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A study into the phenomena of multimodality in wind farm layout optimisation problems is presented. Little previous work has studied multimodality so this work aims to begin providing quantifiable results on multimodality in farm layout optimisation. The problems of optimising the location of a four and nine turbine farm within a bound circular domain are considered. Multi-start gradient-based optimisation is used to determine optima present in each case. Clear multimodality was found in all cases tested. With increasing farm size, the number of optima present increases, however the difference in performance of those optima is small. Therefore, while multimodality is present, for large farms, the chance of locating a local minima that has a detrimental performance compared to the global optimum, is small.

This paper presents a high-fidelity aerodynamic optimisation framework designed to decrease the cost of optimisation of large wind turbine blades. The framework is presented in the context of the IEA 15MW reference turbine, but is applicable to all large turbine geometries. Optimisation is performed using a surrogate model, built through latin hypercube sampling of the design space, with a GPU accelerated CFD code. Aerofoil parameterisation is handled through the use of singular value decomposition of the aerofoil nodes, built on a database of 1300 aerofoils. A preliminary optimisation study is performed on the surrogate model to demonstrate the capability and functionality of such a system.