翻訳と辞書 Words near each other ・ Bousselange ・ Boussemghoun ・ Boussenac ・ Boussenois ・ Boussens ・ Boussens, Haute-Garonne ・ Boussens, Switzerland ・ Boussera Department ・ Bousseraucourt ・ Bousseviller ・ Boussey ・ Boussicourt ・ Boussie ・ Boussin ・ Boussinesq approximation ・ Boussinesq approximation (buoyancy) ・ Boussinesq approximation (water waves) ・ Boussingault (crater) ・ Boussingaultite ・ Boussières ・ Boussières-en-Cambrésis ・ Boussières-sur-Sambre ・ Bousso ・ Bousso Airport ・ Bousso's holographic bound ・ Boussois ・ Boussoit ・ Boussou Department ・ Boussouar El Maghnaoui ・ Boussougou Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Boussinesq approximation (buoyancy) ： ウィキペディア英語版 Boussinesq approximation (buoyancy) In fluid dynamics, the Boussinesq approximation (, named for Joseph Valentin Boussinesq) is used in the field of buoyancy-driven flow (also known as natural convection). It ignores density differences except where they appear in terms multiplied by ''g'', the acceleration due to gravity. The essence of the Boussinesq approximation is that the difference in inertia is negligible but gravity is sufficiently strong to make the specific weight appreciably different between the two fluids. Sound waves are impossible/neglected when the Boussinesq approximation is used since sound waves move via density variations. Boussinesq flows are common in nature (such as atmospheric fronts, oceanic circulation, katabatic winds), industry (dense gas dispersion, fume cupboard ventilation), and the built environment (natural ventilation, central heating). The approximation is extremely accurate for many such flows, and makes the mathematics and physics simpler. ==The approximation== The Boussinesq approximation is applied to problems where the fluid varies in temperature from one place to another, driving a flow of fluid and heat transfer. The fluid satisfies conservation of mass, conservation of momentum and conservation of energy. In the Boussinesq approximation, variations in fluid properties other than density $\backslash scriptstyle\; \backslash rho$ are ignored, and density only appears when it is multiplied by $\backslash scriptstyle\; g$, the gravitational acceleration. If $\backslash scriptstyle\; \backslash mathbf$ is the local velocity of a parcel of fluid, the continuity equation for conservation of mass is :$\backslash frac\; +\; \backslash nabla\backslash cdot\backslash left(\backslash rho\backslash mathbf\backslash right)\; =\; 0.$〔 If density variations are ignored, this reduces to The general expression for conservation of momentum (the Navier–Stokes equations) is :$\backslash frac\; +\; \backslash mathbf\backslash cdot\backslash nabla\backslash mathbf\; =\; -\backslash frac\backslash nabla\; p\; +\; \backslash nu\backslash nabla^2\; \backslash mathbf\; +\; \backslash frac\backslash mathbf,$ where $\backslash scriptstyle\; \backslash nu$ is the kinematic viscosity and $\backslash scriptstyle\; \backslash mathbf$ is the sum of any body forces such as gravity.〔 In this equation, density variations are assumed to have a fixed part and another part that has a linear dependence on temperature: :$\backslash rho\; =\; \backslash rho\_0\; -\; \backslash alpha\backslash rho\_0\backslash Delta\; T,$ where $\backslash scriptstyle\; \backslash alpha$ is the coefficient of thermal expansion.〔 If $\backslash scriptstyle\backslash mathbf=\backslash rho\backslash mathbf$ is the gravitational body force, the resulting conservation equation is + \mathbf\cdot\nabla\mathbf = -\frac\nabla p + \nu\nabla^2 \mathbf - \mathbf\alpha\Delta T.〔|}} In the equation for heat flow in a temperature gradient , the heat capacity per unit volume, $\backslash scriptstyle\; \backslash rho\; C\_\backslash rho$, is assumed constant. The resulting equation is where $\backslash scriptstyle\; J$ is the rate per unit volume of internal heat production and $\backslash scriptstyle\; \backslash kappa$ is the thermal diffusivity.〔 The three numbered equations are the basic convection equations in the Boussinesq approximation. 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「Boussinesq approximation (buoyancy)」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.