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Experimental analysis of the log-law at adverse pressure gradient

Knopp, Tobias and Reuther, Nico and Novara, Matteo and Schanz, Daniel and Schülein, Erich and Schröder, Andreas and Kähler, Christian (2021) Experimental analysis of the log-law at adverse pressure gradient. Journal of Fluid Mechanics, 918 (A17), pp. 1-32. Cambidge University Press. doi: 10.1017/jfm.2021.331. ISSN 0022-1120.

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Official URL: https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/experimental-analysis-of-the-log-law-at-adverse-pressure-gradient/7BC65474763BDE7E29D5CE17BF45277D#article

Abstract

The experimental data for the mean velocity are analysed in the inner layer for a turbulent boundary layer at significant adverse pressure gradient and Reynolds numbers up to Re-theta=57000. The aim is to determine the resilience of the log law for the mean velocity, the possible change of the von Karman constant kappa and the appearance of a square-root law above the log law at significant adverse pressure gradients. In the wind-tunnel experiment, the adverse pressure gradient is imposed by an S-shaped deflection of the contour model which is mounted on a wind-tunnel sidewall. A large-scale particle imaging velocimetry method is applied to measure the streamwise evolution of the flow over a streamwise distance of 15 boundary layer thicknesses. In the adverse pressure gradient region, microscopic and three-dimensional Lagrangian particle tracking velocimetry are used to measure the mean velocity and the Reynolds stresses down to the viscous sublayer. Oil-film interferometry is used to determine the wall shear stress. The log law in the mean-velocity profile is found to be a robust feature at adverse pressure gradient, but its region is thinner than its zero pressure gradient counterpart, and its slope is altered. A square-root law emerges above the log law, extending to the wall distance the log law typically occupies at zero pressure gradient. Lower values for kappa are found than for zero pressure gradient turbulent boundary layers, but the reduction is within the uncertainty of the measurement.

Item URL in elib:https://elib.dlr.de/137860/
Document Type:Article
Title:Experimental analysis of the log-law at adverse pressure gradient
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Knopp, Tobiastobias.knopp (at) dlr.dehttps://orcid.org/0000-0002-3161-5353
Reuther, NicoUniversität der Bundeswehr, MünchenUNSPECIFIED
Novara, Matteomatteo.novara (at) dlr.dehttps://orcid.org/0000-0002-8975-0419
Schanz, Danieldaniel.schanz (at) dlr.dehttps://orcid.org/0000-0003-1400-4224
Schülein, ErichErich.Schuelein (at) dlr.dehttps://orcid.org/0000-0002-1125-8504
Schröder, Andreasandreas.schroeder (at) dlr.dehttps://orcid.org/0000-0002-6971-9262
Kähler, ChristianUniversität der Bundeswehr, Münchenhttps://orcid.org/0000-0001-9336-2091
Date:10 July 2021
Journal or Publication Title:Journal of Fluid Mechanics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:918
DOI :10.1017/jfm.2021.331
Page Range:pp. 1-32
Editors:
EditorsEmailEditor's ORCID iD
UNSPECIFIEDCambridge University PressUNSPECIFIED
Publisher:Cambidge University Press
ISSN:0022-1120
Status:Published
Keywords:turbulent boundary layer; adverse pressure gradient; log-law
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Efficient Vehicle
DLR - Research area:Aeronautics
DLR - Program:L EV - Efficient Vehicle
DLR - Research theme (Project):L - Digital Technologies
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > CASE, GO
Institute for Aerodynamics and Flow Technology > High Speed Configurations, GO
Institute for Aerodynamics and Flow Technology > Experimental Methods, GO
Deposited By: Knopp, Dr.rer.nat. Tobias
Deposited On:12 Nov 2021 08:13
Last Modified:24 Nov 2021 18:04

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