Year: 2025
Type: article
Abstract: We analyse the small-scale characteristics, such as enstrophy, total strain and normality/non-normality, in the three-dimensional, separated flow around a NACA 0018 wing using direct numerical simulations. The angle of attack is $10^\circ$ and the Reynolds number (based on the chord length) is $Re_c=5000$ . The role of non-normality is investigated by performing Schur decomposition of the velocity gradient tensor. We also apply the Schur decomposition to derive new expressions for the production of enstrophy and total strain arising from the mean flow inhomogeneity. We focus on two sections of the flow, across the recirculating zone and along the transitioning shear layer, and compare our results with homogeneous isotropic turbulence (HIT). Within the recirculating region, the non-normality index is approximately 0 (and close to the HIT value), indicating almost equal normal and non-normal contributions. However, in the separating layer non-normal effects strongly dominate, especially in the region of kinetic energy growth. Only in the decay region do the values of the non-normality index gradually approximate HIT values. The production of enstrophy due to vortex stretching is dominated by the mixed (interaction) term, where normal strain stretches non-normal vorticity. The same component also dominates the strain self-amplification term. The contributions of different QR regions to the production terms are also examined. Production due to mean strain rate is triggered upstream compared with production due to fluctuating strain fields.
Source: Journal of Fluid Mechanics
DOI: 10.1017/jfm.2025.309
Institution: Imperial College London
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,550
Awards: UK Turbulence Consortium, The Materials and Molecular Modelling Hub, Inverting turbulence: flow patterns and parameters from sparse data, G417250887, G4292927314, G4310967859, Contrails from SAF and H2 combustion; from lab experiments to global mitigation policy, The shadow of turbulence: algorithms and applications, Tier 2 Hub in Materials and Molecular Modelling, Introducing heterogeneous HPC solutions to UK's MMM community, G8997374688, G90098195
OpenAlex ID: W4410240412