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.

Near-field modeling of the Mamala Bay outfalls

1995 ◽  
Vol 32 (2) ◽  
pp. 159-166 ◽  
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Coastal Waters ◽  
Input Data ◽  
Near Field ◽  
Density Stratification ◽  
Statistical Characteristics ◽  
Considerable Variability ◽  
Field Modeling ◽  
Long Time ◽  
The Mathematical Model ◽  
Acoustic Doppler Current Profilers

Preliminary results of near-field modeling of the wastefield formed by the Sand Island, Honolulu, outfall are presented. Over one thousand simulations were run with the mathematical model RSB using as input data long time series of effluent flowrate and oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers (ADCPs), and density stratification measured by thermistor strings. It was found that considerable variability in plume behavior occurs, whose extremes depend on particular combinations of flowrate, current, and density stratification. The wastefield is predicted to be submerged, usually deeply, about 90% of the time for the conditions simulated. It is demonstrated that the use of these recently developed instruments combined with appropriate mathematical models can lead to greatly improved predictions of the statistical characteristics of wastefield behavior in coastal waters than has been previously possible.

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.

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.

Dilution and Transport Predictions for Ocean Outfalls

1989 ◽  
Vol 21 (8-9) ◽  
pp. 969-979 ◽  
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Travel Time ◽  
Rio De Janeiro ◽  
Stratified Flows ◽  
Far Field ◽  
Ocean Bottom ◽  
Bacterial Mortality ◽  
Visitation Frequency ◽  
Ocean Outfall

Dilution and transport predictions for an ocean outfall proposed for the Barra da Tijuca, Rio de Janeiro are summarized. The initial characteristics of the wastefield are predicted using the results of recent experiments on submerged wastefield characteristics in stratified flows. Using measured currents and stratifications, it is predicted that the proposed design will result in a wastefield which is always submerged, whose thickness varies from 8.5 to 23.1 m and whose dilution varies from about 200 to well over 2000. The wastefield will often stay near the ocean bottom. Far field transport due to currents is calculated and expressed in terms of spatial “visitation frequency,” the probability of the wastefield visiting any location. It is shown that no effluent reaches shore with a travel time less than 5.5 hours, and computations including oceanic diffusion and bacterial mortality suggest maximum shoreline coliform concentrations of 500 per 100 mℓ, and 98% of the time they will be less than this. For reasons discussed these estimates of shoreline bacteria are conservatively high, and much lower than computed by methods assuming steady onshore currents.

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.

The use of Current Data in Ocean Outfall Design

1986 ◽  
Vol 18 (11) ◽  
pp. 111-120 ◽  
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Time Series ◽  
San Francisco ◽  
Coastal Waters ◽  
Puget Sound ◽  
Current Data ◽  
Far Field ◽  
Initial Dilution ◽  
Visitation Frequency ◽  
Time Series Analyses ◽  
Ocean Outfall

Some of the ways in which current meter data can aid in the design of ocean outfalls are discussed. Examples are given, which include time series analyses of currents obtained in Puget Sound, near Alki Point, the prediction of initial dilution of San Francisco, the prediction of far field dilution and transport in Southern California coastal waters, and prediction of the visitation frequency, or transport probability, off Alki Point.

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