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April 14, 2011, 12:28 
force on gmo with prescribed motion

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jiko
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I am analysing vertical force of water on a vertically (z, axis of gravity) oscillating GMO. the amplitude and frequency of the gmo is prescribed.
now since it is oscillating in still water I thought the initial force would be 0 at 0 time. but it is not. could someone please explain why the vertical force is not zero at zero time. or is something wrong in my simulation setup ? thanks in advance. 

April 26, 2011, 11:00 

#2  
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jiko
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it's quite surprising that no one seems to have any idea of buoyancy 

July 25, 2011, 14:45 

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mohammad hossein shfiei
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July 25, 2011, 18:02 

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Jeff Burnham
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Force is calculated from acceleration (of the water on the object). If there is gravity, then the force is nonzero. If there is motion, then the force is nonzero. At t=0, when using the GMO harmonic oscillation model, acceleration is nonzero. Therefore, the initial state of the fluid is nonzero: although it is not 'in motion' (no advection is occurring), it is accelerating, correct? Therefore, the force on the GMO is also nonzero. Note that velocity works the same way, since it is also following a harmonic oscillation: GMO velocity at t=0 is not zero.


July 29, 2011, 01:21 

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michael barkhudarov
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