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/

Zendy Plus

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

Zendy Tools

Zendy Open

This paper serves as a review of our recent new DNS study on physics of lateboundary layer transition. This includes mechanism of the large coherent vortexstructure formation, small length scale generation and flow randomization. Thewidely spread concept vortex breakdown to turbulence,which was considered asthe last stage of flow transition, is not observed and is found theoreticallyincorrect. The classical theory on boundary layer transition is challenged andwe proposed a new theory with five steps, i.e. receptivity, linear instability,large vortex formation, small length scale generation, loss of symmetry andrandomization to turbulence. We have also proposed a new theory aboutturbulence generation. The new theory shows that all small length scales(turbulence) are generated by shear layer instability which is produced bylarge vortex structure with multiple level vortex rings, multiple level sweepsand ejections, and multiple level negative and positive spikes near the laminarsub-layers.Therefore, turbulence is not generated by vortex breakdown butrather positive and negative spikes and consequent high shear layers. Shearlayer instability is considered as the mother of turbulence. This new theorymay give a universal mechanism for turbulence generation and sustenance whichshows that the energy is brought by large vortex structure through multiplelevel sweeps.

DNS Study on Physics of Late Boundary Layer Transition