# Kutta Joukowski theorem for flow over a rotating cylinder

Question asked by Theo Linders on Aug 20, 2016
Latest reply on Aug 25, 2016 by Bill McEachern

Hi,

I try to simulate the flow over a rotating cylinder in order to prove the Magnus effect. The diameter is 1 meter, length is 5 m, velocity is 40 m/s, the cylinder turns 90 rpm and the density is 1.2 kg/m3 so just in normal air. I used a computational domain in 2D with a width of 10 cms so, 1/50th of the total length of the cylinder.

Because i want to simulate the flow around the cilinder i don't use a rotating region but i define a real wall as a boundary condition with the velocity and rotational speed; I defined a local and global mesh (see files included).

When i calculate the lift by hand (Kutta Joukowski theorem from Lift of a Rotating Cylinder from the NASA site) the results are a lift force of 3552  N but when I use flow simulation and multiply the calculated 0.485 N with 50 (the comp. domain was 1/50 of the exact size) I only get a lousy 24.3 N.

So i guess i'm doing something totally wrong.

can anyone help me?

thx

Theo