Flows in a two-dimensional model of the Weis-Fogh mechanism.

Flow patterns in a two-dimensional model of the Weis-Fogh mechanism are investigated by the discrete vortex method and a flow-visualization technique using tracers of aluminum particles. Two cases of the wing motion, that is, the opening and the closing cases are studied and the results of the two methods agree well with each other. In the opening case, the flow separates at the leading edge and forms a large separation bubble, and then reattaches on the wing. When the wing transrates, the separation bubble moves with the wing. In the closing case, a jet is produced between the two wings and a separation bubble near the trailing edge moves downstream. A jetlike region of a high speed flow is also detected on the backside of the wing.