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RitchieLinford (Aerospace)
9 Apr 04 13:08
Hello all,
New to this site, i am currently at uni studying Aerospace Engineering.
I am doing a project using a CFD package, (PHOENICS) which will only give me pressure and velocity values at points. But i need to work out how much lift the shape is creating, i have undergone the pain staking processes of taking 100 pressure readings around each of the airfoils i am useing, but i now need to turn these pressure valules into lift figures, so i can calcualte how much lift is being produced. I am getting really confussed as what seems a simple process i just can't get my head around it.
Any help would be greatly recived
Many Thanks
Ritchie
IRstuff (Aerospace)
12 Apr 04 14:38
My understanding is that Bernoulli's law does not fully explain airfoil lift, and that conservation of momentum must be considered to get the correct lift values. 字串4
In any case, there is a pressure on the bottom surface and a pressure on the top surface; the difference in net force is the amount of generated lift. TTFN
GregLocock (Automotive)
13 Apr 04 8:49
Let's see. The force exerted on a small patch area A is P.A, normal to the patch. If you add, vectorially, all those Fs then you will have the net effective force on the airfoil.
IRstuff, I think you are right, but pressure is the only way (apart from shear effects) the air can 'talk' to the airfoil. Certainly if you just use Bernouilli in a simple manner and ignore circulation then you won't necessarily get any lift, eg from thin flat panels at an angle to the airstream.
Cheers
Greg Locock
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