Turbulent/non-turbulent interface interacting with nonlinear waves

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K13682
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Nagoya University
• Principal Investigator: Watanabe Tomoaki 名古屋大学, 工学研究科, 助教 (70772292)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Keywords: 乱流 / 乱流・非乱流界面 / 安定密度成層 / 圧縮性流れ / 衝撃波

Outline of Final Research Achievements

Direct numerical simulations (DNS) and experiments of turbulent flows were conducted for investigating turbulent/non-turbulent interfacial (TNTI) layers. A stably stratified fluid can support propagation of internal gravity waves. The wave characteristics within the TNTI layer were revealed with DNS of stably stratified shear layers. In the DNS, long elongated flow structures and hairpin vortices were identified in the stably-stratified shear layers. Interaction between turbulence and shock wave was also studied with DNS and experiments, which confirmed that inhomogeneity of turbulence is one of the important factors of the interaction. Turbulent mixing near the TNTI layer was studied with DNS of turbulent jets and boundary layers, and a model for scalar dissipation rate is proposed for low-cost simulations of turbulent reacting flows. Two-color particle image velocimetry system was developed with pulse-operated laser diodes and a new algorithm for color contamination correction.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

工業機器や環境中で見られる多くの流れにおいて、乱流は空間的に局在しており、外部の非乱流領域と乱流は乱流・非乱流界面層により隔てられている。熱や物質の活発な混合を伴う乱流領域は界面層を介した非乱流流体の取り込みによって成長する。流体中では浮力を復元力とする内部重力波や圧力波が伝播し、乱流の特性に影響を与える。本研究では、こうした波の伝播を伴う乱流における乱流・非乱流界面層の特性を調査することで、界面層の特性から乱流による拡散現象などを明らかにした。また、物質の活発な混合を伴う界面層における分子拡散の数値計算モデルを提案し、乱流による物質拡散の低計算コストな低い数値計算手法に適用した。