[Nek5000-users] 2D simulation for 3D perturbation mode with a 2D baseflow
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Wed Oct 23 12:06:13 CDT 2013
Hi Neks,
I have a 2D baseflow and I am doing 3D perturbation mode calculation at
a prescribed spatial wavelength lambda=2pi/k (k the wavenumber) in the
third direction. The baseflow is assumed to be invariant in this third
direction therefore the perturbation can be chosen in the form
u=uhat(x,y,t) e(ikz) where z is the third direction and u=(u,v,w) and
the baseflow is in the form (U,V)(x,y) (in particular W=0).
In this case the 3D linearized equations simplify to the following form
duhat/dx+dvhat/dy+kwhat=0
duhat/dt + U duhat/dx + V duhat/dy = -uhat dU/dx - vhat dU/dy + nu (
d^2uhat/dxx+d^2uhat/dyy-k^2uhat )
dvhat/dt + U dvhat/dx + V dvhat/dy = -uhat dV/dx - vhat dV/dy + nu (
d^2vhat/dxx+d^2vhat/dyy-k^2vhat )
dwhat/dt + U dwhat/dx + V dwhat/dy = nu ( d^2what/dxx+d^2what/dyy-k^2what )
I am currently doing 3D perturbation simulations with the box dimension
in the third dimension set to lambda but I was wondering if Nek offers
the possibility to run 2D simulations instead to solve for uhat(x,y,t).
Indeed in the above equations, one does not need any mesh in the z
direction. A 2D mesh is enough but this means modifying slightly the
linearized equations to insert the k terms.
I have been looking in the source files and I have found nothing like
that so I guess this is not currently in Nek.
Any idea if that would be possible/easy to implement?
Thanks a lot,
Vincent.
More information about the Nek5000-users
mailing list