Three dimensional analysis of the vertical jet in a density stratified fluid

• Project/Area Number: 15K17972
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Fluid engineering
• Research Institution: Kyoto University
• Principal Investigator: Okino Shinya 京都大学, 工学研究科, 助教 (30711808)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Project Status: Completed (Fiscal Year 2017)
• Budget Amount: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2017: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2016: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2015: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
• Keywords: 密度成層 / 高シュミット数 / ジェット / 乱流遷移 / 内部重力波 / 塩分成層流体

Outline of Final Research Achievements

The flow around a sphere descending at a constant speed in a salt-stratified fluid is investigated by the shadowgraph method and the PIV method. The thickness of the axisymmetric jet behind the sphere is estimated by the square root of the Froude number divided by the Reynolds number in accordance with the prediction by a dimensional analysis. We have found that the jet becomes turbulent in a very strongly stratified fluid (at the Froude number less than 0.1) even though the Reynolds number is as small as 50. Our direct numerical simulations have reproduced the non-axisymmetric/axisymmetric vortex shedding at the Froude number larger than 10, which was observed by the previous experiments.

Research Products

• [Journal Article] Velocity distribution around a sphere descending in a linearly stratified fluid (2017)
  • Author(s): Okino Shinya、Akiyama Shinsaku、Hanazaki Hideshi
  • Journal Title: Journal of Fluid Mechanics Volume: 826 Pages: 759-780
  • DOI: 10.1017/jfm.2017.474
  • Peer Reviewed
• [Presentation] Velocity distribution around a sphere descending in a salt-stratified water (2017)
  • Author(s): H. Hanazaki, S. Akiyama & S. Okino
  • Organizer: 70th Annual Meeting of the APS Division of Fluid Dynamics
  • Int'l Joint Research
• [Presentation] 成層流体中を鉛直移動する球まわり流れのラグランジュ的解析 (2017)
  • Author(s): 松本光平, 新井一馬, 沖野真也, 花崎秀史
  • Organizer: 日本流体力学会年会2017
• [Presentation] 塩分成層流体中の乱流と物体まわりの流れ (2016)
  • Author(s): 沖野真也
  • Organizer: 機械学会関西支部流体工学懇話会
  • Place of Presentation: 関西大学（大阪府吹田市）
  • Year and Date: 2016-12-10
  • Invited
• [Presentation] 強い成層下での球の鉛直移動による流れ (2016)
  • Author(s): 秋山真作, 和氣悠将, 沖野真也, 花崎秀史
  • Organizer: 日本流体力学会年会2016
  • Place of Presentation: 名古屋工業大学（愛知県名古屋市）
  • Year and Date: 2016-09-26
• [Presentation] 強成層の流体中を鉛直移動する球まわりの流れ場 (2016)
  • Author(s): 和氣悠将, 秋山真作, 野口真之介, 沖野真也, 花崎秀史
  • Organizer: 第53回日本伝熱シンポジウム
  • Place of Presentation: グランキューブ大阪（大阪府大阪市）
  • Year and Date: 2016-05-24
• [Presentation] 強成層の流体中を鉛直移動する球まわりの流れ場 (2016)
  • Author(s): 和氣悠将, 秋山真作, 野口真之介, 沖野真也, 花崎秀史
  • Organizer: 第53回日本伝熱シンポジウム
  • Place of Presentation: 大阪府大阪市
  • Year and Date: 2016-05-24
• [Presentation] PIV measurements of the flow around a sphere descending in a salt stratified fluid (2015)
  • Author(s): S. Akiyama, Y. Waki, S. Okino and H. Hanazaki
  • Organizer: The 15th Kyoto-Tsinghua-Seoul National University thermal engineering conference
  • Place of Presentation: 京都府京都市
  • Year and Date: 2015-12-12
  • Int'l Joint Research