Reply To: Validation of HLBM

[avrachan]

Hi Stephan,

I have attached here the information about trying the drag on one packing fraction at 0.4.

The correct value of the friction coefficient should be around 20 according to Ladd et al [1], but I am getting a value of ~14.

I have realized that I have to reduce the value of tau to near 0.5 to get a value closer to what the Ladd et al shows.

Since this is a fundamental test, I am unable to resolve the issue.

`[UnitConverter] —————– UnitConverter information —————–
[UnitConverter] — Parameters:
[UnitConverter] Resolution: N= 15
[UnitConverter] Lattice velocity: latticeU= 1.64572e-07
[UnitConverter] Lattice relaxation frequency: omega= 1.96078
[UnitConverter] Lattice relaxation time: tau= 0.51
[UnitConverter] Characteristical length(m): charL= 14.6265
[UnitConverter] Characteristical speed(m/s): charU= 1.64572e-07
[UnitConverter] Phys. kinematic viscosity(m^2/s): charNu= 0.00333333
[UnitConverter] Phys. density(kg/m^d): charRho= 1
[UnitConverter] Characteristical pressure(N/m^2): charPressure= 0
[UnitConverter] Mach number: machNumber= 2.85047e-07
[UnitConverter] Reynolds number: reynoldsNumber= 0.000722134
[UnitConverter] Knudsen number: knudsenNumber= 0.000394729
[UnitConverter] Characteristical CFL number: charCFLnumber= 1.64572e-07
[UnitConverter]
[UnitConverter] — Conversion factors:
[UnitConverter] Voxel length(m): physDeltaX= 1
[UnitConverter] Time step(s): physDeltaT= 1
[UnitConverter] Velocity factor(m/s): physVelocity= 1
[UnitConverter] Density factor(kg/m^3): physDensity= 1
[UnitConverter] Mass factor(kg): physMass= 1
[UnitConverter] Viscosity factor(m^2/s): physViscosity= 1
[UnitConverter] Force factor(N): physForce= 1
[UnitConverter] Pressure factor(N/m^2): physPressure= 1
[UnitConverter] ————————————————————-`

[1] Ladd, A. J. C. Numerical Simulations of Particulate Suspensions via a Discretized Boltzmann Equation. Part 2. Numerical Results. J. Fluid Mech. 1994, 271, 311–339. https://doi.org/10.1017/S0022112094001783.