3.3. Two-dimensional fluidized bed, Discrete Element Model (DEM)¶
This tutorial shows how to create a two dimensional fluidized bed simulation using the Discrete Element Model. The model setup is:
Property |
Value |
---|---|
geometry |
15 cm x 90 cm x 0.4 cm |
mesh |
15 x 45 x 1 |
solid diameter |
4000 microns (\(4000 \times 10^{-6}\) m) |
solid density |
2700 kg/m2 |
gas velocity |
42.0 m/s |
temperature |
298 K |
pressure |
101325 Pa |
3.3.1. Create a new project¶
On the main menu, select
New project
Create a new project by double-clicking on “Blank” template.
Enter a project name and browse to a location for the new project.
When prompted to enable SMS workflow, answer No, we will use the standard workflow for this tutorial.
3.3.2. Select model parameters¶
On the
Model
pane, enter a descriptive text in theDescription
fieldSelect “Discrete Element Model (MFiX-DEM)” in the
Solver
drop-down menu.
3.3.3. Enter the geometry¶
On the Geometry
pane:
Enter
0.15
meters for the maximum x valueEnter
0.90
meters for the maximum y valueEnter
0.004
meters for the maximum z value
3.3.4. Enter the mesh¶
On the Mesh
pane, Background
sub-pane:
Enter
15
for the x cell valueEnter
45
for the y cell valueEnter
1
for the z cell value
Note
Since there is only one cell in the Z direction, this model is effectively a 2D simulation.
3.3.5. Create regions for initial and boundary condition specification¶
On the Regions
pane:
Click the (all) button to create a new region that covers the entire domain to be used for the bed initial condition.
Enter a name for the region in the
Name
field (“bed”)Change the
To Y
field to be “ymax/2”Click the (bottom) button to create a new region to be used by the gas inlet boundary condition.
Enter a name for the region in the
Name
field (“inlet”)Enter
0.07
in theFrom X
field and0.08
in theTo X
field.Click the (top) button to create a new region to be used by pressure outlet boundary condition.
Enter a name for the region in the
Name
field (“outlet”)
3.3.6. Create a solid¶
On the Solids
pane, Materials
sub-pane:
Enter a descriptive name in the
Name
field (“solids”)Enter the particle diameter of
0.004
m in theDiameter
fieldEnter the particle density of
2700
kg/m2 in theDensity
field
Select the
Solids
pane,DEM
sub-paneCheck the
Enable automatic particle generation
checkbox, so that the bed Initial Condition, defined later, will be filled with solids
3.3.7. Create Initial Conditions¶
On the Initial conditions
pane:
Select the already populated “Background IC” from the region list. This will initialize the entire flow field with air.
Enter
101325
Pa in thePressure (optional)
field
Select the bed region created previously for the bed Initial Condition (“bed” region) and click the
OK
button.
Select the solid (named previously as “solid”) sub-pane and enter a volume fraction of
0.4
in theVolume Fraction
field. This will fill the bottom half of the domain with solids.Note the estimated number of particles and inventory (around 3,200 particles or 0.3 kg). When running DEM simulations on a single core machine, it is recommended to stay below 100,000 particles to get reasonable run times.
3.3.8. Create Boundary Conditions¶
On the Boundary conditions
pane:
On the
Select region
dialog, select “Mass Inflow” from theBoundary type
drop-down menuSelect the “inlet” region and click
OK
On the “Fluid” sub-pane, enter a velocity in the
Y-axial velocity
field of “42” m/s
On the
Select region
dialog, select “Pressure outflow” from theBoundary type
combo-boxSelect the “outlet” region and click
OK
Note
The default pressure is already set to 101325 Pa, no changes need to be made to the outlet boundary condition.
Note
By default, boundaries that are left undefined (here the left, right, front, and back planes) will behave as No-Slip walls.
3.3.9. Select output options¶
On the Output
pane:
On the
Basic
sub-pane, check theWrite VTK output files (VTU/VTP)
checkbox
Select the
VTK
sub-paneSelect “Particle Data” from the ‘Output type’ drop-down menu.
Select the “Background IC” region from the list to save all the particle data
Click
OK
to create the output
Enter a base name for the
*.vtu
files in theFilename base
field (“particles”)Change the
Write interval
to0.01
secondsSelect the
Diameter
andTranslational Velocity
checkboxes
3.3.10. Change run parameters¶
On the Run
pane:
Change
Stop time
to1.0
secondsChange
Time step
to1e-2
secondsChange
Maximum time step
to1e-2
seconds
3.3.11. Run the project¶
3.3.12. View results¶
Results can be viewed, and plotted, while the simulation is running.
Create a new visualization tab by pressing the next to the Model tab
Select an item to view, such as plotting the time step (dt) or click the
3D view
button to view the vtk output files.On the
VTK
results tab, the visibility and representation of the*.vtk
files can be controlled with the menu on the side.