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科技小制作吹不开的球儿童科学实验幼儿园小学生益智玩具手工diy

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  • Description
 
 
 
 
 

                                                吹不开的球课程课件

   涡流是一种交替旋转方向的气流漩涡。这种气流漩涡与形成于超流体内部的漩涡结构存在某种关联性。前者只需要普通的温度环境,而后者需要则需要极低的温度。实验室使用液态汞来创造出极低的温度,形成超导态。在这种极端的情况下,电子的流动突然变成毫无阻碍了,称之为超流体。卡门涡流是流体力学中重要的现象,在自然界中常可遇到,在一定条件下的定常来流绕过某些物体时,物体两侧会周期性地脱落出旋转方向相反、排列规则的双列线涡,经过非线性作用后,形成卡门涡流。如水流过桥墩,风吹过高塔、烟囱、电线等都会形成卡门涡街。卡门涡街有一些很重要的应用,因此有必要了解其研究历史及有关的应用情况。

   涡流的破坏:如果涡街的交替脱落频率与物体的声学驻波频率相重合,还会出现共振。工业上的预热器、锅炉等多由圆管组成,流体绕流圆管时,卡门涡街的交替脱落会引起预热器箱中气柱的振动,如果涡街的交替脱落频率与物体的声学驻波频率相重合,就会引发声学共振,使管箱激烈振动,严重时,预热器管箱振鼓错开,甚至破裂。如果改变管箱和气体的固有频率,使之与卡门涡街的脱落频率错开,避免发生共振,则可防止设备的破坏。undefined

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Update time:20240827110901


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