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楼1970-01-01 08:00:00
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找到一些相关的精华帖子，希望有用哦~
科研从小木虫开始，人人为我，我为人人
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【答案】应助回帖
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5楼2016-03-25 09:08:55
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2楼2011-12-12 22:16:19
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静水四叶草金虫 (小有名气)
小笨蛋精灵
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3楼2011-12-13 09:14:03
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静水四叶草金虫 (小有名气)
小笨蛋精灵
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4楼2011-12-13 10:46:12
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, then molecules at different places in the flow will move with the same convective velocity, and it is only diffusion rate which will differentiate between them. However, now consider a flow in which gradients exist, for example fully developed pipe flow. The fluid at the center of the pipe is moving much faster than the fluid close to the walls. If there is diffusion in the radial direction, then molecules can hop over from one streamline to the next, and thereby will be transported over different distances due to the difference in velocities. This smearing out (or being transported over different distances) caused indirectly by diffusion (in the radial direction) is the physical interpretation of dispersion. Surprisingly, the amount of dispersion reduces with increasing diffusion coefficient. This is because, then, the molecules will just be hopping from one streamline to another constantly and will not get "enough" time to be transported far from each other. The above physical model of dispersion is explained beautifully in the book "Analysis of Transport Phenomena" by William M. Deen. You should have a look, if possible!
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