Turbulent hotspots in channel flows
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The present study discusses the near-wall vortical structures with extreme TKE dissipation rate events within a channel configuration across various Reynolds numbers. Statistical evidence confirms the presence of quasi-streamwise (QS) vortices near regions with extreme TKE dissipation rates, consistent with earlier experimental studies. The temporal behavior of QS vortices during extreme TKE dissipation events is investigated using the Connected Component Labeling and a temporal tracking algorithm based on the velocity of labeled regions. The lifecycle of QS vortices, including the stages of coupled counter-rotating streamwise vortices, tilting, and dissipation, are analyzed. A roll-up phenomenon is observed at the tail of QS vortices when the TKE dissipation rate peaks during the temporal evolution.
