Hi all. I want to 3D simulate flow around cylinder with helical strakes. ı used tetra element and my results agrement with literature. But y+ is high. How to reduce ? I used Ansys mesh 14. Could you give me any suggestion ?
Thanks
Hi Tahir, how much is your Y+ now?
Usually it should be less than 5 or greater than 30, i.e. the first node should be either in sub-layer or the log layer and never be in the transitional layer.
If it is in the range 30
Hi Rajesh, I added my y+ graph I used transient k-w SST model. I also used body sizing and I have opproximtly 5 million element. if I reduced ement size , mesh element is too increased.
Thanks a lots.
Using hybrid meshing will be better option. Hex elements near boundary and then tet elements elsewehere. Few layers of hex can be made as fine as possible near boundary. This option is available in ICEM.
Hi Swapnil. I used inflation layer and reduced maximum y+ up to 2. but I have variable y+ along the cylinder especially in the range 0 to 1. How do I improve it ? Thanks alots
You have find out what should be the thickness of first layer of mesh to have y+ below 1 and then make it finer near the cylinder surface.
My problem is it that how I make finer mesh near the cylinder. I calculated y+ make to 1 and give first layer thickness as 0.13 mm. I want to inrease minumum y+ and reduce maksimum y+ Because my y+ too variable along the cylinder
Hi Tahir, hardly your y+ will be fall below 2 for all regions without have a lot of elements, it is common to have some regions with a y+ higher than you expected. But is not a issue always. With SST, if you fall in the viscous sublayer k-w model dominates, and if you have a y+>11.05 ( if I'm not wrong) the k-e model will dominates. This is controlled by the blend functions of the models. By your figures, the maximum y+ is
In my point of view, it is better to use ICEM CFD in your problem which will give you full control when generating prism layers that are actually represent your boundary layer in this case. y+ should be in the range of 1 and ICEM will help you greatly in this case.
Try to use First Layer Thickness in Ansys Meshing Inflation command to make your y+ in the range of 1.
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