Abstract: Open boundary condition (OBC) is one of the most challenge subjects in the field of computational method for infinite domain. There are already many different kinds of OBCs in wave problems. But, they still lack practical comparisons of effectiveness. This article devotes to such comparisons of several important OBCs at the artificial boundaries for the nonlinear wave equation Boussinesq equation. A test example is given on the diffraction of solitary wave by a hump at the sea bottom. 3-D scattering wave diagrams are also given. The effectiveness is analyzed with instructive conclusion.

Key words: solitary wave, diffractiom, open boundary condition, Boussinesq equation, artificial boundary