While doing a number of CFD simulations on variety of propellers, I've observed that:
- Solidworks results differ from theoretical (ideal) calculations by ~ 50%
- Solidworks results differ from real calculations by ~30%
I.e., 48" diameter (1.2m), 8.5" pitch (21cm), 2400RPM.
Theoretical maximum (Abbott f-la): 153N (or 17.2 kg) of Thrust.
By considering the propeller efficiency (70%-80%), expected results are in range from 107N to 122N
Solidworks gave 87N.
To further debug the problem, I've ran a force analysis on each of the propeller surfaces.
The results were rather surprising. The bottom surfaces seem to generate the opposite thrust of ~1/3 of upper surfaces' thrust.
My physics knowledge can't explain this.
By excluding these opposing (2x 25N) values, we would get ~138N.
That would be a fairly good estimate, because it would indicate a propeller efficiency of ~90%.
This is ok, because FEM cannot account for non-linear losses.
Are my assumptions reasonable?