Dear community,
I generated a 2D wind field in the lateral and vertical directions, ((y,z)), using MATLAB and exported it as a .bts file. The wind field has a sampling frequency of 10 Hz and a total duration of about 2 hours.
I then used this wind field as input to InflowWind coupled with OpenFAST, using the IEA 22 MW reference wind turbine. The simulation runs normally. However, when I compare the wind-speed time series at one grid point from the original .bts file with the corresponding wind output obtained from OpenFAST, I observe the following:
The two signals look very similar in the time domain, but their PSDs differ in the frequency domain. In particular, the OpenFAST output appears to contain more energy at frequencies above 5 Hz.
Since the original wind field is sampled at 10 Hz, 5 Hz is the Nyquist frequency. I suspect that this difference may be related to the interpolation performed by InflowWind when the wind field is queried at the OpenFAST time step. However, I have not been able to find a clear description of this interpolation process in the InflowWind documentation.
Could anyone clarify how InflowWind/OpenFAST interpolates wind histories from a .bts file in time and space? In particular, I would like to understand whether this interpolation could introduce apparent energy above the Nyquist frequency of the original wind field.
The comparison I am referring to is shown below.
Best regards
