velocity in diffusion process

reyeszjj · March 20, 2010, 15:05

I have some confusions after modeling diffusion process in CFD-ACE

I'm doing fluid diffusion, namely, different solution in concentration, and using transient setup

In post processing, I can see the concentration change in the software, but velocity is always zero

So my question is, is that I can not expect any macro-scale velocity in diffusion process because there's actually no "real flow" created, just diffusion caused by the average kinetic energy of the molecules in the microscale?

what if I need to get the velocity field in this process, is that not possible? but actually according to my intuition, the point in the field should feel the velocity like a flow in someway, can I treat this velocity field in some way in CFD?

Anyone can help me?
Thanks in advance

George Chen 28 · March 21, 2010, 04:24

Did you mean that difference in concentration leads to the varity of density in different area, so the gravity drives the fluid to flow? I am a new, just hope to join any discussion of interest.

March 20, 2010, 15:05	velocity in diffusion process	#1
reyeszjj New Member Jianjing Join Date: Mar 2010 Posts: 6 Rep Power: 16	I have some confusions after modeling diffusion process in CFD-ACE I'm doing fluid diffusion, namely, different solution in concentration, and using transient setup In post processing, I can see the concentration change in the software, but velocity is always zero So my question is, is that I can not expect any macro-scale velocity in diffusion process because there's actually no "real flow" created, just diffusion caused by the average kinetic energy of the molecules in the microscale? what if I need to get the velocity field in this process, is that not possible? but actually according to my intuition, the point in the field should feel the velocity like a flow in someway, can I treat this velocity field in some way in CFD? Anyone can help me? Thanks in advance

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March 21, 2010, 04:24		#2
George Chen 28 New Member Join Date: Mar 2010 Posts: 22 Rep Power: 16	Did you mean that difference in concentration leads to the varity of density in different area, so the gravity drives the fluid to flow? I am a new, just hope to join any discussion of interest.