8. GUI reference

8.1. Main toolbar

The Main toolbar is located at the top of the GUI window. The following table illustrates the icons in the toolbar.

Icon

Description

Menu

Menu

Save

Saves the current project file

Start

Start/resume MFIX simulation

Pause

Pause simulation

Stop

Stop simulation

Reset

Reset - clear output files

Build

Build dialog

Parameters

Parameter dialog

The interactive solver sends its status during the simulation, and the solver controls will be enabled or disabled, depending on the solver state.

Solver controls:

Solver state is….

…Running and….

…Stopped with…

…Unpaused.

…Paused.

no RES.

RES.

Start Start

Disabled

Unpause

Start

Resume

Pause Pause

Pause

Disabled

Stop Stop

Stops the solver

Disabled

Reset Reset

Disabled

Clear RES

If no MFiX job is currently running, the Start button will open the run dialog where settings for a job can be changed. The simulation can be started from this dialog. If an MFiX job is running, you can pause it with the pause button and un-pause it with the start button. You can stop a running MFiX job with the stop button. A stopped job leaves restart (*.RES) and output files to resume the simulation. Starting a job by pressing the Start button with *.RES files present will resume the job where it stopped. The Reset button will allow the option to delete the *.RES files and output files from the project directory. This will allow the simulation to start from the beginning the next time the Start button is pressed.

8.1.1. Run dialog

The run dialog is used for entering options on starting the solver.

Different solvers can be selected.

If a custom solver is compiled with SMP or DMP support, the following options may be available:

  • Threads (number of threads used for OpenMP)

  • NODESI (number divisions in X direction)

  • NODESJ (number divisions in Y direction)

  • NODESK (number divisions in Z direction)

\(NODESI \times NODESJ \times NODESK = n\) where \(n\) is the number of MPI processes running. If not using MPI, \(NODESI=NODESJ=NODESK=1\).

The GUI supports running both locally as well as submitting to a queue.

Note

SMP and DMP options are disabled for the default solver. You will need to build a custom solver with DMP or SMP flags to enable these options.

8.1.1.1. Run locally

To run locally, select a solver from the drop-down list or click the browse button to specify a solver that is not in the list. Usually the default installed solver should be sufficient. If running a case with UDFs, you need to first build a case-specific MFiX as described in the Getting started. You may want to build your own solver for other reasons, such as specifying various compiler flags to optimize the executable for your specific hardware.

Make sure the “Submit to queue” checkbox is unchecked, and click “Run” in the Run dialog to start the solver.

8.1.1.2. Submit to queue

To submit a job to a queue (submit to queuing system, e.g. Grid Engine, PBS, SLURM), select the “Submit to Queue” tab. Select an executable from the drop-down list or click the browse button to specify an executable that is not in the list. Next, select a template from the drop-down list or click the browse button to choose a template that is not in the drop-down list. Based on the selected template, the widgets in the “queue options” section will update automatically. Once the options are specified, click “submit” in the run dialog to submit the job to the queue.

Custom queue scripts are supported. The format for this script is described in the Queue Templates section.

8.1.2. Build dialog

The build dialog is used for building custom solvers in project run directories. This is used to build Building Custom Interactive Solver.

There is a combo box to select the Fortran compiler command. It will be populated with any known Fortran compilers in PATH. Alternatively, type in the command for the compiler.

There is a field to type in the flags for the Fortran compiler. See your compiler manual for details, such as the GNU Fortran Manual.

There are checkboxes for building with SMP or DMP support. Note that DMP support requires both checking the DMP box, and selecting an MPI compiler (such as mpifort). The “Build solver in parallel” checkbox will run make with multiple jobs. DMP and SMP are not available on Windows.

If “Enable developer mode” is checked in Settings, then there will be a checkbox for building either the interactive solver or the batch solver.

“Build command” displays the command line used for building the solver with the selected options.

8.1.3. Reset dialog

The Reset dialog allows for optional deleting of output files from the run directory. These files include:

File type

Wild-card match

Restart

*.RES

SPx

*.SP?

VTK

*.vtp, *.vtu, *.pid

Other

*.OUT, *.pid, *.error, *.e[0-9]*, *.pe[0-9]*, *.po[0-9]*

*.RES and *.SPx files have to be removed from the run directory before a simulation can be played from the beginning. It is recommended to remove VTK files from the run directory as well because they will be over-written.

Note

If there are restart files present in the run directory, some widgets will be disabled because certain model parameters can not be edited during a resume, or restart state.

8.1.4. Parameter dialog

The parameter dialog allows users to create parameters, or variables, that can then be referenced in widgets that support the use of these parameters. This functionality allows user to create relationships among various inputs and change the values of multiple items by changing the value of a single parameter. In many respects, this is similar to features present in most commercial CAD packages.

There are six special parameters; xmin, xmax, ymin, ymax, zmin, and zmax that reference the simulation domain extents, entered on the geometry pane. These parameters make it easy to setup regions that automatically adjust to the simulation domain if the extents change.

8.3. Model panes

Each pane in the main window allows editing of different options for an MFiX project. The Panes are ordered in a logical progression for traditional CFD problem setups: Model defines the overall solver type (TFM, DEM, PIC). Geometry and Mesh define the overall domain space of the solver. Regions are geometrical surfaces and volumes within the overall domain. Fluid and Solids specify details on the phases the solver deals with. Initial Conditions (ICs), Boundary Conditions (BCs), Point Sources (PSs), and Internal Surfaces (ISs) depend on Regions, Fluid, and Solids, so they come next. Chemistry provides options for reacting cases, and Numerics specifies details on the Eulerian solver. Output specifies how output data is written. Monitors provides options to probe the flow field at select locations and compute basic quantities of interest. Run specifies how long to run the solver for. (Post is not yet implemented).

Note

Selections on panes may enable or disable widgets based on what input parameters are required or available.

8.3.1. Model setup

The Model pane is used to specify overall options for the project. Depending on what is selected, other panes may be enabled or disabled. Options that are specified on this pane include:

  • Solver (Single Phase, Two-Fluid Model, DEM, PIC, Hybrid)

  • Option to disable the fluid phase

  • Option to enable thermal energy equations

  • Option to enable turbulence, if the fluid phase is enabled

  • Gravity in the x, y, and z directions

  • Drag Model including parameters for the selected drag model

Other advanced options that can be selected include:

  • Momentum formulation (Model a, Model B, Jackson, or Ishii)

  • Sub-grid model (only available with TFM, Wen-Yu drag model, etc…)

  • Sub-grid filter size

  • Sub-grid wall correction

8.3.2. Geometry

8.3.3. Mesh

8.3.4. Regions

8.3.5. Fluid

The fluid pane is used to define the physical properties of the fluid phase. This includes adding fluid phase species which can either be imported from the BURCAT thermodynamic database or created by the user. The GUI will generate the correct data format to use thermodynamic data in MFiX.

8.3.6. Solids

The solids pane is used to define the physical properties of each solid(s) phase. Names can be given to each solid. This name will be used throughout the GUI to reference that solid phase (i.e. when defining initial conditions, boundary conditions, etc.). The solid phase model (TFM, DEM, or PIC) can also be specified here, however the selectable solid phase model depends on the solver selected on the model pane.

The selected solver will also enable/disable the TFM, DEM, and PIC sub-panes where various options for those solids models can be accessed.

8.3.7. Initial Conditions (ICs)

The initial conditions pane is used to define initial conditions for a selected Region (defined on each Region pane) for each phase (defined on Fluid or Solids panes). Initial conditions are required to cover the entire domain and provide an initial value for certain quantities that the solver will use to start the simulation. Experienced CFD users realize that providing reasonable initial values for volume fraction, temperature, pressure, and velocity allow simulations to reach/meet convergence criteria more quickly.

To create a new initial condition, press the Add button which will bring up the Region Selection dialog. Select a region to associate with the new initial condition and press OK. Regions that are not volumes or are already used by another initial condition will not be selectable.

Once the region has been created, values can be edited. Sub-panes will be created dynamically based on model parameters as well as the number of solid phases.

Note

Initial condition regions may overlap. When an overlap occurs, the initial condition with the higher IC number will be used at that location.

8.3.8. Boundary Conditions (BCs)

The boundary conditions pane is used to define boundary conditions for a selected Region (defined on each Region pane) for each phase (defined on Fluid or Solids panes). This is where inflow, outflow, pressure, walls, and cyclic boundary conditions are created.

To create a new boundary condition, press the Add button which will bring up the Region Selection dialog. Next, select a boundary type from the combo box. Regions will be enabled/disabled based on the selected boundary type and whether or not the region is already used by a boundary condition. Boundary conditions must be surfaces, either planes or collections of facets (STL). Pressing OK will create the boundary condition.

The sub-panes are created dynamically for each boundary condition based on the boundary condition type as well as other model parameters including the number of solid species.

Note

Two boundary surfaces must not intersect.

8.3.9. Point Sources (PSs)

Point sources (PSs) are used in place of mass inlets where either the geometry and/or grid resolution prohibit traditional boundary condition specification. For example, a point source may be used to model an injector with dimensions smaller than the grid. Point sources may be defined within a single computational cell, along a plane, or as a volume of computational cells.

Point sources introduce mass directly into a computational cell unlike a boundary condition which specifies flow along a cell face. One consequence of this implementation is that point sources are subjected to convection/diffusion forces and may not travel parallel to the specified directional preference. Directional preference is specified with a velocity vector (i.e., PS_U_g, PS_V_g, etc.), however, it is not required.

To create a new point source, press the Add button which will bring up the Region Selection dialog. Select a region to associate with the new point source and press OK.

The sub-panes are created dynamically for each point source based on the model parameters including the number of solid species.

8.3.10. Internal Surfaces (ISs)

Internal surfaces allow the user to create a zero-thickness walls that are normal to one of the coordinate directions and coincide with one of the faces of the scalar control volume.

Two types of internal surfaces are available: Impermeable, which acts as a free-slip wall for both gas and solids phases, and Semi-Impermeable, which allows only the gas phase to pass through the internal surface.

To create a new internal surface, press the Add button which will bring up the Region Selection dialog. Select a region to associate with the new Internal Surface. Select the type of Internal surface and press OK. For Semi-Impermeable surfaces, the fluid permeability and Internal Resistance Coefficient must be provided as well.

Typically, the region associated with an Internal Surface will be a plane. To specify a large number of internal surfaces in a region, a 3D region may be selected. In this case, a prefix (X_, Y_, or Z_) is added to the Internal Surface type to indicate the direction of the internal surfaces; e.g., X_IMPERMEABLE specifies impermeable internal surfaces parallel to the X coordinate.

Internal surfaces act as free-slip walls in stress computations. This default condition cannot be changed.

8.3.11. Chemistry

Setting up a project with chemical reactions is a multi-step process that requires coding the reactions rates in usr_rates.f for TFM or usr_rates_des.f for DEM. The solver needs to be built to take the reaction rates into account. A brief overview is outlined below. The Silane pyrolysis tutorial is an good way for the user to familiarize him/herself with setting up chemical reactions in MFiX.

  • Check the “Enable user-defined subroutine” checkbox in the “Model” pane.

  • Check the “Enable Species equations” checkbox and define species in the “Fluid” and “Solids” panes.

  • In the “Chemistry” pane, define chemical equations by pressing the Add button. Define the reaction equation name, and add reactants and products with the Add button. Select the phase and species from the dropdown list, and enter the stoichiometric coefficient. Repeat until all products and reactants are defined, and press OK to validate. Specific heats of reactions are computed automatically, but this setting can be manually overwritten if needed by checking the “Specify Heat of Reaction” checkbox, entering the heat of reaction and assigning the gas and solids phases fractions.

  • (Optional) turn on the stiff chemistry solver in the “Chemistry” pane by checking the “Enable stiff chemistry solver” checkbox.

  • Edit and save the usr_rates.f or usr_rates_des.f UDF, and any other UDF needed for the reaction rates calculation.

  • Build the custom solver by pressing the Build button.

8.3.12. Numerics

The Numerics panes defines various numerical parameters, which are grouped in several sub panes:

  • Residuals: Defines convergence criteria for each type of equation, as well as the maximum number of iterations and residual normalization options.

  • Discretization: Defines temporal, spatial discretization schemes and relaxation factors for each equation.

  • Linear Solver: Defines the Linear Equation solver, tolerance and maximum number of iterations for each equation.

  • Preconditioner: Defines the preconditioner options for each equation.

  • Advanced: Defines less common parameters, such as the maximum inlet velocity factor, drag and IA theory underrelaxation factors and fourth order interpolation scheme.

8.3.13. Outputs

A variety of output formats can be written by the solver including restart files (*.RES), VTK files (*.pvd, *.vtp, *.vtu), and legacy Single Precision files (*.SP?). The VTK files can be read by and displayed in the GUI. Most of these files can be viewed with the post-processing programs ParaView and VisIt.

The Basic sub-pane is where the restart file write frequency as well as the VTK and SPx outputs can be enabled. Once these are enabled, the associated sub-pane will be enabled, allowing for specific control over these outputs.

The VTK output has the most flexibility. Selected particle data or cell data variables can be exported at a specific region and write frequency. To create a new VTK output, press the Add button which will bring up the Region Selection dialog. Next, select an output type (particle or cell), select a region, and press OK. The file pattern name, write frequency, and variables can be selected for the newly created VTK output.

The following table lists the files typically associated with an MFiX run. In addition, their associated file type, data content and readability by ParaView and VisIt is indicated.

Table 8.1 Output Format Table

Filename

File Type

Fluid Data

Particle Data

Paraview

Visit

<RUN_NAME>.RES

MFiX Binary

Yes

No

Yes

Yes

<RUN_NAME>_###_DES.RES

MFiX Binary

No

Yes

No

No

<RUN_NAME>.pvd

VTK

Yes

No

Yes

No

<RUN_NAME>_###.vtu

VTK

Yes

No

Yes

Yes

<VTK_REGION>.pvd

VTK

Yes

No

Yes

No

<VTK_REGION>_###.vtu

VTK

Yes

No

Yes

Yes

<RUN_NAME>_DES.pvd

VTK

No

Yes

Yes

No

<RUN_NAME>_DES_###.vtp

VTK

No

Yes

Yes

Yes

<VTK_REGION>.pvd

VTK

No

Yes

Yes

No

<VTK_REGION>_###.vtp

VTK

No

Yes

Yes

Yes

8.3.14. Monitors

8.3.15. Run

The Run pane is used to define parameters related to how long the solver runs, time-step controls, as well as options to cleanly terminate a solver after a certain amount of time. These options are particularly useful when running in a queue environment because they allow the solver to cleanly exit before the job gets killed by the queuing system. This minimizes the chance of corrupting output files if the process is killed while writing a file.

8.4. Visualization window

The visualization window provides a collection of 3D views and 2D plots for visualizing the model setup and model outputs. New windows, or tabs, can be created by pressing the Add button. Once the tab has been added, the type of view can be selected. A Tab can be closed by pressing the Close button located in its upper right hand corner.

8.4.1. Model

The Model tab is always present and cannot be closed. This 3D view shows the setup of the project including the background mesh, geometry, and regions.

The scene can be manipulated with the mouse and the toolbar buttons defined in the following table:

Icon

Description

Overscan

Reset view, make all items visible

XY

Change to XY view

XZ

Change to XZ view

YZ

Change to YZ View

Perspective

Toggle between perspective and parallel projections

Camera

Save an image of the current view

Visibility

Change the visibility and properties of actors

The visibility menu allows the user to manipulate objects in the scene by:

  • changing the visibility with the Visibility button

  • changing the representation (wire, solids, edges, and points)

  • changing the color

  • changing the transparency of the objects

8.4.2. Plot Tab(s)

The plot tab(s) can be used to graph live statistics from the solver while it is running. Values such as the time step (dt), number of iterations (nit), and the simulated time (time) can be plotted. The plot can be manipulated with the mouse, and a right-click menu provides access to options that can be changed. In addition, export options for saving an image of the plot or exporting the data to a text file are available in this menu.

Note

Plotting only available when solver is running

8.4.3. VTK Tab(s)

The VTK tab provides a way to quickly view results from the solver. For more complex visualization of solver data, ParaView or VisIt is recommended.

The tab automatically sets-up VTK pipelines for reading and displaying the content of *.vtu and *.vtp files.

Note

The directory is automatically searched every second for *.pvd files. If a *.pvd file is found, the GUI will read and show the new VTK file if the Play button is pressed.

Results display can be “played” as well as manipulated using the following toolbar:

Icon

Description

Overscan

Reset view, make all items visible

XY

Change to XY view

XZ

Change to XZ view

YZ

Change to YZ View

Perspective

Toggle between perspective and parallel projections

Camera

Save an image of the current view

Visibility

Change the visibility and properties of actors

First

Go to the first frame

Back

Go back one frame

Play

Play available frames, starting at the current frame

Next

Go to the next frame

Last

Go to the last frame

Speed

Change the playback speed, or the amount of time in between frames

The visibility menu allows for the manipulation of how the objects in the scene represented including:

  • visibility

  • the data array used to color

  • color bars

  • transparency

Further options for the points can be adjusted by clicking the More button next to the label including:

  • Maximum number of particles to be displayed

  • The mapper (sprites requires VTK version 7.0+)

  • The glyph object

8.5. Terminal window

The terminal window displays the output of the solver job that would be displayed when running the solver on the command line. Error messages and warnings, from both the GUI and a running solver, are displayed and colored in red.

Informational messages from the GUI unrelated to the solver are colored in blue.

8.6. Mode bar

The Mode bar allows switching the GUI between various modes including:

  • Mesher, used to set up a mesh when in SMS mode

  • Modeler, used to set up and run simulations

  • Nodeworks, feature to support creation, management, post processing, and optimization of projects.

A status bar is also present, showing the current status of the GUI or a running solver, including a progress bar showing the current progress of the solver and elapsed time.