Identification and Characterization of Vortex Stretching Events in Turbulent Channel Flow Using Combined BKM-Q Criterion

The study investigates extreme vorticity events in turbulent channel flow using a combined diagnostic approach based on the Beale–Kato–Majda (BKM) criterion and Q-criterion visu- alization. Direct numerical simulation data from the Johns Hopkins Turbulence Database (𝑅𝑒𝜏 ≈ 1000) is analyzed to identify and characterize near-singular vortex stretching events. Several events are visualized, with two representative cases included in detail. Each exhibiting consistent patterns of vorticity amplification, BKM growth, and spatial alignment of vorticity and Q maxima. The predicted evolution—from initial intensification in strain-dominated re- gions (negative Q) to coherent, rotation-dominated structures—is confirmed through isosurface visualizations. Temporal dynamics range from rapid BKM spikes to gradual alignment over extended durations. Events detected in the near-wall, buffer, and log layers follow expected trends across wall-normal regions, supporting the robustness of the BKM–Q framework for capturing extreme vorticity dynamics and potential finite-time singularities in wall-bounded turbulence.