[reynolds_master]

Hi! I have to compute the pressure coefficient (cp) distribution with the data obtained with a wind tunnel for a NACA0012 airfoil. The values are obtained in kPa and the Vinfinite in m/s.

The Pinfinite is 1013mbar. I've tried to convert the pressures (both) to Pa but then the cp is about ~120 and this is wrong. The values of the P obtained are about ~-0.035 for the upper surface. I'm using the formula attached.

Does anybody know which mistake I'm doing? I've googled the theoretical distribution and it is not even close so the problem is not about the tunnel.

THANKS!

[lovecraft22]

Don't know how you are recording the data and where you recorded -0.035 and what's your free stream velocity and what's your angle of attack. In fact, you didn't provide anything more or less but…


-0.035kpa=-35 pa

Assuming this is relative pressure and assuming your free stream velocity to be 10 m/s you have:

Cp=-35/(0.5*1.225*10^2)=-0.57 which is a reasonable value.

[reynolds_master]

Originally Posted by lovecraft22

Don't know how you are recording the data and where you recorded -0.035 and what's your free stream velocity and what's your angle of attack. In fact, you didn't provide anything more or less but…


-0.035kpa=-35 pa

Assuming this is relative pressure and assuming your free stream velocity to be 10 m/s you have:

Cp=-35/(0.5*1.225*10^2)=-0.57 which is a reasonable value.

I was considering the pressure given as the absolute one and it was the manometric one.... So dumb of me. Thanks!