Enrichment Methods for Inflow Turbulence Generation in the Atmospheric Boundary Layer

We investigate the feasibility of introducing synthetic turbulence into finite-domain large-eddy simulations (LES) of the wind plant operating environment. This effort is motivated by the need for a robust mesoscale-to-microscale coupling strategy in which a microscale (wind plant) simulation is driven by mesoscale data without any resolved microscale turbulence. A neutrally stratified atmospheric boundary layer was simulated in an LES with 10-m grid spacing. We show how such a fully developed turbulence field may be reproduced with spectral enrichment starting from an under-resolved coarse LES field (with 20-m and 40-m grid spacing). The velocity spectra of the under-resolved fields are enriched by superimposing a fluctuating velocity field calculated by two turbulence simulators: TurbSim and Gabor Kinematic Simulation. Both forms of enrichment accurately simulated the autospectra of all three velocity components at high wavenumbers, with agreement between the enriched fields and the full-resolution LES observed at 400 m from the inflow boundary. In contrast, the spectra of the unenriched fields reached the same fully developed state at four times the downstream distance.