Buoyancy force calculation question

[Martz]

Hi,

I'd like to calculate the buoyancy force exerted on a gate in an intake channel (see picture in attachment). Since the gate is not totally surrounded by water, I guess that the normal buoyancy formula doesn't apply here, am I right ? Is there a rule of thumb for this kind of problem ?

Thanks

Martz

 

[Martz]

Hey guys,

Seeing not a lot of people have actually seen the picture, I thought I'd host it somewhere else so it could be shown directly on the page.

http://img140.imageshack.us/img140/6809/buoyancy.png

Also, I guess I could add more data in order for you to help me.

The buoyancy rule states : "A body immersed in a fluid experiences a vertical buoyant force equal to the weight of the fluid it displaces."

So if we say that the gate is "immersed in water", the buoyant force would be Gate_Volume [m³] * 1000 [kg/m³] * 9.81 [m/s²]. The problem is; is the gate considered "immersed in water" if there is air (we suppose atmospheric pressure) on one of its side ?

Thanks in advance for your help.