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Old   August 7, 2013, 19:15
Question ineffective wall roughness
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Hi experts.
I'm simulating a weir. I want to know the effect of roughness of weir on velocity. I've done mesh sensitivity analysis and I checked various values of roughness but nothing has been changed. does anyone know where the problem is?
any help would be appreciated.
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Old   August 8, 2013, 08:01
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Glenn Horrocks
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Maybe roughness does not significantly influence your flow?
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Old   August 10, 2013, 10:15
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Quote:
Originally Posted by ghorrocks View Post
Maybe roughness does not significantly influence your flow?
thank you for your reply.
the effect of various roughnesses are the same. roughness of 4 mm, 8 mm and 20 mm!
could it be from fault or inappropriate setting or something else?
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Old   August 10, 2013, 12:07
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How do you specify the roughness parameter in your simulation?
Is it part of the wall boundary condition or do you have a geometrical roughness? What about the rest of your setup?
Be descriptive!
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Old   August 10, 2013, 21:34
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Let me state my point a different way. If a hurricane was heading your way, do you think putting a piece of sand paper on the ground would make a difference? What about if you put a piece of sand paper on the ground which had double the surface roughness?

Obviously a hurricane is so big it does not matter what you do, the hurricane is going to progress unaffected. So my point is that if the surface roughness does not significantly affect the flow then it does not matter what surface roughness you use you will still get the same result.
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Old   August 14, 2013, 17:27
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thank you all for your replays.
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Old   August 14, 2013, 17:30
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Quote:
Originally Posted by flotus1 View Post
How do you specify the roughness parameter in your simulation?
Is it part of the wall boundary condition or do you have a geometrical roughness? What about the rest of your setup?
Be descriptive!
it's wall boundary condition. I'm trying geometrical roughness now.
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