
[Sponsors] 
April 14, 2011, 11:28 
force on gmo with prescribed motion

#1 
Member
jiko
Join Date: Sep 2010
Posts: 31
Rep Power: 8 
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, 10:00 

#2  
Member
jiko
Join Date: Sep 2010
Posts: 31
Rep Power: 8 
Quote:
it's quite surprising that no one seems to have any idea of buoyancy 

July 25, 2011, 13:45 

#3 
New Member
mohammad hossein shfiei
Join Date: Jul 2011
Posts: 2
Rep Power: 0 

July 25, 2011, 17:02 

#4 
Senior Member
Jeff Burnham
Join Date: Apr 2010
Posts: 204
Rep Power: 9 
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, 00:21 

#5  
Senior Member
michael barkhudarov
Join Date: Mar 2009
Posts: 332
Rep Power: 11 
Quote:


Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Moving mesh  Niklas Wikstrom (Wikstrom)  OpenFOAM Running, Solving & CFD  122  June 15, 2014 06:20 
Prescribed object motion and 6DOF  vinz  OpenFOAM Running, Solving & CFD  1  September 23, 2013 07:37 
DEFINE_CG_MOTION and pressure force  Teo Fumagalli  FLUENT  0  April 11, 2008 10:25 
Convergence moving mesh  lr103476  OpenFOAM Running, Solving & CFD  30  November 19, 2007 15:09 
Automatic Mesh Motion solver  michele  OpenFOAM Running, Solving & CFD  10  September 26, 2005 08:21 