A vorticity stretching diagnostic for turbulent flows
2011 (English)In: Proc. 7th International Symposium on Turbulence and Shear Flow Phenomena, 2011Conference paper (Refereed)
Vorticity stretching in wall-bounded turbulent and transitionalflows has been investigated by means of a new diagnostic,designed to pick up regions with large amounts of vorticitystretching. It was found that the largest occurrence ofvorticity stretching in fully turbulent channel flows is presentat a wall-normal distance of y+ = 6.5, i.e. in the transitionbetween the viscous sublayer and the buffer region. Instantaneousdata showed that the coherent structures associated withthese stretching events have the shape of flat ‘pancake structures’in the vicinity of high-speed streaks, here denoted ‘htype’events. The other event found, also studied in an asymptoticsuction boundary layer, is the ‘l-type’ event present ontop of an unstable low-speed streak. These events are furtherthought to be associated with the exponential growth ofstreamwise vorticity in the turbulent near-wall cycle.
Place, publisher, year, edition, pages
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-86827OAI: oai:DiVA.org:kth-86827DiVA: diva2:501054
7th International Symposium on Turbulence and Shear Flow Phenomena. 28-31 July 2011. Ottawa, Canada
QC 201203302012-02-132012-02-132012-03-30Bibliographically approved