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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 Burgers vortex ： ウィキペディア英語版 Burgers vortex In fluid dynamics, the Burgers vortex is an exact solution to the Navier–Stokes equations governing viscous flow. The Burgers vortex describes a stationary, self-similar flow. An inward, radial flow, tends to concentrate vorticity in a narrow column around the symmetry axis. On the same time, viscous diffusion tends to spread the vorticity. The stationary Burgers vortex arises when the two effects balance. The Burgers vortex, apart from serving as an illustration of the vortex stretching mechanism, may describe such flows as tornados, where the vorticity is provided by continuous convection-driven vortex stretching. == Flow field == The flow for the Burgers vortex is described in cylindrical $(r,z,\backslash phi)$ coordinates. Assuming axial symmetry (no $\backslash phi$-dependence), the vorticity equation is solved by the flow field: :$v\_r=-\backslash frac12\; \backslash alpha\; r,$ :$v\_z=\backslash alpha\; z,$ :$v\_\backslash phi=v\_\backslash phi(r),$ where $\backslash alpha>0$ is a constant. The flow satisfies the continuity equation by the two first of the above equations. The vorticity equation only gives a non-trivial component in the $z$-direction, where it becomes :$\backslash frac=\backslash zeta\backslash frac+\backslash nu\backslash nabla^2\backslash zeta,$ where $D/Dt$ denotes the convective derivative and $\backslash nu$ the viscosity. Note that the first term on the right-hand side is the vortex stretching term which tends to ''amplify'' the vorticity, while the second term, due to viscosity, attenuates (or rather spreads) vorticity. The solution can be found as :$\backslash zeta=\backslash zeta\_0\; \backslash exp(-\backslash frac),$ where $\backslash zeta\_0$ is a constant. The vorticity is thus distributed as a Gaussian of width :$R=2\backslash sqrt\}.$ 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「Burgers vortex」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.