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Evaluation of Skin Friction Drag Reduction in the Turbulent Boundary Layer Using Riblets

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Research and Development Directorate, Japan Aerospace Exploration Agency, Kakuda, Miyagi 981-1525, Japan
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Aeronautical Technology Directorate, Japan Aerospace Exploration Agency, Chofu, Tokyo 182-8522, Japan
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Author to whom correspondence should be addressed.
This paper is an extended version of paper published in 56th Aerospace Sciences Meeting (AIAA SciTech 2018), Kissimmee, FL, Florida, USA, 8–12 January 2018. Paper No.: AIAA-2018-0839.
Appl. Sci. 2019, 9(23), 5199; https://doi.org/10.3390/app9235199
Received: 10 October 2019 / Revised: 27 November 2019 / Accepted: 27 November 2019 / Published: 29 November 2019
(This article belongs to the Section Mechanical Engineering)
A unique approach to evaluate the reduction of skin friction drag by riblets was applied to boundary layer profiles measured in wind tunnel experiments. The proposed approach emphasized the turbulent scales based on hot-wire anemometry data obtained at a sampling frequency of 20 kHz in the turbulent boundary layer to evaluate the skin friction drag reduction. Three-dimensional riblet surfaces were fabricated using aviation paint and were applied to a flat-plate model surface. The turbulent statistics, such as the turbulent scales and intensities, in the boundary layer were identified based on the freestream velocity data obtained from the hot-wire anemometry. Those turbulent statistics obtained for the riblet surface were compared to those obtained for a smooth flat plate without riblets. Results indicated that the riblet surface increased the integral scales and decreased the turbulence intensity, which indicated that the turbulent structure became favorable for reducing skin friction drag. The proposed method showed that the current three-dimensional riblet surface reduced skin friction drag by about 2.8% at a chord length of 67% downstream of the model’s leading edge and at a freestream velocity of 41.7 m/s (Mach 0.12). This result is consistent with that obtained by the momentum integration method based on the pitot-rake measurement, which provided a reference dataset of the boundary layer profile. View Full-Text
Keywords: riblet; turbulent boundary layer; hot-wire anemometry; skin friction drag; statistical evaluation riblet; turbulent boundary layer; hot-wire anemometry; skin friction drag; statistical evaluation
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Takahashi, H.; Iijima, H.; Kurita, M.; Koga, S. Evaluation of Skin Friction Drag Reduction in the Turbulent Boundary Layer Using Riblets. Appl. Sci. 2019, 9, 5199.

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