Dear Yingyu,
We pulled the most recent version of WT_Perf from our website because users ran into problems that we didn’t have time to fix. Please see the following forum topic for information about WT_Perf’s status: WT_Perf being removed from distribution.
Our effort recently has been on updating the BEM solver of AeroDyn, from which we developed a standalone wrapper that will replace WT_Perf. The release of this overhaul of AeroDyn will happen later this month.
The forum topic linked above recommends CCBlade (nwtc.nrel.gov/CCBlade) as a replacement for WT_Perf, which was developed under NREL’s Systems Engineering initiative, but will be replaced by the new standalone AeroDyn.
Another option is FAST.
Best regards,