Mixed and directionMixed bc

Fried · April 8, 2011, 05:43

Hallo everyone,
I have to say I am quite new with using OpenFOAM.
I would like to impose a velocity boundary condition with a fixed value for two velocity components and a normal derivative for the remaining component, e.g.:
(u=const. dv/dn=assigned w=const.)
To me, the mixed type bc looked the right choice - or maybe the directionMixed, depends if I can give a different valuefraction for every component), but I am not able to find out anywhere how to specify it.
Is there anyone who can tell me the right assignment template?
Something like:
{
type mixed
refValue ...
reg gradient ...
...
}
Thanks in advance,
F.

yongxiang · April 5, 2017, 11:10

Hello Fried,
did you solve this problem in the end? I am also setting such BC as you wised, (u = 1, dvdn = 0, dw/dn= 0). Would you please show me how to specify such a BC?
Thanks very much.
Regards
YX.

Fried · April 6, 2017, 06:27

Hello Yong Xiang,
no, unluckily I never got any reply and some time afterwords I was not working on this anymore. But quite some time has past, maybe now it's possible/easier to implement it?
Regards,
F.

yongxiang · April 7, 2017, 08:56

Hello Fried,
after some search online, I found one boundary condition which may do the bc, which is called directionMixed, which setting partly fixedValue and partly fixedGradient for corresponding velocity component are possible. Below is an example I used, for your info:

type directionMixed;
refValue uniform (5 0 0);
refGradient uniform (0 0 0);
valueFraction uniform (1 0 0 0 0 0);
value uniform (5 0 0);

regards
YX.

April 8, 2011, 05:43	Mixed and directionMixed bc	#1
Fried New Member Join Date: Apr 2011 Posts: 9 Rep Power: 15	Hallo everyone, I have to say I am quite new with using OpenFOAM. I would like to impose a velocity boundary condition with a fixed value for two velocity components and a normal derivative for the remaining component, e.g.: (u=const. dv/dn=assigned w=const.) To me, the mixed type bc looked the right choice - or maybe the directionMixed, depends if I can give a different valuefraction for every component), but I am not able to find out anywhere how to specify it. Is there anyone who can tell me the right assignment template? Something like: { type mixed refValue ... reg gradient ... ... } Thanks in advance, F.

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April 5, 2017, 11:10		#2
yongxiang Member Join Date: Sep 2014 Posts: 32 Rep Power: 12	Hello Fried, did you solve this problem in the end? I am also setting such BC as you wised, (u = 1, dvdn = 0, dw/dn= 0). Would you please show me how to specify such a BC? Thanks very much. Regards YX.

April 6, 2017, 06:27		#3
Fried New Member Join Date: Apr 2011 Posts: 9 Rep Power: 15	Hello Yong Xiang, no, unluckily I never got any reply and some time afterwords I was not working on this anymore. But quite some time has past, maybe now it's possible/easier to implement it? Regards, F.

April 7, 2017, 08:56		#4
yongxiang Member Join Date: Sep 2014 Posts: 32 Rep Power: 12	Hello Fried, after some search online, I found one boundary condition which may do the bc, which is called directionMixed, which setting partly fixedValue and partly fixedGradient for corresponding velocity component are possible. Below is an example I used, for your info: type directionMixed; refValue uniform (5 0 0); refGradient uniform (0 0 0); valueFraction uniform (1 0 0 0 0 0); value uniform (5 0 0); regards YX.