Effects of Gust on Aerodynamic Power Consumption of Flapping Wings

Flapping-Wing Micro Air Vehicles (FWMAVs) may encounter different kinds of airflows in nature, with the action of which the aerodynamic forces as well as power consumption will be affected. Previous studies mainly focused on the effects of gust on flight behavior and aerodynamic forces of flapping wing while less on aerodynamic power. Motivated by this, we numerically study the effects of gust in different directions on the aerodynamic power requirement of flapping wings. In case of frontal gust, the aerodynamic power increases and decreases when wing flaps against and along the gust. The period-average aerodynamic power changes simultaneously with the gust velocity. However, aerodynamic power averaged in the entire gust period increases by 3% at most, almost equal to that without gust. In lateral gust, the aerodynamic power has similar changes between upstroke and downstroke. The average aerodynamic power in root-to-tip gust (tip-to-root gust) increases by 14% (decreases by 5%) at most compared to that without gust. The aerodynamic power decreases by 16% at most, linearly with the downward gust but differently, it increases by 3% at most, non-linearly with the upward gust. Besides, whatever wing gust direction, the gust has approximately same effects on the average aerodynamic power as the steady wind who has the same mean velocity as the gust. The average aerodynamic power of flapping wing is affected most in the vertical gust, but the instantaneous power all varies much in the three kinds of gusts. As instantaneous power significantly influences the performance of motor, power changes in gust should be considered in the motor design, especially for FWMAVs.