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Issues with variable expression.
Posted Mar 29, 2012, 4:18 p.m. EDT Computational Fluid Dynamics (CFD) Version 4.2a 1 Reply
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Hi,
I am trying to model the settling of particles in a tank. Attached is the model.
It has turbulent flow with particles flowing in. I have added a downward settling velocity that is calculated separately.
I started stepwise from turbulrnt flow, then added transport of dilute species, then a reaction, then a settling velocity. The model solves, but refuses to calculate the settling velocity. I am not sure if there is just an error in the expression of the settling velocity or some issue with BCs or numerical restrictions?
Settling velocity is calculated based on the equations:
Settling velocity= u_set= (uo*e^(-rh*x_j))-(uo*e^(-rp*x_j))
and 0<u_set<u_max
where x_j= m*c-x_min
uo, rh,rp and u_max are model parameters and values are determined from previous studies.
I would apprciate any help!
Thanks,
Preethi
I am trying to model the settling of particles in a tank. Attached is the model.
It has turbulent flow with particles flowing in. I have added a downward settling velocity that is calculated separately.
I started stepwise from turbulrnt flow, then added transport of dilute species, then a reaction, then a settling velocity. The model solves, but refuses to calculate the settling velocity. I am not sure if there is just an error in the expression of the settling velocity or some issue with BCs or numerical restrictions?
Settling velocity is calculated based on the equations:
Settling velocity= u_set= (uo*e^(-rh*x_j))-(uo*e^(-rp*x_j))
and 0<u_set<u_max
where x_j= m*c-x_min
uo, rh,rp and u_max are model parameters and values are determined from previous studies.
I would apprciate any help!
Thanks,
Preethi
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1 Reply Last Post Mar 30, 2012, 3:00 a.m. EDT
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Posted:
1 decade ago
Hi,
You did not select the domain to which the settling velocity applies. Furthermore, you defined the settlign velocity using eps which is an extremely small number, if you want to use the euler number you need the function exp(). However, if you use the settling velocity you get an udenfined value for the concentration and the computation stops, so I think you need to look at the definition of the sttling velocity, there may be something wrong.
Cheers
You did not select the domain to which the settling velocity applies. Furthermore, you defined the settlign velocity using eps which is an extremely small number, if you want to use the euler number you need the function exp(). However, if you use the settling velocity you get an udenfined value for the concentration and the computation stops, so I think you need to look at the definition of the sttling velocity, there may be something wrong.
Cheers