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Fundamental and Advanced Topics in Wind Power Part 6

Tham khảo tài liệu 'fundamental and advanced topics in wind power part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Efficient Modelling of Wind Turbine Foundations 139 2. A lumped-parameter model providing approximately the same frequency response is calibrated to the results of the rigorous model. 3. The structure itself in this case the wind turbine is represented by a finite-element model or similar and soil-structure interaction is accounted for by a coupling with the LPM of the foundation and subsoil. Whereas the application of rigorous models like the BEM or DTM is often restricted to the analysis in the frequency domain at least for any practical purposes the LPM may be applied in the frequency domain as well as the time domain. This is ideal for problems involving linear response in the ground and nonlinear behaviour of a structure which may typically be the situation for a wind turbine operating in the serviceability limit state SLS . It should be noted that the geometrical damping present in the original wave-propagation problem is represented as material damping in the discrete-element model. Thus no distinction is made between material and geometrical dissipation in the final lumped-parameter model they both contribute to the same parameters i.e. damping coefficients. Generally if only few discrete elements are included in the lumped-parameter model it can only reproduce a simple frequency response i.e. a response with no resonance peaks. This is useful for rigid footings on homogeneous soil. However inhomogeneous or flexible structures and stratified soil have a frequency response that can only be described by a lumped-parameter model with several discrete elements resulting in the presence of internal degrees of freedom. When the number of internal degrees of freedom is increased so is the computation time. However so is the quality of the fit to the original frequency response. This is the idea of the so-called consistent lumped-parameter model which is presented in this section. 4.1 Approximation of soil-foundation interaction by a rational filter The .