Effect of the centrifugal force on laminar-turbulent transition on a rotating cone

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20406
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0301:Mechanics of materials, production engineering, design engineering, fluid engineering, thermal engineering, mechanical dynamics, robotics, aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: Shinshu University
• Principal Investigator: Kato Kentaro 信州大学, 学術研究院工学系, 助教 (40967163)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: 三次元境界層 / 乱流遷移 / 流れの不安定性 / 光学計測 / 流れの可視化 / 渦

Outline of Final Research Achievements

Laminar-turbulent transition in the boundary layer on a rotating cone in axial flow is investigated through flow visualization and evaluation of Goertler-number scaling, which is known as a measure representing the centrifugal force. The visualizations show that flow structures develop along the generating line, collapse and lead to transition. In the axial flow, the transition location is determined by Reynolds number based on the local wall velocity and radius that depends on the axial velocity normalized by the rotational rate and kinematic viscosity. In still fluid, however, transition Reynolds number on the cone rotating is not determined uniquely. On the other hand, Goertler number dominates transition for a wide range of axial flow and half-cone angle, assuming the laminar similarity solution. This indicates that the centrifugal effects play an important role in the boundary-layer transition on rotating cones.

Free Research Field

流体力学

Academic Significance and Societal Importance of the Research Achievements

本研究は，流体機械，輸送機械上に発達する三次元的な境界層流れの単純化されたモデルとして回転する円錐上の乱流遷移を可視化実験により観察し，これまで知られていなかった乱流遷移へ影響を与える因子を明らかにした．また，これまでの遷移研究で一般的に用いられてきたレイノルズ数に加えて，遠心力に注目したゲルトラー数で流れを評価することの有用性を示した．