CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

Problem obtaining normal vectors on blade loading line

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 27, 2014, 06:21
Default Problem obtaining normal vectors on blade loading line
  #1
New Member
 
francois
Join Date: Jun 2010
Location: Stellenbosch
Posts: 9
Rep Power: 7
francois louw is on a distinguished road
Dear all

I am currently investigating the flow field in an axial flow fan using Ansys software. The solving is done in Fluent and I am currently conducting some post processing in CFD-Post. My problem involves obtaining the face normal vectors on the "blade loading" line (a line along the blade surface at a specified radius as shown in the picture). For some reason I am able to obtain information such as the shear stress, static pressure etc., but when I try to graph and export the normal vector components (Normal X, Normal Y, Normal Z) as CSV files, it just gives an answer of 0 all along the blade surface for each of the components.

It seems that obtaining the normal vectors should be a straightforward task, yet I am struggling. I've tried searching the user manual and some of the other threads, but cannot find a solution to the problem. Is it due to the fact that turbomode is used? Or maybe that some of the mesh information is not passed on from Fluent?

Help would be a appreciated.

Kind regards
Francois Louw
Attached Images
File Type: jpg Loading line.jpg (35.6 KB, 11 views)
francois louw is offline   Reply With Quote

Old   March 27, 2014, 07:54
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,824
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
No, I suspect the problem is that you are exporting parameters along a line and the normal vector along a line is not defined. Surface normal is defined for a surface, so you will have to use a surface object to get the surface normals.

One idea to try would be to export the line feature you have created, then export the surface normals of the blade surface. Then using a matlab/python/fortran/whatever program match each point on the line with its nearest surface point and get the surface normal. A little ugly but should be do-able.
ghorrocks is offline   Reply With Quote

Old   March 27, 2014, 08:25
Default
  #3
New Member
 
francois
Join Date: Jun 2010
Location: Stellenbosch
Posts: 9
Rep Power: 7
francois louw is on a distinguished road
Hi Glenn

Ah! Thank you very much. I suspect you are right and think what you have suggested is most probably the best way of finding the face normals. It would have been neat if CFX was able to do this (linking the line nodes to the nearest face nodes) since it gives you the option to export a normal on the line, only with no result.

I do some postprocessing of results in Python and will try to give it a shot using it. I'll maybe post something again to say whether it worked or not. I suppose it will take some time.

Lastly, thank you for your reply and all your other posts as well. It really is helpful.

Kind regards
Francois Louw
francois louw is offline   Reply With Quote

Old   June 13, 2014, 03:41
Default Found some from of solution
  #4
New Member
 
francois
Join Date: Jun 2010
Location: Stellenbosch
Posts: 9
Rep Power: 7
francois louw is on a distinguished road
I said I would reply if I found some solution for the problem I posted in the previous posts... Sorry for the delay.

I was after the normal forces and vectors at a certain span location on the fan blade I was modelling. After some playing around and help from Glenn, I was able to obtain the 'Normalized force components' at a certain specified location (in my case a 'turbo line' at a certain radius along the blade profile), which is a force value given in N per m length. I was able to obtain this by first setting up a 'balde loading' plot in the 'turbo' tab of CFD-post and plotting any random values ('Normalized force' values cannot be selected in turbo mode for some reason). Thereafter I went back to the 'outline' tab where the 'blade loading chart' appears in the tree. By editing this chart one can edit the plotting variables. Only in the 'outline' tab can one select the 'Normalized force on blade loading line' and all of its components, as well as the boundary face normals.

I don't know whether this is trivial, but hope the post helps anyone in the future.

Regards
Francois
francois louw is offline   Reply With Quote

Reply

Tags
blade loading line, csv, normal, normal vector

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
determining displacement for added points CFDnewbie147 OpenFOAM Native Meshers: snappyHexMesh and Others 1 October 22, 2013 09:53
Problem in conducting CFD of analysis of wind turbine blade atulpat CFX 16 August 17, 2013 04:09
1.7.x Environment Variables on Linux 10.04 rasma OpenFOAM Installation 9 July 30, 2010 04:43
Problem of compilation OF 14Allwmake command not found erik_d OpenFOAM Bugs 13 September 13, 2008 21:45
Problems of Duns Codes! Martin J Main CFD Forum 8 August 14, 2003 23:19


All times are GMT -4. The time now is 11:10.