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[OLAFLOW] The height of wave generated by OF1806 is too small compared to theorectical wave

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Old   November 29, 2018, 07:53
Default The height of wave generated by OF1806 is too small compared to theorectical wave
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Luo_Bingjun
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I use OF1806 to generate a 3D Stokes I wave. The wave properties parameters are as follows. The wave height can be seen in the following picture. The blue one is the wave I generate and the red one is theorectical wave height. Obviously, the wave height is much smaller than the theorectical one. I guess it was because the wave absorption method doesn't work well.
Are there any parameters that I set wrongly? Or which parameters do I need to adjust so that the wave height can match the theorectical one?
Besides, I learn a little about olaFlow. what's the relationship between olaFlow and IHFOAM?
Thanks!

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Old   December 6, 2018, 06:36
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Pablo Higuera
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Hi Luo_Bingjun,

please change the tag of the post, since you are not using olaFlow, but IHFOAM.

If you want to find out more about olaFlow you can check https://github.com/phicau/olaFlow and https://sites.google.com/view/olaflowcfd , although the last site is not available in China.

Best,

Pablo
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Old   December 6, 2018, 23:08
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Hello,Phicau!Thank you for your answering my questoin.
Actually, first I use IHFOAM to generate the wave I mention above. I have already learned ablout the information of the above two websites.
Later, I also try olaFlow17xx version. I get the similar results. I generate the 3D StokesI wave, the results are that near the inlet, the wave height is colse to the theorcetical wave and sometimes a little larger, but in the locations which are far away the inlet, the wave height is much smaller than the theorectical one, especially after 150 second. The following shows the parameters I set and the wave in different locations. The blue line is the wave height I generate by using olaFlow17xx version and the red line is the theorectical wave height. The depth of water is 200m.
I hope your answer. Thank!




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Old   December 7, 2018, 03:55
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Pablo Higuera
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Hi Luo_Bingjun,

that seems better! Your wave conditions are in deep waters and active wave absorption is for shallow waters, therefore you might experience some deviations because of that. I will soon release an active wave absorption theory that works for deep waters too and I am positive that you will experience improvements.

About the decay. Are you using a turbulence model? The decay that you experience is typical from the turbulence models used in OpenFOAM. If that is the case, there is a solution, see: https://sites.google.com/view/olaflo...ions-revisited
If you use Larsen's corrections you can avoid wave damping to a major extent.

By the way, if you are in China and cannot access the website, see the PDF attached.

Best,

Pablo
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File Type: pdf Turbulence models for wave simulations revisited.pdf (120.2 KB, 4 views)
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Old   December 9, 2018, 08:58
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Hello, Pablo! Thank you for your answering my question.
I first don't use any turbulence model. I treat the wave as laminar. After seeing your reply, I try to generate the above wave using kOmegaSST model and kOmegaSSTBuoyancy model. The latter model is put forward by Larsen. However, the result seems no difference. The wave heights in different locations generated by using turbulence model are the same as the picture I show you before(the blue line).
That is, the wave height I generate is too small, especially in the time after 150 second. So, the problem has no matter with the turbulence model. Maybe it's the shallow water absorption problem. I hope that you can release the deep water absorption theory soon.
Thank you!
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Old   December 9, 2018, 21:20
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Pablo Higuera
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Hi Luo_Bingjun,

you are right if you are running a laminar case this is likely to be caused by the shallow water active wave absorption theory.

Right now we are very busy closing things before the year ends, so I cannot announce a release date, but I will try to make it as soon as possible.

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