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residuals behaviour on steady state simulations

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Old   October 18, 2011, 21:47
Default residuals behaviour on steady state simulations
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Domenico
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Dear All,

I was running a simulation with a coarse mesh at the boundary layer such that the value of y plus was about 1000 and I used the SST turbulence model. Of course this is wrong and then I moved to refine the mesh at the boundary layer in order to decrease the y plus towards 1. By doing this operation I noticed that the residuals of the mass and momentum conservation presented a higher frequency and amplitude of oscillation with the iteration number.

Does someone knows what is going on??

The simulated system consists in an intake coupled with a fan. If you need to know more details, please let me know.

Thank you in advance!
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Old   October 19, 2011, 05:41
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Sijal Ahmed Memon (turboenginner@gmail.com)
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1. May be the problem is transient, which was not shown in the coarse mesh.

2. are you modeling complete intake and fan or somoe sector?

3. pls write down Over all mesh size and aspect ratio?.

4. Also give details of time scale, like time step size, auto or physcial time scale?
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Old   October 19, 2011, 05:43
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Last but not the least : pls always try to put the some pics of mesh, goemtry, residual plot
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Old   October 19, 2011, 06:43
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Glenn Horrocks
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And a large y+ is not necessarily wrong, and y+=1 is not necessarily right. Do a sensitivity study to find out what near wall spacing you need.

But if you are doing a turbomachinery application you almost certainly need a small y+, but it could be much larger than 1.
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Old   October 20, 2011, 09:25
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Guys, for this discussion can we contact privately please. My email address is: d.dicugno@yahoo.com

Cheers
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Old   October 20, 2011, 17:20
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