Abstract: The present invention relates to a method and apparatus for oscillating a foil in a fluid. The method according to the invention comprises the steps of —generating an oscillating heave motion of the foil in the fluid, the oscillation cycle of the heave motion consisting of two strokes of the foil in opposite direction; —generating an oscillating pitching motion of the foil in the fluid; characterized by —controlling the heave motion; and —adjusting the pitch during the oscillation cycle of the heave motion; such that —over 65% to 85% of the oscillation cycle of the heave motion, for each stroke of the foil, the absolute angle of attack is more than 60% of the maximum absolute angle of attack during the stroke.

Abstract: The invention relates to an apparatus for oscillating a foil in a fluid. The apparatus according to the invention comprises a first crank mechanism and a second crank mechanism connected to a foil. Said first crank mechanism and said second crank mechanism have different crank pin offsets, are functionally connected such that when driven the speed of revolution of said first crank mechanism is the same as the speed of revolution of said second crank mechanism, and are out of phase with each other.