In this work, the performance of biomimetic device that consists of including a rotating, vertically mounted, biomimetic wing, supported by an arm linked at a pivot point on the mid-chord is evaluated using a numerical model is considered and results are presented concerning the performance. Activated by a controllable self-pitching motion, the system performs angular oscillations around the vertical axis in incoming flow. The performance of the above flapping-foil, biomimetic flow energy harvester, is calculated and the results are compared against experimental data. By systematical application of the model the power extraction and efficiency of the system is presented for various cases including different geometric, mechanical, and kinematic parameters, and the optimal performance of the system is determined. Also comparisons of the calculated performance are presented against predictions for other tidal energy devices, such as the stream energy converters based on the vortex-induced angular oscillations of a cylinder.