4.8.1 Getting started - WindSim

A grid sensitivity study41Figure 28. Energy > Report. Wake losses computed with 20 sub-sectors.A grid sensitivity studyReferring to the AEP forecasted in the exercise of the tutorial 1 a quite large difference canbe noted in the AEP predicted by the two climatologies, about 7 GWh/y. Large part of thediscrepancy observed in the two predictions comes from the fact that this exercise was runwith the evaluation copy of WindSim, where there is a limit of 5000 cells; discretization errorsare therefore considerable. A typical procedure that is followed in CFD computations is topass from coarse grids to finer and finer grids in order to minimize the discretization errors,the ideal situation is achieved when the errors are negligible, when grid independency hasbeen reached. In the following Figures 29-33 you can see the effects of grid sensitivity studyon the AEP obtained with further refinements.Table 1. Table of cases run.N Nx Ny Nz4370 23 19 1024320 38 32 2090280 74 61 20375000 150 125 20750480 212 177 20