Setting Up a Transient Dispersion

Load your saved Tutorial 3 file into in:Flux before continuing. If any visualizations or other project items (such as monitor points) are showing, turn off their visibility by deselecting the checkboxes next to their name in the Project Items Tab.


In this section we will setup a transient dispersion simulation using an already defined inflow and ventilation case.


  1. From the Add Item tab, select Dispersion Simulation from the Select Item: dropdown menu.

  2. Tutorial 3 only has one ventilation simulation so the Westerly, 5 m/s should already be selected as the Ventilation case

  3. Similarly, HP Release 01 should already be selected for the Inflow

  4. Expand the Transient panel indicated by the red box in the figure below


    Tutorial 8 - Figure 01 - indication of where to open the transient option for a dispersion case


  5. In the panel that appears, change the Scheme option to Transient


    Tutorial 8 - Figure 02 - changing the Scheme of the simulation to transient


  6. In the Duration textbox enter a value of "40" seconds. This means that the simulation will simulate a duration of 40 seconds.

  7. Be sure to Save Results for Every Time Step. To reduce file size, you may opt to save results at every 1, 2, 5, 10, 30 or 60 second intervals. Each project will be different so choose the option most applicable for your application. 

  8. Ensure the Run Now checkbox is selected and click Add Item.


You should now see the simulation added to the Project Items tab under the dispersion simulations section with a small clock next to the gas plume icon in front of the name .


The simulation monitor will have some new text at the bottom of the window stating what time step is currently being calculated, and how much time has been simulated. The time step is the division of time that the simulation progresses at each time-iteration. The time step is initially small (calculated from the Courant number of 1) and then adaptively increases at each time-iteration until a maximum is reached.


Tutorial 8 - Figure 03 - indication of time step in the simulation monitor that is currently being calculated


Once the simulation has completed continue to the next section to review the results. Note that for in:Flux transient simulations tend to take about 50% longer than steady state simulations.