Smoke Stratification Under Awning – Unexpected Behavior

[Alexg2991]

I am running an FDS simulation under an awning. The awning is enclosed on the top and has sides extending downward, leaving a 6m gap between the lowest edge of the sides and the floor. One side is fully closed, two sides are partially enclosed with the 6m gap, and the last side is completely open.

I expected the smoke to accumulate under the awning and spill out through the gaps. However, after reaching steady state, the smoke remains at a certain height and does not fill the volume below.

Possible causes I’ve considered:

Temperature Stratification – Hot gases may be forming a stable layer at the upper part of the awning due to buoyancy.
Grid Resolution – A coarse grid might be suppressing turbulence and proper smoke mixing.

I have attached the .fds file for reference. Any insights on why this is happening and how to improve the simulation?
Thank you all
Awning.txt

[drjfloyd]

The backside in this image is an OPEN boundary. Smoke is just going to flow right out the opening. There is nothing to cause the smoke to form a layer that would get deeper then the lower edge of the awning seen on the front side of the image.

[Alexg2991]

Beautiful catch, thank you!

I have the mesh at the back of the awning right after the wall, so the wall was excluded from the model, and I didn’t even see the smoke spill out.