scholarly journals A Reasoned Comparison between Two Hydrodynamic Models: Delft3D-Flow and ROMS (Regional Oceanic Modelling System)

2019 ◽  
Vol 7 (12) ◽  
pp. 464 ◽  
Author(s):  
Stefano Putzu ◽  
Francesco Enrile ◽  
Giovanni Besio ◽  
Andrea Cucco ◽  
Laura Cutroneo ◽  
...  
Keyword(s):  
Eddy Viscosity ◽  
Numerical Models ◽  
Rectangular Channel ◽  
Free Surface Flows ◽  
Water Levels ◽  
Closure Model ◽  
Hydrodynamic Models ◽  
Tangential Stresses ◽  
The 1960S ◽  
Vertical Eddy

Useful information, such as water levels, currents, salinity and temperature dynamics in water bodies, are obtained through numerical models in order to pursue scientific research or consultancy. Model validation dates back long ago, since such models started to be developed in the 1960s. Despite their usefulness and reliability in complex situations, some issues related to well-known benchmarks are still present. This work aims to analyse in detail the behaviour of the velocity profile, vertical eddy viscosity and tangential stresses at the bed in two cases of free surface flows; namely: uniform flow in an inclined rectangular channel and a wind-induced circulation in a closed basin. Computational results strongly depend on the turbulence closure model employed and a reasoned comparison is necessary to highlight possible improvements of these models. The strong differences that arise are deeply analysed in this work.

scholarly journals Experimental and Numerical Analysis of a Dam-Break Flow through Different Contraction Geometries of the Channel

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1124 ◽  
Author(s):  
Selahattin Kocaman ◽  
Hasan Güzel ◽  
Stefania Evangelista ◽  
Hatice Ozmen-Cagatay ◽  
Giacomo Viccione
Keyword(s):  
Wave Propagation ◽  
Numerical Models ◽  
Rectangular Channel ◽  
Dam Break ◽  
Water Levels ◽  
Experimental Results ◽  
Complex Flow ◽  
Related Field ◽  
Dam Break Flow ◽  
Irregular Topography

Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding this type of complex flow problems. To contribute to the related field, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically. Laboratory tests were carried out in a smooth rectangular channel with a horizontal dry bed for three different lateral contraction geometries. A non-intrusive digital imaging technique was utilized to analyze the dam-break wave propagation. Free surface profiles and time variation of water levels in selected sections were obtained directly from three synchronized CCD video camera records through a virtual wave probe. The experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε turbulence model. Good agreements were obtained between computed and measured results. However, the RANS solution shows a better correspondence with the experimental results compared with the SWEs one. The presented new experimental data can be used to validate numerical models for the simulation of dam-break flows over irregular topography.

scholarly journals Applying of depth-averaged hydrodynamic modeling with different methods of turbulence closure for flow near channel groyne. Part II – Analysis of simulation

2018 ◽  
Vol 23 ◽  
pp. 00010
Author(s):  
Ryszard Ewertowski
Keyword(s):  
Eddy Viscosity ◽  
Rectangular Channel ◽  
Point Of View ◽  
Two Dimensional ◽  
Flow Conditions ◽  
Hydrodynamic Models ◽  
Training Structures ◽  
Flow Phenomena ◽  
Training Structure ◽  
Averaged Model

Training structures in flow stream play an important role in shaping flow and bed properties. To investigate consequences of introducing training elements like groins or dikes into the river stream one can successfully use numerical modelling. This paper is the second part of the research concentrated on utilizing some hydrodynamic models for resolving the problem. In the first part some hydrodynamic background has been described and here the analysis of applying two-dimensional depth-averaged model for straight rectangular channel with a groyne is discussed. Three models of eddy viscosity were applied to investigate their influence on results of simulation and to attempt choosing the most suitable method of modelling the flow phenomena around the groin. Results of simulation in steady flow conditions show that from the hydrodynamic point of view the more profitable method of turbulence description is the mixed-length or even the parabolic method instead of the broadly suggested k-e model. They allow producing the most reliable vortexes in the shear layer of flow behind the training structure end well preserve the mass balance contrary to the results obtained with k-e model of eddy viscosity.

scholarly journals Observing river stages using unmanned aerial vehicles

2016 ◽  
Author(s):  
Tomasz Niedzielski ◽  
Matylda Witek ◽  
Waldemar Spallek
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Water Surface ◽  
Water Levels ◽  
Hydrodynamic Models ◽  
Surface Areas ◽  
Aerial Vehicles ◽  
Potential Applications ◽  
Sw Poland ◽  
High Flows ◽  
Student’S T

Abstract. We elaborated a new method for observing water surface areas and river stages using unmanned aerial vehicles (UAVs). It is based on processing multitemporal m orthophotomaps produced from the UAV-taken visual-light photographs of n sites of the river, acquired with a sufficient overlap in each part. Water surface areas are calculated in the first place, and subsequently expressed as fractions of total areas of water-covered terrain at a given site of the river recorded on m dates. The logarithms of the fractions are later calculated, producing m samples of size n. In order to detect statistically significant increments of water surface areas between two orthophotomaps we apply the asymptotic and bootstrapped versions of the Student's t-test, preceded by other tests that aim to check model assumptions. The procedure is applied to five orthophotomaps covering nine sites of the Ścinawka river (SW Poland). The data have been acquired during the experimental campaign, at which flight settings were kept unchanged over nearly 3 years (2012–2014). We have found that it is possible to detect transitions between water surface areas produced by all characteristic water levels (low, mean, intermediate and high stages). In addition, we infer that the identified transitions hold for characteristic river stages as well. In the experiment we detected all increments of water level: (1) from low stages to: mean, intermediate and high stages; (2) from mean stages to: intermediate and high stages; (3) from intermediate stages to high stages. Potential applications of the elaborated method include verification of hydrodynamic models and the associated predictions of high flows using on-demand UAV flights performed in near real-time as well as monitoring water levels of rivers in ungauged basins.

Renewed thinking on groundwater age

2021 ◽  
Author(s):  
Grant Ferguson ◽  
Mark Cuthbert ◽  
Kevin Befus ◽  
Tom Gleeson ◽  
Chandler Noyes ◽  
...  
Keyword(s):  
Environmental Flows ◽  
Numerical Models ◽  
Groundwater Age ◽  
Holistic Approach ◽  
Water Levels ◽  
Residence Times ◽  
Groundwater Sustainability ◽  
Long Time ◽  
Mean Residence Times ◽  
Recharge Rates

<p>Groundwater age and mean residence times have been invoked as measures of groundwater sustainability, with the idea that old or "fossil" groundwater is non-renewable. This idea appears to come from the link between groundwater age and background recharge rates, which are also of questionable use in assessing the sustainability of groundwater withdrawals. The use of groundwater age to assess renewability is further complicated by its relationship with flow system geometry. Young groundwaters near recharge areas are not inherently more renewable than older groundwaters down gradient. Similarly, there is no reason to preferentially use groundwater from smaller aquifers, which will have smaller mean residence times than larger aquifers for the same recharge rate. In some cases, groundwater ages may provide some information where groundwater recharge rates were much higher in the past and systems are no longer being recharged. However, there are few examples where the relationship between depletion and changes in recharge over long time periods has been rigorously explored. Groundwater age measurements can provide insights into the functioning of groundwater flow systems and calibration targets for numerical models and we advocate for their continued use, but they are not a metric of sustainable development. Simple metrics to assess groundwater sustainability remain elusive and a more holistic approach is warranted to maintain water levels and environmental flows.</p>

INTRODUCING GRADUATE STUDENTS INTO PRE-PROCESSING TECHNIQUES FOR ADVANCED NUMERICAL MODELS: APPLICATION TO HYDRODYNAMIC MODELS

2016 ◽  
Author(s):  
Carmen Zarzuelo Romero ◽  
Alejandro López-Ruiz ◽  
Manuel Díez-Minguito ◽  
Antonio Moñino ◽  
Pedro Magaña ◽  
...  
Keyword(s):  
Graduate Students ◽  
Numerical Models ◽  
Hydrodynamic Models ◽  
Processing Techniques

scholarly journals Evaluation of LNAPL Behavior in Water Table Inter-Fluctuate Zone under Groundwater Drawdown Condition

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2337
Author(s):  
Reza Azimi ◽  
Abdorreza Vaezihir ◽  
Robert Lenhard ◽  
S. Hassanizadeh
Keyword(s):  
Numerical Models ◽  
Water Levels ◽  
Injection Point ◽  
Monitoring Wells ◽  
Water Pumping ◽  
Two Factors ◽  
Injection Water ◽  
Phase Liquid ◽  
Flow Through ◽  
Material Grain Size

We investigate the movement of LNAPL (light non-aqueous phase liquid) into and out of monitoring wells in an immediate-scale experimental cell. Aquifer material grain size and LNAPL viscosity are two factors that are varied in three experiments involving lowering and rising water levels. There are six monitoring wells at varying distances from a LNAPL injection point and a water pumping well. We established steady water flow through the aquifer materials prior to LNAPL injection. Water pumping lowered the water levels in the aquifer materials. Terminating water pumping raised the water levels in the aquifer materials. Our focus was to record the LNAPL thickness in the monitoring wells under transient conditions. Throughout the experiments, we measured the elevations of the air-LNAPL and LNAPL-water interfaces in the monitoring wells to obtain the LNAPL thicknesses in the wells. We analyze the results and give plausible explanations. The data presented can be employed to test multiphase flow numerical models.

scholarly journals Seasonal variation of the principal tidal constituents in the Bohai Sea

Ocean Science ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Daosheng Wang ◽  
Haidong Pan ◽  
Guangzhen Jin ◽  
Xianqing Lv
Keyword(s):  
Seasonal Variation ◽  
Harmonic Analysis ◽  
Sea Level ◽  
Seasonal Variations ◽  
Eddy Viscosity ◽  
Bohai Sea ◽  
Phase Lag ◽  
Vertical Eddy Viscosity ◽  
Tidal Constituents ◽  
Vertical Eddy

Abstract. The seasonal variation of tides plays a significant role in water level changes in coastal regions. In this study, seasonal variations of four principal tidal constituents, M2, S2, K1, and O1, in the Bohai Sea, China, were studied by applying an enhanced harmonic analysis method to two time series: 1-year sea level observations at a mooring station (named E2) located in the western Bohai Sea and 17-year sea level observations at Dalian. At E2, the M2 amplitude and phase lag have annual frequencies, with large values in summer and small values in winter, while the frequencies of S2 and K1 amplitudes are also nearly annual. In contrast, the O1 amplitude increases constantly from winter to autumn. The maxima of phase lags appear twice in 1 year for S2, K1, and O1, taking place near winter and summer. The seasonal variation trends estimated by the enhanced harmonic analysis at Dalian are different from those at E2, except for the M2 phase lag. The M2 and S2 amplitudes show semi-annual and annual cycles, respectively, which are relatively significant at Dalian. The results of numerical experiments indicate that the seasonality of vertical eddy viscosity induces seasonal variations of the principal tidal constituents at E2. However, the tested mechanisms, including seasonally varying stratification, vertical eddy viscosity, and mean sea level, do not adequately explain the observed seasonal variations of tidal constituents at Dalian.

scholarly journals Anthropogenic Influences on Environmental Changes of Lake Bosten, the Largest Inland Freshwater Lake in China

2020 ◽  
Vol 12 (2) ◽  
pp. 711 ◽  
Author(s):  
Wen Liu ◽  
Long Ma ◽  
Jilili Abuduwaili
Keyword(s):  
Central Asia ◽  
Lake Sediments ◽  
Human Activities ◽  
Environmental Changes ◽  
Living Environment ◽  
Water Levels ◽  
Aral Sea ◽  
Anthropogenic Factors ◽  
Large Spatial Scale ◽  
The 1960S

A short lacustrine sediment core (41 cm) from Lake Bosten in arid central Asia was used to investigate the environmental changes that occurred in the past ≈150 years based on the superposition of climate and anthropogenic factors. Geochemical elements, total organic carbon (TOC) and nitrogen (TN), and stable isotope data (δ13Corg and δ15N) were used to identify abnormal environmental changes. The average C/N ratio in the sediments of Lake Bosten suggested that the organic matter in lake sediments was mainly from aquatic plants. The δ13Corg and δ15N in the lake sediments mainly reflect changes in the structure of the lake’s ecosystem. Before the 1960s, the primary productivity of the lake was relatively low with a relatively stable lake water environment. From the 1960s to the mid-1980s, the lake’s ecosystem was closely related to a significant decline in water levels caused by human activities and an increase in salinity. From the late 1980s to ≈2000, the aquatic plant structure of Lake Bosten did not change significantly. After 2000, the upper part of the sedimentary record suggested enhanced productivity due to urban and industrial development in the catchment area. However, sedimentary perspectives of the responses of different environmental proxies in sediments to human activities were anisochronous, and the increasing heavy metal (Pb and Cu) and P accumulations appeared in 1970, reflecting heightened human impacts. Through the comparison between the Aral Sea and Lake Bosten, it was inferred that, under the intervention of human activities, the lake experienced a completely different evolution trend. Humans, as geological agents, should protect our living environment while satisfying social development. The results will provide an important supplement to a large spatial scale study of the influences of human activities on the environment in Central Asia, which also has some significant implications for the protection of the ecological environment and the realization of sustainable development in arid regions.

scholarly journals Applying of depth-averaged hydrodynamic modeling with different methods of turbulence closure for flow near channel groyne. Part I – hydrodynamic background

2018 ◽  
Vol 23 ◽  
pp. 00009
Author(s):  
Ryszard Ewertowski
Keyword(s):  
Eddy Viscosity ◽  
Rectangular Channel ◽  
Simulation Models ◽  
Shear Stresses ◽  
Research Activity ◽  
Simulation Experiments ◽  
Hydrodynamic Simulation ◽  
Training Structures ◽  
Averaged Model ◽  
Bed Shear Stresses

Training structures in flow stream play an important role in shaping flow and bed properties. Planning to introduce such training elements like groins or dikes into the river stream one need to know consequences they may introduce into flow field and bed shear stresses. These consequences can be investigated by laboratory experiments on hydraulic models or by numerical modelling using hydrodynamic simulation models. In the paper the second possibility is exploited by applying two-dimensional depth-averaged model for straight rectangular channel with a groyne. This paper contains the first part of the research results and it describes hydrodynamic background of the flow phenomenon, concentrating on hydrodynamic equations for depth-averaged flow, types of eddy viscosity method used and kind of boundary conditions applied. Based on the hydrodynamic descriptions, different simulation experiments have been conducted for the flow problem and the whole analysis of simulation results for flow in channel near groyne is contained in the second part of the research activity (Part II = Analysis of simulation).

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