Subgrid Modelling in Depth Integrated Flows

Madsen, P. A.; Rugbjerg, M.; Warren, I. R.

doi:10.1061/9780872626874.036

Cited by 10 publications

(13 citation statements)

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“…This value has been selected based on Madsen et al . [] but, as it is the case for the bed roughness, should be calibrated with measurements for nonidealized applications. In ROMS, a 20 s baroclinic (three‐dimensional) time step is used with a mode‐splitting ratio of 10 leading to a barotropic (two‐dimensional) time stepping of 2 s.…”

Section: Model Setup and Analyzed Casesmentioning

confidence: 99%

The role of morphology and wave‐current interaction at tidal inlets: An idealized modeling analysis

2014

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The outflowing currents from tidal inlets are influenced both by the morphology of the ebbtide shoal and interaction with incident surface gravity waves. Likewise, the propagation and breaking of incident waves are affected by the morphology and the strength and structure of the outflowing current. The 3-D Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system is applied to numerically analyze the interaction between currents, waves, and bathymetry in idealized inlet configurations. The bathymetry is found to be a dominant controlling variable. In the absence of an ebb shoal and with weak wave forcing, a narrow outflow jet extends seaward with little lateral spreading. The presence of an ebb-tide shoal produces significant pressure gradients in the region of the outflow, resulting in enhanced lateral spreading of the jet. Incident waves cause lateral spreading and limit the seaward extent of the jet, due both to conversion of wave momentum flux and enhanced bottom friction. The interaction between the vorticity of the outflow jet and the wave stokes drift is also an important driving force for the lateral spreading of the plume. For weak outflows, the outflow jet is actually enhanced by strong waves when there is a channel across the bar, due to the ''return current'' effect. For both strong and weak outflows, waves increase the alongshore transport in both directions from the inlet due to the wave-induced setup over the ebb shoal. Wave breaking is more influenced by the topography of the ebb shoal than by wave-current interaction, although strong outflows show intensified breaking at the head of the main channel.

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Section: Model Setup and Analyzed Casesmentioning

confidence: 99%

The role of morphology and wave‐current interaction at tidal inlets: An idealized modeling analysis

2014

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“…Bed friction was computed assuming the “law of the wall.” Bed-roughness lengths were chosen as 0.02 cm over sandy areas and 0.78 cm over the oyster reefs, according to [22]. Eddy viscosity was set to 0.05 m 2 /s, based on Madsen et al [23]. To simulate the salinity ranges observed, the model boundaries were forced with a tidal wave at the southern boundary and constant fresh-water discharge of 5, 10 and 20 m 3 /s at the northern boundary.…”

Section: Methodsmentioning

confidence: 99%

Freshwater Detention by Oyster Reefs: Quantifying a Keystone Ecosystem Service

et al. 2016

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Oyster reefs provide myriad ecosystem services, including water quality improvement, fisheries and other faunal support, shoreline protection from erosion and storm surge, and economic productivity. However, their role in directing flow during non-storm conditions has been largely neglected. In regions where oyster reefs form near the mouth of estuarine rivers, they likely alter ocean-estuary exchange by acting as fresh water “dams”. We hypothesize that these reefs have the potential to detain fresh water and influence salinity over extensive areas, thus providing a “keystone” ecosystem service by supporting estuarine functions that rely on the maintenance of estuarine (i.e., brackish) conditions in the near-shore environment. In this work, we investigated the effects of shore-parallel reefs on estuarine salinity using field data and hydrodynamic modeling in a degraded reef complex in the northeastern Gulf of Mexico. Results suggested that freshwater detention by long linear chains of oyster reefs plays an important role in modulating salinities, not only in the oysters’ local environment, but over extensive estuarine areas (tens of square kilometers). Field data confirmed the presence of salinity differences between landward and seaward sides of the reef, with long-term mean salinity differences of >30% between sides. Modeled results expanded experimental findings by illustrating how oyster reefs affect the lateral and offshore extent of freshwater influence. In general, the effects of simulated reefs were most pronounced when they were highest in elevation, without gaps, and when riverine discharge was low. Taken together, these results describe a poorly documented ecosystem service provided by oyster reefs; provide an estimate of the magnitude and spatial extent of this service; and offer quantitative information to help guide future oyster reef restoration.

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“…Unlike most estuaries and coastal shallow flow studies, the water depth (h) in contact tanks is generally much larger than the grid size (Áx), and the eddy viscosity is much more important in predicting the flow pattern (Madsen et al, 1988).…”

Section: Theorymentioning

confidence: 99%

“…However, it should be noted that the constant C s differs from the value established for three-dimensional flows. Madsen et al (1988) suggested that C s should be in the range of 0.4 to 0.8. Difference Schemes for Advection Terms.…”

Section: Theorymentioning

confidence: 99%

Flow and Transport Simulation Models for Prediction of Chlorine Contact Tank Flow‐Through Curves

Wang

Shao²,

Falconer³

2003

Water Environment Research

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Turbulent flow, solute transport, and chemical and biological decay are some of the basic processes encountered in water treatment plants. This paper presents recent developments in the numerical simulation of turbulent flow and disinfection processes in disinfection contact tanks. Simulation runs have been conducted for various tank design alternatives and in different grid resolutions. The accuracy of simulated contact tank flow and the disinfection process depends largely on calculations of the hydrodynamic and solute transport characteristics in the tanks. A key factor of this is the accuracy of advection and shear stress term computations, which can be affected by the use of different hydrodynamic submodels and numerical schemes. The performance of a simulation model relies to a great extent on the right combination of such submodels and numerical schemes. In this study, a number of simulation models were tested against realistic tank configurations and measurements to evaluate the various combinations of turbulence models and difference schemes by analyzing predicted flow and solute transport patterns, as well as the corresponding flow‐through curves. Models for disinfection tank simulations are recommended based on comparisons of simulation results with measurements. These models may also be applied to other water treatment processes such as wastewater treatment.

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Subgrid Modelling in Depth Integrated Flows

Cited by 10 publications

References 0 publications

The role of morphology and wave‐current interaction at tidal inlets: An idealized modeling analysis

The role of morphology and wave‐current interaction at tidal inlets: An idealized modeling analysis

Freshwater Detention by Oyster Reefs: Quantifying a Keystone Ecosystem Service

Flow and Transport Simulation Models for Prediction of Chlorine Contact Tank Flow‐Through Curves

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