Boundary Conditions

Wave generation

Wave generation is critical in numerical coastal engineering simulations. Generating waves is always the beginning of the vast majority of the cases we are dealing with. An accurate wave generation process lays the foundations of realistic final results. If the starting point is not accurate, all the errors introduced in this initial step will propagate until the end.

This boundary condition has been coded from scratch to realistically generate three-dimensional waves at the boundaries according to a number of wave theories, including:

  • Stokes I, II and V, Cnoidal and Streamfunction regular waves.
  • Boussinesq, Grimshaw and McCowan solitary wave.
  • Irregular (random) directional waves, first and second order.
  • Piston-type wavemaker velocity profile replication.
  • Extern File as input for the wavepaddle.
  • Hybrid modelling between IH2VOF and IHFOAM

Furthermore, wave generation has been linked with active wave absorption to work simultaneously on the same boundaries. This generates the target waves while absorbing the boundary  incident waves.

Active wave absorption

Active absorption of waves is one of the key features of physical and numerical experiments in coastal engineering. On the sea, reflected waves travel away from the study zone. However, in numerical experiments this is not the case, as the domains are constrained in dimensions due to computational restrictions. This situation causes inconvenient reflections that, if not handled adequately, can distort the results.

In this sense, active wave absorption is a great advance, as it allows waves to be absorbed on the boundaries without adding noticeable computational costs to the model. This feature contrasts with the already available relaxation zone absorption, which adds a large domain to the zone of interest (in the order of magnitude of 1.5-2 wave lengths) and is known to produce an increment in the mean water level due to  wave damping, as shown in Mendez et al. (2001).

IHFOAM includes the active wave absorption as presented in Schäffer and Klopman (2000) and enhanced for the model.

All the theories are stable and have an adequate performance for all the relative water depths, presenting reflection coefficients typically below 10%..