According to my (quite short) experience with ALM simulations of wind turbines, determination of the cell size in rotor plane and time step size plays an important role in the convergence and agreement with experimental measurements. There are many turbines in various sizes and operating at various speeds but I have hypothesized the following as key parameters:
- In a time step; linear distance traveled by the blade tip or angular travel of the rotor should not exceed a certain value,
- Cell size in the rotor region should be decided on a "per rotor radius" basis (should this also depend on the number of airfoil sections defined?)
- Question: Should blade tip travel more than one cell in a time step?
- Question: Should the cell size in rotor plane depend on the sectional chord length for an accurate relative velocity / AoA calculation?
Would you agree with these or add some other "rules of thumb", or have some such values you consider in your simulations according to your experience so far? It would be the most valuable.
Hüseyin Can Önel