LBM example code in python has factor of 2 missing

#1

Hi,
just thought I’d point out that the LBM sample code in python: lbmFlowAroundCylinder.py has a factor of two missing in the viscosity equation.
In the code:
nulb = uLB * r / Re
should be:
nulb = uLB * 2 * r / Re

Because the characteristic length for a cylinder is it’s diameter not it’s radius.

#2

where is this code? (i can’t remember :-))

#3

It’s at:
https://palabos.unige.ch/get-started/lattice-boltzmann/lattice-boltzmann-sample-codes-various-other-programming-languages/
about half way down the page.

#4

you are completely right. thanks. we’ll correct that.

#5

No problem, I’ve had a lot of run with this code. I added tracer particles to it and made the following video: https://www.youtube.com/watch?v=Kj53PGlIJaE Maybe someday I’ll upgrade my computer and get Palabos up and running.

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#6

Very nice! can you share how you make the particle tracing algorithm please

#7

For the 2D simulation, the tracer particles are stored in a NumPy array of size p[N,3]

where N is the number of particles.

p[k,0] is the x position in lattice units for particle k.

p[k,1] is the y position in lattice units for particle k.

p[k,2] is the color map index for particle k.

The modified version of lbmFlowAroundCylinder.py with tracer particles is here:

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