Periodic bc

[nipinl]

I am simulating Poiseuille flow in a corrugated pipe, with periodic bc using body force (as in Poiseuille3D example). I notice that the estimated friction factor increases (or converged average x-velocity reduces) as I increase the periodic domain length (>2 times for L=2D Vs L=5D).
In order to understand the reason, I wanted to know how periodic bcs are implemented in OpenLB, but I could not locate that in the code base. Can anyone point me to the implementation? Any thoughts on the variation in friction factor? The flow is at Re=400. D =2mm with resolution 400x400x(400*L/D)

Thanks!!
Nipin

[mathias]

Periodicity is implemented in OpenLB in a way that the populations are copied from one side to the other. It is dealt with within the cuboidGeometry class..

[nipinl]

Hi Mathias,
Thanks for the lead.I understand that the setPeriodicity() function in the cuboidGeometry class sets the periodicity.
Actually, I was looking for a stream-wise periodic boundary condition for channel/pipe flow with pressure gradient. One can achieve this with body force, but I read here that it is only applicable if the cross-section area is constant. Periodic bc with pressure gradient might include modification of the inlet density[Kim 2007]. I was wondering if this is already implemented in OpenLB?

Thanks!!
Best,
Nipin

[mathias]

Might work with a combination of the defineRho (impose the rho distribution you want) method and the setPeriodicity

[nipinl]

Sounds good!! Thanks again.

[Author]

Posts