The source term due to the effect of a structure can be written
(6.20)
where A is the area of the cell/element in the mesh in which the structure is located, c is the reflection factor, cg is the group celerity and E(s,q) is the energy density.
The contribution from the convective transport to the time-deriative wave action density due to the effect of a structure can be written
(6.21) 
where A is the area of the cell/element in the mesh in which the structure is located and the normal flux through the element edge, Fn, is multiplied with the length Dl and summed over the number of edges.
