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diamondx February 10, 2012 13:23

Is my mesh correct
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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

Far February 10, 2012 14:22

Did you try the SST model and what is the y+ on pitot tubes. Keep Y+ around 2-10.

diamondx February 10, 2012 16:00

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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

Far February 10, 2012 16:04

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.

diamondx February 10, 2012 17:12

1 Attachment(s)
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

Far February 11, 2012 02:49

here you can find the details

diamondx February 13, 2012 15:36

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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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