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Rough Wall Functions Troubleshooting: (OF 1.6.x, incompressible)

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Old   October 15, 2013, 22:09
Default Rough Wall Functions Troubleshooting: (OF 1.6.x, incompressible)
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A Chan
Join Date: May 2012
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So I've been banging my head against the wall for about a month now trying to find out how to work the wall functions in OF1.6.x. I've gotten it to work in OF 2.1.1, but the solver we are working on is most stable in OF1.6.x.

Case info: Just a nozzle with diameter = 300 microns, velocity of the water is 41 m/s maximum. A ~ 600kPa pressure drop.

That being said, here's my assumptions of how the wall functions work:

In the 0/mut for my ROUGH WALL CASE:

type nutRoughWallFunction;
Ks uniform 0.00003;
Cs uniform 0.5;
value uniform 0;

Ks: sand grain roughness measured in meters
Cs: roughness constant

This should ideally simulate a rough wall along "wall" of roughness height = 30 microns.

In the 0/mut of my SMOOTH WALL CASE:

type nutWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0;

Where these are all default values.

Running these both separately yield the EXACT SAME SOLUTION. Even for Ks= 0.0015 and Cs = 0.8 separately, (remember the diameter is 0.0003) so it should most definitely be different.

Anything sticking out? I was thinking since I am compressible, my 0/mut should be 0/nut, but it wasn't yelling at me. I am trying out one of the rough wall cases with a 0/nut instead of 0/mut, but with the same contents.

Thanks for any and all help!
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