Wave Generation And Active Absorption In a Numerical Wave Flume

A numerical wave flume is simulated using a Boundary Element Method (BEM) model combined with a time stepping procedure. The boundary conditions in the BEM are similar to those in a physical wave flume, e.g. with a wavemaker at one end boundary and an absorbing condition at the other. The free water surface is described by two nonlinear boundary conditions, and the sea bed by a no-flux condition. Active absorption by a wave paddle is used for eliminating outgoing waves at the two ends of the wave flume. These waves are: I) the progressive waves propagating towards the outflow boundary, and 2) the waves coming back to the generation boundary due to reflection from the outflow boundary. The method used at the Danish Hydraulic Institute for simultaneous generation and active absorption of waves in flumes is implemented as boundary conditions and tested for regular as well as irregular waves. Comparison with theoretical prediction of absorption coefficients shows good agreement. Although the active absorption system has previously been successfully tested in a physical wave flume, the numerical flume provides an attractive tool for further