NEGATIVE STREAMWISE SKIN-FRICTION IN NEAR-WALL TURBULENCE etc15 Tracking Number 204Presentation: Session: Wall-bounded flows 6 Room: Room B Session start: 10:30 Fri 28 Aug 2015 Christoph Bruecker bruecker@imfd.tu-freiberg.de Affifliation: Institute of Mechanics and Fluid Dynamics, TU Freiberg, Germany Topics: - Wall bounded flows Abstract: The recent discovery of rare backflow events in turbulent boundary layer flows based on the analysis of DNS data has raised again the need of experimental visualizations of wall-shear stress (WSS) fields in such unsteady flows. Of importance is the localization of critical points which are thought to strongly correlate with large-scale events in the log-layer. Up to now there is no experimental prove of these rare events and their topological patterns in the skin-friction field. Their existence in a turbulent boundary-layer flow is shown herein by means of imaging with 2D arrays of flexible micropillars attached at the wall. |