Analysis of Geometric Parameter Characteristics of Oscillating Hydrofoils with Double Fowler Flaps

In order to improve the energy extraction capability of oscillating hydrofoils, a dual-Fowler-flap structure is adopted as a device to increase lift. According to the motion of the oscillating hydrofoil, the double Fowler flaps retract and swing to increase the chord length and curvature of the entire hydrofoil. This article investigates the geometric parameter characteristics of an oscillating hydrofoil with Fowler flaps. Under the condition of a fixed Reynolds number Re = 2 × 106, the effects of Fowler motion F and slot value S on the overall performance of the hydrofoil are studied. The numerical results show that the Fowler flap structure can increase the camber and chord length of the integral hydrofoil, and the movement of the Fowler flap is combined with the motion of the oscillating hydrofoil to increase the lift coefficient of the hydrofoil, thus increasing the energy collection efficiency of the oscillating hydrofoil—the maximum increase is 50%. By affecting the flow structure and pressure distribution around the trailing edge of the hydrofoil, the Fowler flap helps to generate lift, resulting in a higher power coefficient. U (overlap amount) = 0% is a dividing point, and the S (gap amount) value at this position has the greatest influence on the average power coefficient. The structure of the Fowler flaps maintains the streamlined state of the entire hydrofoil, and when S = 0 and F = 200, the lift and drag fluctuations of the oscillating hydrofoil are minimal. This is very beneficial for the stable operation of the hydrofoil.