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Old   February 10, 2012, 12:23
Default Is my mesh correct
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Ghazlani M. Ali
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i'm trying to simulate a flow around seven pitot tubes in a row, i have joined below a screenshot of my mesh, i tried to refine as much as possible next to the pitot tubes as you can see. i get a very big shock wave in front of them at mach=1.5. wich i think is normale. my boss disagree. the source of the problem may be the mesh wich is too refined and non uniforme. can somebody give his opinion on this ?
Thank you very much in advance
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File Type: jpg extended_mach1.5.jpg (63.4 KB, 40 views)
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Old   February 10, 2012, 13:22
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Sijal Ahmed Memon (turboenginner@gmail.com)
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Did you try the SST model and what is the y+ on pitot tubes. Keep Y+ around 2-10.
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Old   February 10, 2012, 15:00
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I dont really know what Y+ means as i just got into CFD. i do remember i read about it in a tutorial of an airfoil in fluent. But i didn't get the idea.
Below is a screenshot of Y+ by fluent, is it ok ??? i can see blue region wish problably not good ???!!! i dont now why since the mesh is just a simple quad mesh !!
thank you so much for you help
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Old   February 10, 2012, 15:04
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Y+ should not be less than 0.1. This will seriously affect the solution.


Just google the paper of Menter on SST model applied to flat plate for different yplus values.
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Old   February 10, 2012, 16:12
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Im trying change to a new mesh. Below you can see a picture of two pitot tube.
In order to get a good value of Y+. i need to refine as mush as possible betwenn the two pitot tube. as you can see below. i tried a linear mesh law of 8, i know it's not enough. what mesh law do you suggest and how much node number can i put there. (am using a cluster that means that i dont really worry about the time of computing)
Thank you very much
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Old   February 11, 2012, 01:49
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here you can find the details Weighted Mesh / Gradually Coarsening Mesh
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Old   February 13, 2012, 14:36
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hy there,
Here i'm back with a new mesh , less refined but more uniform. But i still get a too low Y+ like the other one no matter how much i refine or coarsen the mesh. i'm lacking ideas i spent a hole week-end looking for a good documentation about y+.
How can i get a good Y+. sorry if i'm too demanding but i' really stuck !
Thanks in advance
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