A generating‐absorbing boundary condition for dispersive waves
Mart Borsboom, Niels G. Jacobsen
Abstract
Abstract The detailed modeling of free‐surface waves and their interaction with bottom‐mounted or floating structures requires large computational resources, which is why efficient boundary conditions with low spurious reflection are desirable. The present work presents a review of existing generating‐absorbing boundary conditions (GABCs) for dispersive waves and their reflection characteristics. Hereafter, an adaptation of the classical Sommerfeld condition is proposed by using a depth‐varying coefficient to improve absorption efficiency over a range of wave numbers. An analytical model is proposed to analyse the reflection characteristics for both propagating and evanescent modes, and a considerable improvement in comparison to the Sommerfeld condition is documented over a broad frequency range (reflection coefficients below 5% for nondimensional wave numbers in the range [0, 10]). The new boundary condition is implemented in OpenFoam (waves2Foam) and the functioning for regular, irregular, solitary, and phase‐focused waves is presented.