**Preface to "Numerical Simulation of Wind Turbines"**

It is undisputed that wind energy has become a consolidated industry, probably representing the leading form of energy conversion from renewables. Wind turbines are, however, not only the largest rotating machines on Earth, but also very complex systems, whose design and optimization require the contribution of several disciplines, from aerodynamics to structural analyses, from control to electric engineering. At the moment, however, a truly holistic approach to wind turbine design is still missing, with different groups of experts often working not sufficiently close to each other. To achieve it, it is apparent that simulation will play a key role since it represents the common framework, within which the different disciplines and sciences can communicate. Developments are needed in each of them, from more accurate, but computationally affordable, simulation techniques, to innovative control logics or innovative design solutions. The contributions from the research works included in the Special Issue *Simulation of Wind Turbines* offer new data, information, and findings to continue the R&D effort in wind turbine simulation, with the aim of stimulating the research community to further contribute to the development of the field.

> **Alessandro Bianchini, Giovanni Ferrara** *Editors*
