第20回 ESCセミナー
Simulation and analysis of strongly stratified turbulent flows
- 日時
- 2006年9月20日 (水) 15:30-16:30
- 場所
- 横浜研究所 地球シミュレータ研究棟1階 大会議室
- 講演者
- Geert Brethouwer (Department of Mechanics, KTH, Stockholm, Sweden)
- 使用言語
- 英語
要旨
Stratified fluids have been investigated in many theoretical, experimental and numerical studies owing to its importance for understanding geophysical flows. It remains a topic of dispute if the dynamics of stratified turbulence at low Froude number (strong stratification) is essential two-dimensional with a inverse cascade of energy or three-dimensional with a forward cascade due to internal gravity waves.
An alternative hypothesis developed recently by Lindborg states that the turbulence is strongly anisotropic three-dimensional turbulence with a forward energy cascade. This hypothesis is based on the scaling analysis of the governing equations of stratified flows by Billant & Chomaz.
In the present study we proceed the scaling analysis of by Billant & Chomaz. The aim of our study is to investigate systematically the influence of the Reynolds and the Froude number on the dynamics of strongly stratified fluids, in particular on turbulence, length scales and instabilities using direct numerical simulations (DNS) and validate our scaling analysis. A series of DNS of homogeneous turbulence with a linear stratification have been carried out with varying Reynolds and Froude numbers.
The simulation results reveal the existence of anisotropic three- dimensional turbulence with a forward cascade of energy and thereby confirms Lindborg's hypothesis, but three-dimensional turbulence is only observed under certain conditions.
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