Abstract:
The numerical investigation based on the effect of trapezoidal pitching motion along with
chordwise deformation on the energy extraction performance of semi active flapping
hydrofoil is performed. The effect of flexibility along the chord for semi active flapping
based on non – sinusoidal motion is not explored until now. Therefore, the incompressible
Navier – Stokes equation are solved using finite volume approach. The explicit Runge –
Kutta method are modelled for estimation of displacement, velocity and acceleration of
hydrofoil. Firstly, the optimal parameters are identified based on the pitching amplitude θ0
= 75o and flapping frequency f* = 0.16 due to sinusoidal motion. Then the effect on power
extraction and efficiency due to non – sinusoidal motion (β) with variation in flapping
frequency (f*), pitching amplitude (θ0), and flexure affect (α) along the chord are performed
and compared with optimum efficiency achieved due to sinusoidal motion along with
respective rigid hydrofoil. The power extraction and efficiency based on the transformation
of pitching motion towards non – sinusoidal till β = 1.5 with flexible hydrofoil is greater
than the optimum efficiency based on rigid hydrofoil at non – optimal parameters (θ0 = 65o
and f* = 0.14). However, the performance of hydrofoil due to chordwise flexure (α) and
non – sinusoidal motion (β) at optimum amplitude (θ0 = 75o) remains lower than the
optimum efficiency except at β = 1.25 and α = 20%, where same as optimum efficiency is
achieved. Therefore, it is suggested that flexible hydrofoil with non – sinusoidal motion is
effectively contributing at non – optimal parameters θ0 = 65o with 43.17% rise in efficiency
w.r.t rigid hydrofoil.
