[waves2Foam] INLET relaxation boundary interface diffusion during irregular sea state

Marc Batlle · June 2, 2020, 11:58

Good afternoon,

These days I have been understanding and testing different features of the application waves2Foam with OF-v1912. My purpose is to reproduce different irregular sea states.

I created my own script as an input for the wavesProperties, similarly as the function "setWaveParameters". The irregular case is calibrated using a JONSWAP spectrum, with; Hs= 1m, Tp= 9s, peak enhancement=3.3 and a random phase.

The thing is, the free surface elevation seems to be well reproduced inside the relaxation zone but some kind of "dissipation" occurs at the boundary between the relaxation zone and the computation region. Lowering the whole wave heights and thus giving a very low energy spectrum within the computational zone.

I tested different lengths for the wave INLET region without any improvements, among other tests.

I attach one of my cases, where hopefully an experienced eye can find if this situation is due to a wrong case setup.

Thanks foamers,

Marc

ngj · June 3, 2020, 07:05

Hi Marc,

Please read this post on giving sufficient information:

Guide: How to ask a question on the forums

For instance, you do not provide information on the grid and resolution, so it is very likely that the dissipation that you observe it due to too large cells. Also, you do not show an example of the claimed dissipation, which would also be useeful.

Kind regards

Niels

ngj · June 3, 2020, 08:01

I made a quick check and your problem is most likely in your own script. Reverse engineering suggests that you have calculated the wave numbers based on shallow water wave theory and this is not generally applicable for irregular wave spectra.

Repeat your calculation with spectra calculated using the setWaveParameters tool and your results are most likely to improve considerably.

Kind regards

Niels

Marc Batlle · June 5, 2020, 11:39

Hi Niels,

First thanks for your contribution and dedication to CFD Online as well as OpenFOAM.
Secondly, thanks for your quick and helpful reply.

A simulation is ongoing at the moment with the corresponding correction on the wave number definition. So far, the issue seems that no longer happens.

Thanks again, I really appreciate your time.

Marc

Ps: I will pay more attention to the "ask a question" recommendations next time

June 3, 2020, 07:05		#2
ngj Senior Member Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Copenhagen, Denmark Posts: 1,900 Rep Power: 37	Hi Marc, Please read this post on giving sufficient information: Guide: How to ask a question on the forums For instance, you do not provide information on the grid and resolution, so it is very likely that the dissipation that you observe it due to too large cells. Also, you do not show an example of the claimed dissipation, which would also be useeful. Kind regards Niels __________________ Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.

June 3, 2020, 08:01		#3
ngj Senior Member Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Copenhagen, Denmark Posts: 1,900 Rep Power: 37	I made a quick check and your problem is most likely in your own script. Reverse engineering suggests that you have calculated the wave numbers based on shallow water wave theory and this is not generally applicable for irregular wave spectra. Repeat your calculation with spectra calculated using the setWaveParameters tool and your results are most likely to improve considerably. Kind regards Niels __________________ Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.

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June 5, 2020, 11:39		#4
Marc Batlle New Member Marc Batlle Join Date: Mar 2017 Posts: 9 Rep Power: 9	Hi Niels, First thanks for your contribution and dedication to CFD Online as well as OpenFOAM. Secondly, thanks for your quick and helpful reply. A simulation is ongoing at the moment with the corresponding correction on the wave number definition. So far, the issue seems that no longer happens. Thanks again, I really appreciate your time. Marc Ps: I will pay more attention to the "ask a question" recommendations next time