Dragonflies are one of the most manueverable of the insect flyers. They are capable of sustained gliding flight as well as hovering, and are able to change direction very rapidly. Exactly how they use their wings to generate aerodynamic forces remains unknown.; A new method was developed for solving 2D incompressible viscous flow problems [46] in order to numerically model the fluid response and forces generated by multiple flapping wings. This finite difference scheme uses the streamfunction-vorticity formulation on a regular grid, and handles multiple moving irregular boundaries.; To test the usefulness of this model, dragonflies were tethered to a vertical force sensor and filmed using high-speed digital video. This allowed the correlation of specific wing kinematics to the vertical force generated, so that when these kinematics are modeled numerically the forces calculated can be compared with experiment.; The results include detailed descriptions of two distinct wing kinematic patterns, out of four observed. These kinematics resemble motions described by previous researchers in free flight conditions except for the phase between the fore and hind wings. The forces calculated from applying the numeric method to a 2D approximation of these movements compare well to measured forces. The differences seen can be attributed to 3D effects and to the simplified wing cross-section used in the model.; We show that wing inertia is a large component of the instantaneous forces experienced by a dragonfly, and that the dragonfly generates productive force during both the downstroke and the upstroke. The counter-stroking behavior seen in free flight is shown to require less power than the in-phase motion observed in the tethered dragonfly, while producing the same average vertical force. We also show evidence suggesting that during hovering flight wing rotation is passively driven by fluid forces, while during forward flight rotation at the end of the downstroke is actively driven by the dragonfly. Finally, the effectiveness of applying such a 2D model to the problem is examined, and suggestions are made for future research to improve modeling ability.
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