In this work a three dimensional computational fluid dynamic (CFD) model has been constructed based on a 1/50 scale heaving point absorber wave energy converter (PAWEC). The CFD model is validated first via wave tank tests and then is applied in this study to investigate the joint effects of device geometry and power take-off (PTO) damping on wave energy absorption. Three PAWEC devices are studied with the following geometrical designs: a cylindrical flat-bottom device (CL); a hemispherical streamlined bottom design (CH) and a 90-conical streamlined bottom structure (CC). A PTO force via varying damping coefficient is applied to compare the power conversion performances of the aforementioned devices. Free decay, wave-PAWEC interaction and power absorption tests are conducted via the CFD model. The results show that for CH and CC designs the added mass and hydrodynamic damping decrease by up to 60% compared with the CL device. Moreover, the CC design is the best of the three structures since its amplitude response increases by up to 100% compared with the CL. Applying an appropriate PTO damping to the CC device prominently increases the achievable optimal power by up to 70% under both regular and irregular waves (compared with the CL device). (C) 2018 Elsevier Ltd. All rights reserved.