A near‐field model of the parametric radiator

1976 ◽  
Vol 59 (S1) ◽  
pp. S28-S29 ◽  
Author(s):  
R. H. Mellen
Keyword(s):  
Field Model ◽  
Near Field

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

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.

A Two-Region Model for Gradient Modification of Salt-Gradient Solar Ponds by Radial Injection

1996 ◽  
Vol 118 (1) ◽  
pp. 37-44 ◽  
Author(s):  
G. A. Eghneim ◽  
S. J. Kleis
Keyword(s):  
Turbulence Model ◽  
Field Model ◽  
Numerical Study ◽  
Numerical Models ◽  
Domain Boundary ◽  
Near Field ◽  
Solar Ponds ◽  
Numerical Predictions ◽  
Region Model ◽  
Salt Gradient

A combined experimental and numerical study was conducted to support the development of a new gradient maintenance technique for salt-gradient solar ponds. Two numerical models were developed and verified by laboratory experiments. The first is an axisymmetric (near-field) model which determines mixing and entrainment in the near-field of the injecting diffuser by solving the conservation equations of mass, momentum, energy, and salt. The model assumes variable properties and uses a simple turbulence model based on the mixing length hypothesis to account for the turbulence effects. A series of experimental measurements were conducted in the laboratory for the initial adjustment of the turbulence model and verification of the code. The second model is a one-dimensional far-field model which determines the change of the salt distribution in the pond gradient zone as a result of injection by coupling the near-field injection conditions to the pond geometry. This is implemented by distributing the volume fluxes obtained at the domain boundary of the near-field model, to the gradient layers of the same densities. The numerical predictions obtained by the two-region model was found to be in reasonable agreement with the experimental data.

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.

3D near-field model for uniform slanted fiber gratings

2003 ◽  
Vol 38 (5) ◽  
pp. 428-432 ◽  
Author(s):  
C. Jáuregui ◽  
A. Cobo ◽  
J. M. López-Higuera
Keyword(s):  
Field Model ◽  
Near Field ◽  
Fiber Gratings

Pollutant dispersion in the nearshore region: modelling and measurements

1995 ◽  
Vol 32 (9-10) ◽  
pp. 169-178 ◽  
Author(s):  
A. Rodriguez ◽  
A. Sánchez-Arcilla ◽  
J. M. Redondo ◽  
E. Bahia ◽  
J. P. Sierra
Keyword(s):  
Field Model ◽  
Surf Zone ◽  
Initial Conditions ◽  
Numerical Models ◽  
Dispersion Model ◽  
Near Field ◽  
Pollutant Dispersion ◽  
Hydrodynamic Models ◽  
Wave Induced ◽  
Sea Outfalls

Some results on pollutant dispersion modelling and tracer measurements for the Mediterranean Spanish coast are presented. Two hydrodynamic models have been used to simulate wind and wave induced circulation in the nearshore and surf zones respectively. A “near field” model has been used in order to simulate the initial conditions for the local “far field” dispersion model. Two study cases are presented: The first one shows the mixing of conservative tracers in a Mediterranean surf zone from an experimental and numerical models used to predict bacterial dispersion from the main sea outfalls of Barcelona City. The comparison between dye dispersion experiments and model in the surf zone is good, while the outfall predictions show the importance of accurately modelling the effects of buoyancy on the plume.

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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