Abstract
We experimentally investigate unsteady aerodynamic mechanisms of insect flapping wings. Measurements of unsteady aerodynamic forces and flow visualization around the flapping wing using PIV are conducted with dynamically scaled mechanical models in a water tunnel, which simulates hovering and forward flapping flights. We experimentally clarify the effects of three unsteady aerodynamics on the aerodynamic characteristics of a flapping wing: delayed stall, rotational circulation, and wake capture. The contribution of delayed stall to the total lift accounts for about 90%. The feathering rotation during the flapping translation contributes to an increase of power rather than lift. The wake capture is dependent on the reduced frequency and the timing of feathering rotation. In addition, we investigate the flow interaction between fore- and hindwings like a dragonfly. The phase difference between the fore- and hindwings are effective on the aerodynamic characteristics of the tandem wings.
