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How to explain the lift force in SU2's source code? |
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#1 |
New Member
Jay Wee
Join Date: Oct 2022
Posts: 6
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I know the drag always aligns with the freestream direction, so it is quite easy to compute drag by:
drag = <total force vector> * <unit vector of freestream direction> However, the lift force's direction is not obvious. I think the lift formula should be <lift vector> = <total force vector> - drag * <unit vector of freestream direction> then the magnitude of lift could be got by lift = sqrt(<lift vector> * <lift vector>), which is a complex formula. But in the SU2's code, the lift formula is very simple: (click here to check source code: https://github.com/su2code/SU2/blob/...Base.inl#L1979) ![]() InvCoeff.CL[iMarker] = -ForceInviscid[0] * sin(Alpha) + ForceInviscid[2] * cos(Alpha); It looks strange to me, b/c lift has no dependence on Beta. Anyone could help to explain or post some reference link? Thanks. Last edited by jaywee; October 11, 2022 at 08:17. |
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#2 |
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Ercan Umut
Join Date: Aug 2022
Posts: 50
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As a graduate student I am really not sure about this but I guess they are taking normal and axial force's coefficients and using them on the lift and drag calculations. When I first saw the eqns. in code I tought they reminded me of something and found them on the Anderson's Fundamentals of Aerodynamics book. I attached 2 pictures as reference. In my opinion, they are not as easy as they look, at first glance at least
![]() Last edited by CleverBoy; October 22, 2022 at 16:02. |
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#3 |
Senior Member
Pedro Gomes
Join Date: Dec 2017
Posts: 466
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The result of <force vector> - drag * <drag direction> is not the lift vector, but rather lift + sideforce
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lift, source code, su2 |
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