[jiko]

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.

[jiko]

Originally Posted by jiko

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.

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

[mohammadhosainshfie]

Originally Posted by jiko

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

i think u mast do 2 work:
1. simulate your model and calculate time for stability
2. add this time to general time and told to software start your own problem after calculate time for stability.

[JBurnham]

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

[MuxaB]

Originally Posted by jiko

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.

It is the buoyancy force, like you said, that is computed at t=0. It should be close to the weight of the fluid displaced by the object