higher aspect ratio problem

Eng.Mahmoud abd elsalam · August 17, 2015, 03:43

hi , everyone
i face the problem of higher aspect ratio and lower orthogonal quality and can not find any way to solve this problem ...
thank you advanced for any information
http://i.imgur.com/1Y8tfZ7.png

Eng.Mahmoud abd elsalam · August 17, 2015, 13:35

is there anyone can help me ??

xuhuang · August 18, 2015, 06:16

Which soft ware do you use to genreate you mesh. I am using ICEM.

Can you show the grids near the tip of your model? I guess maybe the problem comes from there.

Eng.Mahmoud abd elsalam · August 18, 2015, 06:46

hi, xuhuang
also , i am using ICEM
this is grid near the tip
http://i.imgur.com/HKlPSeg.jpg
thanks xuhuang for your reply

xuhuang · August 18, 2015, 06:55

Is it possible to attach the ICEM files?
The picture does not show the details.

Eng.Mahmoud abd elsalam · August 18, 2015, 07:02

ok .. these are ICEM files
http://www.mediafire.com/download/1z...ju/ICEMCFD.rar

xuhuang · August 18, 2015, 07:25

you set an order of 10^-6 for the first layer perpendicular to the wall surface, but an order of 1 along the surface.
Therefore, the aspact ratio is of order 10^6.
I check the angle, the minimum is 38 degree. This should be ok.

Why do you set such a small value perpendicular to the wall surface?

Eng.Mahmoud abd elsalam · August 18, 2015, 07:52

first . i am sorry for repeating of posts
second .. i watched this tutorial
https://www.youtube.com/watch?v=9Bc0NBk-urM
and did it step by step , when reached the step to calculate the Y+ distance i put my inputs velocity and density of air then i put boundary layer length the chord of my blade (i think this is the mistake ) after , the value of estimated wall distance is 1.2e-6

xuhuang · August 18, 2015, 08:23

I think how fine the mesh near the wall depends on how you treat near wall region in your simulation. If you use fluent, you can check it in the theory guide.
for example,
standard wall function requires: the lower limit for y* in the order of y*~15.
enhanced wall function: typically with the first near-wall node placed at y+~1 is fine enough to be able to resolve the viscous sublayer

Good luck!

August 17, 2015, 03:43	higher aspect ratio problem	#1
Eng.Mahmoud abd elsalam New Member Mahmoud Join Date: Mar 2015 Posts: 16 Rep Power: 11	hi , everyone i face the problem of higher aspect ratio and lower orthogonal quality and can not find any way to solve this problem ... thank you advanced for any information http://i.imgur.com/1Y8tfZ7.png

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August 17, 2015, 13:35		#2
Eng.Mahmoud abd elsalam New Member Mahmoud Join Date: Mar 2015 Posts: 16 Rep Power: 11	is there anyone can help me ??

August 18, 2015, 06:16		#3
xuhuang New Member Xu Huang Join Date: Apr 2015 Location: Netherlands Posts: 23 Rep Power: 11	Which soft ware do you use to genreate you mesh. I am using ICEM. Can you show the grids near the tip of your model? I guess maybe the problem comes from there.

August 18, 2015, 06:46		#4
Eng.Mahmoud abd elsalam New Member Mahmoud Join Date: Mar 2015 Posts: 16 Rep Power: 11	hi, xuhuang also , i am using ICEM this is grid near the tip http://i.imgur.com/HKlPSeg.jpg thanks xuhuang for your reply

August 18, 2015, 06:55		#5
xuhuang New Member Xu Huang Join Date: Apr 2015 Location: Netherlands Posts: 23 Rep Power: 11	Is it possible to attach the ICEM files? The picture does not show the details.

August 18, 2015, 07:02		#6
Eng.Mahmoud abd elsalam New Member Mahmoud Join Date: Mar 2015 Posts: 16 Rep Power: 11	ok .. these are ICEM files http://www.mediafire.com/download/1z...ju/ICEMCFD.rar

August 18, 2015, 07:25		#7
xuhuang New Member Xu Huang Join Date: Apr 2015 Location: Netherlands Posts: 23 Rep Power: 11	you set an order of 10^-6 for the first layer perpendicular to the wall surface, but an order of 1 along the surface. Therefore, the aspact ratio is of order 10^6. I check the angle, the minimum is 38 degree. This should be ok. Why do you set such a small value perpendicular to the wall surface?

August 18, 2015, 07:52		#8
Eng.Mahmoud abd elsalam New Member Mahmoud Join Date: Mar 2015 Posts: 16 Rep Power: 11	first . i am sorry for repeating of posts second .. i watched this tutorial https://www.youtube.com/watch?v=9Bc0NBk-urM and did it step by step , when reached the step to calculate the Y+ distance i put my inputs velocity and density of air then i put boundary layer length the chord of my blade (i think this is the mistake ) after , the value of estimated wall distance is 1.2e-6

August 18, 2015, 08:23		#9
xuhuang New Member Xu Huang Join Date: Apr 2015 Location: Netherlands Posts: 23 Rep Power: 11	I think how fine the mesh near the wall depends on how you treat near wall region in your simulation. If you use fluent, you can check it in the theory guide. for example, standard wall function requires: the lower limit for y* in the order of y*~15. enhanced wall function: typically with the first near-wall node placed at y+~1 is fine enough to be able to resolve the viscous sublayer Good luck!