This work focuses on the validation of the two-phase Navier-Stokes model interFoam, part of the OpenFOAM finite volume framework, applied to the case of a fixed oscillating water column. The model is validated against experimental results from the Technical University of Denmark. Both twoand one-way absorption, i.e. only the upor downstroke is used to drive the flow through the orifice, are investigated. For the one-way absorption cases a numerical one-way valve is employed. The results show a good fit to the experimental values for the two-way absorption, but for the one-way absorption the pressure, and subsequently power generation, is off. The reason is unresolved problems with the numerical one-way valve. Further, for the two-way absorption a formal solution verification was performed, showing the simulations had less than 7% numerical uncertainty arising from the spatial discretization