Reply To: Validation of HLBM

[avrachan]

Hi Stephan,

I define an L X L X L cube with periodic BC in all direction. I place a sphere at the center whose radius is varied to change the packing fraction of the system (vol-sphere/L^3).

All fluid nodes are subjected to a arbitrary small force in the y direction. I have used forcing::ForcedHLBM and defined the FORCE field in the lattice.

Upon reaching steady state, the force acting on the sphere is equal to the total force applied to the fluid nodes.

Here we measure the force acting on the sphere in the y direction (F), the mean velocity in the whole system in y direction (U).

Then I plot F/U*(1/6 pi eta a) where eta is the shear viscosity and a is the radius of the sphere, w.r.t to the packing fraction.

I have tried L = 16,32,64,128. I tried packing fractions from ~0 to 0.4. I have tried the relaxation tau close to 0.5 to 1.0. The forcing magnitude from 1e-5-1e-7 ( Re < 1).

The steady state values of the friction coefficient is largely independent of the choices of tau, forcing magnitude and system size (as it should be).

I feel like I am missing something!

Thanks for reading.