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【求助】密度负值的原因

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发表于 2011-3-9 16:10:01 | 显示全部楼层 |阅读模式

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如题,计算宏观量时出现密度为负值,一般是什么原因引起的?谢谢!
发表于 2011-3-9 20:43:56 | 显示全部楼层
LBM适用的若干条件有一条或者多条不满足,边界条件处理失当等
发表于 2011-3-9 22:40:17 | 显示全部楼层
If Mach number is too large, or the "tau" is too close to 0.5, density can be
negative.
发表于 2011-3-10 01:06:24 | 显示全部楼层
We are all honored to draw instructions from you, Prof. Luo.
 楼主| 发表于 2011-3-10 11:13:34 | 显示全部楼层
Thank you very much,  onesupeng and Prof. Luo.
The negative density appeared when I implemented the  immersed moving boundary method. In short, the result was good when the obstacle was motionless, while moving would cause negative density. The Ma=0.09333 and tau=0.502 are suitable since the former(motionless)  ran correctly.  Did it relate to a question of boundary conditons? Or ...?
Thanks in advance!
发表于 2011-3-10 11:23:04 | 显示全部楼层
If you use LBGK model, this is not surprising. You can slow the obstacle and/or increase tau to about 1.0, and you will see the results improve.
 楼主| 发表于 2011-3-10 12:09:25 | 显示全部楼层
Thank you very much for your kind help, Prof. Luo
发表于 2011-3-10 15:19:58 | 显示全部楼层
got it
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