Transport from the Canister to the Biosphere: Using an Integrated Near-and Far-Field Model

1996 ◽  
Vol 465 ◽  
Author(s):  
B. Gylling ◽  
L. Romero ◽  
L. Moreno ◽  
I. Neretnieks
Keyword(s):  
Field Model ◽  
Near Field ◽  
Coupled Model ◽  
Compartment Model ◽  
Far Field ◽  
Model Concept ◽  
Channel Network ◽  
Transport Barrier ◽  
Damage Level ◽  
Field Release

ABSTRACTA coupled model concept which may be used for performance assessment of a nuclear repository is presented. The tool is developed by integration of two models, one near field and one far field model. A compartment model, NUCTRAN, is used to calculate the near field release from a damaged canister. The far field transport through fractured rock is simulated by using CHAN3D, based on a three-dimensional stochastic channel network concept. The near field release depends on the local hydraulic properties of the far field. The transport in the far field in turn depends on where the damaged canister(s) is located. The very large heterogeneities in the rock mass makes it necessary to study both the near field release properties and the location of release at the same time. In order to demonstrate the capabilities of the coupled model concept it is applied on a hypothetical repository located at the Hard Rock Laboratory in Äspö, Sweden. Two main items were studied; the location of a damaged canister in relation to fracture zones and the barrier function of the host rock. In the study of the near field rock as a transport barrier the effect of different tunnel excavation methods which may influence the damage level of the rock around the tunnel was addressed.

Far field modeling of the Mamala Bay outfalls

1998 ◽  
Vol 38 (10) ◽  
pp. 323-330
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Field Model ◽  
Near Field ◽  
Far Field ◽  
Field Modeling ◽  
Visitation Frequency ◽  
Statistical Variation ◽  
Long Time ◽  
Harmonic Average ◽  
Ocean Outfall ◽  
Acoustic Doppler Current Profilers

The results of far field modeling of the wastefield formed by the Sand Island, Honolulu, ocean outfall are presented. A far field model, FRFIELD, was coupled to a near field model, NRFIELD. The input data for the models were long time series of oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers and density stratification measured by thermistor strings. Thousands of simulations were made to predict the statistical variation of wastefield properties around the diffuser. It was shown that the visitation frequency of the wastefield decreases rapidly with distance from the diffuser. The spatial variation of minimum and harmonic average dilutions was also predicted. Average dilution increases rapidly with distance. It is concluded that any impact of the discharge will be confined to a relatively small area around the diffuser and beach impacts are not likely to be significant.

Estimating residential air exchange rates in rural Bangladesh using a near field-far field model

2021 ◽  
pp. 108325
Author(s):  
Darpan Das ◽  
Emma Moynihan ◽  
Mark Nicas ◽  
Eric D. McCollum ◽  
Salahuddin Ahmed ◽  
...  
Keyword(s):  
Exchange Rates ◽  
Field Model ◽  
Near Field ◽  
Far Field ◽  
Rural Bangladesh ◽  
Air Exchange

scholarly journals Coupling Methodology for Studying the Far Field Effects of Wave Energy Converter Arrays over a Varying Bathymetry

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2899 ◽  
Author(s):  
Gael Verao Fernandez ◽  
Philip Balitsky ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Numerical Simulations ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Computational Time ◽  
Far Field ◽  
Field Effects ◽  
Numerical Tool

For renewable wave energy to operate at grid scale, large arrays of Wave Energy Converters (WECs) need to be deployed in the ocean. Due to the hydrodynamic interactions between the individual WECs of an array, the overall power absorption and surrounding wave field will be affected, both close to the WECs (near field effects) and at large distances from their location (far field effects). Therefore, it is essential to model both the near field and far field effects of WEC arrays. It is difficult, however, to model both effects using a single numerical model that offers the desired accuracy at a reasonable computational time. The objective of this paper is to present a generic coupling methodology that will allow to model both effects accurately. The presented coupling methodology is exemplified using the mild slope wave propagation model MILDwave and the Boundary Elements Methods (BEM) solver NEMOH. NEMOH is used to model the near field effects while MILDwave is used to model the WEC array far field effects. The information between the two models is transferred using a one-way coupling. The results of the NEMOH-MILDwave coupled model are compared to the results from using only NEMOH for various test cases in uniform water depth. Additionally, the NEMOH-MILDwave coupled model is validated against available experimental wave data for a 9-WEC array. The coupling methodology proves to be a reliable numerical tool as the results demonstrate a difference between the numerical simulations results smaller than 5% and between the numerical simulations results and the experimental data ranging from 3% to 11%. The simulations are subsequently extended for a varying bathymetry, which will affect the far field effects. As a result, our coupled model proves to be a suitable numerical tool for simulating far field effects of WEC arrays for regular and irregular waves over a varying bathymetry.

scholarly journals Irregular Wave Validation of a Coupling Methodology for Numerical Modelling of Near and Far Field Effects of Wave Energy Converter Arrays

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 538 ◽  
Author(s):  
Gael Fernández ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Experimental Data ◽  
Wave Field ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Far Field ◽  
Engineering Research ◽  
Field Effects

Between the Wave Energy Converters (WECs) of a farm, hydrodynamic interactions occur and have an impact on the surrounding wave field, both close to the WECs (“near field” effects) and at large distances from their location (“far field” effects). To simulate this “far field” impact in a fast and accurate way, a generic coupling methodology between hydrodynamic models has been developed by the Coastal Engineering Research Group of Ghent University in Belgium. This coupling methodology has been widely used for regular waves. However, it has not been developed yet for realistic irregular sea states. The objective of this paper is to present a validation of the novel coupling methodology for the test case of irregular waves, which is demonstrated here for coupling between the mild slope wave propagation model, MILDwave, and the ‘Boundary Element Method’-based wave–structure interaction solver, NEMOH. MILDwave is used to model WEC farm “far field” effects, while NEMOH is used to model “near field” effects. The results of the MILDwave-NEMOH coupled model are validated against numerical results from NEMOH, and against the WECwakes experimental data for a single WEC, and for WEC arrays of five and nine WECs. Root Mean Square Error (RMSE) between disturbance coefficient (Kd) values in the entire numerical domain ( R M S E K d , D ) are used for evaluating the performed validation. The R M S E K d , D between results from the MILDwave-NEMOH coupled model and NEMOH is lower than 2.0% for the performed test cases, and between the MILDwave-NEMOH coupled model and the WECwakes experimental data R M S E K d , D remains below 10%. Consequently, the efficiency is demonstrated of the coupling methodology validated here which is used to simulate WEC farm impact on the wave field under the action of irregular waves.

MODELING DEEPWATER OIL SPILLS WITH NEAR FIELD AND FAR FIELD MODELS

2005 ◽  
Vol 2005 (1) ◽  
pp. 725-730
Author(s):  
Zhen-Gang Ji ◽  
Walter R. Johnson ◽  
Charles F. Marshall ◽  
James M. Price
Keyword(s):  
Environmental Impact ◽  
Gulf Of Mexico ◽  
Deep Water ◽  
Oil And Gas ◽  
Field Model ◽  
Oil Spills ◽  
Near Field ◽  
Far Field ◽  
Oil Gas ◽  
The U.S

ABSTRACT As a Federal agency within the U.S. Department of the Interior (DOI), the Minerals Management Service (MMS) maintains a leasing program for commercial oil and gas development on the U.S. Outer Continental Shelf (OCS). Oil and gas activities in deep water (areas deeper than 340 meters) have proceeded at an unprecedented rate, and have led to concerns regarding the accidental release of oil near the seafloor. As production increases, the potential for an oil/gas spill increases. In addition to the environmental impacts of the oil spilled, major concerns from a deepwater oil/gas spill include fire, toxic hazard to the people working on the surface installations, and loss of buoyancy by ships and any floating installations. Oil and natural gas releases in deep water behave much differently than in shallow water, primarily due to density stratification, high pressures, and low temperatures. It is important to know whether oil will surface and if so, where, when, and how thick the oil slick will be. To meet these new challenges, spill response plans need to be upgraded. An important component of such a plan would be a model to simulate the behavior of oil and gasses accidentally released in deep water. This has significant implications for environmental impact assessment, oil-spill cleanup, contingency planning, and source tracing. The MMS uses the Clarkson Deepwater Oil and Gas Blowout (CDOG) plume model to simulate the behavior of oil and gas accidentally released in deepwater areas. The CDOG model is a near field model. In addition, MMS uses an adaptation of the Princeton Ocean Model called the Princeton Regional Ocean Forecast and Hindcast System for the Gulf of Mexico (PROFS-GOM). This model is a far field model and is employed to provide three dimensional current, temperature, and salinity data to the CDOG model. The PROFS-GOM model and the CDOG model are used to simulate deepwater oil spills in the Gulf of Mexico. Modeling results indicate that the two models can provide important information on the behavior of oil spills in deepwater and assist MMS in estimating the associated environmental risks. Ultimately, this information will be used in the pertinent environmental impact assessments MMS performs and in the development of deepwater oil-spill response plans.

scholarly journals Near-Field Mass Transfer in Geologic Disposal Systems: a Review

1987 ◽  
Vol 112 ◽  
Author(s):  
T. H. Pigford ◽  
P. L. Chambré
Keyword(s):  
Mass Transfer ◽  
Surface Water ◽  
Near Field ◽  
Far Field ◽  
Field Mass ◽  
Theoretical Approaches ◽  
Field Release ◽  
Geologic Disposal ◽  
Radioactive Species ◽  
Geologic Media

AbstractA primary purpose of performance assessment of geologic repositories for radioactive waste is to predict the extent to which radioactive species are released from the waste solids and are transported through geologic media to the environment. Reliable quantitative predictions must be made of rates of release of radionuclides from the waste into the rock, transport through the geologic media, cumulative release to the accessible environment, and maximum concentrations in ground water and surface water. Here we review theoretical approaches to making the predictions of near-field release from buried waste solids, which provide the source terms for far-field release. The extent to which approaches and issues depend on the rock media and on regulatory criteria is discussed.

Dynamic coupling of near field and far field models for simulating effluent discharges

2013 ◽  
Vol 67 (10) ◽  
pp. 2210-2220 ◽  
Author(s):  
Robin Morelissen ◽  
Theo van der Kaaij ◽  
Tobias Bleninger
Keyword(s):  
Field Model ◽  
Near Field ◽  
Engineering Practice ◽  
Far Field ◽  
Ambient Conditions ◽  
Dynamic Coupling ◽  
Coupled Modelling ◽  
Hydrodynamic Processes ◽  
Different Characteristics ◽  
Mixing Behaviour

In many cases, (processed) wastewater or thermal effluents are discharged into the marine environment, rivers or lakes. To accurately determine the dispersion, recirculation and environmental impacts of outfall plumes, it is important to be able to model the different characteristics of the outfall plume in detail – from the near field (metres around the outfall) to the far field (up to kilometres away). The solution for engineering practice is to combine different types of models (near and far field models) that each focus on specific scales, with corresponding optimised resolutions and processes. However, to adequately describe the hydrodynamic processes on these different scales, it is essential to couple these models in a dynamic and comprehensive way. To achieve this, a dynamic coupling between the open-source Delft3D-FLOW far field model and the CORMIX near field expert system is proposed. This coupled modelling system is able to use the computed far field ambient conditions in the near field computations and, conversely, to use the initial near field dilution and mixing behaviour in the far field model. Preliminary results are presented to provide a first indication of the potential of the method for modelling the complete trajectory of effluent outfall plumes, allowing an accurate assessment of the environmental effects and the design of possible mitigating measures.

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