Abstract
Methods have been developed for the calculation of environmental loads, as input to the STAS wind power plant analysis program. A spectral model of rotationally-sampled atmospheric turbulence was extended using the multi-blade coordinate transformation. This gives the correct frequency spectra, dominated by multiples of 3P, seen by the support structures. For wave loads on the foundation, the Morison equation was extended using a full first-order potential solution, which is valid when the pile diameter is on the same order as the wavelength. The computation of loads is performed in the time domain, and subsequently transformed to the frequency domain. The first-order velocity profiles are stretched to the instantaneous free-surface, and velocity-squared terms are retained in Bernoulli's equation, in order to capture the most important sum-frequency effects which may excite tower resonance. The method was validated by comparison against published calculations, laboratory experiments, and field measurements.
