Aerodynamics of hovering true hoverflies

The aerodynamic force production of true hoverfly which can hover with an inclined stroke plane (body being approximately horizontal) was investigated, using the method of numerically solving the Navier-Stokes equation. The power requirement was computed using the aerodynamic moment and the inertia of the wing. The aerodynamic force production and power requirement were compared with that of the normal hovering whose stroke plane was horizontal. The main results are as following. The major part of the weight-supporting vertical force is produced in the downstroke and it is contributed by both the lift and the drag of the wing, unlike the normal-hovering case in which the lift principle is mainly used to produce the weight supporting force. The mass specific power is 31.71 W · kg ^-1 that is similar to the normal hovering case. Because of the body being horizontal, immediate forward acceleration and roll maneuvering can be made, but no more power is needed.