Fire simulation in dead end road

[Ariexi]

Hi 

Any way I can simulate a fire in a dead end road? No forced air into it.

Regards

[Martin Griffith]

Hi, 

This is a tricky challenge for the fire modelling because there is no initial airflow; in reality the airflow is generated directly from the fire. So you need to introduce some airflow to the fire somehow.

One way to do this is to use the Rollback feature. This feature basically breaks up airways into two levels, so that they can have airflow flowing in different directions along the ceiling and along the floor of an airway. Select the dead end, and the under the Draw tool select Construct Rollback. You'll see the airway split up. Try the Fire Simulation now and have a play with it, try different things. Once finished you can Clear Rollback. 

[Ariexi]

Thanks Martin.

I tried that and it worked but the airflow got all mess up. After doing the simulation it seems like Ventsim can't recalculate properly the airflow and allocates big airflows to the area of the rollback, even after clearing the roll back.

Regards

Martin

[Martin Griffith]

Hi, that doesn't sound good. If you like, send us the model and we can try to to recreate the problem. Or perhaps some screenshots. Fire in a low airflow area can be tricky to model. 

[Ariexi]

Hi Martin

I have uploaded a few screenshots to show the air flow changes: before building the rollback, after building the rollback, after the fire simulation, and after fire simulation and have run the air simulation.

Hope it helps

Regards

Martin

[Martin Griffith]

Hi, 

I might be wrong, but it looks like the rollback has not been cleared yet in the final screenshot. If the rollback remains in the model and with the very hot fire temperatures, then the Air Simulation will simulate flow through there. Go to Clear Rollback in the menu under the Draw Tool. If that doesn't revert the rollback back to its original form, then you may have to delete the rollback yourself and rebuild the dead end. 

[Ariexi]

Hi

See attached screenshot, the airflows remain high. The problem is not in the rollback area, as you can see the airflows in there have gone back to cero but outside there the values remain high any idea why.

 

[Martin Griffith]

Hi, 

At the end of the Fire Simulation, you have the option to return the model to its original state. If you don't, then the very hot temperatures that you might have had from a fire will remain and these can significantly affect the results. That would be my main guess why; check if the temperatures are still very high. If so, you can reset the model or run a new Heat Simulation to get back to normal operating temperatures. 

That would be my best guess as to what is going on. 

Let me know how you go.