WIND in PyroSim

FDS version 6.6.0 added a new WIND namelist to describe wind and atmospheric conditions. Support for WIND was included in PyroSim 2018.1. This post demonstrates this feature.

The new WIND namelist is described in the FDS User Guide, Chapter 10 – Atmospheric Effects and Wind. The FDS User Guide describes the wind_example.fds input file:

The computational domain is a flat landscape that is 1 km by 1 km by 100 m high. There are various rectangular blocks scattered about to represent buildings. The wind speed varies with height as shown in the first plot of Fig. 10.1. The wind also turns a full 360◦ in 50 s, starting and ending in the westerly direction (270◦). This turn of the wind is not realistic, but this case is intended to test the ramp and mean forcing functionality.

Figure 1 shows the geometry of the problem. The wind initially blows from left to right.

Figure 1: Geometry of wind example.
Figure 1: Geometry of wind example. The wind blows from the side boundaries.

To run this problem in PyroSim:

  • Save the wind_example.fds input file that is provided below. You can also download this file directly from the NIST verification examples.
  • In PyroSim, on the File menu click Import FDS/CAD File and select wind_example.fds. PyroSim will inform you how it handled any unsupported data. In this case, the data is added to the Additional Records section of each object. All data is handled correctly.
  • After the file is imported, you can run PyroSim. No other action is required.

To explore where the WIND parameters were added to PyroSim:

  • On the Analysis menu, click Simulation Parameters.
  • Click the Environment tab and click the Edit button associated with Configure Wind.
  • Now you can see which parameters have been set. To match the wind_example input file, the Wind Profile has been set to Morin-Obukhov Similarity, the Thermal Stability has be set to Very Unstable, for Landscape z0 has been set to 0.01, and the Speed is 5.
  • Click the Speed Change over Time tab. Click the Edit Values button for Horizontal Speed to see the time history table.
  • Close the Wind Parameters dialog.
  • Other parameters that have been changed are the Start Time and End Time on the Time tab and the DT_DEVC_LINE on the Misc tab.
  • Close the Simulation Parameters dialog.

The vents on the boundary also have special properties. If you edit the properties for one of these vents, you will notice that:

  • The Surface type is PERIODIC.
  • The WIND option has been added on the Advanced tab.

After you run the simulation, you can plot results. At 30 seconds, the wind has swirled around the obstructions, as shown in Figure 2.

Figure 2: Wind vectors at 30 seconds.

Download Input Files

Download the PyroSim input files here:

wind_example.psm

Comments or Questions

This post was written by Daniel Swenson. For comments or questions, send email to support@thunderheadeng.com.


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