Investigations of Correlation and Coherence in Turbulence from a Large-Eddy Simulation

Abstract. Microscale flow descriptions are usually given in terms of statistics of turbulence quantities and/or spectral analysis. Those metrics, while valuable, give limited information about coherent turbulent structures. This work investigates the structure of an atmospheric boundary layer using coherence and correlation in space and time with a range of separation distances. To that end, we obtain spatial correlation of entire planes of velocity fluctuations, which allow us to have a better understanding of the correlation along different directions at different spacings. Similarly, coherence of the three velocity components over separations in the three directions is also investigated. We apply these analyses to a mesoscale-to-microscale coupled scenario with time-varying conditions and examine nuances in spatial correlations that are often overlooked. Through these analyses, we highlight the importance of spatial correlation and coherence for disciplines like wind energy structural dynamic analysis, in which blade loading and fatigue depend strongly on turbulence structure. We emphasize the additional wealth of data that can be provided by typical atmospheric boundary layer large-eddy simulation when correlation and coherence analysis is included, and we also state the limitations of large-eddy simulation data, which inherently truncate the smaller scales of turbulence.