Analyzing a turbulent pipe flow via the one-point structure tensors: Vorticity crawlers and streak shadows

• Published in: Computers & fluids 2016-11, Vol.140, p.450-477
• Main Authors: Stylianou, F.S., Pecnik, R., Kassinos, S.C.
• Format: Article
• Language: English
• Subjects: Active structure; Computational fluid dynamics; Computer simulation; Diagnostic systems; Direct numerical simulation; DNS; Ejection; Energy; Fluid flow; High speed; Inactive structure; Kinetic energy; Kinetics; Mathematical analysis; Mathematical models; Mathematical morphology; Pipe flow; Pipes; Proximity; Reynolds number; Shadows; Stream vector; Structure tensors; Tensors; Turbulence; Turbulence structure; Turbulent flow; Turbulent pipe flow; Vorticity
• ISSN: 0045-7930; 1879-0747; 1879-0747
• DOI: 10.1016/j.compfluid.2016.10.010

•Direct Numerical Simulation of fully developed turbulent pipe flow has been performed at bulk Re=5300.•Direct Numerical Simulation is used to study turbulent structures in the extreme wall vicinity.•We introduce a new structure identification technique, based on the instantaneous values of the structure tensors.•The new eduction method allows the identification of inactive structures.•We report vorticity crawlers & streak shadows, large-scale structures with low energy content. Efforts to identify and visualize near-wall structures typically focus on the region y+≳5, where large-scale structures with significant turbulent kinetic energy content reside, such as the high-speed and low-speed streaks associated with sweep and ejection events. While it is true that the level of the turbulent kinetic energy drops to zero as one approaches the wall, the organization of near-wall turbulence does not end at y+≈5. Large-scale structures with significant streamwise extent and spatial organization exist even in the immediate proximity of the wall y+