Suppression of transients in wave-excited response testing

• Long transient responses of a wave maker excited floating body can be undesirable.
• Methods for suppressing such transients in a numerical tank are developed here.
• They are applied to a heaving buoy excited from rest in sinusoidal waves.
• Steady-state sinusoidal response is achieved after a few cycles of the wave maker.
• The implications of non-linearity are considered.

When a floating body in a wave tank has low hydrodynamic damping, for example in the heave mode, very long duration transient responses can arise if it is excited from a state of rest by sinusoidal waves. Such behaviour can be undesirable when steady state response characteristics are the object of investigation in a numerical tank, because of the consequential need for very long computations. The present paper develops a method for suppressing such transient behaviour in computational models. The success of the approach is demonstrated in the context of the heaving motion of a simple buoy. A linear model of such a buoy initially at rest in a wave tank, excited by propagating sinusoidal waves, is used here for a preliminary investigation of the removal of transients. The technique is then incorporated into a fully nonlinear potential flow simulation of the buoy, and the approach is shown to be effective.