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-   -   gas solid flow in circulating fluidized bed with different gas velocity (http://www.cfd-online.com/Forums/fluent/99498-gas-solid-flow-circulating-fluidized-bed-different-gas-velocity.html)

kongl1986 April 4, 2012 15:29

gas solid flow in circulating fluidized bed with different gas velocity
 
Hey
i am simulating gas solid flow in circulating fluidized bed with different gas velocities.
my problem is that when i decrease the gas velocity at inlet, the solid volume fraction near the wall decreased and solid volume fraction in main flow area increased.
As i found in literature, lower gas velocity should lead to higher volume fraction in the whole radial profile.
Is there anyone has this experience or some suggestions?
thank you.

the wall condition is that: specularity coefficient:0.000135, j-j restitution coefficient 0.9

Musa April 4, 2012 21:13

During the the start up of the simulation i.e. first 5 seconds it is normal to obtain such a result. For how many seconds have you been running your simulation? Try running it for a long time say 20 seconds and average the last 15 seconds. It also depends from which position you are getting your result. Try and get the result at a position where the flow is fully developed.

kongl1986 April 5, 2012 22:23

Quote:

Originally Posted by Musa (Post 353205)
During the the start up of the simulation i.e. first 5 seconds it is normal to obtain such a result. For how many seconds have you been running your simulation? Try running it for a long time say 20 seconds and average the last 15 seconds. It also depends from which position you are getting your result. Try and get the result at a position where the flow is fully developed.

thank you for your reply Musa.
I found the reason that the solid inlet velocity i input is too big which is close to the gas veloticy, when i turn it down , and increase the inlet solid volume fraction to keep the solid flux same, the change is acceptable.
thank you again


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