Dear Readers,
We begin 2019, the 20th year of publication of the Journal of Turbulence, with a Special Issue on Wind Energy. Over the next years, the journal will publish several thematic issues such as this, to highlight topics that, in the opinion of the Editorial Board, are interesting, important and timely. They will be anchored by a review article, and contain a number of technical papers.
The inaugural Thematic Issue is opened by a thought-provoking article by Charles Meneveau (a former Editor-in-Chief of this journal), who poses seven questions for turbulence research in this area. They address topics of varying degree of complexity, from the development of analytical models to the integration of wind-farm simulations with geophysical models, and point out directions in which turbulence research could result in significant improvements in design and analysis capabilities.
Three technical papers complete the Special Issue. They illustrate how field experiments, wind tunnel experiments and numerical simulations can be used in complementary fashion to understand the complex physics of turbulence in wind farms.
Tobin and Chamorro discuss the results of wind-tunnel experiments aimed at understanding how turbulence is affected when passing through a rotor. By cross-correlating the velocity fluctuations measured synchronously upstream and downstream of the rotor, they determine the dispersion of different time-scales.
Ali and co-workers present the numerical results obtained from large-eddy simulations of wind farms in thermally stratified conditions. They examine the budgets of turbulent kinetic energy (TKE), and perform quadrant analysis of the data, to find the effects of stable and unstable conditions on the mechanisms that govern the TKE.
Archer and co-workers describe a field-measurement campaign, the VERTEX campaign, carried out in Delaware in 2016, to study the effect of wind turbines on surface properties. The methodology used to obtain and post-process the data is described in detail, and two case studies illustrate how these data can be used to determine the vertical mixing in the wake of the turbine.
The Editorial Board hopes that you, the Readers, will find these Thematic Issues interesting and stimulating. We would be happy to entertain suggestions for future topics.
Sincerely, Ugo Piomelli, Editor in Chief