# [ICEM] What is the reason for this negative determinant?

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January 25, 2013, 12:05
What is the reason for this negative determinant?
#1
Member

Ye Zhang
Join Date: Dec 2009
Location: Delft,Netherland
Posts: 92
Rep Power: 9
Hello,guys.

Now I want to simulate the flow over wind turbine rotor, but when I am doing the mesh, there is a problem that says negative determinant when I check the mesh. you can see the bad cells(green) in the picture. so I want to know what is the reason for negative determinant and how to improve the bad cells? Thank you in advance.

Regards
Ye
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 mesh2.jpg (62.0 KB, 56 views)

 January 25, 2013, 12:40 #2 Super Moderator     Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,382 Blog Entries: 23 Rep Power: 22 sometimes a simple update of the blocking can solve the problem. best way to track those element is by using the scan edge or cut plane... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

 January 25, 2013, 13:28 #3 Member   Ye Zhang Join Date: Dec 2009 Location: Delft,Netherland Posts: 92 Rep Power: 9 Hi, M.Ali Thank you for your reply. I can track(see)the bad cell, what I don't know is how to improve it? The green cells that have negative determinant looks quite triangle, right? but after the sharp trailing edge, I have get two blocks, is this the right method to deal with sharp edge? regards, Ye

 April 18, 2013, 09:59 #4 Member   Join Date: May 2010 Posts: 57 Rep Power: 9 kiddmax have you found a way to sort this? I'm having the exact same problem with a sharp edge. The geometry and even the histogram look frighteningly similar too,, Let me know. Best,

 April 18, 2013, 10:13 #5 Member   Ye Zhang Join Date: Dec 2009 Location: Delft,Netherland Posts: 92 Rep Power: 9 Hi, Catthan What about your blade? is it 3D or 2D? I advice you to use C grid for the sharp trailing edge. This is a tutorial on youtube. http://www.youtube.com/watch?v=mgjRT4WY_iA and make sure to use a block for "boundary layer", that will be much better. just like this

April 18, 2013, 10:15
#6
Member

Ye Zhang
Join Date: Dec 2009
Location: Delft,Netherland
Posts: 92
Rep Power: 9
this is the picture
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 April 18, 2013, 10:59 #7 Super Moderator     Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,382 Blog Entries: 23 Rep Power: 22 scan plane and cut plane are the best tools to look for thoe negative elements... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

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