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-   -   Questions about gas-solid fluidized bed simulation (http://www.cfd-online.com/Forums/fluent/43545-questions-about-gas-solid-fluidized-bed-simulation.html)

Sinferm January 30, 2007 16:01

Questions about gas-solid fluidized bed simulation
 
There is a paper having the following description for setting the intial and boudary condition for the simulation of gas-solid fluidized bed. (see below for details).

Now, my questions are that:

(1)In Fluent, how to set "Initially the riser column was empty"? When I set the solid fraction to be zero in Fluent Intilization section, I found the gas fraction equals unit. It seems not to correspond to the "empty".

(2)For gas-solid system, the solid-wall interaction should be considered. As noted in that paper, the classical "Johnson and Jackson (1987) boundary condition was used". Now, my question is: How to set the Jackson condition in Fluent? Especially for the proper choice of restitution coefficents concerned.

Really hope to get the help and ideas from those who have specific experiences in treating the gas-solid fluidized bed simulation. Thnaks in advance.

************************************************** ********* "...The definition of appropriate initial and boundary conditions is critical for carrying out of a realistic simulation. Initially the riser column was empty and the velocities of both phases were assumed to be zero. At the outlet, atmospheric pressure was prescribed. Particularly important is also the specification of appropriate boundary conditions at the wall. For the gas a no-slip boundary condition was used. For the granular temperature wall boundary condition the Johnson and Jackson (1987) boundary condition was used. It was obtained by equating the granular flux to collisional dissipation with a correction for slip, as shown in Table 1...."


Ganna January 31, 2007 15:54

Re: Questions about gas-solid fluidized bed simula
 
Hi, Sinferm,

I met the same problem. In my simulation, the Euler-Euler approach is used to simulate the gas-sloid riser. Johnson and Jackson condition is used as solid-wall boundary condition. But I always find that the axial solid velocity at the wall boundary is zero, albeit I do not use the no-slip condition. I guess I do not manage the boudary setting,too.

I want to know why? and how to avoid it?



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