Reviewing Internal Ventilation Results

 

Similar to external ventilation cases, post-processing visualization such as contours, vectors, isosurfaces and streamlines can be added for internal ventilation simulations.

 

Adding Contours for Internal Ventilation

Although velocity magnitude and streamwise velocity variables can be viewed for internal ventilation cases, a more pertinent variable is the Mean Age-of-Air.

 

Described earlier in Tutorial 4, the Mean Age-of-Air variable shows how old the air is within the domain of the simulation. Follow the steps below to add a contour of this variable to the project:

  1. From the Add Item tab, select Contour from the Select Item tab

  2. Leave the name as its automatically defined one and ensure the Simulation is set to Internal Ventilation in the dropdown menu

  3. Set the Variable to Mean Age-of-Air, s

  4. Choose XY Plane as the On Plane option

  5. Set the Offset to "2 meters"

  6. Click the Add Item button

 

Tutorial 9 - Figure 25 - Mean Age-of-Air contour added for the internal ventilation simulation, the Building layer has been toggled off

 

Here we can see the contour does not go outside the walls of the building, ensuring that the calculation remained internal. From this angle we see that the air is oldest in the center of the building as well as a small spot in the south-western corner. Ideally one needs to see this data at all elevations. A contour could be defined on the YZ or ZX planes, but this tutorial will add an isosurface to create a 3D view of the oldest air in the building. This would represent regions where if a gas leak were to occur it would not be dissipated and could be considered a 'worst case' scenario to try and mitigate against or prevent.

 

 

Adding Isosurfaces for Internal Ventilation

To facilitate the contour defined above, an isosurface of the Mean Age-of-Air will be defined:

  1. From the Add Item tab, select Isosurface from the Select Item tab

  2. Leave the name as its automatically defined one and ensure the Simulation is set to Internal Ventilation in the dropdown menu

  3. Set the Variable to Mean Age-of-Air, s

  4. From  the contour's legend in Figure 25, we can see the oldest air is at 690s. As this is the upper limit of the variable enter a value of "600" as the Value of the isosurface variable.

  5. Set the Color to be Red by selecting the swatch ( ) from the available options in the dropdown menu to match the color of the contour legend.

  6. Click the Add Item button

 

Tutorial 9 - Figure 26 - 600s isosurface added to the project showing where the oldest air of the facility is present

 

Add another isosurface at a lower value to get a better understanding of the airflow:

  1. Return to the Add Item tab, select Isosurface from the Select Item tab

  2. Leave the name as its automatically defined one and set the Variable to Mean Age-of-Air, s

  3. Enter a value of "550" as the Value of the isosurface variable.

  4. Set the Color to be a transparent orange by:

    1. Selecting the orange swatch ( ) from the available options in the dropdown menu

    2. Click the swatch again and select the Advanced button and set the fourth channel labeled A for alpha to a value of 130 as shown in the below figure.

       

      Tutorial 9 - Figure 27 - Selection of a transparent orange color for the isosurface

       

  5. Click the Add Item button

     

Your 3D window should be similar to Figure 28 below. Here all the regions within the orange isosurface indicates stagnant areas where the air is oldest in the domain.

 

Tutorial 9 - Figure 28 - in:Flux window showing the defined isosurfaces

 

 

Adding Streamlines for Internal Ventilation

  1. From the Add Item tab, select Streamline from the Select Item tab

  2. Leave the name as its automatically defined one and ensure the Simulation is set to Internal Ventilation in the dropdown menu

  3. Set the Direction as Forward and Backward

  4. Ensure the Auto-Seed checkbox is selected and enter a value of "7 meters" as the Offset

  5. Click the Add Item button

 

Tutorial 9 - Figure 29 - streamlines defined for the internal ventilation simulation

 

 

Turn off all visualizations before continuing.

 

In the next section the Mean Age-of-Air contour and isosurfaces will be used to setup a small high pressure gas leak and determine a worst case event to be simulated.