Pressure gradient effects on the distribution of velocity fluctuations in turbulent boundary layers

ORAL

Abstract

This research investigates the wall-normal distribution of the streamwise and wall-normal velocity fluctuations in turbulent boundary layers with zero pressure gradient (ZPG) and a strong adverse pressure gradient (APG). High-spatial-resolution (HSR) two-component – two- dimensional (2C-2D) particle image velocity (PIV) measurements of the strong APG-TBL at Reδ2 = 9, 650 and β = 30, are compared with the 2C-2D PIV measurements of the ZPG-TBL at Reδ2 = 7,750 (where Reδ2 is the momentum-thickness based Reynolds number and β is the Clauser’s pressure gradient parameter). The streamwise velocity fluctuations are skewed towards the larger values and the wall-normal velocity fluctuations towards the smaller values whereas this trend is reversed in the wake region. The extent of asymmetry in the near-wall and wake regions increases with an increase in the imposed APG. The locations of the zero skewness and the minimum flatness of the streamwise velocity fluctuations collapse with the location of the maximum Reynolds streamwise stress in both boundary layers, irrespective of the imposed pressure gradient. The same is observed for the wall-normal velocity fluctuations too.

*The authors would like to acknowledge the support of the Australian Government for this research through an Australian Research Council Discovery grant. Callum Atkinson was supported by an ARC Discovery Early Career Researcher Award (DECRA) fellowship. Muhammad Shehzad acknowledges PhD scholarship from the Punjab Educational Endowment Fund (PEEF), Punjab, Pakistan. Bihai Sun gratefully acknowledges the support through an Australian Government Research Training Program (RTP) Scholarship. The research also benefited from computational resources provided by the NCI Facility supported by the Australian Government with access provided via the NCMAS grant, the partner share of the NCI facility provided by Monash University through an ARC LIEF grant and the access to MASSIVE.

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Presenters

  • Muhammad Shehzad

    • Monash University

Authors

  • Muhammad Shehzad

    • Monash University

  • Bihai Sun

    • Laboratory for Turbulence Research in Aerospace \& Combustion (LTRAC), Department of Mechanical and Aerospace Engineering, Monash University, Clayton, 3800, Victoria, Australi

  • Callum Atkinson

    • Laboratory for Turbulence Research in Aerospace \& Combustion (LTRAC), Department of Mechanical and Aerospace Engineering, Monash University, Clayton, 3800, Victoria, Australi

  • Julio Soria

    • Laboratory for Turbulence Research in Aerospace \& Combustion (LTRAC), Department of Mechanical and Aerospace Engineering, Monash University, Clayton, 3800, Victoria, Australi