Calculating Lift From Pressure

[RitchieLinford]

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]

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.

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]

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