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Antwerpen, Belgium

Wei X.,Technical University of Delft | Schramkowski G.P.,Flanders Hydraulics Research | Schuttelaars H.M.,Technical University of Delft
Journal of Physical Oceanography | Year: 2016

Understanding salt dynamics is important to adequately model salt intrusion, baroclinic forcing, and sediment transport. In this paper, the importance of the residual salt transport due to tidal advection in well-mixed tidal estuaries is studied. The water motion is resolved in a consistent way with a width-averaged analytical model, coupled to an advection-diffusion equation describing the salt dynamics. The residual salt balance obtained from the coupled model shows that the seaward salt transport driven by river discharge is balanced by the landward salt transport due to tidal advection and horizontal diffusion. It is found that the tidal advection behaves as a diffusion process, and this contribution is named tidal advective diffusion. The horizontal diffusion parameterizes processes not explicitly resolved in the model and is called the prescribed diffusion. The tidal advective diffusion results from the correlation between the tidal velocity and salinity and can be explicitly calculated with the dominant semidiurnal water motion. The sensitivity analysis shows that tidal advective diffusivity increases with increasing bed roughness and decreasing vertical eddy viscosity. Furthermore, tidal advective diffusivity reaches its maximum for moderate water depth and moderate convergence length. The relative importance of tidal advective diffusion is investigated using the residual salt balance, with the prescribed diffusion coefficient obtained from the measured salinity field. The tidal advective diffusion dominates the residual salt transport in the Scheldt estuary, and other processes significantly contribute to the residual salt transport in the Delaware estuary and the Columbia estuary. © 2016 American Meteorological Society.

Lataire E.,Ghent University | Vantorre M.,Ghent University | Delefortrie G.,Flanders Hydraulics Research
Ocean Engineering | Year: 2012

The hydrodynamic behaviour of a vessel changes when sailing in shallow and/or confined water. The restricted space underneath and alongside a vessel has a noticeable influence on both the sinkage and trim of a vessel, also known as squat. To assess these influences an extensive model test program has been carried out in the Towing Tank for Manoeuvres in Shallow Water (cooperation Flanders Hydraulics Research - Ghent University) in Antwerp, Belgium with a scale model of the KVLCC2 Moeri tanker. This benchmark vessel was selected for its full hull form, to maximize the effects of the blockage. To thoroughly investigate the influences of the blockage on the squat of the vessel, tests have been carried out at different water depths, widths of the canal section and forward speeds (2 up to 16 knots full scale whenever possible). The squat observed during the model tests is compared with the squat predicted with a mathematical model based on mass conservation and the Bernoulli principle. The correlation between measured and modelled squat for each canal width for all tested speeds and water depths is very good, but shows a constant slope deviation. An improved model for the squat is proposed and takes into account the forward speed, propeller action, lateral position in the fairway, total width of the fairway and water depth. © 2012 Elsevier Ltd.

Lataire E.,Ghent University | Vantorre M.,Ghent University | Delefortrie G.,Flanders Hydraulics Research | Candries M.,Ghent University
Ocean Engineering | Year: 2012

The transfer of liquid cargo (crude oil and LNG) from a larger ship (the ship to be lightered, STBL) to a smaller vessel (service ship) when both ships are moored to each other and sail at a (slow) constant forward speed is known as lightering. These ship to ship operations are expected to increase in the near future and are expected to take place in harsher environmental conditions (polar regions). In order to better understand the hydrodynamic phenomena involved in this specific manoeuvre, a knowledge-building project with user involvement entitled Investigating Hydrodynamic Aspects and Control Strategies for Ship-to-Ship Operations was carried out in 2007-2011. As a part of this project, more than two thousand captive model tests were carried out at the towing tank for manoeuvres in shallow water (co-operation Flanders Hydraulics Research - Ghent University) in Antwerp, Belgium. A model of a very large crude oil carrier (VLCC) was attached to the main frame of the towing carriage and a model of an Aframax tanker was attached to the computer controlled planar motion carriage. Forces, moments and vertical positions were measured on both models. This paper covers the analysis of the extensive model test data reported by Lataire et al. (2009a) and the influence of different parameters on the manoeuvre. Particular attention is paid to the forces and moments induced on the service ship by the proximity of the ship to be lightered. A mathematical model of lightering manoeuvres for both the service ship and the ship to be lightered is derived. This model can be implemented in a ship manoeuvring simulator for training purposes. © 2012 Elsevier Ltd.

Kellens W.,Ghent University | Zaalberg R.,Sudan University of Science and Technology | Neutens T.,Ghent University | Vanneuville W.,Sudan University of Science and Technology | De Maeyer P.,Flanders Hydraulics Research
Risk Analysis | Year: 2011

In recent years, perception of flood risks has become an important topic to policy makers concerned with risk management and safety issues. Knowledge of the public risk perception is considered a crucial aspect in modern flood risk management as it steers the development of effective and efficient flood mitigation strategies. This study aimed at gaining insight into the perception of flood risks along the Belgian coast. Given the importance of the tourism industry on the Belgian coast, the survey considered both inhabitants and residential tourists. Based on actual expert's risk assessments, a high and a low risk area were selected for the study. Risk perception was assessed on the basis of scaled items regarding storm surges and coastal flood risks. In addition, various personal and residence characteristics were measured. Using multiple regression analysis, risk perception was found to be primarily influenced by actual flood risk estimates, age, gender, and experience with previous flood hazards. © 2011 Society for Risk Analysis.

Vandenbruwaene W.,University of Antwerp | Vandenbruwaene W.,Flanders Hydraulics Research | Bouma T.J.,Netherlands Institute for Sea Research | Meire P.,University of Antwerp | Temmerman S.,University of Antwerp
Earth Surface Processes and Landforms | Year: 2013

The long-term (10-100years) evolution of tidal channels is generally considered to interact with the bio-geomorphic evolution of the surrounding intertidal platform. Here we studied how the geometric properties of tidal channels (channel drainage density and channel width) change as (1) vegetation establishes on an initially bare intertidal platform and (2) sediment accretion on the intertidal platform leads to a reduction in the tidal prism (i.e. water volume that during a tidal cycle floods to and drains back from the intertidal platform). Based on a time series of aerial photographs and digital elevation models, we derived the channel geometric properties at different time steps during the evolution from an initially low-elevated bare tidal flat towards a high-elevated vegetated marsh. We found that vegetation establishment causes a marked increase in channel drainage density. This is explained as the friction exerted by patches of pioneer vegetation concentrates the flow in between the vegetation patches and promotes there the erosion of channels. Once vegetation has established, continued sediment accretion and tidal prism reduction do not result in significant further changes in channel drainage density and in channel widths. We hypothesize that this is explained by a partitioning of the tidal flow between concentrated channel flow, as long as the vegetation is not submerged, and more homogeneous sheet flow as the vegetation is deeply submerged. Hence, a reduction of the tidal prism due to sediment accretion on the intertidal platform, reduces especially the volume of sheet flow (which does not affect channel geometry), while the concentrated channel flow (i.e. the landscape forming volume of water) is not much affected by the tidal prism reduction. © 2012 John Wiley & Sons, Ltd.

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