Wave modelling

To gain a reliable estimate of the nearshore wave climate within a study area, such as a harbour or along a specific coastline, Herrington Consulting has developed numerical wave modelling capabilities.

The prediction of wave heights in areas of complex bathymetry and coastal structures is governed by a combination of factors, including; the seabed topography, tidal currents and the presence of any coastal structures located within the area of interest. These features cause temporal and spatial changes in the wave field, and to analyse the interaction of these features within the study area an advanced nearshore wave propagation model is required to inform clients of the potential design implications.

To undertake this type of analysis for their clients, Herrington Consulting applies a Boussinesq wave model that is now part of the U.S. Army Corps of Engineers (USACE). As a phase-resolving nonlinear wave model, it can be used in the modelling of various wave phenomena including:

The model is used to construct a detailed Cartesian grid, based on the bathymetry and topography of the study area. The existing coastal structures are represented within the model domain using a coastal boundary layer and input boundary conditions are taken from offshore wave data.

The wave model enables the user to simulate various sea states, including a multidirectional sea state and by testing a range of scenarios based on extreme wave height and water level combinations, it enables the user to ascertain which set of wave conditions would have the greatest impact within the study area.

The model itself employs a time-domain solution of fully nonlinear Boussinesq-type equations, valid from deep to shallow water, representing the depth-integrated equations of conservation of mass and momentum for waves propagating in water of variable depth. Waves propagating out of the computational domain are absorbed in damping layers placed around the perimeter of the domain, and both damping and porosity layers can also be used to simulate the reflection and transmission characteristics of marine structures existing within the model boundaries.