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

I haven't looked at your model yet, but I'm not sure about your math. When I calculate the theoretical lift according to the simplified theorem, I only get 711 N/m, this is the equation I used: Wolfram|Alpha: Computational Knowledge Engine

Your calculate force from the model is .485 N / 10cm = 4.85 N/m. So still pretty far off, but different numbers from what you have.