Three measuring techniques for assessing the mean wall skin friction in wall-bounded flows

Funding Number

20 F 0301

Funding Sponsor

Bundesministerium für Wirtschaft und Technologie

Author's Department

Mechanical Engineering Department

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https://doi.org/10.1134/S086986431402005X

Document Type

Research Article

Publication Title

Thermophysics and Aeromechanics

Publication Date

1-1-2014

doi

10.1134/S086986431402005X

Abstract

The present paper aims at evaluating the mean wall skin friction data in laminar and turbulent boundary layer flows obtained from two optical and one thermal measuring techniques, namely, laser-Doppler anemometry (LDA), oil-film interferometry (OFI), and surface hot-film anemometry (SHFA), respectively. A comparison among the three techniques is presented, indicating close agreement in the mean wall skin friction data obtained, directly, from both the OFI and the LDA near-wall mean velocity profiles. On the other hand, the SHFA, markedly, over estimates the mean wall skin friction by 3.5-11.7% when compared with both the LDA and the OFI data, depending on the thermal conductivity of the substrate and glue material, probe calibration, probe contamination, temperature drift and Reynolds number. Satisfactory agreement, however, is observed among all three measuring techniques at higher Reynolds numbers, Rex>106, and within ±5% with empirical relations extracted from the literature. In addition, accurate velocity data within the inertial sublayer obtained using the LDA supports the applicability of the Clauser method to evaluate the wall skin friction when appropriate values for the constants of the logarithmic line are utilized. © 2014 Pleiades Publishing, Ltd.

First Page

179

Last Page

190

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