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Why blockage does not contribute to momentum?

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Old   April 21, 2003, 10:59
Default Why blockage does not contribute to momentum?
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Song
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Hi,

I just noticed something very interesting. When I put a plate in the computational domain, the plate will contribute to the momentum balance and shown in the result file for u, v or w. However, when I put a blockage inside the computational domain, it doesn't contribute to the momentum balance and not shown in the result file for u, v or w balance. Why is it like this? What should I do if I want the block contribute to the momentum balance? Should I put plate on all the sides of the blockage?

Thanks,

Song
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Old   April 22, 2003, 12:47
Default Re: Why blockage does not contribute to momentum?
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John Ludwig, CHAM
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The block does contribute to the momentum, unless you choose material 199 which is frictionless.

The momentum losses for a plate object are introduced via PATCH commands, and the sources from these are reported in the RESULT file. The sources from a blockage are introduced directly by the EARTH solver without the need for PATCHes. The EARTH solver looks to see which fluid cells are adjacent to a solid, and automatically applies the wall friction. See the POLIS Encyclopaedia entry on Earth-Generated-Wall-Functions http://www.cham.co.uk/phoenics/d_pol...enc_e.htm#egwf for more information.

If you create a duct with a plate on one side, and a blockage on the other, you should still see a symmetrical boundary layer from each side. Increasing the viscosity will exaggerate the effect and make it easier to see.
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Old   April 22, 2003, 17:23
Default Re: Why blockage does not contribute to momentum?
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Song
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Thanks. Your explaination is really helpful.

Song
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