Setting normal gradient as BC

Dozer_94 · May 3, 2019, 09:27

Hi all,

I am editing icoFoam for a specific calculation in which I want to set the normal gradient of a patch as a boundary condition.

So normally scalar field 'c' would be solved using the BCs for the values of 'c', but now I would like OF to use normal gradient 'dc/dn' as BC.

I know that 'c.boundaryField()[patch].snGrad()' would return the values of the normal gradient, but I'd like it vice versa.

Anyone know if this is possible at all?

Thanks in advance,

fumiya · May 7, 2019, 08:14

Hi,

You can use the fixedGradient boundary condition to set a patch normal gradient to a user-specified value.

Hope this helps,
Fumiya

Dozer_94 · May 7, 2019, 11:22

Hi Fumiya,

Thanks for your reply. I was aware that this was the way to go for the initial conditions. However, I would like OF to do this for me as a BC that changes each timestep.

To give a bit more information: I am using an external solver that calculates dc/dn from other quantities. The goal is to set this calculated dc/dn as BC for the next timestep. Therefore, I need a way (be it a provided member function or a more elaborate method) to incorporate this in the solver itself.

Thanks,

fumiya · May 8, 2019, 09:54

Hi Dozer_94,

The following thread will be of help:
Updating Boundary Conditions Each Iteration

Fumiya

Dozer_94 · May 21, 2019, 10:33

Thank you Fumiya, this was exactly what I was searching for. Seems like something I could have figured out myself, though.

May 3, 2019, 09:27	Setting normal gradient as BC	#1
Dozer_94 New Member Join Date: Dec 2016 Posts: 21 Rep Power: 6	Hi all, I am editing icoFoam for a specific calculation in which I want to set the normal gradient of a patch as a boundary condition. So normally scalar field 'c' would be solved using the BCs for the values of 'c', but now I would like OF to use normal gradient 'dc/dn' as BC. I know that 'c.boundaryField()[patch].snGrad()' would return the values of the normal gradient, but I'd like it vice versa. Anyone know if this is possible at all? Thanks in advance,

May 7, 2019, 08:14		#2
fumiya Senior Member Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 266 Blog Entries: 1 Rep Power: 16	Hi, You can use the fixedGradient boundary condition to set a patch normal gradient to a user-specified value. Hope this helps, Fumiya __________________ [Personal] Blog: https://caefn.com/ Twitter: https://twitter.com/FumiyaNozaki SlideShare: http://www.slideshare.net/fumiyanozaki96

May 8, 2019, 09:54		#4
fumiya Senior Member Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 266 Blog Entries: 1 Rep Power: 16	Hi Dozer_94, The following thread will be of help: Updating Boundary Conditions Each Iteration Fumiya Gerry Kan likes this. __________________ [Personal] Blog: https://caefn.com/ Twitter: https://twitter.com/FumiyaNozaki SlideShare: http://www.slideshare.net/fumiyanozaki96

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May 7, 2019, 11:22		#3
Dozer_94 New Member Join Date: Dec 2016 Posts: 21 Rep Power: 6	Hi Fumiya, Thanks for your reply. I was aware that this was the way to go for the initial conditions. However, I would like OF to do this for me as a BC that changes each timestep. To give a bit more information: I am using an external solver that calculates dc/dn from other quantities. The goal is to set this calculated dc/dn as BC for the next timestep. Therefore, I need a way (be it a provided member function or a more elaborate method) to incorporate this in the solver itself. Thanks,

May 21, 2019, 10:33		#5
Dozer_94 New Member Join Date: Dec 2016 Posts: 21 Rep Power: 6	Thank you Fumiya, this was exactly what I was searching for. Seems like something I could have figured out myself, though.