CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > Siemens > STAR-CCM+

Ugly mesh around cylinder

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 8, 2012, 12:58
Default Ugly mesh around cylinder
  #1
Member
 
Join Date: Dec 2011
Location: State College, PA
Posts: 87
Rep Power: 14
rks171 is on a distinguished road
I can't seem to get a nice looking mesh around a cylinder I'm modeling. See picture below. The cylinder goes perpendicular to the screen. The flow is in the same direction. This is a cross-sectional shot of the cylinder in the flow field. I don't see why I can't get the prism layer to be nice consistent squares around the cylinder. Why does the trim mesh have so many non-square funky looking cells?




Here's the mesh portion of the summary report if that helps:

Code:
 | +-1 Mesh 1 	Verbose Output	false
  | | |  	OOC translation	false
  | | |  	Per-Region Meshing	false
  | | |  	Use Parallel Meshing	false
  | | |  	Interpolation Option	Nearest neighbor
  | | |  	Interfaces	[]
  | | |  	Regions	[Body 1]
  | | +-1 Models 	 	 
  | | | +-1 Prism Layer Mesher 	Stretching Function	Geometric Progression
  | | | |  	Stretching Mode	Stretch Factor
  | | | |  	Gap Fill Percentage	49.0
  | | | |  	Minimum Thickness Percentage	10.0
  | | | |  	Layer Reduction Percentage	10.0
  | | | |  	Boundary March Angle	50.0
  | | | |  	Concave Angle Limit	0.0
  | | | |  	Convex Angle Limit	360.0
  | | | |  	Near Core Layer Aspect Ratio	0.0
  | | | |  	Generate Standard Cells Only	false
  | | | |  	Improve Subsurface Quality	true
  | | | +-2 Surface Remesher 	Do curvature refinement	true
  | | | |  	Do proximity refinement	true
  | | | |  	Do compatibility refinement	false
  | | | |  	Retain geometric features	true
  | | | |  	Create aligned meshes	true
  | | | |  	Minimum face quality	0.05
  | | | |  	Enable automatic surface repair	true
  | | | `-3 Trimmer 	Coordinate System	Laboratory
  | | |    	Do mesh alignment	false
  | | |    	Template mesh type	Hexahedra
  | | |    	Template mesh growth type	Simple
  | | |    	Run Optimizer	true
  | | +-2 Reference Values 	 	 
  | | | +-1 Base Size 	Value	0.05 m
  | | | +-2 Automatic Surface Repair 	Connected surface count limit	None
  | | | | |  	Connected surface size limits	None
  | | | | +-1 Minimum Proximity 	Minimum Proximity	0.05
  | | | | `-2 Minimum Quality 	Minimum Quality	0.01
  | | | +-3 CAD Projection 	Project to CAD	true
  | | | +-4 Maximum Cell Size 	Size type	Relative to base
  | | | | `-1 Relative Size 	Percentage of Base	10000.0
  | | | |    	Absolute Size	5.0 m
  | | | +-5 Number of Prism Layers 	Number of Prism Layers	1
  | | | +-6 Prism Layer Stretching 	Prism Layer Stretching	1.5
  | | | +-7 Prism Layer Thickness 	Size type	Relative to base
  | | | | `-1 Relative Size 	Percentage of Base	1.0
  | | | |    	Absolute Size	5.0E-4 m
  | | | +-8 Surface Curvature 	Enable curvature deviation distance	false
  | | | | `-1 Basic Curvature 	# Pts/circle	36.0
  | | | +-9 Surface Growth Rate 	Surface Growth Rate	1.3
  | | | +-10 Surface Proximity 	# Points in gap	2.0
  | | | |  	Search Floor	0.0 m
  | | | +-11 Surface Size 	Relative/Absolute	Relative to base
  | | | | |  	Size Method	Min and Target
  | | | | +-1 Relative Minimum Size 	Percentage of Base	1.0
  | | | | |  	Absolute Size	5.0E-4 m
  | | | | `-2 Relative Target Size 	Percentage of Base	10.0
  | | | |    	Absolute Size	0.0050 m
  | | | `-12 Template Growth Rate 	Default Growth Rate	Medium
  | | |    	Boundary Growth Rate	Medium
  | | `-3 Volumetric Controls
rks171 is offline   Reply With Quote

Old   May 8, 2012, 14:59
Default
  #2
Member
 
Paul Hancock
Join Date: Mar 2009
Location: Bellingham, WA
Posts: 31
Rep Power: 17
Paulh is on a distinguished road
My guess is that you're cutting plane is located on a plane of cell faces. Try moving your section location just a bit. Your problem might be just a visualization issue.
Paulh is offline   Reply With Quote

Old   May 8, 2012, 15:03
Default
  #3
Member
 
Join Date: Dec 2011
Location: State College, PA
Posts: 87
Rep Power: 14
rks171 is on a distinguished road
I also thought that, but when I moved the plane, the mesh looks almost the same. I didn't mention that the cross-sectional area doesn't change at all. The cylinder and flow section dimensions are constant moving in the z-direction (in and out of the screen). So I don't see why mesh cell dimensions and cross-sectional area should change in the z-direction. At least, I don't want it to be changing in the z-direction.
rks171 is offline   Reply With Quote

Old   May 8, 2012, 17:11
Default
  #4
Member
 
Ryan Coe
Join Date: Jun 2010
Location: Albuquerque, NM
Posts: 98
Rep Power: 16
ryancoe is on a distinguished road
Meshing a circular cylinder with cubes will inherently result in misshapen cells.

Alternatively, you could use a cylindrical mesh (gridgen and pointwise can do this, but Star-CCM+ cannot). Within Star-CCM+, you could try the polyhedral mesh...
__________________
Ryan
ryancoe is offline   Reply With Quote

Old   May 9, 2012, 15:35
Default
  #5
Member
 
Join Date: Dec 2011
Location: State College, PA
Posts: 87
Rep Power: 14
rks171 is on a distinguished road
I was able to improve this mesh simply by reducing the base size of my mesh cells from 0.05 m to 0.03 m. I played with a lot of other features, too, but that seems to be the one that made the funny looking cells go away around the cylinder.

rks171 is offline   Reply With Quote

Reply

Tags
cylinders, starccm+, trimmer

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[snappyHexMesh] No layers in a small gap bobburnquist OpenFOAM Meshing & Mesh Conversion 6 August 26, 2015 10:38
[ICEM] Injector Tube into a Big Cylinder - How to mesh? Leepox ANSYS Meshing & Geometry 2 November 25, 2011 11:45
rotating cylinder using sliding mesh Tim Daly FLUENT 1 November 10, 2008 00:02
ICEM block mesh with a ball in a cylinder tube Li CFX 6 August 11, 2008 06:44
mesh problem for cylinder akr FLUENT 1 January 30, 2007 00:43


All times are GMT -4. The time now is 01:31.