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HutchMan December 7, 2012 21:15

2D Inviscid Airfoil model zero lift angle
Hi all,

New to the forum and to CFD but my thesis is on the simulation of flow around an airfoil so thought this would be a handy resource.

I'm performing an initial inviscid flow sim on a NACA4412 before I move on to turbulent models. Basically I'm following this tutorial which I understand is widely used:

I'm trying to compare my sim data with the Abbott and Von D data and whilst I get a lift curve slope of about 2Pi as expected for a inviscid sim, I can't get the zero lift angle to agree with the Abbott data of -4 degrees. At -4 my sim gives a Cl of about 0.035.

It's as if my correct lift curve has just been shifted along the alpha axis to the left a bit so that the zero lift angles don't agree. At first, myself and my supervisor thought my coordinates were slightly off orientation wise (i.e. not at zero AoA) but I've checked them with other coordinates and confirmed that the chord line runs parallel with the x axis when imported into GAMBIT, as it should.

I've even downloaded the mesh from that Cornell tutorial and run that in Fluent only to get similar results of Cl = 0.035 at -4.

My thinking is that there must be something about the Abbott data that slightly changes the effective AoA or something along those lines.

Or perhaps this is a mesh resolution problem? Just throwing the problem out there for someone to hopefully shed light on. It'd be much appreciated.

It's irritating as I'd like to move on to turbulent models knowing my inviscid sim is as accurate as can be.

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