Three dimensional near-wall events in an adverse pressure gradient boundary layer

Matthew Bross, Christian J. Kähler

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

Time-resolved tomographic flow fieldsmeasured in the viscous sublayer region of a turbulent boundary layer subjected to and adverse pressure gradient (APG) are examined with the aim to resolve and characterize reverse flow events at Reτ = 5000 and 10 000. The fields were measured using a novel high resolution tomographic particle tracking technique. It is shown that this technique is able to fully resolve mean and time dependent features of the complex three-dimensional flow with high accuracy down to very near-wall distances (∼10 μm). From time resolved Lagrangian particle trajectories, statistical information as well as instantaneous topological features of near-wall flow events are deduced. Similar to the zero pressure gradient case (ZPG), it was found that individual events with reverse flow components still occur relatively rarely under the action of the pressure gradient investigated here. However, reverse flow events are shown to appear in relatively organized groupings in both spanwise and streamise directions. Moreover, it was observed that some of the reverse flow events are associated with streamwise vortices that convect along with low-speed streaks. This can be explained by the tilted nature of these vortices with respect to the main flow direction. The reverse flow events associated with tilted streamwise vortices inside low-speed streaks have been observed to spatially extend over 100 viscous units. As different mechanisms can lead to reverse flow events, these events are not universal. However, the results and discussion make it possible to understand the appearance of reverse flow events based on the interaction of well known coherent flow structures.

Original languageEnglish (US)
Title of host publication10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
PublisherInternational Symposium on Turbulence and Shear Flow Phenomena, TSFP10
ISBN (Electronic)9780000000002
StatePublished - 2017
Event10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017 - Chicago, United States
Duration: Jul 6 2017Jul 9 2017

Publication series

Name10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
Volume3

Conference

Conference10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
Country/TerritoryUnited States
CityChicago
Period7/6/177/9/17

All Science Journal Classification (ASJC) codes

  • Atmospheric Science
  • Aerospace Engineering

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