A well known property of Oscillating Water Column (OWC) type wave energy converters is the approximately linear pressure drop-volume flow rate relation due to the Wells turbine equipment. This work presents a novel method where this relation is defined as a boundary condition in time domain simulations. The interaction of the OWC with regular, small waves in a tank is the boundary value problem that is under consideration. The finite volume method-based solver Fluent is used with two dimensional, incompressible, unsteady, two-phase flow assumptions. The turbine parameter that relates the pressure drop and flow rate is determined using linearised theory.