Fluid-structure interaction and vortex identification

Fluid-structure interaction is often associated with 3D large-scale vortical structures in the wake and a near-wake region which is strongly affected by the mean-flow shear. The present paper concentrates on the performance of vortex-identification schemes in the near-wake region of an inclined flat plate. Two widely used methods, the Q-criterion and λ2-criterion, are compared with the triple-decomposition method (TDM) based on the extraction of a local shearing motion near a point. The following conclusion is drawn: to capture the vortical structures in the wake, both the Q-criterion and λ2-criterion cannot-unlike TDM-avoid the bias in showing shearing zones, formed in the close proximity of the plate edges, as vortex regions