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Author Topic: Tunnel boundary conditions  (Read 2378 times)


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Tunnel boundary conditions
« on: October 16, 2018, 11:02:08 am »

Hi guys,

I am trying to simulate a fire within a tunnel by only modeling a section of the tunnel.

In order to be more realistic I should apply a loss coefficient to the portal boundaries to simulate the extension of tunnel (which is not explicitly included in the model).

My initial thought was to use a small HVAC duct and 2 nodes on the boundary and add the loss coefficient, however I am getting a numerical instability mid-way through the simulation.

I have tried increasing the HVAC_PRES_RELAX to 0.9 and also using  DT_HVAC of 1 second as recommended in the user guide to help reduce the sensitivity of the pressure communication between FDS nodes and HVAC nodes, however this has not been successful.

Any suggestions are welcome.
Thanks in advance!
« Last Edit: October 18, 2018, 06:37:38 am by acalado »