Speaker
Description
This work investigates the methodology and applicability of spectral-domain modeling for incorporating multi-variate non-differentiable nonlinearities, focusing on floating renewable energy devices. Spectral-domain modeling provides a highly competitive approach for analyzing floating renewable energy structures, such as wave energy converters (WECs) and floating wind turbines, by combining adequate accuracy with high computational efficiency. Its high accuracy stems from representing nonlinear effects through statistical linearization. However, existing formulations have only been applicable for a limited range of nonlinearities, primarily those with simple, differentiable mathematical expressions. In practice, floating renewable energy devices exhibit complex dynamic mechanisms involving highly nonlinear behaviors, such as external machinery force saturation and nonlinear hydrostatics of non-uniform floaters, which can significantly influence system responses. Extending spectral-domain modeling to accommodate nonlinearities of increasing complexity is therefore essential.
In this work, spectral-domain modeling is extended to address nonlinear effects expressed as multi-variate non-differentiable functions. The mathematical formulation is first reviewed for single-variate differentiable, single-variate non-differentiable, and multivariate differentiable nonlinearities before being generalized to the targeted class of nonlinearities. Several case studies demonstrate the application of the extended approach to representative nonlinearities in floating renewable energy devices. Its accuracy and computational efficiency are assessed against nonlinear time-domain (TD) and linear frequency-domain (FD) models. Despite the complexity of the nonlinearities considered, the extended spectral-domain modeling achieves relative errors below 6%, while requiring computational times comparable to the FD model and remaining thousands of times faster than the TD model. In contrast, the FD model produces relative errors exceeding 70% in some cases.
| Topic Area | Sustainable Ocean Structures |
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