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weird pressure and turbulent intensity when using

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Old   March 16, 2018, 22:45
Unhappy weird pressure and turbulent intensity when using
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hello

I have a big trouble when I using timeVaryingMappedFixedValue.in the /constant/boundayData/inlet/,I put 30000 directory and every directry only contain the U.the deltaT of the inflowData is 0.0001,and my calculating deltaT is also 0.0001,the simulation time is 3 seconds.That means I don't need time interpolation in the inflow data.and in my "points" file,I set 156*56points,so I think every grid on the inlet face can get the data.

my case is a 3d rectangle ,and in my uploading picture,the left side in the inlet and rightside is the outlet.
When I check the result I find the pressure field around the inlet boundary is very weird (looks like discontinuous).and the turbulent intensity is obviouly less than the inflow date.But actually the timeVaryingMappedFixedValue does works.
I upload my picture of my pressure field.
Does anyone can help me,I already struggle with this trouble for 1 month.:
And I have such question.
1. does timeVaryingMappedFixedValue can give a smooth inflow ?what's meaning of the "mapped"?
2.do I have to add the "p" file when I use timeVaryingMappedFixedValue?
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Old   March 18, 2018, 16:33
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Timofey Mukha
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1. Pressure fluctuations near the inlet is a common problem with inflow generation. It is caused by the fact that the solver attempts to enforce a divergence-free velocity field.

Mapped reffers to the fact that the bc can interpolate in space from the points where u provide the data to the face centres of the patch.

2. No, if u provide velocity data the pressure should be set to zero gradient.
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Old   March 18, 2018, 18:57
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Dear tiam

Thank your replying and sorry for my reply late.
In my case I use thetimeVaryingMappedFixedValue BC .If I use tetra unstructure mesh,the turbulent intensity look likes be tweaked and become strange.but when I use hex structure mesh grid system which parallel with inflow direction,the turbulent intensity can be kept very well,Do you know why such condition will appear?

Sincerely
Tang
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Old   March 19, 2018, 00:39
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Uwe Pilz
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Unstructured meshes are most often triangular ones. You have a linear approach here, which is very diffusive. I don't recommend triangular meshes for serious calculations.
Hex meshes have a quadratic approach and are much less diffusive. It is much more expansive to get a local mesh refining with hex meshes, however.
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Old   March 20, 2018, 21:15
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Dear Uwe Pilz

Thank your replying~!
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