[Nek5000-users] Stochastic inflow boundary condition using previous time step velocities?

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

Hello,

I am trying to code a stochastic inlet boundary condition for a backward
facing step case. I am using the PN/PN-2 formualtion at Re=28,000.

In this b.c., we use previous time step values to initialize the
fluctuations and final fluctuations are done using the stochastic model.

  ufluct = u(t-dt) - umean
  ...........
  ...........
  ...........
  ux = uprime + umean

To implement this in subroutine USERBC, I am facing trouble to use the
previous time step values.

Are they stored in VXLAG(LX1,LY1,LZ1,LELV,1)? How can I call those
velocities in USERBC? And can I do this?

  ufluct = vxlag(1,1,1,1,1) - umean

Thanks,

Harish.