# [waves2Foam] Calculating only the buoyancy force of a floating object moving in waves

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 February 5, 2016, 01:34 Calculating only the buoyancy force of a floating object moving in waves #1 Member   Join Date: Jul 2010 Posts: 55 Rep Power: 16 Hi Everyone, Apologies in advance if my question may sound very simple but I cannot figure out the best way to do this. I am interested in calculating only the buoyancy force of a floating object moving in waves. I would like to emphasise I need to seperate the buoyancy from the total force (wave force+buoyancy force). I thought of two ways but none gives exactly what I want: 1) calculate it from the integral of volume fraction over the surface of the body. However, this would only give me the surface area of submerged body. For cylindrical geometries I can convert that into volume and force but not for bodies with complex geometries. 2) integrating the rho*g*h*alpha over the body. If I define gh as Code: `volScalarField gh("gh", g & mesh.C());` then "h" is not measured from the instantaneous free-surface location and is only the coordinates of centre of the mesh. I would highly appreciate any comments/ideas. Many thanks in advance Ashkan

 February 14, 2016, 18:26 #2 Member   Stefan Join Date: Jan 2010 Location: Kiel, Germany Posts: 81 Rep Power: 16 @ashkan Your first approach should be the right one. From divergence theorem you may argue that the ratio of the wetted surface area to the total surface area of your floating body equals displacement, see i.e. equation 3-4 on page 12 here: http://web.mit.edu/flowlab/pdf/Nonli...ve_Impulse.pdf

February 15, 2016, 04:37
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Quote:
 Originally Posted by SD@TUB @ashkan Your first approach should be the right one. From divergence theorem you may argue that the ratio of the wetted surface area to the total surface area of your floating body equals displacement, see i.e. equation 3-4 on page 12 here: http://web.mit.edu/flowlab/pdf/Nonli...ve_Impulse.pdf
Kind regards
Ashkan