翻訳と辞書 Words near each other ・ Bubo (disambiguation) ・ Bubo Na Tchuto ・ Bubble light ・ Bubble Man ・ Bubble Memories ・ Bubble memory ・ Bubble Nebula (NGC 6822) ・ Bubble nest ・ Bubble O' Bill ・ Bubble oxygenator ・ Bubble pipe ・ Bubble point ・ Bubble Pop! ・ Bubble Puppy ・ Bubble rafts ・ Bubble ring ・ Bubble Safari ・ Bubble sensor ・ Bubble Shooter ・ Bubble sort ・ Bubble Spur ・ Bubble Struggle ・ Bubble Symphony ・ Bubble System ・ Bubble Tape ・ Bubble tea ・ Bubble Trip/Sweet Sweet Song ・ Bubble Trouble ・ Bubble Trouble (1991 video game) ・ Bubble Trouble (1996 video game) 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 Bubble ring ： ウィキペディア英語版 Bubble ring A bubble ring, or toroidal bubble, is an underwater vortex ring where an air bubble occupies the core of the vortex, forming a ring shape. The ring of air as well as the nearby water spins poloidally as it travels through the water, much like a flexible bracelet might spin when it is rolled on to a person's arm. The faster the bubble ring spins, the more stable it becomes. Bubble rings and smoke rings are both examples of vortex rings—the physics of which is still under active study in fluid dynamics. Devices have been invented which generate bubble vortex rings.〔United States Patent: (Simple method for the controlled production of vortex ring bubbles of a gas ) Issued patent: 6824125, 30 November 2004.〕〔United States Patent: (Simple, mechanism-free device, and method to produce vortex ring bubbles in liquids ) Patent number: 7300040. 27 November 2007.〕 ==Physics== As the bubble ring rises a lift force pointing downward that is generated by the vorticity acts on the bubble in order to counteract the buoyancy force. This reduces the bubble's velocity and increases its diameter. The ring becomes thinner, despite the total volume inside the bubble increasing as the external water pressure decreases. Bubble rings fragment into rings of spherical bubbles when the ring becomes thinner than a few millimetres. This is due to Plateau-Rayleigh instability. When the bubble reaches a certain thickness, surface tension effects distort the bubble's surface pulling it apart into separate bubbles. Circulation of the fluid around the bubble helps to stabilize the bubble for a longer duration, counteracting the effects of Plateau-Rayleigh instability. Below is the equation for Plateau-Rayleigh instability with circulation as a stabilizing term: ::$\backslash omega^2=\; \backslash left\; (\; \backslash frac\; \backslash right\; )\; \backslash left\; ((1-k^2\; a^2)\; \backslash frac\; -\; \backslash frac\; \backslash right)$ where ω is the growth rate, k is the wave number, a is the radius of the bubble cylinder, T is the surface tension, Γ is the circulation, and K0 and K1 are Bessel functions. When ω is positive the bubble is stable due to circulation and when ω is negative, surface tension effects destabilize it and break it up. Circulation also has an effect on the velocity and radial expansion of the bubble. Circulation increases the velocity while reducing the rate of radial expansion. Radial expansion however is what diffuses energy by stretching the vortex. Instability happens more quickly in turbulent water, but in calm water divers can achieve an external diameter of a metre or more before the bubble fragments. 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「Bubble ring」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.