scholarly journals Effects on circulation and water renewal due to the variations in the river flow and the wind in a Brazilian estuary lagoon complex

2021 ◽  
Vol 16 (2) ◽  
pp. 1
Author(s):  
Cynara De Lourdes da Nóbrega Cunha ◽  
Ada Cristina Scudelari ◽  
Danilo De Oliveira Sant'Ana ◽  
Teresa Elane Bezerra Luz ◽  
Mariana Kummer da Rocha Pinheiro
Keyword(s):  
Free Surface ◽  
River Flow ◽  
Transport Model ◽  
Northeastern Brazil ◽  
Spatial And Temporal Variation ◽  
Open Boundary ◽  
Channel System ◽  
Narrow Channels ◽  
Water Renewal ◽  
Wind Influence

The Mundaú-Manguaba Estuary Lagoon Complex is located on the coast of Alagoas state in Northeastern Brazil, and consists of two shallow lagoons, Mundaú and Manguaba, that form a system of choked lagoons which are connected to the Atlantic Ocean by a series of narrow channels with a single outlet which dynamically alters its position. This study uses the Hydrodynamic Environmental System, SisBaHiA® to investigate how variations in river discharge and wind influence hydrodynamic circulation, water renewal, salinity and temperature in the lagoons. The free surface positions, obtained by model, were compared with the free surface positions measured at two points of the complex, showing good agreement. The analyses were carried out for dry and wet seasons and extreme events with very high freshwater discharge. The channel system of the lagoons is an efficient filter in reducing tidal variability inside the lagoons. The tidal ranges in the Manguaba and Mundaú Lagoons are 90% and 80% lower, respectively, as compared with the values in the open boundary. The residence time calculated varied between 11 and 365 days and between 2 and 180 days for the Manguaba and Mundaú Lagoons, respectively, making it possible to identify possible stagnation areas. The results from the salt and heat transport model show a prolonged period with low salt concentrations and slow salinity recovery after the rainy season; the water temperature in the lagoons shows little spatial and temporal variation.

scholarly journals Spatial and temporal variation of phytoplankton in a tropical eutrophic river

2016 ◽  
Vol 76 (3) ◽  
pp. 600-610 ◽  
Author(s):  
L. M. Santana ◽  
M. E. B. Moraes ◽  
D. M. L. Silva ◽  
C. Ferragut
Keyword(s):  
River Flow ◽  
Light Availability ◽  
Abundant Species ◽  
Northeastern Brazil ◽  
Spatial And Temporal Variation ◽  
Rainy Period ◽  
Lotic Ecosystem ◽  
Phytoplankton Structure ◽  
Accumulated Rainfall ◽  
Eutrophic River

Abstract This study aims to evaluate the environmental factors determining of the changes in phytoplankton structure in spatial (upper, middle and lower course) and seasonal (dry and rainy period) scales in a eutrophic river (Almada River, northeastern Brazil). In the study period, total accumulated rainfall was below of the historic average, resulting in flow reduction, mainly in rainy period. High orthophosphate concentration was found at the sampling sites. Phytoplankton chlorophyll a increased from upstream to downstream. Geitlerinema splendidum (S1) and Chlamydomonas sp. (X2) were the most abundant species in the upper course and several species of diatoms (D), Euglenophyceae (W1, W2) and Chlorophyceae (X1) in the middle and lower course. The functional groups were found to be characteristic of lotic ecosystem, shallow, with low light availability, rich in organic matter and eutrophic environments. We conclude that phytoplankton community structure was sensitive to change of the river flow and nutrient availability in spatial and seasonal scale in a tropical river.

scholarly journals A Basin- to Channel-Scale Unstructured Grid Hurricane Storm Surge Model Applied to Southern Louisiana

2008 ◽  
Vol 136 (3) ◽  
pp. 833-864 ◽  
Author(s):  
Joannes J. Westerink ◽  
Richard A. Luettich ◽  
Jesse C. Feyen ◽  
John H. Atkinson ◽  
Clint Dawson ◽  
...  
Keyword(s):  
Storm Surge ◽  
Unstructured Grid ◽  
River Flow ◽  
Computational Cost ◽  
Skill Assessment ◽  
Open Boundary ◽  
Wind Fields ◽  
Hurricane Wind ◽  
Hurricane Storm Surge ◽  
Southern Louisiana

Abstract Southern Louisiana is characterized by low-lying topography and an extensive network of sounds, bays, marshes, lakes, rivers, and inlets that permit widespread inundation during hurricanes. A basin- to channel-scale implementation of the Advanced Circulation (ADCIRC) unstructured grid hydrodynamic model has been developed that accurately simulates hurricane storm surge, tides, and river flow in this complex region. This is accomplished by defining a domain and computational resolution appropriate for the relevant processes, specifying realistic boundary conditions, and implementing accurate, robust, and highly parallel unstructured grid numerical algorithms. The model domain incorporates the western North Atlantic, the Gulf of Mexico, and the Caribbean Sea so that interactions between basins and the shelf are explicitly modeled and the boundary condition specification of tidal and hurricane processes can be readily defined at the deep water open boundary. The unstructured grid enables highly refined resolution of the complex overland region for modeling localized scales of flow while minimizing computational cost. Kinematic data assimilative or validated dynamic-modeled wind fields provide the hurricane wind and pressure field forcing. Wind fields are modified to incorporate directional boundary layer changes due to overland increases in surface roughness, reduction in effective land roughness due to inundation, and sheltering due to forested canopies. Validation of the model is achieved through hindcasts of Hurricanes Betsy and Andrew. A model skill assessment indicates that the computed peak storm surge height has a mean absolute error of 0.30 m.

Hybrid SW-NS SPH models using open boundary conditions for simulation of free-surface flows

2020 ◽  
Vol 196 ◽  
pp. 106845 ◽  
Author(s):  
Xingye Ni ◽  
Weibing Feng ◽  
Shichang Huang ◽  
Xin Zhao ◽  
Xinwen Li
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Free Surface Flows ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Surface Flows

scholarly journals Magnetospheric convection electric field dynamics andstormtime particle energization: case study of the magneticstorm of 4 May 1998

2004 ◽  
Vol 22 (2) ◽  
pp. 497-510 ◽  
Author(s):  
G. V. Khazanov ◽  
M. W. Liemohn ◽  
T. S. Newman ◽  
M.-C. Fok ◽  
A. J. Ridley
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Transport Model ◽  
Storm Event ◽  
Inner Magnetosphere ◽  
Narrow Channels ◽  
Near Earth Space ◽  
Magnetospheric Convection ◽  
Convection Electric Field ◽  
Seed Population

Abstract. It is shown that narrow channels of high electric field are an effective mechanism for injecting plasma into the inner magnetosphere. Analytical expressions for the electric field cannot produce these channels of intense plasma flow, and thus, result in less entry and adiabatic energization of the plasma sheet into near-Earth space. For the ions, omission of these channels leads to an underprediction of the strength of the stormtime ring current and therefore, an underestimation of the geoeffectiveness of the storm event. For the electrons, omission of these channels leads to the inability to create a seed population of 10-100 keV electrons deep in the inner magnetosphere. These electrons can eventually be accelerated into MeV radiation belt particles. To examine this, the 1-7 May 1998 magnetic storm is studied with a plasma transport model by using three different convection electric field models: Volland-Stern, Weimer, and AMIE. It is found that the AMIE model can produce particle fluxes that are several orders of magnitude higher in the L = 2 – 4 range of the inner magnetosphere, even for a similar total cross-tail potential difference. Key words. Space plasma physics (charged particle motion and acceleration) – Magnetospheric physics (electric fields, storms and substorms)

scholarly journals SPH Open Boundary Simulation of Free-Surface Flow Over Ogee-crested Spillway

2021 ◽  
Vol 28 (2) ◽  
pp. 137-151
Author(s):  
Rizgar Karim ◽  
Jowhar Mohammad
Keyword(s):  
Free Surface ◽  
Open Source ◽  
Water Surface ◽  
Surface Profile ◽  
Free Surface Flow ◽  
The United States ◽  
Surface Flow ◽  
Absolute Difference ◽  
Open Boundary ◽  
Water Surface Profile

This study was conducted to compare water surface profiles with standard ogeecrested spillways. Different methods were used, such as (experimental models, numerical models, and design nomographs for the United States Army Corps of Engineers, USACE). In accordance with the USACE specifications, three different models were constructed from rigid foam and then installed in a testing flume. The water surface profile has been recorded for these models with different design heads. For modeling the experimental model configurations, a numerical model based on the smoothed particle hydrodynamics (SPH) technique was used and is developed to simulate the water surface profile of the flow over the ogee-crested spillway. A 2D SPHysics open-source software has been used in this study, using the SPH formulation to model fluid flow, developing the SPH boundary procedure to handle open-boundary simulations, and modifying the open-source SPHysics code for this purpose. The maximum absolute difference between the measured and computed results of the water surface profile for all head ratios of (H/Hd), does not exceed 4.63% at the crest region, the numerical results for the water surface profile showed good agreement with the physical model results. The results obtained experimentally and numerically by SPH are compared with the CFD results in order to be more reassuring from the results. Additional comparisons were made using interpolated data from USACE, Waterways Experiment Station (WES), and design nomographs. The SPH technique is considered very promising and effective for free surface flow applications.

scholarly journals A Three-Dimensional Flow and Sediment Transport Model for Free-Surface Open Channel Flows on Unstructured Flexible Meshes

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 18 ◽  
Author(s):  
Yong Lai ◽  
Kuowei Wu
Keyword(s):  
Free Surface ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Open Channel ◽  
Transport Model ◽  
Three Dimensional ◽  
Suspended Sediment Transport ◽  
Open Channel Flows ◽  
Sediment Transport Model ◽  
Flow And Sediment Transport

Three-dimensional (3D) hydrostatic-pressure-assumption numerical models are widely used for environmental flows with free surfaces and phase interfaces. In this study, a new flow and sediment transport model is developed, aiming to be general and more flexible than existing models. A general set of governing equations are used for the flow and suspended sediment transport, an improved solution algorithm is proposed, and a new mesh type is developed based on the unstructured polygonal mesh in the horizontal plane and a terrain-following sigma mesh in the vertical direction. The new flow model is verified first with the experimental cases, to ensure the validity of flow and free surface predictions. The model is then validated with cases having the suspended sediment transport. In particular, turbidity current flows are simulated to examine how the model predicts the interface between the fluid and sediments. The predicted results agree well with the available experimental data for all test cases. The model is generally applicable to all open-channel flows, such as rivers and reservoirs, with both flow and suspended sediment transport issues.

scholarly journals SIMULATIONS OF FLOW CIRCULATIONS AND ATRAZINE CONCENTRATIONS IN A MIDWEST U.S. RESERVOIR

2012 ◽  
Vol 19 ◽  
pp. 27-38
Author(s):  
XIANGGUI ZHAO ◽  
ROY R. GU ◽  
CHULING GUO ◽  
KUI WANG ◽  
SHIJIE LI
Keyword(s):  
Management Practices ◽  
River Flow ◽  
Transport Model ◽  
Pollution Prevention ◽  
Fate And Transport ◽  
Reservoir Water ◽  
Various Boundary Conditions ◽  
Seasonal Flow ◽  
Flow Circulation ◽  
High Level

Atrazine is the most commonly used herbicide in the spring for pre-emergent weed control in the corn cropping area in the Midwestern United States. A frequent high level of herbicide concentrations in reservoirs is a great concern for public health and aquatic ecosystems. In this study, a two-dimensional hydrodynamics and toxic contaminant transport model was applied to Saylorville Reservoir, Iowa, USA. The model simulates physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions of a toxic chemical. Model results were validated by measured temperatures and atrazine concentrations. Simulated flow velocities, water temperatures, and chemical concentrations demonstrated that the spatial variation of atrazine concentrations was largely affected by seasonal flow circulation patterns in the reservoir. In particular, the simulated fate and transport of atrazine showed the effect of flow circulation on spatial distribution of atrazine during summer months as the river flow formed an underflow within the reservoir and resulted in greater concentrations near the surface of the reservoir. Atrazine concentrations in the reservoir peaked around the end of May and early June. A thorough understanding of the fate and transport of atrazine in the reservoir can assist in developing operation and pollution prevention strategies with respect to timing, amount, and depth of withdrawal. The responses of atrazine transport to various boundary conditions provide useful information in assessing environmental impact of alternative upstream watershed management practices on the quality of reservoir water.

Two dimensional river flow and sediment transport model

2014 ◽  
Vol 15 (3) ◽  
pp. 595-625 ◽  
Author(s):  
Zoltan Horvat ◽  
Mirjana Isic ◽  
Miodrag Spasojevic
Keyword(s):  
Sediment Transport ◽  
River Flow ◽  
Transport Model ◽  
Two Dimensional ◽  
Sediment Transport Model ◽  
Flow And Sediment Transport
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