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Fluized bed reactors 3d

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Old   June 19, 2012, 15:40
Default Fluized bed reactors 3d
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Luca Pirani
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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??
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Old   June 26, 2012, 06:30
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Ian Benzeval
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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.
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Old   June 28, 2012, 04:04
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Luca Pirani
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Hi,
Thanks for your suggest. I have another question. How to plot volume fraction of solid phase versus high of reactor??in Monitors mený??
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Old   June 28, 2012, 04:24
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Ian Benzeval
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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.
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Old   June 28, 2012, 09:09
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Luca Pirani
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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.
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Old   June 28, 2012, 10:51
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Ian Benzeval
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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!
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