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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Large eddy simulation ： ウィキペディア英語版 Large eddy simulation Large eddy simulation (LES) is a mathematical model for turbulence used in computational fluid dynamics. It was initially proposed in 1963 by Joseph Smagorinsky to simulate atmospheric air currents, and first explored by Deardorff (1970). LES is currently applied in a wide variety of engineering applications, including combustion, acoustics, and simulations of the atmospheric boundary layer. The simulation of turbulent flows by numerically solving the Navier–Stokes equations requires to resolve an ample range of time- and length-scales. Such a resolution can be achieved with Direct numerical simulation (DNS) but is computationally expensive and currently prohibitive for practical problems. The main idea behind LES is to reduce this computational cost by reducing the range of time- and length-scales that are being solved for via a low-pass filtering of the Navier–Stokes equations. Such a low-pass filtering, which can be viewed as a time- and spatial-averaging, effectively removes small-scale information from the numerical solution. This information is not irrelevant and needs further modeling, a task which is an active area of research for problems in which small-scales can play an important role, problems such as near-wall flows , reacting flows,〔 and multiphase flows. == Filter definition and properties == (詳細はLES filter can be applied to a spatial and temporal field $\backslash phi(\backslash boldsymbol,t)$ and perform a spatial filtering operation, a temporal filtering operation, or both. The filtered field, denoted with a bar, is defined as: :$$ \overline = \displaystyle} \int_^ \phi(\boldsymbol,t^) G(\boldsymbol-\boldsymbol,t - t^) dt^ d \boldsymbol where $G$ is the filter convolution kernel. This can also be written as: :$$ \overline = G \star \phi . The filter kernel $G$ has an associated cutoff length scale $\backslash Delta$ and cutoff time scale $\backslash tau\_$. Scales smaller than these are eliminated from $\backslash overline$. Using the above filter definition, any field $\backslash phi$ may be split up into a filtered and sub-filtered (denoted with a prime) portion, as :$$ \phi = \bar + \phi^ . It is important to note that the large eddy simulation filtering operation does not satisfy the properties of a Reynolds operator. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Large eddy simulation」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.