3.1. First Tutorial

This section illustrates how to launch the GUI, open a project, run it, and visualize the results.

This section assumes MFiX is already installed. To install MFiX, see the Setup Guide.

It is also assumed that the terminal shell on Linux and Mac is bash. If this is not the case, type bash at the prompt before activating the environment.

Everything in this section applies to all platforms (Linux, macOS, Windows) unless otherwise noted.

3.1.1. Starting the MFiX GUI

Starting the GUI requires first to activate the environment (to select a given installed version of MFiX):

On Windows, open the Anaconda Prompt and activate the mfix environment

On Linux open a terminal and activate the mfix environment from bash.

On macOS open a terminal and activate the mfix environment from bash.

Next, type mfix at the prompt. The two steps are shown below for each Operating System:

# Windows
conda activate mfix-20.1
(mfix-20.1) C:\> mfix

# Linux or Mac
conda activate mfix-20.1
(mfix-20.1) > mfix

If this is the first time opening the GUI, the main menu will automatically open. Otherwise, the previous project will automatically open.

3.1.2. Creating a Project

A list of project templates is displayed.

The templates are tagged with the following icons. (Some templates have more than one icon).




Single phase Model


Two Fluid Model (TFM)


Particle in Cell Model (PIC)


Discrete Element Model (DEM)


Hybrid Model (TFM + DEM)


Cartesian cut-cell (complex) geometry




The blank template is the default, but it won’t run without customization. It requires a pressure outflow, among other things.

  • Filter the templates by de-selecting the single (single phase), and chemistry (chemistry) icons

  • Double-click on hopper_3d (3D DEM granular flow hopper) to create a new project

  • Enter a project name (or keep the existing name) and browse to a location for the new project.

  • Click Ok

A new project directory will be created in the selected directory, with the name being the project name. Here, a DEM Hopper simulation setup has been loaded and is ready to run. You should see the model geometry in the “model” window (top-right).

3.1.3. Running the Solver

  • Click the play (Start) button to open the Run Dialog.

  • Click Ok to use the default mfixsolver: [default]/mfixsolver

The solver will begin to run, with output displayed in the Terminal window. There is a progress bar along the bottom of the screen where it says MFiX running: elapsed time.

3.1.4. View results

Results can be viewed, and plotted, while the simulation is running.

  • Select the VTK results tab. The visibility and representation of the *.vtk files can be controlled with the menu on the side.

  • Change frames with the first, back, next, and last buttons

  • Click the play button to play the available vtk files.

  • Change the playback speed under the speed section on the sidebar.

3.1.5. Pausing/Unpausing

  • Click the pause (pause) button to pause the solver.

    MFiX paused will be displayed in the Terminal window. The solver process still exists, but is waiting for you to unpause it.

    While the solver is paused, you can change the project. For instance, on the Run Pane you could change stop time to another value to have the solver run for a different amount of time.

  • Click the play (run) button to unpause the solver and continue running.

3.1.6. Stopping/Resuming

  • Click the stop (stop) button to stop the solver.

MFiX stopped will be displayed in the Terminal window. The solver process has ended, with the output files still in the project directory.

You can then resume the solver by:

  • Clicking the play (run) button to open the Run Dialog.

  • Check Restart and select Resume from the drop down list.

  • Click Ok to use the default mfixsolver.

The solver process will start and continue from the point at which the output files were last written.