This paper uses the CFD toolbox OpenFOAM to perform numerical simulations of a single Floating Point Absorber (FPA) Wave Energy Converter (WEC) unit inside a numerical wave flume. The Navier-Stokes fluid solver is coupled with a motion solver to simulate wave-induced rigid body motions restricted to the heave direction only. Laboratory experiments are undertaken to validate the numerical model for a free decay test and specific regular wave trains. A general methodology is reported for modelling a WEC inside a numerical wave flume taking small deviations in geometry and friction into account. Several CFD simulations are presented with varying time step and grid resolution. The obtained heave motion of the WEC during a free decay test shows a good agreement with the experimental data. In addition, the radiated wave field due to the WEC’s motion is captured very accurately by the CFD solver. Even more accurate results are obtained by implementing a linear damper to take the friction in the experimental model in consideration. Subsequently, a WEC is subjected to two specific regular wave trains and both its heave motion and the perturbed wave field are in very good agreement compared to the experimental data. OpenFOAM proofs a suitable and accurate CFD toolbox to study wave-structure interaction of a floating body.