Computational Science for understanding the vortical structure and vortex dynamics in high Reynolds-number turbulence

2014 Fiscal Year Final Research Report

• Project/Area Number: 23560194
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Fluid engineering
• Research Institution: Nagoya University
• Principal Investigator: ISHIHARA Takashi 名古屋大学, 工学(系)研究科(研究院), 准教授 (10262495)
• Co-Investigator(Kenkyū-buntansha): YOSHIMATU Katsunori 名古屋大学, エコトピア科学研究所, 准教授 (70377802) ; OKAMOTO Naoya 名古屋大学, 大学院工学研究科, 助教 (80547414)
• Project Period (FY): 2011-04-28 – 2015-03-31
• Keywords: 高レイノルズ数乱流 / 剪断層 / 間欠性 / 直接数値計算

Outline of Final Research Achievements

Using direct numerical simulation(DNS) of turbulence in a periodic box with a maximum of 4096^3 grid points and Taylor micro-scale Reynolds numbers Rλ up to 1131, it is shown that there is a transition in the forms of the significant vortical structures, from isolated vortices (when Rλ is less than 100) to complex thin-shear layers (when Rλ exceeds about 1000). Within the significant layers, strong vortices are generated with micro-scale thickness 10η (η is the Kolmogorov micro scale). The interfaces of the layers act partly as a barrier to the fluctuations outside the layer.
We also performed the DNS of turbulent boundary layers (TBL) along a flat plate to study the properties of turbulent/non-turbulent (T/NT) interface of the TBL. Analysis of the conditional statistics near the interface shows that conditional cross correlations of the streamwise or the wall-normal velocity change sharply across the interface. This is consistent with the blocking mechanism of the interface.

Free Research Field

流体物理学