# Meshing a Wheel in Pointwise/Fluent problem

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November 28, 2010, 12:38
Meshing a Wheel in Pointwise/Fluent problem
#1
New Member

Luke
Join Date: Nov 2010
Location: U.K.
Posts: 5
Rep Power: 8
Hi All,

I am attempting to mesh an external flow around an aircraft wheel (closed rim) in Pointwise to run using (at first) the k-e RKE model with Enhanced Wall Function.

My mesh is built up in sections, first is the boundary layer. Using Y+ of 1 (0.0057mm) and expansion ratio of 1.2, for a wheel D of 1.4m, and reynolds number of 6.71x10^6, 70m/s. The quarter-wheel profile is meshed in 2d then rotated/mirrored around to cover the whole wheel. This is then built up into the far field cuboid mesh, 5.6m x 5.6m x 4.2m (infront) x 10m (behind), 3.6 million cells in total. (see attachments). Pointwise Wall Spacing examination corresponds to equivalent ~ 0.6>y+>1.6 around the whole wheel.

Now, when I run it in Fluent, I get Continuity divergence after only about 50 iterations, and when I do a Turblence>YPlus contour in fluent I often see huge Y+ values (10^3), although this seems to vary depending on how long i run it, so I don't know whether due to the divergence this examination is irrelevant.

So in summary, according to Pointwise, my y+ is pretty consistent, but I get continuity convergence quickly in fluent. I have re-meshed loads of times with same divergence. So not sure whether it's a Pointwise or Fluent problem.

Any help would be much appreciated.
Attached Images
 Profile Mesh.jpg (27.4 KB, 39 views) Boundary Layer Mesh.jpg (94.6 KB, 53 views) Whole Mesh.jpg (60.1 KB, 33 views)

 November 28, 2010, 17:43 #2 Senior Member   Chris Sideroff Join Date: Mar 2009 Location: Ottawa, ON, CAN Posts: 391 Rep Power: 13 Luke, What are the dimensions of the wheel? I ask because you have to make sure it's scaled properly in Fluent, as it works in meters. For example, if you created a wheel with a diameter of 1000 in Pointwise, representing the units mm, you will have to scale it in Fluent by a factor of 0.001. Since you reported y+ values 3 orders of magnitude higher than you were expecting, my guess is that your Reynolds number is 1000 too large, hence the incorrect scaling. Let me know if that works. -Chris

 November 28, 2010, 19:27 #3 New Member   Luke Join Date: Nov 2010 Location: U.K. Posts: 5 Rep Power: 8 Genius! It worked! Thanks Chris, this had been bugging me for weeks. It was indeed the scaling so Fluent thought my mesh was 10km long! Now I can move on to the proper stuff Many thanks again, I should have posted this ages ago. Yet another reason why CFD online/wiki is an indispensable resource! Luke

 January 22, 2011, 22:49 More scaling/units problem #4 New Member   Join Date: Oct 2010 Posts: 19 Rep Power: 8 Hi, I am using a k-omega SST model on a flow going through a duct. I should get my y+ between 1 and 5 I believe from what I've seen. I found out about a scaling issues in Fluent thanks to your previous posts. However I am still having difficulties obtaining the right y+ values from my mesh. When I try to adapt in Fluent it halves the y+ value but horribly increases the number of cells. My mesh y+ is about 60 so that I can't obtain the correct y+ value with a decent sized mesh in Fluent. I'm wondering if this is another scaling issue in Pointwise (importing from CATIA to Pointwise, or in Pointwise, do I have to set the units ? If I go to Properties the ratio of Grid/Database is about 600 ??). Or am I using the adapt function in Fluent wrong ? Any thoughts or suggestions greatly appreciated. Thank you !!

 January 26, 2011, 22:15 #5 Member   Tobino Join Date: Jan 2011 Location: Osaka,Japan Posts: 33 Rep Power: 7 Dear all, I am meshing a model of ship. Have anybody known How to create structure mesh? please advise me !

 March 14, 2016, 12:40 sclae #6 Member   Join Date: Oct 2015 Posts: 48 Rep Power: 3 hello i create mesh in pointwise i import it in openfoam but i have a problem openfoam in default import mesh in meter but my mesh in mm. can anyone help me? thanks

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