[Simba]

Hello everybody,

We consider classical 2D Rayleigh-Benard convection in a domain with aspect ratio sqrt(2)x1 (sqrt(2) is half of the length of the periodicity cell according to linear theory). At the lower and upper boundaries we set slip conditions ("Rayleigh conditions"), at the left and right boundaries there are also slip conditions (so there are no traveling waves and mean horizontal flow).
For the non-dimensional parameters Pr=11.5968, Ra=56931 there must be a periodic solution (we have already obtained it by means of our own pseudospectral method).
The flow modeled with our pseudospectral code (64x64) can be seen here
http://sibgat.imec.msu.ru/convOF/lin...lines3_c_1.avi
It can be considered as "exact" solution.


Now we take the hotroom case and transform it to the described problem, setting RASModel to laminar and corresponding dimensional parameters to
h = 0.1 (height)
L = 0.1*sqrt(2) (horizontal length)
blockMeshDict (60 40 1)
nu = 1.567e−6
beta = 3.072e−6
Tb = 277.2 (temperature at the lower boundary)
Tu = 276.8 (at the upper boundary)
Tref = Tb

This gave wrong results in buoyantBoussinesqPimpleFoam, as can be seen here
http://sibgat.imec.msu.ru/convOF/OFconv4.2-3.8.mpeg
This regime obviously converges to steady mode.
BuoyantBoussinesqPisoFoam in OF 1.6 gave chaotic motion which does not seem to converge to periodic motion.
Playing with tolerances, nCorrectors, time-integrators, mesh did not give correct results.


Have anybody compared any of these solvers with time-dependent (periodic for instance) laminar flow?
I hope very much there is a solution to this problem...

Thank you!