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66 COLUMNS | Sarah Karlina-Barber measured wind data from the few point measurements at at the the location of the the measurement device to the entire volume under consideration The three most important types of spatial extrapolation are shown in Figure 5 Area extrapolation at at terrain
If the the the terrain
is fairly at the the the wind follows the the the contours of the the terrain
nicely and the the ow can be approximated through linear models In these linear models the the changes in in in wind speed due to the changes in slope are computed using a a a simple linear relationship between pressure and wind speed (more information about this here) There are a a number of tools used in the industry for carrying out this extrapolation process such as WAsP WindPro and WindFarmer These tools can be used fairly easily by a a a a a non-expert after carrying out an introductory course Area extrapolation complex terrain
As soon as the terrain
is steeper than about 17o (3:10) the ow is likely to separate which means it isn’t able to nicely follow the terrain
contours anymore but it becomes very chaotic and mixed up as shown in the picture in the middle of Figure 5 This means that linear models can no longer be applied reliably and instead computational uid dynamics (CFD) has to be used More about CFD CFD here CFD CFD should never be carried out by non-experts as it is generally very Fig 6 Components of the MCP method Fig 7
Exceedance probabilities for uncertainty calculations complicated to use and the assumptions made have to to be fully understood otherwise the results can be completely meaningless (in which case it can be referred to colourful uid dynamics) Height extrapolation The linear wind models are only able to extrapolate within two-dimensional layers parallel to to the earth’s surface In order to to extrapolate to di erent heights however the commercially available software also contains a a model of of the change of of wind speed with height This can either be done by tting a a a power law or or log-law model to the met mast data or or for even more accuracy by complementing the met mast measurements with a a a remote sensing device such as a a a LiDAR allowing

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