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No prism layer mesh is generated, I don't know why...

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Old   April 22, 2014, 18:10
Default No prism layer mesh is generated, I don't know why...
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Radek Capik
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Hello, I have problem with generating prism layer mesh. No prism laeyr is generated...

Three meshing models are selected: surface remesher + polyhedral mesher and prism layer mesher. I have vertical cylinder, 1.0 m high, 0.5 m in diameter. Base size of mesh is 0.005m, number of prism layers is 10. After mesh generating, but no prism layer mesh is generated, just polyhedral mesh. Mesh refining on walls works well for polyhedral mesh, but I prefer prism layers than fine polyhedral mesh on walls.

Does anybody know, what could be the problem?

I use Star-CCM+ 8.04
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Old   April 23, 2014, 04:12
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Maybe you can see only surface mesh. Try to make plane section and show the mesh on it.

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Old   April 24, 2014, 05:39
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Note: boundary conditions (inlet/outlet/wall) should be set before mesh generation; is that correct in your case?
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Old   April 24, 2014, 11:02
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cwl is right. Before starting the meshing you should define which are your boundaries (inlet and outlet), then everything should be Ok
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Old   April 24, 2014, 17:09
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Radek Capik
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I set region and boundaries before meshing. I solve melting of ice + natural convection in melted phase in cylinder. My boundaries are just walls with condition of constant temperatures. I would like prism layer on walls for accurate results.

I talk about this problem with my friend and he send me tube geometry with prism layer mesh - in his simulation I can change number of prism layers, stretching prism layers, etc. without any problem, but if I change dimensions (design parameters in 3D-CAD models) then after regenerating of volume mesh, prism layers vanish.
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Old   April 24, 2014, 21:32
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Check that your prism layer thickness is defined in terms of absolute distance instead of by base size if you're changing dimensions.

Also ensure that your part surfaces are being put into their correct region boundaries after you make a change.

Can you post a picture of the grid?
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Old   April 25, 2014, 06:06
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Radek Capik
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Thank you guys for helping me ;-) becaouse I am really poor beginer in CFD and Star-CCM+. The problem was simple. I really saw just surface mesh. I tried do plane section with mesh representation and after that I saw prism layers ;-) You can see on attached picture.

OK, problem with prism layer mesh is out. Last question - Could anybody tell me if I my procedure in converting simulation from 3D to 2D is correct.

I have vertical cylinder filled with ice (273.10 K). In inner wall i have tepmerature 425.0 K. Other walls are adiabatic. Heat flux cause melting of ice on near wall distance. Natural convection comes in water from melted ice. I need measure amount of melted ice in time (solid volume fraction field function). Diagram of my problem in 3D is on figure (a). But I want to save computational cost and do it in 2D with using Axisymmetric model (b) with axis of rotation (x,y,z)=(1, 0, 0). Dimensions are 1.0m in high, inner radius in 0.05m and outer radius in 0.25m. I supose turbolence will occur in melted part because inner wall is 1m high (Grashof number > 10^9). For turbolence I use k-epsilon model.

I am not sure if my procedure to convert from 3D problem to 2D is right or wrong. I did thin block instead of cylinder. Polyhedral mesh and prism layer mesh wass selected (mesh refining on near wall distance). Base size is 0.005m. This thin block was converted from 3D mesh to 2D and axisymmetric model was selected. Base size of mesh is 0.005m. I am not sure, if two biggest boundaries which will be "removed" after converting to 2D should be symetry planes or walls? Thin block which will be converted to 2D hollow cylinder can be seen on last two pictures.

If you think some type of mesh will be better for this simulation or the procedure converting from 3D to 2D is wrong - let me know please. Thank you very much guys.
Attached Images
File Type: jpg prism layer.jpg (53.0 KB, 113 views)
File Type: jpg ice_melting2.jpg (38.8 KB, 79 views)
File Type: jpg 3D_to_2D.jpg (77.6 KB, 76 views)
File Type: jpg symettry planes.jpg (39.8 KB, 66 views)

Last edited by capikrad; April 25, 2014 at 12:25.
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