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CFD user June 6, 2006 10:48

liquid-solid fluidised bed simulation
 
hai everybody

i am modelling a solid-liquid flow in fluidized bed using two fluid model approach. I define the solid phase through the material group "User" with the thermodynamic state "liquid". Then I entered a value for the solid viscosity of 1e-03 pas. I have included the kinetic theory of granular flow for solid phase with Restitution Coefficient of 0.98 and my initial packed bed of solid fraction is 0.683, while solving

i am geting fatal overflow in linear solver ,whether this error is due to initial solid fraction or something else What I would like to know is:

1.whether the kinetic theory of granular flow is applicable for only solid fraction in the range of below 0.6

2. i have not tick the maximum packing option for solid phase , whether i have to include the maximum packing option with value of 0.6

if any further needs then i will put my ccl of def. file Any help is much appreciated.

Regards, cfd user


Joe June 6, 2006 10:58

Re: liquid-solid fluidised bed simulation
 
I define the solid phase through the material group "User" with the thermodynamic state "liquid". <- wrong! The solid phase should obviously have the thermodynamic state of "solid".

There is no such thing as a solid viscosity, outside of the kinetic theory of granular motion.

1) Depends on the specific shape of the particulates. The general formulation of solid kinetic theory can handle a wide range of solid packings consequent to a wide range of particulate shapes. Generally kinetic theory is supposed to prevent the solids from over packing beyond their maximum packing fraction and is hence more fragile numerically. IOW its not surprising you are having convergence issues. There is a best practice guide in the manual regarding multiphase flow. Read it ...

2) Obviously for a fluidised bed application you MUST include the maximum packing option to prevent non-physical collapse of the fluidised bed.

CFD user June 6, 2006 23:11

Re: liquid-solid fluidised bed simulation
 
hai joe, thanks for ur response, in my case, what value i have to enter for maximum packing of solid fraction, since my intial solid fraction is 0.683 wht u suggested for thermodynamic state for solid phase, that i will correct it,

with regards panneer


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