scholarly journals SHIP-GENERATED WAVES OVER A COMPLEX BATHYMETRY

2018 ◽  
pp. 35
Author(s):  
Björn Almström ◽  
Magnus Larson ◽  
Lars Granath ◽  
Hans Hanson
Keyword(s):  
Numerical Models ◽  
Water Levels ◽  
Empirical Formulas ◽  
Wave Regime ◽  
Ship Waves ◽  
Ship Wave ◽  
Energy Environment ◽  
Length Width ◽  
Stockholm Archipelago ◽  
New Formula

Problems related to shipping have increased worldwide during the last decades as a result of more traffic travel-ling at higher speeds and using larger vessels. When ships move in a restricted fairway they generate primary (drawdown) and secondary (transverse and divergent) waves (Bertram 2000) that often cause adverse impact to adjacent shores. An example of this is the Furusund fairway in Sweden, which since the 1980’s has experienced increased traffic and larger ships. This has resulted in a loss of natural fine sediment habitats along the shores as well as structural damages to piers and jetties (Granath 2015). Furusund is an important fairway into Stockholm, the capital of Sweden, and is located about 25 km north of the city within the Stockholm archipelago. It is mainly trafficked by large ferries (length/width/draft: 200x30x7m). The wind-wave regime in the fairway can be described as a low-energy environment, due to the short fetches and no swell. Hence, ship waves have a significant impact on the shores in terms of bed and bank erosion. This study aims at determining the primary ship wave characteristics and their relationship to ship properties and bathymetric conditions in the Furusund fairway. Measured water levels were collected for this purpose during three months at three locations. Existing empirical formulas for drawdown are evaluated based on the measurements and compared with a new formula derived for the specific fairway. The results are used for designing nature-based protection against ship-generated waves along the shores and to validate analytical and numerical models that can be employed for ship wave generation and propagation.

scholarly journals Comparison of Hydrodynamics Simulated by 1D, 2D and 3D Models Focusing on Bed Shear Stresses

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 226 ◽  
Author(s):  
Kurt Glock ◽  
Michael Tritthart ◽  
Helmut Habersack ◽  
Christoph Hauer
Keyword(s):  
Flow Resistance ◽  
Numerical Models ◽  
3D Models ◽  
Water Levels ◽  
Shear Stresses ◽  
Flow Conditions ◽  
Empirical Formulas ◽  
2D And 3D ◽  
Bed Shear Stresses ◽  
Measured Water

For centuries, scientists have been attempting to map complex hydraulic processes to empirical formulas using different flow resistance definitions, which are further applied in numerical models. Now questions arise as to how consistent the simulated results are between the model dimensions and what influence different morphologies and flow conditions have. For this reason, 1D, 2D and 3D simulations were performed and compared with each other in three study areas with up to three different discharges. A standardized, relative comparison of the models shows that after successful calibration at measured water levels, the associated 2D/1D and 3D/1D ratios are almost unity, while bed shear stresses in the 3D models are only about 62–86% of the simulated 1D values and 90–100% in the case of 2D/1D. Reasons for this can be found in different roughness definitions, in simplified geometries, in different calculation approaches, as well as in influences of the turbulence closure. Moreover, decreasing 3D/1D ratios of shear stresses were found with increasing discharges and with increasing slopes, while the equivalent 2D/1D ratios remain almost unchanged. The findings of this study should be taken into account, particularly in subsequent sediment transport simulations, as these calculations are often based on shear stresses.

scholarly journals The geometric formulas of the Lewis’s law and Aboav-Weaire’s law in two dimensions based on ellipse packing

2019 ◽  
Author(s):  
Kai Xu
Keyword(s):  
Two Dimensions ◽  
Empirical Formulas ◽  
Von Neumann ◽  
Upper Limit ◽  
Edge Distribution ◽  
Cell Topology ◽  
Neighbor Relationship ◽  
New Formula ◽  
Geometric Formula ◽  
Ellipse Packing

The two-dimensional (2D) Lewis’s law and Aboav-Weaire’s law are two simple formulas derived from empirical observations. Numerous attempts have been made to improve the empirical formulas. In this study, we simulated a series of Voronoi diagrams by randomly disordered the seed locations of a regular hexagonal 2D Voronoi diagram, and analyzed the cell topology based on ellipse packing. Then, we derived and verified the improved formulas for Lewis’s law and Aboav-Weaire’s law. Specifically, we found that the upper limit of the second moment of edge number is 3. In addition, we derived the geometric formula of the von Neumann-Mullins’s law based on the new formula of the Aboav-Weaire’s law. Our results suggested that the cell area, local neighbor relationship, and cell growth rate are closely linked to each other, and mainly shaped by the effect of deformation from circle to ellipse and less influenced by the global edge distribution.

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>

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 A NEW HYBRID APPROACH IN THE CALIBRATION OF BOUSSINESQ-TYPE WAVE BREAKING MODELS

2018 ◽  
pp. 24
Author(s):  
Joaquín Moris ◽  
Patricio Catalán ◽  
Rodrigo Cienfuegos
Keyword(s):  
Wave Height ◽  
Wave Breaking ◽  
Numerical Models ◽  
Hybrid Approach ◽  
Boussinesq Equations ◽  
Water Levels ◽  
Statistical Parameters ◽  
Time Space ◽  
Forcing Mechanisms ◽  
Set Up

Wave breaking is one of the main forcing mechanisms in coastal hydrodynamics, driving mean water levels and currents. Understanding its behavior is key in the goal of improving our comprehension of coastal morphodynamics variations. One way to improve our understanding is through the use of numerical models, such as phase-resolving numerical models based on the Boussinesq equations (Kirby, 2016), which are modified to include breaking by the inclusion of a breaking criteria and a dissipation mechanism. Since there is not a universal law capable of characterizing the wave breaking, the existing models must be calibrated. Traditionally, this is done by adjusting wave height profiles and other free surface statistical parameters without explicitly considering the time-space location and duration of the breaking process. Consequently, it is possible to calibrate a model that accurately represents wave elevation statistics parameters, such as wave height and wave set-up; however, it might not necessarily represent the breaking location-duration and therefore, the forcing.

Gold coast seaway smartrelease decision support system: optimising recycled water release in a sub tropical estuarine environment

2009 ◽  
Vol 60 (8) ◽  
pp. 2077-2084 ◽  
Author(s):  
G. Stuart ◽  
A. Hollingsworth ◽  
F. Thomsen ◽  
S. Szylkarski ◽  
S. Khan ◽  
...  
Keyword(s):  
Water Quality ◽  
Decision Support ◽  
Decision Support System ◽  
Support System ◽  
Numerical Models ◽  
Water Levels ◽  
Gold Coast ◽  
Recycled Water ◽  
Water Release ◽  
The Impact

Gold Coast Water is responsible for the management of the water, recycled water and wastewater assets of the City of the Gold Coast on Australia's east coast. Excess treated recycled water is released at the Gold Coast Seaway, a man-made channel connecting the Broadwater Estuary with the Pacific Ocean, on an outgoing tide in order for the recycled water to be dispersed before the tide changes and re-enters the Broadwater estuary. Rapid population growth has placed increasing demands on the city's recycled water release system and an investigation of the capacity of the Broadwater to assimilate a greater volume of recycled water over a longer release period was undertaken in 2007. As an outcome, Gold Coast Water was granted an extension of the existing release licence from 10.5 hours per day to 13.3 hours per day from the Coombabah wastewater treatment plant (WWTP). The Seaway SmartRelease Project has been designed to optimise the release of the recycled water from the Coombabah WWTP in order to minimise the impact to the receiving estuarine water quality and maximise the cost efficiency of pumping. In order achieve this; an optimisation study that involves intensive hydrodynamic and water quality monitoring, numerical modelling and a web-based decision support system is underway. An intensive monitoring campaign provided information on water levels, currents, winds, waves, nutrients and bacterial levels within the Broadwater. This data was then used to calibrate and verify numerical models using the MIKE by DHI suite of software. The Decision Support System will then collect continually measured data such as water levels, interact with the WWTP SCADA system, run the numerical models and provide the optimal time window to release the required amount of recycled water from the WWTP within the licence specifications.

scholarly journals A 2D HLL-based weakly coupled model for transient flows on mobile beds

2020 ◽  
Vol 22 (5) ◽  
pp. 1351-1369
Author(s):  
Robin Meurice ◽  
Sandra Soares-Frazão
Keyword(s):  
Numerical Models ◽  
Morphological Evolution ◽  
Coupled Model ◽  
Dam Break ◽  
Water Levels ◽  
Test Cases ◽  
Transient Flows ◽  
Dam Breaks ◽  
Weakly Coupled ◽  
High Interaction

Abstract We propose a finite-volume model that aims at improving the ability of 2D numerical models to accurately predict the morphological evolution of sandy beds when subjected to transient flows like dam-breaks. This model solves shallow water and Exner equations with a weakly coupled approach while the fluxes at the interfaces of the cells are calculated thanks to a lateralized HLLC flux scheme. Besides describing the model, we ran it for four different test cases: a steady flow on an inclined bed leading to aggradation or degradation, a dam-break leading to high interaction between the flow and the bed, a dam-break with a symmetrical enlargement close to the gate and a dam-break in a channel with a 90° bend. The gathered results are discussed and compared to an existing fully coupled approach based on HLLC fluxes. Although both models equally perform regarding water levels, the weakly coupled model looks to better predict the bed evolution for the four test cases. In particular, its results are not affected by an excessive numerical diffusion encountered by the coupled model. Moreover, it usually better estimates the amplitudes of the maximum deposits and scours. It is also more stable when subject to high bed–flow interaction.

The role of coastal wetlands in reducing back bay flooding: New Jersey Back Bays case study

2020 ◽  
Author(s):  
Gregory Slusarczyk ◽  
Mary Cialone
Keyword(s):  
New Jersey ◽  
Flood Risk ◽  
Coastal Wetlands ◽  
Numerical Models ◽  
Atlantic Coast ◽  
Water Levels ◽  
Army Corps ◽  
Priority List ◽  
Us Army ◽  
Bay Area

<p>This paper will provide an analysis of the numerical modeled water levels in the vicinity of New Jersey Back Bays (NJBB) coastal wetlands in response to wave and surge forcing. The main focus of the analysis is to evaluate the contribution of the wetlands to reduce storm and flood risk, resist and recover from storms, and mitigate for degradation of the NJBB shorelines.  In order to provide information that addresses these needs, the US Army Corps of Engineers (USACE) Engineer Research and Development Center (ERDC) evaluated a set of “high” ranked Engineering with Nature (EWN)/ Natural and Nature Based Features (NNBF) measures through an application of the predictive numerical models ADvanced CIRCulation (ADCIRC) and STeady-state spectral WAVE (STWAVE) coupled via the Coastal Storm Modeling System (CSTORM-MS).</p><p>The ERDC modeling team developed a priority list of wetland configurations to evaluate, grouped into four categories: 1) Base Option designed to determine the maximum feasible benefits from a subset of NNBF measures, 2) Option 1 designed to determine how the benefits scale with NNBF size, 3) Option 2 designed to determine how the current marsh extent contributes to flood risk, 4) Option 3 designed to determine the interaction of waves with proposed NNBF measures predominantly in the Barnegat Bay area.</p><p>The above configurations were subject to wind forcing composed of a statistically-selected subset of synthetic tropical cyclones that were part of North Atlantic Coast Comprehensive Study (NACCS) storm suite. An analysis of the effectiveness of the wetland configurations was performed with respect to the following criteria: maximum surge envelopes, water level time series, and characteristics of tropical storm forcing conditions.</p>

scholarly journals Transfer Entropy as a Tool for Hydrodynamic Model Validation

Entropy ◽  
2018 ◽  
Vol 20 (1) ◽  
pp. 58 ◽  
Author(s):  
Alicia Sendrowski ◽  
Kazi Sadid ◽  
Ehab Meselhe ◽  
Wayne Wagner ◽  
David Mohrig ◽  
...  
Keyword(s):  
Water Level ◽  
Numerical Models ◽  
Water Levels ◽  
Transfer Entropy ◽  
Spatial And Temporal Scales ◽  
River Deltas ◽  
Level Data ◽  
Water Level Data ◽  
Wax Lake Delta ◽  
Validation Tool

The validation of numerical models is an important component of modeling to ensure reliability of model outputs under prescribed conditions. In river deltas, robust validation of models is paramount given that models are used to forecast land change and to track water, solid, and solute transport through the deltaic network. We propose using transfer entropy (TE) to validate model results. TE quantifies the information transferred between variables in terms of strength, timescale, and direction. Using water level data collected in the distributary channels and inter-channel islands of Wax Lake Delta, Louisiana, USA, along with modeled water level data generated for the same locations using Delft3D, we assess how well couplings between external drivers (river discharge, tides, wind) and modeled water levels reproduce the observed data couplings. We perform this operation through time using ten-day windows. Modeled and observed couplings compare well; their differences reflect the spatial parameterization of wind and roughness in the model, which prevents the model from capturing high frequency fluctuations of water level. The model captures couplings better in channels than on islands, suggesting that mechanisms of channel-island connectivity are not fully represented in the model. Overall, TE serves as an additional validation tool to quantify the couplings of the system of interest at multiple spatial and temporal scales.

scholarly journals Modelling origin and transport fate of waste materials on the south-eastern Adriatic coast (Croatia)

2014 ◽  
Vol 11 (6) ◽  
pp. 2939-2969
Author(s):  
M. Tudor ◽  
I. Janeković
Keyword(s):  
Adriatic Sea ◽  
Flash Flood ◽  
Numerical Models ◽  
Remote Sensing Data ◽  
Water Levels ◽  
Waste Material ◽  
Ocean Current ◽  
The South ◽  
South Eastern ◽  
Adriatic Coast

Abstract. The south-eastern parts of the Adriatic Sea coastline were severely polluted by large amounts of accumulated waste material in the second half of November 2010. The waste, reported by major news agencies, accumulated dominantly during 21 November 2010 by favourable wind – ocean current transport system. In the study we analysed meteorological and oceanographic conditions that lead to the waste deposition using available in situ measurements, remote sensing data as well numerical models of the ocean and the atmosphere. The measured data reveal that an intensive rainfall event from 7 till 10 November 2010, over the parts of Montenegro and Albania, was followed by a substantial increase of the river water levels indicating flash floods that possibly splashed the waste material into a river and after to the Adriatic Sea. In order to test our hypothesis we set a number of numerical drifter experiments with trajectories initiated off the coast of Albania during the intensive rainfall events following their faith in space and time. One of the numerical drifter trajectory experiment resulted with drifters reached right position (south-eastern Adriatic coast) and time (exactly by the time the waste was observed) when initiated on 00:00 and 12:00 UTC of 10 November 2010 during the mentioned flash flood event.

Sign in / Sign up

Export Citation Format

Share Document