CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT > Fluent Multiphase

Failed to converge in Fluent Multiphase Granular 2nd phase

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   October 16, 2021, 05:11
Default Failed to converge in Fluent Multiphase Granular 2nd phase
New Member
Johnson Yap
Join Date: Oct 2021
Posts: 1
Rep Power: 0
jonshontwin is on a distinguished road
Hi, I am a master student who currently using ANSYS Fluent V19.0 to run a Eulerian Multiphase simulation, the simulation is simple a 2D tube filled with water (primary phase) and 5mm glass bead (2nd phase), after that I set inlet boundary from bottom of the tube with constant velocity of 0.01 m/s and environment pressure outlet at top of the tube, this is a simple fluidized bed setup. The illustration of the initial condition of simulation setup are shown below:


The setup detail of the model is shown below:
Simulation type : Eulerian Multiphase with VOF
Analysis type : Transient Implicit
Time Step : 0.001 s
Total Time : 60 second
Glass bead phase : granular 2nd phase with VOF phase localized discretization of 0 (because in future I need to include air bubble into the simulation, so for glass bead 2nd phase, I use VOF phase localized discretization of 0 which is similar to diffused phase setting)
Glass bead density : 2230kg/m3 (denser than water)
Glass bead diameter : 5mm
Drag Model : Wen Yu
Maximum Packing limit : 0.6
Initial volume fraction of glass bead : 0.6 (same as packing limit)

I found out if the inlet velocity is too low (let say 0.01m/s) and cannot achieve minimum fluidized bed (mean the glass bead fludizied bed is stationary, like packed bed and no blow up), the model become unstable, the residual value sudden jump up and failed to converge in the interval of around every 30 time steps (0.03 second), the residual plot are shown below:


When I increase the velocity to 0.04m/s and above (over the minimum fluidized velocity), the fluidized bed starts to increase in height, the volume fraction starts to reduce below 0.6, and the simuulation do not have convergence problem anymore.
I suspect this phenomenon is due to the volume fraction of 2nd granular phase is close to 0.6 (maximum packing limit) and the 2nd phase is unstable. (Just my opinion)
In future I will migrate this fluidized bed from this simple tube to a stirred tank. I believe after the stirred tank flow achieved steady state (around 60 second), the velocity in this fluidized bed will over the minimum fluidized velocity and no convergence problem. However, the real case is, just after the stirrer of the tank start to rotate, the velocity in the fluidized bed is still close to zero, it will take time for that region to achieved certain velocity, it will unstable/fail to converge before the tank achieved steady state.
Anyone have idea of how to stabilize the granular 2nd phase (fluidized bed) even with very low inlet velocity?
jonshontwin is offline   Reply With Quote

Old   November 18, 2021, 06:44
New Member
pitroda jimesh
Join Date: Nov 2021
Posts: 2
Rep Power: 0 is on a distinguished road
have you solved the problem? is offline   Reply With Quote


convergence failure, fluent - parallel, fluidized bed granulation, granular phase, multiphase mixture model

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
how to run fluent from matlab without using aas toolbox? artemis96 ANSYS 7 May 23, 2022 12:16
looking for a smart interface matlab fluent chary FLUENT 24 June 18, 2021 09:07
Linux Fluent HPC parallel system check failed saad3000 FLUENT 1 January 8, 2021 03:34
How to go about modeling injection nozzle two phase flow in FLUENT? skonda2 Fluent Multiphase 0 March 17, 2015 07:52

All times are GMT -4. The time now is 00:00.