Abstract: Effects of unsteady deformation of a flapping model insect wing on its aerodynamic force production are studied by solving the Navier-Stokes equations on a dynamically deforming grid. Aerodynamic forces on the flapping wing are not much affected by considerable twist, but affected by camber deformation. The effect of combined camber and twist deformation is similar to
that of camber deformation. With a deformation of 6% camber and 20^。 twist (typical values observed for wings of many insects), lift is increased by 10%-20% and lift-to-drag ratio by around 10\% compared with the case of a rigid flat-plate wing. As a result, the deformation can increase the maximum lift
coefficient of an insect, and reduce its power requirement for flight. For example, for a hovering bumblebee with dynamically deforming wings (6\% camber and 20^。 twist), aerodynamic power required is reduced by about 16% compared with the case of rigid wings.

Key words: unsteady aerodynamic force, computational fluid dynamics, insect, wing deformation