Study on transition processes of streamwise vortices aimed at an innovative creation for the growth of perturbations in a high Mach number

2021 Fiscal Year Final Research Report

• Project/Area Number: 17K05145
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Computational science
• Research Institution: Osaka Prefecture University
• Principal Investigator: Toshihiko Hiejima 大阪府立大学, 工学(系)研究科(研究院), 講師 (60316007)
• Project Period (FY): 2017-04-01 – 2022-03-31
• Keywords: 高マッハ数 / 縦渦 / 流れの不安定性 / 渦崩壊 / 数値流体力学

Outline of Final Research Achievements

Although streamwise vortices become the nucleus for vortical structures of turbulent transition, transitions of the vortices on high-speed flows have not been so known as those on low-speed flows. Compressibility effects suppress a disturbance growth as the mainstream Mach number increases. The present study demonstrated that the cause is related to the growth of entropy fluctuation. It was also shown that vortex breakdown without a stagnation point is caused by a flow acceleration in supersonic flows. Furthermore, it was found that the effect of helicity on instability succeeds in beating the compressibility effects in a high Mach number.

Free Research Field

流体力学，航空宇宙工学

Academic Significance and Societal Importance of the Research Achievements

本研究で対象とした縦渦遷移機構，つまり，高速流での縦渦の安定化・不安定化がもたらすその層流化・乱流化における知見は，航空宇宙分野における将来の課題である超音速旅客機や宇宙往還機のエンジン性能の向上，超音速での騒音低減および再突入時に生じる空力加熱に対する機体の熱防御に関する問題等への貢献が期待できる基礎となるものである。加えて，このような高マッハ数での縦渦遷移の内部理解は，高速流遷移分野を切り開く流体力学的にも価値が高い研究である。