differences between them are illustrated using both a simplified 1D advection–diffusion model and a realistic two-dimensional model of the Scheldt Estuary (Belgium and the Netherlands). The residence time of a water parcel in a control domain is the time taken by this parcel to leave the control domain for the first time. The influence time is the time required to replace the water in the domain of interest by renewing water. For steady flows, the influence time is numerically identical to the age of the renewing water, but the two timescales differ for unsteady flows. The residence timemeasures the influence of a hypothetical point discharge on a control domain. In environmental studies, it provides a measure of the effectiveness of hydrodynamic processes at helping a semi-enclosed basin to recover froma local pollution event. The influence time quantifies the local influence of a tracer that would be uniformly distributed in the control domain at the initial time. It is therefore a relevant diagnostic tool in impact studies focusing on the local persistence of a pollution problem. [less ▲]

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See detailModelling phytoplankton succession and nutrient transfer along the Scheldt estuary (Belgium, The Netherlands)
Gypens, N.; Delhez, Eric ULiege; Vanhoutte-Brunier, A. et al

in Journal of Marine Systems (2013), 128

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See detailDiagnosis of the transport of adsorbed material in the Scheldt estuary: A proof of concept
Delhez, Eric ULiege; Wolk, Frank ULiege

in Journal of Marine Systems (2013), 128

Many contaminants can attach to suspended particles. Their transport differs therefore from the transport of dissolved substances, especially in highly turbid environment like estuaries. In this paper, we ... [more ▼]

Many contaminants can attach to suspended particles. Their transport differs therefore from the transport of dissolved substances, especially in highly turbid environment like estuaries. In this paper, we show how the Constituent Age and Residence time Theory (CART — www.climate.be/CART) can be adapted to quantify in a rigorous manner the transport rate of contaminants that are present in both the dissolved and adsorbed phases. On the basis of numerical experiment using a 1D model of the Scheldt estuary, it is shown that the interaction with suspended particles significantly affects the transport of contaminants with partition coefficients larger than 1000 ml/g. The mean transit time from Ghent to Vlissingen of such contaminants can reach 160 days while it is only 60 days for water and dissolved constituents. This increase of the transit time is mainly due to the fact that adsorbed constituents spend long periods of time on the bottom. Surprisingly, the downstream transport of adsorbed constituents in the water column appears more effective than that of dissolved constituents. This transport affects however a small fraction of the adsorbed constituent and is therefore not sufficient to compensate for the long resting phase on the bottom of the bulk of the constituent. The concept and methodology introduced in this paper are easily applicable to most model studies and provide powerful and flexible tools for the detailed understanding of the transport of contaminants in estuaries. In particular, the concept of age and modified ages taking into account specifically the time spent in the water column or in the bottom provide new diagnostic tools to understand and quantify the dynamics of contaminants. [less ▲]

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See detailAn optimum PML for scattering problems in the time domain
Modave, Axel ULiege; Kameni, Abelin; Lambrechts, Jonathan et al

in European Physical Journal : Applied physics (2013), 64(2), 24502

In electromagnetic compatibility, scattering problems are defined in an infinite spatial domain, while numerical techniques such as finite element methods require a computational domain that is bounded ... [more ▼]

In electromagnetic compatibility, scattering problems are defined in an infinite spatial domain, while numerical techniques such as finite element methods require a computational domain that is bounded. The perfectly matched layer (PML) is widely used to simulate the truncation of the computational domain. However, its performance depends critically on an absorption function. This function is generally tuned by using case-dependent optimization procedures. In this paper, we will present some efficient functions that overcome any tuning. They will be compared using a realistic scattering benchmark solved with the Discontinuous Galerkin method. [less ▲]

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See detailA PML for convex truncated domains in time-dependent acoustics with a DG-FE discretization
Modave, Axel ULiege; Lambrechts, Jonathan; Delhez, Eric ULiege et al

in Proceedings of the 11th International Conference on Mathematical and Numerical Aspects of Waves (WAVES 2013) (2013, June 03)

A new perfectly matched layer (PML) is proposed for convex truncated domains in the context of time-dependent acoustics. With this formulation, the size of the computational domain can be reduced when ... [more ▼]

A new perfectly matched layer (PML) is proposed for convex truncated domains in the context of time-dependent acoustics. With this formulation, the size of the computational domain can be reduced when classical shapes of truncated domains are less appropriate. A numerical discretization based on the discontinuous Galerkin method is then described and validated. An example of realistic three-dimensional application is finally proposed. [less ▲]

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See detailOn the concept of exposure time
Delhez, Eric ULiege

in Continental Shelf Research (2013), 71

The concept of exposure time offers an interesting alternative to the residence time for the quantitative assessment of the water renewal of estuaries and semi-enclosed basins. It can cope with the ... [more ▼]

The concept of exposure time offers an interesting alternative to the residence time for the quantitative assessment of the water renewal of estuaries and semi-enclosed basins. It can cope with the oscillations or meandering of the flow around the boundary of the control domain and is therefore particularly suited for tidal seas and sub-basins with strong mesoscale activity. We show however that the exposure time in a control domain \omega cannot be properly defined if \omega is part of a larger bounded system unless some removal process is taken into account. It is therefore suggested to revise and extend the definition of the exposure time by including a first order decay : ``the exposure time for the rate constant \lambda is the total time spent in a control domain \omega by particles subject to a first order decay with a rate constant $\lambda$, irrespective of their possible excursions in and out the control domain''. The exposure time revised in this way is well-defined in all circumstances provided that the decay rate differs from zero but depends on the rate constant \lambda. Alternatively, in order to diagnose the movement of water masses, the first order decay can be considered only outside the control domain. [less ▲]

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See detailAn optimum PML for scattering problems in the time domain
Modave, Axel ULiege; Delhez, Eric ULiege; Kameni, Abelin et al

in Proceedings of the 7th European Conference on Numerical Methods in Electromagnetism (NUMELEC 2012) (2012, July 05)

The Perfectly Matched Layer (PML) is widely used for unbounded problems. However its performances depend critically on an absorption coefficient. This coefficient is generally tuned by using case ... [more ▼]

The Perfectly Matched Layer (PML) is widely used for unbounded problems. However its performances depend critically on an absorption coefficient. This coefficient is generally tuned by using case-dependent optimization procedures. In this paper we will present some efficient profiles of the coefficient that overcome every tuning. These profiles and others will be compared by using a scattering benchmark solved with the Discontinuous Galerkin method. [less ▲]

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See detailEstuarine Hydrology
Wolanski, Eric; Andutta, Fernando; Delhez, Eric ULiege

in Bengtsson, Lars; Herschy, Reginald; Fairbridge, R. W. (Eds.) Encyclopedia of Lakes and Reservoirs (2012)

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See detailOptimisation des PML dans des contextes discrets
Modave, Axel ULiege; Delhez, Eric ULiege; Geuzaine, Christophe ULiege

Conference (2012, May 21)

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See detailResidence and exposure times : when diffusion does not matter
Delhez, Eric ULiege; Deleersnijder, Eric

in Ocean Dynamics (2012), 62

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See detailWater renewal timescales in the Scheldt Estuary
de Brye, Benjamin; de Brauwere, Anouk; Gourgue, Olivier et al

in Journal of Marine Systems (2012), 94

Detailed reference viewed: 40 (12 ULiège)