On the relaxation approach for wave absorption in numerical wave tanks

In CFD modelling, relaxation methods are widely used in numerical wave tanks (NWTs) for wave absorption; however, this method can be very expensive as part of the NWT must be dedicated to a relaxation zone. In this short technical note, a parametric study on the effects of the relaxation approach on absorbing different types of waves is reported. In addition, a simple modification to the relaxation method is suggested. The results appear to show that the modified relaxation approach helps to reduce the length of the relaxation zone by nearly half whilst retaining good performance in terms of wave absorption. •Effects of the relaxation method on wave absorption in numerical wave tanks is reported.•A simple modification to the relaxation method is suggested.•The modification appears to improve the efficiency of the relaxation method.