Fluized bed reactors 3d

Lucaaa · June 19, 2012, 16:40

Hi everyone,

First of all i would to exscuse me for my bad English.
I try to simulate a 3d fluized bed reactor but when I calculate the solution in Fluent appear this error "divergence detected: pressure correction". I see different posts in this forum but the problem remains. I try to change the urf to minimum for pressure. My simulation is unsteady and the bc are v-inlet at inlet and p-outlet at outlet. The solution method is SIMPLE. My step size is 0.015s and 400 time-steps in total.Do you have any suggests??

IanB · June 26, 2012, 07:30

Hi, depending on mesh size and the type of fluidisation, I would suggest the time step is your problem. When I have tried modelling fluidisation I have used a step size of 1e-5s. Takes a lot more time to model, but it is more stable.

Lucaaa · June 28, 2012, 05:04

Hi,
Thanks for your suggest. I have another question. How to plot volume fraction of solid phase versus high of reactor??in Monitors menù??

IanB · June 28, 2012, 05:24

In the solution window, or the results window? Either way, if you want an XY plot of vof against height, I would suggest you draw a line along the centreline of your bed (in solution, it is in graphics and animations, set-up, new surface, line/rake). With this in place you can then export the desired data on that line (file, export, profile). Similar process will do this in the results section.

Hope that helps.

Lucaaa · June 28, 2012, 10:09

Ho IanB,
I create my line but I would that in X axes time steps and in Y the heigh of my bed. This plot if possible to update every time steps during calculation?? I hope you understand.

IanB · June 28, 2012, 11:51

I am not aware of how to do that automatically. You can use a macros in execute commands to write a file of vof against height every time step. You would then need to either manually, or via some sort of excel visual basic macros, find the height and update the bedheight against time graph. It may be possible to write some sort of udf to do this, but it would require an if loop and some other things, I wouldn't know where to begin.

If you are using time steps as low as 1e-5s, you'll want to only record the height every 100 or 1000 time steps, else you'll have masses of data.

Have fun!

June 19, 2012, 16:40	Fluized bed reactors 3d	#1
Lucaaa New Member Luca Pirani Join Date: Jun 2012 Posts: 5 Rep Power: 14	Hi everyone, First of all i would to exscuse me for my bad English. I try to simulate a 3d fluized bed reactor but when I calculate the solution in Fluent appear this error "divergence detected: pressure correction". I see different posts in this forum but the problem remains. I try to change the urf to minimum for pressure. My simulation is unsteady and the bc are v-inlet at inlet and p-outlet at outlet. The solution method is SIMPLE. My step size is 0.015s and 400 time-steps in total.Do you have any suggests??

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Multiphase liquid-solid spouted bed: pressure problem	ghost82	FLUENT	7	November 10, 2013 13:12
Fluidized bed modeling	Kartus	CFX	9	June 30, 2011 05:41
Fluidized bed simulation VS particle tracking	windhair	CFX	2	June 28, 2011 22:10
how to model heat transfer inside a slow moving bed?	bigfans	FLUENT	1	October 9, 2009 01:12
Bed lifting	Fatnes	CFX	1	August 22, 2009 07:00

June 26, 2012, 07:30		#2
IanB New Member Ian Benzeval Join Date: Jun 2012 Posts: 3 Rep Power: 14	Hi, depending on mesh size and the type of fluidisation, I would suggest the time step is your problem. When I have tried modelling fluidisation I have used a step size of 1e-5s. Takes a lot more time to model, but it is more stable.

June 28, 2012, 05:04		#3
Lucaaa New Member Luca Pirani Join Date: Jun 2012 Posts: 5 Rep Power: 14	Hi, Thanks for your suggest. I have another question. How to plot volume fraction of solid phase versus high of reactor??in Monitors menù??

June 28, 2012, 05:24		#4
IanB New Member Ian Benzeval Join Date: Jun 2012 Posts: 3 Rep Power: 14	In the solution window, or the results window? Either way, if you want an XY plot of vof against height, I would suggest you draw a line along the centreline of your bed (in solution, it is in graphics and animations, set-up, new surface, line/rake). With this in place you can then export the desired data on that line (file, export, profile). Similar process will do this in the results section. Hope that helps.

June 28, 2012, 10:09		#5
Lucaaa New Member Luca Pirani Join Date: Jun 2012 Posts: 5 Rep Power: 14	Ho IanB, I create my line but I would that in X axes time steps and in Y the heigh of my bed. This plot if possible to update every time steps during calculation?? I hope you understand.

June 28, 2012, 11:51		#6
IanB New Member Ian Benzeval Join Date: Jun 2012 Posts: 3 Rep Power: 14	I am not aware of how to do that automatically. You can use a macros in execute commands to write a file of vof against height every time step. You would then need to either manually, or via some sort of excel visual basic macros, find the height and update the bedheight against time graph. It may be possible to write some sort of udf to do this, but it would require an if loop and some other things, I wouldn't know where to begin. If you are using time steps as low as 1e-5s, you'll want to only record the height every 100 or 1000 time steps, else you'll have masses of data. Have fun!