# Can butterfly only simulate thermal pressure ventilation?

I want to simulate a model like this. There is an atrium in it and windows on four walls are all inlet windows, window on the roof will be set as outlet.

And I refer to the atrium-buoyancy example file. But it doesn’t work well. Then I set inlets only on one wall(south wall) , windows on the north and the roof window are set as outlets. Only this time, it works, and as the pic above, wind pressure ventilation influences the results.

Can butterfly only simulate thermal pressure ventilation?
If can, how to set inlets and the wind vector, and most importantly, the temperature of each faces.
BTW I can’t find tutorials of butterfly buoyancy on the internet, can anybody send me one?

Hi, Cordelia

I’m Takeru, architectural student.

Now I’m struggling to run a simulation whose purpose is to check the effect of only thermal pressure/buoyancy ventilation?

Thank you and best regards
Takeru

I think you can do it by setting the boundary conditions other than temperature and pressure at the opening to `zeroGradient`, but be careful because the calculation will be unstable. In some cases, you may want to consider placing the building in a very slow flow.
The heat source can be set by the wall temperature or by the method described in the following link.

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Hi, @kinonotofu
Thank you again!

I did as you said about the boundary set by using “Butterfly_boundary” component.
The simulation itself worked. But the result is not so good because the wind exit through the skylight and the lower window.
My prediction is that it will be with air entering through the lower window and exiting through the ceiling window.

Each boundary tempreature set is below and attached my gh file.
Roof : 40℃
walls : 35℃
floor : 30℃
inlet : 25℃
outlet : 30℃

No wind analysis.gh (77.6 KB)

Kind reagards
Takeru

If you set the boundary condition for velocity to zeroGradient, the boundary for pressure should not be zeroGradient.
Try to set the boundary condition condition of p_rgh to zero with fixedValue.

It may be difficult to obtain a stable flow field with only the heat flow from the wall.