The future of the DIA

Hydraulic EngineeringCivil Engineering and Geoscience

Computation of the nonlinear energy transfer in a narrow gravity wave spectrum with a method derived by Dungey and Hui

In this report the method of Dungey and Hui is summarized and extended to include the effect of skewness of the directional distribution. Additional information is given about the derivation and computation of the single integrations mentioned above. The method of Dungey and Hui is applied to a number of theoretical spectra. The results of these computations are compared with the results of exact computations by Sell and Hasselmann (1972) and Hasselmann and Hasselmann (1981). Finally, some comments are made about computational aspects of the method of Dungey and Hui.Hydraulic EngineeringCivil Engineering and Geoscience

Analysis SWAN hindcasts Wadden Sea, Oosterschelde and Slotermeer

Results of hindcast studies with the SWAN wave model in the Amelander Zeegat, the Oosterschelde estuary and the Slotermeer were analyzed to detect the cause of under-prediction of low-frequency wave energy in the coastal zone, the causes of prediction errors in the presence of currents and the underprediction of wave heights In depth-limited conditions. The results of this study show that the under-prediction of low-frequency energy is most likelycaused by propagation effects, although the whitecapping formulation and bottom friction may also play a role. Wave heights are overpredicted in opposing current and th is is made worse by application of the adapted whitecapping formulation of WL (2007). The under-prediction of the wave heights in depth-limited situations is clearly worse for steep waves. It was also found that shallow water source terms affect the total source term balance. The under-prediction was the least by applying the surf breaking term with the breaking parameter gamma=O.8.SB

Preliminary investigation into the occurance of wave groups in seas and swell / Toetsing van het model van Kimura voor de beschrijving van golfgroepen

Het doel van deze studie is het onderzoeken van het model van Kimura (1980) voor de beschrijving van golfgroepen. Zoals in deel 1 van dit verslag werd aanbevolen, bestaat dit onderzoek uit de volgende onderdelen 1. Toetsen van het model van Kimura aan metingen. Beoordeling van groeplengteverdelingen met een statistische toets. 2. Vergelijking van methoden om de correlatiecoefficient tussen opeenvolgende golfhoogten te berekenen. 3. Nagaan wat de invloed is van correlaties tussen niet opeenvolgende golfhoogten op de groeplengteverdeling.VloeistofmechanicaHydraulic EngineeringCivil Engineering and Geoscience

Efficient algorithms for non-linear four-wave interactions

This paper addresses the on-going activities in the development of efficient methods for computing the non-linear four-wave interactions in operational discrete third-generation wind-wave models. It is generally assumed that these interactions play an important role in the evolution of wind generated surface gravity waves. Therefore, present day wave models contain parameterizations of these interactions. Despite the fact that a closed mathematical formulation is available for the description of these interactions, a full solution is not applicable in operational modelling as it requires excessive computational requirements. To overcome this limitation, various approximate methods have been developed that retain most of the basic properties of the full solution. However, the present operational parameterisations of these interactions have various weaknesses that degrade model performance and which generally lead to too broad spectra. Efficient and more accurate algorithms are therefore needed to improve model performance. As with each approximate method, a gain in computational speed goes together with a loss in accuracy in evaluating the basic integral, but this may not translate in less accurate wave model results. Therefore the definition of efficiency in the context of approximate methods for computing the four-wave interactions is addressed. Two main lines of development are identified in the development of efficient algorithms: extended Discrete Interaction Approximations, and reduced quasi-exact solution techniques.Hydraulic EngineeringCivil Engineering and Geoscience

Het gebruik van SWAN en SWASH voor het ontwerp van kustconstructies

Doel: Mogelijkheden laten zien van het gebruik van de numerieke golfmodellen SWAN en SWASH voor het ontwerp van kustconstructies. Beschrijving golfparameters en processen voor correcte keuze en toepassing van deze modellenHydraulic EngineeringCivil Engineering and Geoscience

Directional response of wind waves to turning winds

Civil Engineering and Geoscience

Onderzoek onzekerheid extreme golfbelastingen: Effect stromingen op golven Stappenplan toepassing SWAN model

Ten behoeve van het ontwerp van zeewerende constructies van nieuwe landaanwinningswerken van de Maasvlakte 2 is onderzoek verricht naar onzekerheden in de bepaling van golfrandvoorwaarden onder ontwerpcondities. In dit deelrapport is gekeken naar het effect van stromingen op de golfcondities voor de zeewerende constructies. Hierbij is gebruik gemaakt van bestaande resultaten van stromingsberekeningen onder gemiddelde springtij situaties. Vervolgens zijn een aantal golfberekeningen uitgevoerd met het SWAN model om het effect van stromingen op de golfcondities te bepalen. Tevens is een stappenplan opgesteld voor het uitvoeren van SWAN berekeningen voor ontwerpcondities

Non-Hydrostatic Wave modeling in Partly Sheltered Harbor Basins

The determination of wave conditions in partly sheltered areas is a challenging task for coastal engineers. Knowledge about these conditions is important for the design of coastal structures, the planning and operation of ports. Numerical models play an important role in the assessment of these conditions. Various types of models have been proposed of which phase averaged and phase resolving models are the most widely used. Here, we present the non-hydrostatic phase resolving SWASH model as a tool to determine wave conditions in partly sheltered areas. Examples are shown of wave diffraction behind a semi-infinite breakwater, and the penetration of waves into the harbour of Limassol, Cyprus. The computational results show good agreement with theoretical and experimental results, indicating that the SWASH model can be used as a tool to determine wave conditions in partly sheltered areas.Hydraulic EngineeringCivil Engineering and Geoscience