Hi,

I fairly new to LBM and I am trying to wrap my head around the choice of units for LBM. I am using the externalFlowAroundObstacle example case as a starting point but when I change the parameters to fit my case the simulation quickly diverges.

I am trying to simulate the following case:

Domain dimensions (length x width x depth) = 3.135 x 0.486 x 0.326 m

Inlet velocity = 0.183 m/s

Kinematic viscosity = 1.0e-6 (m^2/s) [i.e. Water]

Reynolds Number (based on depth) ~ 60000

Lattice Units:

Resolution = 98/0.486 = 200 nodes/m

dx = 4.96e-3

By fixing the lattice velocity at 0.01 to keep the mach number low (incompressible)

dt = 2.71e-4

This results in the relaxation parameter being:

tau = 0.500033057

I am assuming that the reason for the simulation diverging is that tau is too close to 0.5 but any any combination that I try to increase it either leaves me with a ridiculously high resolution or a very high Mach number either of which is unacceptable for the case I am trying to simulate.

Also LES modelling is activated with a Smagorinsky constant of 0.2

Any advice will be greatly appreciated.

Thank you