[OtavioDuarte]

Hello!

I am simulating a wave, using OpenFOAM, however I am having problems with reflections in the tank. To solve this problem I am trying to apply the damping, but without success.
I would like to know about the lambda coefficient used fvoptions in vertical damping. How to know the correct value to use? In the tutorial the value is 0.5, but it does not work for my wave.

Wave used:

************ {
**************** length 65.4;
**************** amplitude 0.5;
**************** phase 0;
**************** angle 0; }

option1
{
type verticalDamping;

selectionMode all;

origin (250 0 0);
direction (1 0 0);
ramp
{
type halfCosineRamp;
start 0;
duration 600;
}

lambda 0.5;

timeStart 0;
duration 1e6;
}

Thank you!

[Thepsy]

did you sucess to your problem ? I have the same.


I do not understand why the damping coefficient works for long domain and not for short.


Could someone help me ?


How to calculate lambda ?

[outlawSun]

My personal experience:

My wave tank was 11m*0.6m*0.6m. Wave parameter being 2s wave for 0.38m of still water level. For a successful 25s simulation coverage, the damping coefficient needs to be increased to 2 or even 3. The problem with this simple vertical damping is that with large damping coefficient, the surface elevation upstream is decreased significantly, while low coefficient (~0.5 or 1) simply is not enough to address the reflection.

If you want to learn about how it is computed, you can try some of the online tutorials, they have some equations in them.

A better option is to define a region in your mesh using topoSet celltoBox and call in the damping (fvOption). In this way, the damping coefficient can be very large and the effect on upstream elevation is not as strong so wave is damped while not screwing up the useful part. However, some unexplained small scale oscillation is discovered, but I think it is the best result I have so far.