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

kiddmax · January 25, 2013, 11:05

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

diamondx · January 25, 2013, 11:40

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...

kiddmax · January 25, 2013, 12:28

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

Catthan · April 18, 2013, 09:59

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,

kiddmax · April 18, 2013, 10:13

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

kiddmax · April 18, 2013, 10:15

this is the picture

diamondx · April 18, 2013, 10:59

scan plane and cut plane are the best tools to look for thoe negative elements...

January 25, 2013, 11:40		#2
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 28	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

April 18, 2013, 10:59		#7
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 28	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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January 25, 2013, 12:28		#3
kiddmax Member Ye Zhang Join Date: Dec 2009 Location: Delft,Netherland Posts: 92 Rep Power: 16	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
Catthan Member Join Date: May 2010 Posts: 57 Rep Power: 15	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
kiddmax Member Ye Zhang Join Date: Dec 2009 Location: Delft,Netherland Posts: 92 Rep Power: 16	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