English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The correspondence of secondary spanwise structures and pressure gradient isnumerically evaluated for a foil, performing heaving and pitching motion, at arange of phase offsets (90$^\circ$ $\le \phi \le$ 270$^\circ$) and reducedfrequency (0.32 $\le St_c \le$ 0.56). The Reynolds number is $Re =$ 8000. Thewake is shown to be dominated by secondary hairpin-like structures that areformed due to an elliptic instability prompted by the paired primary andsecondary leading edge vortex ($LEV$). The weaker secondary $LEV$ undergoes acore deformation, resulting in streamwise vorticity outflux across the span ofthe foil, and hence, the growth of hairpin-like structures. Evaluating pressuregradients on the surface of the foil reveals a unique fundamental measure toquantitatively characterize the growth of these coherent structures. Theirdominant presence can be directly linked to the growth of the secondary $LEV$formed due to the large-scale interactions under localized adverse pressuregradients. These promote a streamwise flow compression in neighboring regionsof the primary $LEV$. This association also presents a vivid consistency acrossa range of kinematics. Therefore, this correspondence provides a novelprocedure to investigate the mechanisms involved in the formation of secondarystructures in the wake of an oscillating foil.

On the association of secondary hairpin growth and surface pressure gradient for oscillating foils