does SU2 overpredict wing CL?

Marco_Vanderbijl · June 18, 2019, 05:12

In simulating the external flow over my 3d wing I am getting an overprediction of the wing lift. But I am too new to this CFD stuff to know why this would be happening. Thus a question for the more experienced CFD analists.
What is the influence of the farfield?
Suppose I have made my farfield mesh box too small would this lead to a higher then expected CL?
(I think I extended the box far enough in the front, back, and above my wing, But I might have skipped on the distance of my farfield on the side of my wing)

aero_amit · June 18, 2019, 10:17

Depending on the free stream Mach number, you can decide the far-field distance.
In General, for subsonic/transonic cases, one should have far-field boundary from 25 times of the reference length to 100 times the reference length. Yes the far-field distance can affect your solution, if it is not sufficient.
For supersonic cases, you can have relatively smaller far-field distance/Domain.

Marco_Vanderbijl · June 18, 2019, 16:16

thanks for your kind reply,

I think I should then be ok with my farfield size, though I'll make it even bigger to see if it will get the SU2_CFD solution more to what I expect.

June 18, 2019, 05:12	does SU2 overpredict wing CL?	#1
Marco_Vanderbijl New Member marco Join Date: May 2019 Posts: 12 Rep Power: 7	In simulating the external flow over my 3d wing I am getting an overprediction of the wing lift. But I am too new to this CFD stuff to know why this would be happening. Thus a question for the more experienced CFD analists. What is the influence of the farfield? Suppose I have made my farfield mesh box too small would this lead to a higher then expected CL? (I think I extended the box far enough in the front, back, and above my wing, But I might have skipped on the distance of my farfield on the side of my wing)

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June 18, 2019, 10:17		#2
aero_amit Member Amit Join Date: May 2013 Posts: 85 Rep Power: 13	Depending on the free stream Mach number, you can decide the far-field distance. In General, for subsonic/transonic cases, one should have far-field boundary from 25 times of the reference length to 100 times the reference length. Yes the far-field distance can affect your solution, if it is not sufficient. For supersonic cases, you can have relatively smaller far-field distance/Domain.

June 18, 2019, 16:16		#3
Marco_Vanderbijl New Member marco Join Date: May 2019 Posts: 12 Rep Power: 7	thanks for your kind reply, I think I should then be ok with my farfield size, though I'll make it even bigger to see if it will get the SU2_CFD solution more to what I expect.