Three-dimensional numerical simulation of hummingbird forward flight

We have developed a high-fidelity CFD model to analyze fluid dynamics in fast forward flight of a hummingbird, whose three-dimensional wing kinematics were incorporated into the model by extracting the instantaneous wing position from high-speed videos of the bird flying in a wind tunnel. The advance ratio, or the ratio between the flight speed and the wingtip velocity, is around one, and we are particularly interested in how thrust is generated at this fast speed in addition to lift production. Our simulation result has shown that both downstroke and upstroke produce significant amount of thrust for the bird to overcome body drag. This feature places the hummingbird in an interesting position between slow flying insects and fast flying large birds.