Page 261 - Wind Energy Handbook
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BLADE LOADS DURING OPERATION                                           235







                               Ω






                                     d





                                              J        J




                                                         Tower radius = D/2

                            y
                                      x(d)
                                                   x
                                                          Rotor plane
                                               Section J – J








                                          Velocity Profile at rotor plane
                                  Figure 5.12  Tower Shadow Parameters


             where ä is the total width of the deficit region. The slight enhancement of velocities
             beyond the deficit region is usually ignored (see also Section 6.13.2).
               The sharp dip in blade loading caused by tower shadow is more prone to excite
             blade oscillations than the smooth variations in load due to wind shear, shaft tilt
             and yaw, and this aspect is considered in the section on blade dynamic response.



             Wake effects

             Within a wind-farm it is common for one turbine to be operating wholly or partly
             in the wake of another. In the latter case, which is more severe, the downwind
             turbine is effectively subjected to horizontal wind shear, and the blade load
             fluctuations can be analysed accordingly.
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