Huge difference in Fire shape and behaviour between with and without collision (HIP FILE ATTACHED)

[Coz_y_not]

I have a simple fire simulation, emitting from inside the car.

First without collision, so the fire does NOT see the car as a collider, I get this:

Then after I add the car as a collider (static object, geo and vdb as usual):

... I get this very very very different look and behaviour:

I know the fire still goes through the collider with 1 substep, but I just wanted to see how the fire will behave. If I add more substeps the fire gets more and more agitated, like a haunted flame.

The only difference between the two sims is adding the collider, nothing else has changed, absolutely nothing.

Any idea why is the fire looks and behaves completely differently when with collider? it looks a lot more agitated and "nervous", it seems like the collider has given some steroids to the gas disturb nodes that were already there before the collider was added.

I attached the hip file.

burning_car_q.hiplc

Edited Thursday at 01:22 PM by Coz_y_not