WT_Perf uses blade-element momentum theory to predict the performance of wind turbines.  It is a descendent of the PROP code originally developed by Oregon State University.  Over the intervening years, many people from many organizations put their marks on the code.  More recently, the staff at the NWTC rewrote the program, modernized it, and added new functionality and algorithms.

We have not created a theory manual explicitly for WT_Perf.  However, as WT_Perf is a descendent of the PROP code with minor theory changes and is almost identical to AeroDyn, there are a few documents you might find useful:

• WilsonLissaman_AppAeroOfWindPwrMach_1974.pdf
  Applied Aerodynamics of Wind Power Machines
  Robert E. Wilson
  Peter B. S. Lissaman
  Oregon State University
  May 1974

• HibbsRadkey_BEM_Theory.pdf
  Small Wind Energy Conversion Systems (SWECS) Rotor Performance Model Comparison Study (UNPUBLISHED DRAFT)
  B. Hibbs
  R.L. Radkey
  Aerovironment, Inc.
  November 1981

• NREL/CP-500-36881
  AeroDyn Theory Manual
  Pat J. Moriarty
  NREL-NWTC
  A. Craig Hansen
  Windward Engineering
  January 2005

• NREL/CP-500-36834
  A New Empirical Relationship between Thrust Coefficient and Induction Factor for the Turbulent Windmill State
  Marshall L. Buhl Jr.
  NREL-NWTC
  August 2005

You may download the following files from our server:

• WT_Perf Change Log (v3.10, 9 KB, 16-December-2004)

  This is a list of changes made to the code.  Look at this text file to see if we've made worthwhile changes since you received your previous version of WT_Perf.

• WT_Perf User's Guide (v3.1, 94 KB, 17-December-2004)

  This is the WT_Perf User's Guide.  Please refer to it when trying to understand how the program works.

• WT_Perf Archive (v3.10, 1.5 MB, 17-December-2004)

  This is a self-extracting archive of WT_Perf.  It contains the WT_Perf executable file, sample input files, installation-verification test procedure, change log, and user's guide.  It runs on all 32-bit Windows® platforms.  We created the executable file with Intel Visual Fortran® w_fc_pc_8.0.050_pe052.1.

If you want to refer to the WT_Perf website in a report, here is a reference you can use:

NWTC Design Codes (WT_Perf by Marshall Buhl).  http://wind.nrel.gov/designcodes/simulators/wtperf/.  Last modified 23-September-2009; accessed 23-September-2009.

Additional links:

• WT_Perf Verification Page

  We did a verification study in which we compared WT_Perf v3.10 to YawDyn/AeroDyn.  You can view plots of the results of the verification tests we run whenever we release a new version of WT_Perf.

• WT_Perf Alpha-Tester's Page

  If you want to test pre-release versions of WT_Perf, please check this page for the latest alpha version.