2022 Fiscal Year Final Research Report

A Study on Turbulent Frictional Resistance Reduction Method by Suppressing Turbulent Fluctuation Using Acoustic Streaming Radiation

Research Project

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Project/Area Number	20H02379
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 24020:Marine engineering-related
Research Institution	National Institute of Maritime, Port and Aviation Technology
Principal Investigator	Kawashima Hideki 国立研究開発法人海上・港湾・航空技術研究所, その他部局等, 研究員 (20450679)
Co-Investigator(Kenkyū-buntansha)	辻義之名古屋大学, 工学研究科, 教授 (00252255)
Project Period (FY)	2020-04-01 – 2023-03-31
Keywords	音響流 / 流場制御 / 抵抗低減 / 電極型剪断力計 / 剪断力計測
Outline of Final Research Achievements	The piezoelectric material is BGO, which has a surface wave sound velocity similar to that of water, and a unidirectional type circuit is used to develop an acoustic flow radiation type flow field control device that can radiate acoustic flow in one direction at an angle of about 30 degrees from the wall surface. The V-shaped electrode type shear force meter was developed to evaluate not only the absolute value of shear force but also the direction of shear force by forming a rectangular electrode and arranging it in a V-shape. By combining these devices, flow field control experiments were conducted in a channel flow. V-shaped electrode shear force gauges were installed on the upstream and downstream sides of the acoustic flow control device to measure the shear force during flow field control. In some cases, the shear force decreased both upstream and downstream of the acoustic flow control device, confirming that the flow field control can reduce drag.
Free Research Field	流体力学
Academic Significance and Societal Importance of the Research Achievements	開発した音響流型流場制御デバイスは、壁面に対して30°以下の放射角の音響流をほぼ一方向に放射可能で、流速を入力電圧で制御可能な、流場制御に適した特性を持っている。現在、水中において可動部分無しで壁面から直接流体を制御できるデバイスは実用化されていないため、極めて独自性の高い有用な装置である。また開発したV字型電極剪断力計は、壁面上の剪断力の絶対量だけでなく方向も瞬時値として計測することができる画期的な装置である。さらに両者を組み合わせたシステム試験により、チャンネル流れにおいて抵抗低減を示す結果が得られ、水中での乱流摩擦抵抗低減実現の道筋を開くことができた。