【求助】密度负值的原因

pakchoi1987

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！

onesupeng

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

luo@odu.edu

If Mach number is too large, or the "tau" is too close to 0.5, density can be
negative.

onesupeng

We are all honored to draw instructions from you, Prof. Luo.

pakchoi1987

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!

luo@odu.edu

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.

pakchoi1987

Thank you very much for your kind help, Prof. Luo

azhuzhuaba

got it