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Very 'applied' question, but I have nowhere else to turn, so I'm asking the physics experts here: I have a carport whose ceiling is made of very lightweight paneling. I've had several times now that those panels have fallen down, without an evident reason. So I'm wondering: the wind (because of the placement of other buildings in the area) blows very strong underneath the carport. Could it be that strong wind gusts, through the Bernoulli principle, are causing 'pull' on the panels and tearing them from the staples they are attached with? Stated more generally, does a fluid flowing fast beneath a surface cause a force on that surface? Thanks.

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I don't think you can explain this by the Bernoulli principle. However, some lift forces have to be present here. – Bernhard Dec 30 '12 at 13:50
Stick with your last formulation --- aerodynamic forces are indeed likely to cause such a behavior. – Yrogirg Dec 30 '12 at 15:55

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If a downward force was applied to the panels to 'pull' them down it would be the result of a pressure difference on either side of the panel. Consider a flat plate in a wind tunnel. On each side of the plate the freestream velocity is equal, thus the static pressures are equal (assuming the flow is homogeneous and the plate is at zero angle of attack). Because there is no pressure difference, there is no lift on the plate.

If the plate is at an angle of attack, there is lift present. If the wind is impinging on your carport's roof at an angle, this could be the cause. If this is the case there isn't much you can do about it other than improving the structure.

Now instead consider the walls of the wind tunnel. The freestream velocity is the same as in the flat plate case, so the static pressure in the tunnel is the same as before. However, the outside of the tunnel is at approximately stagnation pressure (assuming open-return wind tunnel). In this case there can be a huge pressure difference applied over a large area, resulting in a huge force.

If there is a open sealed cavity above the panels in your carport, a strong gust of wind could setup this pressure difference and cause a large downward force. If possible, maybe try drilling some ventilation holes in the panel to reduce the pressure difference.

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