Effect of Stroke Deviation on Forward Flapping Flight

The performance of a rigid, thin surface flat-plate flapping wing in forward flight, at Re = 10,000 using different stroke deviation trajectories, has been investigated to assess the different capabilities that such kinematics might offer. The instantaneous lift and thrust profiles were observed to be influenced by a combination of the leading-edge vortex and the trailing-edge vortex structures existing in the flow at any given time. Unlike regular no-deviation flapping cycles, the trailing-edge vortex is shown to be significant for out-of-plane trajectories. Both clockwise and anticlockwise variations for trajectory choice are analyzed for their efficacy as an improved kinematic choice over a no-deviation base case. The power requirements for the different cases, based on the fluid torques, are used as an index of the cost of performance across all cases. The anticlockwise eight-cycle deviation is shown to be very complex with high power costs albeit having better performance. The clockwise 0 cycle holds promise with being used as a viable stroke deviation trajectory for forward flight over the base case.