Morten

Hi Old Forum Archivist, The way WEng calculates TI is first to run a flow model, which predicts fields of wind speed and 3D velocity gradients. For specific sites WEng then predicts local turbulence spectra by the deformations by the mean flow and gradual adjustments to surface roughness changes. The variance of the local velocity perturbations and the turbulence intensity is then found by integration. The calculations are repeated for a number of wind directions. More details are found in: J Mann (2000) The spectral velocity tensor in moderately complex terrain, J. Wind Eng. Ind. Aerodyn. Vol. 94(2006) p. 581–602 There are certain limitations. WEng TI is for neutral stability only and it does not include turbulence produced in wakes of upstream turbines, obstacles, or behind steep terrain. Observed turbulence would include such effects and especially at low wind speeds you would see some scatter around the mean. Sorry about the late reply. I am relatively new to this forum. Aim to be more active in the future.

*.wtg files can have multiple performance tables, which you can add with the WASP turbine editor. If you want to model wake turbulence in WAT you may also need to modify the thrust-coefficient curves in the performance tables - although this effect could be small if you are only changing air density and the turbine operates with the same tip-speed ratio and pitch regulation (better consult a specialist on this). Certain WAT versions have a known problem reading *.wtg files (a work around methodis to input data in *.pow format). But once I get this fixed, you should again be able to right-click on the 'table' child object to the turbine object and set the appropriate performance table in the pop-up window.