Free Surface - Wave model - VOF
 

Hello!

I am trying to simulate regular waves. And it seems that I am having some problems because the waves that I obtain are not regular. Their amplitude decrease with the time
I represent the free surface using Volume fraction of Water, that is the Eulerian Multiphase I created.
Does anybody understand the difference between Volume fraction of Water and Volume Fraction of Heavy Fluid of First Order VOF Wave??
Heavy one could only be used in the initial conditions and in boundary condition?


Thanks in advance!

Hello raquelcfd,
not sure that i can help you ,cause i'ma also new in Star CCm, but i could try to. I have modeled boat in wave and i don'y have your type of "errors" if i can said.
So you wanted to know if "Does anybody understand the difference between Volume fraction of Water and Volume Fraction of Heavy Fluid of First Order VOF Wave??"....
Okay..i effectively use Volume Fraction of Heavy fluid when i choose the initial conditions and the properties at the boundary. I suppose that the software understand it like the proprties at the boundaries
Now for the Volume fraction of water, i only use it when i want to represent scenes....
Like i said ,not sure that, that can help you. But i don't have this kind of problem.
PS: You also have to look the dimension of your block containing your Boat...maybe it is not too large so you may the phenomene if refraction of waves.

Still same problem
 

Hello @BRICE P.
First of all, thanks for your answer.
Im still have that “error” trying to simulate a wave with these parameters: Wave amplitude of 0.5m and period of 6 seconds, with a wave depth of 80 meters.
I am also using the Volume Fraction of Heavy Fluid as initial or boundary conditions, and then the Volume fraction of water, just to represent the free surface (as an isosurface of 0.5 volume fraction of water).
I do not understand why the amplitude of my waves is decreasing with time..

Please, find attached the plot of my free surface at 20 seconds of simulation, 40 seconds and 60 seconds)…
Axis x is the longitudinal axis of the tank (the horizontal plane) and y axis is the z position of the free surface at thta x value.

My tanks dimensions are at least 5-6 wave periods.
I have put damping condition in the outlet.
As it could be seen, the amplitude of the waves is decreasing along the tanks (x axis) and with the time (from 20 seconds to 60).
it should be 0.5 and even at 20 seconds does not reach that value

Any recomendation?? :confused::confused:

Hi
Do you know where you damping point begin?
When you see the theory below, you may understand how Star CCm represents the damping in the simulation.
Now, when i look on your pic, maybe the point where the damping start is to close from your boat.
Maybe you should put it far away from the boat or even try to remove first the damping and see how it goes (if the amplitude is still decreasing).