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Old   October 5, 2008, 03:24
Default shear-layer edge velocity
  #1
turbinesv
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Hi everyone

I simulated a airfoil flow field using CFX. How can I get the shear-layer edge velocity along the airfoil surface? Can you help me?

Thanks in advance.

Regards
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Old   October 6, 2008, 23:57
Default Re: shear-layer edge velocity
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Glenn Horrocks
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Hi,

Pardon my ignorance but what is the shear layer edge velocity?

Glenn Horrocks
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Old   October 7, 2008, 03:56
Default Re: shear-layer edge velocity
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turbinesv
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Thank you very much,Glenn Horrocks .

Shear layer edge velocity can also be called boundary layer streamwise velocity or boundary layer edge velocity. I want to got it because I am going to calculate the turbulence intensity whose definition is Tu=u'/Ue (Ue is the boundary layer edge velocity).

Regards,

Lan
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Old   October 7, 2008, 21:33
Default Re: shear-layer edge velocity
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Glenn Horrocks
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Hi,

You will have to construct its definition in CFX-Post. Are you defining the edge of the boundary layer as the 99% free stream velocity point? In that case an isosurface defined at 1% of the airfoil's velocity will show you boundary layer edge from that definition. You might need to clean it up a bit to remove features like separations etc.

Then you can use that isosurface as a surface body to do an area average of velocity magnitude, and you have it.

Glenn Horrocks
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Old   October 7, 2008, 22:15
Default Re: shear-layer edge velocity
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turbinesv
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Thank you very much, Glenn!

But I met problem again. I want to compare the computational results with an existing experiment data. The definition of the turbulence intensity is Tu=u'/Ue. The problem comes from that Ue is the local boundary layer edge velocity. The free stream velocity of the airfoil varies rapidly along the streamwise, so does the local boundary layer edge velocity. I am afraid the contour method can't work well in this situation.

Regards, Lan

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Old   October 8, 2008, 19:00
Default Re: shear-layer edge velocity
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Glenn Horrocks
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Hi,

Well, you have to define it somehow! However you define it then build it up in CFX-Post.

Glenn Horrocks
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