During storms, long-period water level oscillations can occur on the North Sea. The meteorological phenomena that cause these oscillations are known to a large extent and include atmospheric single pulse perturbations or oscillations of longer duration and larger spatial scale (De Jong in Origin and prediction of seiches in Rotterdam harbour basins, Delft University of Technology, ISBN 90-9017925-9, 2004). During such events, standing waves, or 'seiches', can occur in the ports along the Dutch North Sea coast. These seiches need to be considered in the height criteria for the dikes and other flood protection works around the port basins. Over the last decades, several projects on the climatology of seiching have been performed by Deltares under assignment by the Dutch Ministry of Public Works. Results of these projects served to update the height criteria for the storm surge barriers in the Port of Rotterdam, and as input to the design of two large new sea locks for other coastal ports, in IJmuiden and Terneuzen. This paper describes the three project locations: the statistical and hydrodynamical analyses of seiche events at these locations and the translation of the results into a buffer, or 'seiche allowance', to the height criteria.
Wave penetration is a challenge for port engineers as it governs vessels' safe sailing and mooring and unequivocally regulates the handling of port operations. A complete way to describe this phenomenon is by a physical scale model. However, this approach can be time consuming and expensive, therefore the use of a numerical model is a valid alternative. In this study, wave penetration is simulated with the non-hydrostatic model SWASH (Zijlema, 2011). To validate the model, the output of an open benchmark dataset of physical scale model tests (Van der Ven, 2018) is used. This study evaluates to what degree SWASH models correctly simulate wave penetration per wave process, separately in simplified models and in combination in the full harbour layout, to identify their role in the model accuracy.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/Y8ds-sW4VIQ
<p>Wave penetration is a challenge for hydraulic engineers as it governs vessels&#8217; sailing and mooring and regulates port operations. A complete approach to describe this phenomenon is by a physical scale model, which is time consuming and expensive. Therefore, a numerical model is a valid alternative. In this study, wave penetration is simulated with the non-hydrostatic model SWASH (Zijlema, 2011). To validate the model, part of an open benchmark dataset of physical scale model tests (Deltares, 2016) is used. This research addresses regular waves conditions and a simple harbour basin layout, in which reflection and diffraction are the main wave processes. This study assesses SWASH&#8217;s capability to model these processes, separately and in combination, in the full harbour layout.</p><p>1. Methodology</p><p>Reflection outside and inside the harbour is studied by two simplified 1D SWASH models, while diffraction inside the harbour by a simplified 2D model. The final SWASH model represents the full harbour layout. In all the models the water level time series at the output locations are compared qualitatively to the respective series measured at the wave gauges. Moreover, the measured steady state wave height is compared to the SWASH outputs. The &#8220;Difference&#8221;, Eq. (1), is computed to evaluate the model accuracy and to quantify the relative importance of each wave process.</p><p>Difference/diff.=(H<sub>SWASH,mean</sub>-H<sub>measured,mean</sub>)/H<sub>measured,mean&#160;&#160;</sub>(1)</p><p>Where H<sub>SWASH,mean </sub>; H<sub>measured,mean </sub>: mean steady state wave height obtained by SWASH or measured respectively [m].</p><p>2. Results</p><p>Although the reflection trends are reproduced qualitatively in SWASH, the exact steady state wave height values may deviate significantly (diff.>30%). Moreover, the initial diffraction trends are also identified in SWASH despite their short duration in the measurements. Regarding the steady state wave height, diffraction influences considerably the total measured wave penetration inside the harbour. In the final SWASH model, the overall changes in the wave height are reproduced by SWASH. The agreement between the measured and the computed wave height is good at many output locations (diff.<10%). However, at some locations the accuracy is low (diff.>40%), owing to standing wave patterns which change fast within a short horizontal distance. Thus, the wave height can vary significantly at the area close to a specific wave gauge.&#160; Finally, for relatively high waves and/or breaking waves, numerical instabilities are detected. Higher spatial resolution is required to capture such phenomena.</p><p>3. Conclusions</p><p>The study shows SWASH capability to reproduce qualitatively the most important reflection and diffraction trends. To a large extend, diffraction is the main process determining the wave height inside the harbour; reflection at the harbour end comes second. Outside the harbour, reflection off a quay wall is the dominant process, while reflection off a gravel slope is noteworthy. All in all, it is concluded that for non-breaking, relatively low waves, SWASH accuracy in modelling wave penetration is sufficient for engineering purposes. With further validation to guarantee the model stability, the implemented methodology can be a useful tool to understand the performance of SWASH in modeling wave penetration per wave process and in combination.</p>
Moored vessels often experience low-frequency vessel motions when moored in a port due to wave excitation. Under such conditions the loading and offloading of vessels may be hampered when these movements become too large [1,2,3]. Innovative mooring techniques can be used for reducing issues with excessive motions of moored vessels in waves [4,5,6]. Considering applying such techniques as part of the design of mooring facilities and ports is expected to make different approaches to port or mooring facility designs possible. Such techniques, like the ShoreTension (ST) system, are already applied successfully worldwide in ports [7,8,9], however the application and performance limits of such systems under extreme conditions are not well known. This paper describes the results of a research project using physical scale modelling to systematically verify and extend the applicability and performance limits of innovative mooring systems. It resulted in a solid validation database for validating numerical models. The knowledge developed in this research will benefit developers of mooring facilities (including ports) to significantly reduce costs by limiting the need for structures providing shelter from waves. Furthermore, this may also help lowering the impact of port infrastructure on the coastal system when using less invasive infrastructure.
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