# Extreme WIG simulation-reality results divergence

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 May 7, 2012, 07:44 Extreme WIG simulation-reality results divergence #1 New Member   Jake Billingham Join Date: Apr 2012 Posts: 4 Rep Power: 6 Hello everyone, I've been doing a project on modelling the Ground Effect with a NACA0012 aerofoil for my final year and have found that at a h/c value of 0.1 the numbers simply don't make sense. Between 1.0 and 0.2 they match the experimentally established values well but at 0.1 things go horribly wrong. I've checked my boundary conditions and they're the same as all the others and I can't explain why this has occurred. Here are the numbers from 0.2: Angle of attack: 4 degrees Lift: 113.31N Drag: 17.71N Cl: 0.43525 Cd: 0.06803 h/c = 0.1 Angle of attack: 4 degrees Lift: -22891.56N Drag: -239.04 Cl: -87.9323 Cd: -0.918214 Does anyone know anything that might be able to explain what's happened here? Thanks, Jake Last edited by Jeb51; May 7, 2012 at 08:03.

 May 9, 2012, 06:01 #2 Member   alireza Join Date: Jul 2009 Posts: 31 Rep Power: 8 Hello when h/c=0.1, (extreme ground effect) negative lift can be found. if you increases your angle of attack, you will see positive lift. albeit: in many of papers reported different data.for example positive lift in Ahmed paper and negative lift in moore papre. (for symmetrical airfoil)

 May 9, 2012, 06:48 #3 New Member   Jake Billingham Join Date: Apr 2012 Posts: 4 Rep Power: 6 The issue here isn't that it's negative, I expected that from looking at published data. The problem is the magnitude of it. I'm getting aerodynamic efficiencies of 90 upwards. I can't explain how the simulation has diverged so far from the expected values as given by the material I'm comparing to.

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