# Mixed and directionMixed bc

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 April 8, 2011, 04:43 Mixed and directionMixed bc #1 New Member   Join Date: Apr 2011 Posts: 9 Rep Power: 8 Sponsored Links 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.

 April 5, 2017, 10:10 #2 New Member   Join Date: Sep 2014 Posts: 18 Rep Power: 4 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, 05:27 #3 New Member   Join Date: Apr 2011 Posts: 9 Rep Power: 8 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, 07:56 #4 New Member   Join Date: Sep 2014 Posts: 18 Rep Power: 4 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.

 Tags directionmixed bc, mixed bc

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