Computation of the Force with mesh deformation

adenlan · August 10, 2012, 06:05

Hello everyone,

I have been trying to simulate the oscillation of a box, to compute oscillatory hydrodynamic coefficient.
For that, I use a mesh deformation, that is, the box is oscillating in calm water.
Normally, I would expect a sinusoidal force result in the direction of motion (thus I would compute hydrodynamic coefficients from Morison force equation).
However, I get very noisy results. When I try to reduce this supposedly numerical noise by increasing the timestep, the sinusoid is deformed and results are messy.
I precise that I alternatively used both SST and SAS turbulence models and the simulation is run with parallel recursive coord bisection (Metis failed).
Can anyone provide some insights to resolve this troubling issue ?

Thank you in advance

adenlan · August 13, 2012, 03:09

I assume nobody has encountered this issue before ?

ghorrocks · August 13, 2012, 03:28

Your initial question was unclear so I did not bother replying. Sorry to be cruel but with some many posts on-line I rather spend my time on better written questions.

Can you post an image of what you are seeing, some plots of what is "messy", and some images of your geometry so we know what you are talking about.

singer1812 · August 13, 2012, 09:53

Are you using slight incompressible water for water material properties?

August 10, 2012, 06:05	Computation of the Force with mesh deformation	#1
adenlan New Member Join Date: Aug 2010 Posts: 7 Rep Power: 15	Hello everyone, I have been trying to simulate the oscillation of a box, to compute oscillatory hydrodynamic coefficient. For that, I use a mesh deformation, that is, the box is oscillating in calm water. Normally, I would expect a sinusoidal force result in the direction of motion (thus I would compute hydrodynamic coefficients from Morison force equation). However, I get very noisy results. When I try to reduce this supposedly numerical noise by increasing the timestep, the sinusoid is deformed and results are messy. I precise that I alternatively used both SST and SAS turbulence models and the simulation is run with parallel recursive coord bisection (Metis failed). Can anyone provide some insights to resolve this troubling issue ? Thank you in advance

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August 13, 2012, 03:09		#2
adenlan New Member Join Date: Aug 2010 Posts: 7 Rep Power: 15	I assume nobody has encountered this issue before ?

August 13, 2012, 03:28		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Your initial question was unclear so I did not bother replying. Sorry to be cruel but with some many posts on-line I rather spend my time on better written questions. Can you post an image of what you are seeing, some plots of what is "messy", and some images of your geometry so we know what you are talking about.

August 13, 2012, 09:53		#4
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	Are you using slight incompressible water for water material properties?