[Mamin]

The charR is not mentioned in the user documentation at all. So it is hard to get info from there. And I’m not requesting a complete intro, I will come for to the spring school for that but some hints will help people to continue their projects and keep using openLB.
Thanks

[Mamin]

Thanks for answering. Since I can’t set a pressure boundary at the inlet and out let as well. I ran Navier-Stokes on Comsol for the same system and place the pressure boundaries at the inlet and outlet then obtained the velocity at the inlet and add as boundary condition in openLB. However, I obtained much lower pressure at the inlet.
Maybe it is not a good idea but I know that LBM should converge to NS at the continuum regime. However, there is something missing here.

[Mamin]

I have 0 pressure at the outlet. Thanks

[Mamin]

Hi mgaedtke,
I have defined the charRho as the density of helium at 100 Pascal (0.00016). However, what I get at the inlet is a pressure of 10 Pascal instead (U=15 m/s, charNu=0.12). I was expecting to get 100 Pascal at the inlet. Any hint?
Thanks

[Mamin]

I looked at the examples. However, they always assume zero pressure at the outlet. I’m planning to attend the spring school but I can’t just wait 6 month to run the simulations.
Thank you

[Mamin]

Thank you very much. Do you know if openLB model compressible fluid?

[Mamin]

Thank you. Would you please explain why it won’t work? I’m new to the method but since I could do that in Navier-Stokes I want to know how to make similar system in LB in order to benchmark.
(Since LB should converge to Navier-Stokes in the continuum regime)

Thanks again

[Mamin]

I realized that this happened whrn I replaced
bc.addVelocityBoundary( superGeometry, 3, omega );
with:
bc.addPressureBoundary( superGeometry, 3, omega );
sLattice.defineRhoU( superGeometry, 3, rho, u );

for the inflow boundary condition.

Do you know why this happens? I thought I can choose velocity or pressure as boundary conditions.
Thanks

[Mamin]

I want to simulate a gas (helium) in a aerodynamic lens (or just a cylinder of 1 cm radius) with smaller outlet (1mm). The pressure at the inflow is 2 mbar and 0 on the outflow.
Thank you

[Mamin]

Sorry the figure just missed up. they are just 4 cylinders connected to each other with different radii. r1-r2-r3-r4 where r1=r3 and they are greater than r2 and r4.
Thanks

[Mamin]

Thanks Mathias,
I tried to build the following figure using 4 cylinders
______ _______
|__| |___
___ ___
______| |_______|

IndicatorCylinder3D<T> inflow( C0, C1, radius1 );
IndicatorCylinder3D<T> cyl1( C1, C2, radius1 );
IndicatorCylinder3D<T> cyl2( C2, C3, radius2 );
IndicatorCylinder3D<T> cyl3( C3, C4, radius1 );
IndicatorCylinder3D<T> cyl4( C4, C5, radius3 );
IndicatorCylinder3D<T> outflow( C5, C6, radius3 );
The geometry preparation went OK. However, I got segmentation fault:

[prepareGeometry] Prepare Geometry … OK
[prepareLattice] Prepare Lattice …
[prepareLattice] Prepare Lattice … OK
[Timer] step=0; percent=0; passedTime=0.502; remTime=1.004e+07; MLUPs=0
[LatticeStatistics] step=0; t=0; uMax=0; avEnergy=0; avRho=1
[Timer] step=0; percent=0; passedTime=0.967; remTime=1.934e+07; MLUPs=0
[LatticeStatistics] step=0; t=0; uMax=0; avEnergy=nan; avRho=nan
Segmentation fault: 11
I’m trying to figure what I did wrong.
Thanks

[Author]

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