Effect of microbubbles on the structure of turbulence in a turbulent boundary layer |
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Authors: | Hiroharu Kato Tomoaki Iwashina Masaru Miyanaga Hajime Yamaguchi |
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Affiliation: | (1) Department of Mechanical Engineering, Toyo University, 2100 Kujirai, Kawagoe 350-8585, Japan, JP;(2) Department of Environmental and Ocean Engineering, University of Tokyo, Japan, JP |
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Abstract: | The time-averaged velocity and turbulence intensity distributions were measured by a laser Doppler velocimeter in a turbulent boundary layer filled with microbubbles. The void fraction distribution was also measured using a fiber-optic probe. The velocity decreased in the region below 100 wall units with an increase in bubble density. This led to a decrease in the velocity gradient at the wall, which was consistent with a decrease in shearing stress on the wall. The turbulence intensity in the buffer layer increased at a low microbubble density, and then began to decrease with an increasing microbubble density. Based on the present measurements, the mechanism of turbulence reduction by microbubbles is discussed and a model is proposed. Received for publication on Dec. 3, 1999; accepted on April 18, 2000 |
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Keywords: | : microbubble bubble turbulence drag frictional resistance boundary layer |
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