# Does Bernoulli's equation describe why my curtains stick to the mesh?

I was sitting right in front of a big window (with a mesh) with curtains open, suddenly wind swooshes in, curtains sway forth and back. While they sway backward, they stick to the window(mesh) as if they are being sucked due to a vacuum. Somewhat like the image below:

Now my explanation for this phenomenon was using Bernoulli's Equation:

$$P_0+\frac{\rho v^2}{2}+\rho g h = \text{constant}$$

taking $$h=0$$ (because I'm assuming that Air is acting $$\perp$$ to the curtain surface,) one can observe that: when fast blowing air moves past the curtains, Pressure in the region between window(mesh) and curtains drops causing them to sway back (and stick to mesh).

Is that right?

Any corrections and further insights into the problem are appreciated.

Edit: To better understand the problem and diagram, you can consider visualizing the "Curtain swaying back" part in the diagram as if the direction of the wind reverses when curtains start getting back to there equilibrium position, i.e. wind is pushing the curtains into mesh!

• I am still trying to make sure I understand the scenario, but I would recommend looking at some misapplications of Bernoulli's principle just in case :) May 28, 2020 at 20:57
• Could you perhaps make a diagram of the system? I still don't fully understand the scenario. May 28, 2020 at 21:03
• Thanks for the diagram. How large is the room? Does the air coming in have anywhere to go? May 28, 2020 at 21:26
• Room is kinda big, I don't know about the actual size, and Yes air has a lot of space to go i.e. Room is not sealed if you're taking that part into consideration.But curtains cover the window completely May 28, 2020 at 21:30
• Do the curtains always get sucked in when pushed out or is it random? If it is random I think your arrows are in the wrong direction. Turbulent wind can come in different directions and cause the curtains to be pushed towards the window if the wind is travelling parallel to the outside wall via Bernoulli's equation.
– Cell
May 28, 2020 at 21:39

The most likely reason is that, for whatever reason$$^*$$, air rushing into your room then tries to rush out. This pushes the curtains against the mesh. Without actually being there and seeing it / doing other tests I am not sure if there is more I can speculate about though.
$$^*$$ My guess is that, since before the wind is blowing, the air in your room / house(?) is at equilibrium with outside air (concentration wise), and so when more air rushes in it will then eventually try to rush back out.