Within the framework of the Netherlands Center for Coastal Research (NCK), research has been conducted on the behaviour of low-frequency waves (also known as infragravity, subharmonic or long waves) in the nearshore and in harbors. One project involved the 2DH numerical modelling of the low-frequency wave climate near Duck, NC, USA. After validation against data collected during the Delilah experiment, the model was used to show, among other aspects, that the infragravity wave climate was determined by the directional spreading and not by the bathymetry. The relative strength of the forcing terms and the occurrence of bar-trapped edge waves were also investigated. A data set of forced low-frequency waves over a barred bathymetry as measured in a research flume has been used to analyse the growth and relative phase change of long waves incident on a beach. In addition, a new data set has been collected for examples of a plane sloping beaches. These data sets and numerical simulations with the numerical model "Surfbeat" show that at the shoreline or near a structure, the long wave is in phase with the short wave heights, which means that the mean surface is temporarily elevated when the highest short waves reach the shore. This effect increases wave loads and up until now has not been taken into account in design formulas. The "Surfbeat" numerical model has been applied to the case of long wave motion in the port of Saldanha Bay in South Africa.
References and reprints of published papers (three J. of Geophys. Res and two conference papers) are available upon request.
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