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sonicFoam unexpected pressure damping

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Old   November 24, 2016, 06:21
Default sonicFoam unexpected pressure damping
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Max Braun
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Hello everybody,

I am trying to run a simple case with sonicFoam and got some undesired damping. I build a tube, 2 meters long, with an oscillating pressure (p' = 1000*sin(t) Pa) as inlet and a waveTransmissive condition as outlet. I was hoping to see a nice sin wave moving through the domain, but there is some kind of damping, even though there is no viscosity (mu = 0). I attached a picture of some pressure probes located a 0.01m, 0.2m 1m and 1.9m. The violet probe at 0.01m shows my nice sin wave but the other ones, especially at 1m (blue) and 1.9m (yellow) show a different amplitude.

I am using OpenFoam 4.1 and the simulation is run at 293.15 K and 100,000 Pa without flow (U = (0 0 0)). I already tried different meshes (1D and 2D, 40-100 cells per wave length), different lInf's in the waveTransmissive condition (0.1-20), different time steps (around 1e-05), different frequencies (170-340 Hz), different amplitudes (100-1000) and different conditions for U and T (zeroGradient, waveTransmissive).

Nothing worked so far to preserve the amplitude so I was hoping for some advise. Like I said, there is a picture attached with the pressure probe data and you may find my inlet and outlet condition for the pressure below.

Thank you very much in advance.



two of my boundary conditions for p:

type uniformFixedValue; //formerly oscillatingFixedValue
uniformValue sine;
frequency 170;
amplitude 1000;
scale 1;
level 100000;

type waveTransmissive;
field p;
psi thermo:psi;
gamma 1.4;
fieldInf 100000;
lInf 3;
value uniform 100000;
Attached Images
File Type: jpg 1Dtube.jpg (123.0 KB, 9 views)
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damping, pressure, sonicfoam

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