Max and min wave height variating in time with 5order stokes waves

lucaoggi · October 22, 2014, 04:20

Hi everybody, I am currently running a simulation of a floating body in 5order stokes waves (1.8s period, 0.3m hight, 10mdepth).

What happens is that max and min wave height oscillates with a low frequency (ca.0.2Hz) resulting in large oscillations (on the same frequency) in the heave response whcih are summing to the supposed heave response due to the wave height/period. I have created my mesh following the suggestions that i found on the Steve forum and refining the free surface area as follow:
X & Y sizes to about 1/80th to 1/100th of the VOF wave wavelength.
Z size to about 1/20th of the wave amplitude.
second order unsteady solver time step relatively to the wavelength division chosen, using the following equation: if the dx chosen was 1/80th, then use (wave period) / (2.4 * 80).

The boundary conditions chosen are
velocity inlet for top, inlet and bottom
pressure outlet for outlet
symmetry for sides

I am having a long domain enough domain to damp my waves and i applied the damping to the pressure outlet boundary My model is 0.25m in diameter and i have and my domain size is 33m (from -8m to +25m)m, 10m, 20m. The model is placed 8m after the inlet.

Any clue about why this is happening?

Thanks in advance!

dai549592484 · October 31, 2014, 08:16

give your result plot plz.

October 22, 2014, 04:20	Max and min wave height variating in time with 5order stokes waves	#1
lucaoggi New Member lucaoggi Join Date: Mar 2012 Posts: 2 Rep Power: 0	Hi everybody, I am currently running a simulation of a floating body in 5order stokes waves (1.8s period, 0.3m hight, 10mdepth). What happens is that max and min wave height oscillates with a low frequency (ca.0.2Hz) resulting in large oscillations (on the same frequency) in the heave response whcih are summing to the supposed heave response due to the wave height/period. I have created my mesh following the suggestions that i found on the Steve forum and refining the free surface area as follow: X & Y sizes to about 1/80th to 1/100th of the VOF wave wavelength. Z size to about 1/20th of the wave amplitude. second order unsteady solver time step relatively to the wavelength division chosen, using the following equation: if the dx chosen was 1/80th, then use (wave period) / (2.4 * 80). The boundary conditions chosen are velocity inlet for top, inlet and bottom pressure outlet for outlet symmetry for sides I am having a long domain enough domain to damp my waves and i applied the damping to the pressure outlet boundary My model is 0.25m in diameter and i have and my domain size is 33m (from -8m to +25m)m, 10m, 20m. The model is placed 8m after the inlet. Any clue about why this is happening? Thanks in advance!

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October 31, 2014, 08:16		#2
dai549592484 Member David Join Date: Nov 2011 Posts: 39 Rep Power: 15	give your result plot plz.