[Nek5000-users] Impose velocity BC on the wall

[nek5000-users at lists.mcs.anl.gov]

Yes - ...


If you simply define the region(s) of interest with 'v   ' for your BC,

then you can simply user userbc.  For example


      omega = 3


      ux=0

      uy=sin(omega*time)

      uz=0


would be one such function.


Paul


________________________________
From: Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov> on behalf of nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
Sent: Wednesday, August 1, 2018 2:42:36 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] Impose velocity BC on the wall

Hi,

if I am not mistaken, 'W' will always impose zero velocity. You may want to use 'v' instead. If you set zero velocity, it will behave like a wall.

In addition, there are several things you should change:
1) you should do this in the userbc subroutine that is called once for each point on the boundary where it needs a value (so you don't have to write the loop yourself).
2) there you need to set the variables ux, uy, uz instead of vx, vy, vz. Probably similar to what you do for inflow.
3) be careful checking equalities with floating point numbers, in some cases you could have y very small but non zero.

Guillaume

Le 01/08/2018 à 07:01, nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov> a écrit :

Dear Nek users,


I am trying to impose a periodic velocity to simulation blowing and suction on a flat plate. The current inlet has a specified velocity whereas the top and outlet are specified as 'O'. The bottom is wall, 'W'. Does anyone has any experience of specifing a temporally periodic velocity on a narrow strip of the wall? I tried to define this velocity in the usrchk like,


do i = 1, n

    x = xm1(...)

    y = ym1(...)

    IF (y .eq. 0) then

      if(x.LT... .and. x.GT...) then

        vy (...)= ...

      endif

    ENDIF

enddo


But this does not work. Could anyone give me some suggestions please?


Thanks in advance



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