Thrust Extraction from Vorticity Fields in Steady and Unsteady Flows

The possibility to compute the thrust from numerically computed vorticity fields in steady and unsteady flows is investigated. In particular, an extension of a well assessed Lamb vector based formula is proposed for the analysis of both steady and unsteady cases. In the case of steady flow, the formula is adopted for the computation of the thrust generated by an actuator disk. In the case of unsteady flow another derived mixed inertial-non inertial formula is used to compute the force exerted by a pure plunging airfoil. A possible drag-thrust bookkeeping is proposed dividing the total force in a reversible and an irreversible contribution. The formulae are tested by post-processing CFD solutions and the results are compared with reference values.