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ID 117153
Title Alternative
Relaminarization of accelerated turbulent boundary layer under favorable pressure gradient with sink flow type (Coherent structure and two-point statistics)
Author
Nakamura, Ikuo Nagoya University
Nakata, Masaki Tokushima University
Keywords
Relaminarization
Reverse transition
Boundary layer
Turbulence
Sink flow
Coherent structure
Space correlation
Content Type
Journal Article
Description
The relaminarization process of a turbulent boundary layer under a sink flow was investigated experimentally. The boundary layer was accelerated because of the contraction of the flow area. The mean and fluctuating velocity components were measured using a hot-wire anemometer. With relaminarization, the fluctuating velocity, which was normalized by the free-stream velocity, decreased. The degree of decrease differed between the streamwise and wall-normal components, depending on the distance from the wall. The conditional probabilities that two hot-wire probes separated in the spanwise direction simultaneously observed turbulent and nonturbulent flows were obtained. A spanwise-wide turbulent region was spread near the wall, but its width decreased as the distance from the wall increased. When the layer was relaminarized, this decrease in the spanwise width started near the wall. The low-speed streak spacing of the coherent structure was obtained from the lateral correlation coefficient of the streamwise fluctuating velocity and average spanwise spectra, and both parameters were somewhat consistent. Both the spanwise spacing of the streaks and the vertical scale of the coherent structure increased because of relaminarization. The conditional lateral correlation coefficient of the streamwise fluctuating velocity based on turbulence or nonturbulence was calculated. The streak spacing was slightly wider under nonturbulent conditions. This trend is consistent with the spreading behavior of the streak spacing, owing to relaminarization. With relaminarization, coherent structures became less frequent.
Journal Title
Transactions of the JSME (in Japanese)
ISSN
21879761
Publisher
日本機械学会
Volume
88
Issue
909
Start Page
22-00010
Published Date
2022-05-25
Rights
この記事はクリエイティブ・コモンズ[表示-非営利-改変禁止4.0国際]ライセンスの下に提供されています。(https://creativecommons.org/licenses/by-nc-nd/4.0/deed.ja)
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language
jpn
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departments
Science and Technology