WAVE TANK star-ccm+ . wave height dampens. WHY?

muhsin · August 4, 2012, 06:55

HI all.
I am trying to simulate wave tank with dimensions [ 26m*.6m*1m = L*B*H ]

Boundary conditions:
1. same as DFBI tutorial
2. Velocity inlet [ wave field function], [bottom, sides and end] as walls and top as pressure outlet.[atmospheric pressure]

In both conditions I am not getting proper wave height at different positions from velocity inlet.
It seems that wave is getting damped as it progresses. NO VOF WAVE DAMPING WAS ACTIVATED.

You can see in the images below

this is for IMPLICIT UNSTEADY time step=.01s
When i use time step of .001s results are better but even then wave dampens as it progress.
cut section through wave tank

BrenS · August 10, 2012, 18:50

My first thought is that it is a meshing issue. Often a coarse mesh will damp out waves. Thus, it is important to have a fine enough mesh from the inlet to the area of interest in order to maintain the full size of the wave. Additionally, some mesh size and time step combinations can cause odd issues with the free surface such as unwanted damping and wave reflections.

Henry Arrigo · September 5, 2012, 06:18

BrenS is right. One good remedy is to refine the mesh in the vicinity of the free surface.

zouzou0 · October 9, 2012, 13:24

hi! how did things go with you . I am trying simulate a wave tank so if you can send me a tutorial or any link that can help. I am still new to cfd so please any help will be appreciated.

August 4, 2012, 06:55	WAVE TANK star-ccm+ . wave height dampens. WHY?	#1
muhsin New Member muhsin Join Date: Jun 2011 Posts: 9 Rep Power: 14	HI all. I am trying to simulate wave tank with dimensions [ 26m.6m1m = LBH ] Boundary conditions: 1. same as DFBI tutorial 2. Velocity inlet [ wave field function], [bottom, sides and end] as walls and top as pressure outlet.[atmospheric pressure] In both conditions I am not getting proper wave height at different positions from velocity inlet. It seems that wave is getting damped as it progresses. NO VOF WAVE DAMPING WAS ACTIVATED. You can see in the images below this is for IMPLICIT UNSTEADY time step=.01s When i use time step of .001s results are better but even then wave dampens as it progress. cut section through wave tank Kelysamex likes this.

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August 10, 2012, 18:50		#2
BrenS New Member Brendan Smoker Join Date: May 2010 Posts: 7 Rep Power: 15	My first thought is that it is a meshing issue. Often a coarse mesh will damp out waves. Thus, it is important to have a fine enough mesh from the inlet to the area of interest in order to maintain the full size of the wave. Additionally, some mesh size and time step combinations can cause odd issues with the free surface such as unwanted damping and wave reflections.

September 5, 2012, 06:18		#3
Henry Arrigo Senior Member Henry Arrigo Join Date: Jun 2010 Location: Italy Posts: 100 Rep Power: 15	BrenS is right. One good remedy is to refine the mesh in the vicinity of the free surface.

October 9, 2012, 13:24		#4
zouzou0 New Member Bilal Zeidan Join Date: Oct 2012 Posts: 2 Rep Power: 0	hi! how did things go with you . I am trying simulate a wave tank so if you can send me a tutorial or any link that can help. I am still new to cfd so please any help will be appreciated.