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What is the propriate usage of patch boundary conditions?

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Old   June 3, 2021, 05:48
Default What is the propriate usage of patch boundary conditions?
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Furkan Türkmen
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Hello,


When I use the inflow discharge options to set inlet boundary conditions, I realized that the inflow velocity changed (it can be read from the main log file, Ui). I have tried to set water level fixed at the inlet boundary conditions to remain velocity same during simulation but it did not remain same. I used ioflow and discharge options to make that.



I have also tried patch boundary conditions, I turned off the ioflow, then there was no velocity at the inlet. I think that I do not understand the usage of patchBC. There is different options for patch boundary condition in the last release 21.05. What is the correct combination of these settings to make constant the velocity at the inlet? Actually I want to give the velocity magnitude and direction directly for the inlet BC.



PS: I used CFD solvers, free surface analysis.


Thank you,

Best regards,
Furkan
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Old   June 6, 2021, 04:44
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Hans Bihs
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If you set the discharge as a boundary condition, the inlet velocity is defined as U =Q/A. So when the free surface level changes, the velocity is adjusted so that the discharge condition is fulfilled.

The main idea of patchBC is that it defines inflows/outflows in a very flexible way. Wall boundaries are converted by patchBC using the options B 440, B 441 and B 442 in REEF3D, so at any boundary in the domain. For this, you use wall boundaries for all sides in DIVEMesh.
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Old   June 7, 2021, 02:41
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Furkan Türkmen
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Hello Prof. Bihs,


Thank you for the answer, I will try.


Regards
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Old   October 16, 2021, 05:44
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Hao hao
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Quote:
Originally Posted by valgrinda View Post
If you set the discharge as a boundary condition, the inlet velocity is defined as U =Q/A. So when the free surface level changes, the velocity is adjusted so that the discharge condition is fulfilled.

The main idea of patchBC is that it defines inflows/outflows in a very flexible way. Wall boundaries are converted by patchBC using the options B 440, B 441 and B 442 in REEF3D, so at any boundary in the domain. For this, you use wall boundaries for all sides in DIVEMesh.
Hi Han bihs What functions can I use to simulate Wave + Current,
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Old   October 17, 2021, 15:39
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Hi Hao Hao,

the wave libraries are currently not connected to the patchBC system. This is something we currently work on.

At the moment you can use the regular wave tank by using B 60. See the NWT tutorial examples. You can add current to waves by using W 10. Then waves and current are generated from the same inlet.
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Old   October 18, 2021, 22:43
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Originally Posted by valgrinda View Post
Hi Hao Hao,

the wave libraries are currently not connected to the patchBC system. This is something we currently work on.

At the moment you can use the regular wave tank by using B 60. See the NWT tutorial examples. You can add current to waves by using W 10. Then waves and current are generated from the same inlet.
Hi Han Bihs
Thank you so much for your useful advice,which will be of great help to me in learning REEF3D in the future.
Best regards
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