The Proceedings of the Fluids engineering conference
Online ISSN : 2424-2896
2018
Session ID : OS3-5
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Comparison of void fraction change and local shear stress fluctuation in channel flow
*Hayato NAKAMURASatoshi OGAMIYoshihiko OISHIHideki KAWAIYuichi MURAI
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Abstract

We have succeeded in grasping changes in shear stress by using a Laser Doppler Shear Stress Sensor to directly measure the time fluctuation of shear stress in turbulent flow. A decrease in stress is confirmed in the two-phase flow. However, it has not been investigated what kind of bubbles will affect the stress. In this research, we investigated the influence of bubbles on wall shear stress by measuring shear stress using direct measurement method of bubble flow and visualizing bubbles covering sensor surface. At the void fraction α=1.0, it was found that the shear stress did not decrease but rather increased at 5 m/sec, 7 m/sec. It was found that to reduce the shear stress, it is necessary to cover the area of more than 5% with bubbles in the local area.

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© 2018 The Japan Society of Mechanical Engineers
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