Dear all,
I’m currently using OpenFAST to prescribe sinusoidal surge and pitch motions to a wind turbine using the ExtPtfm module. So far, I’ve been using a constant time step of 0.01 for all the simulations and the turbine undergoes 50 periods of oscillation per simulation but I think I may be using too small and too large of a time step and number of periods, respectively. The goal is to extract the average Cp, Ct, the spanwise loads and their spectra along the blades and the stall margins.
Regarding the time step)
- The range of surge frequencies and amplitudes I’m using is [0;0.1] Hz and [0;10] m which means that in highest frequency oscillation, there are 1000 time steps per period which seems to much using the rule of thumb of having at least 10 time steps per period. However, drawing from some CFD experience, the time step should be somehow a function of the surge velocity during the simulation so that the information propagates accordingly. Is this question about the timely information propagation relevant for OpenFAST since it is not CFD? If so, is there a criterion I should use to define the time step of each simulation?
Regarding using 50 periods)
- I will perform a convergence study to on the variables I want to extract to see whether 50 periods are too much but do you have an opinion on this?
Best regards
Ricardo Amaral