An Investigation of the Suitability of Different Mesoscale-Microscale Coupling Techniques during Unsteady Meteorological Conditions for Wind Energy Applications

Different mesoscale-microscale coupling strategies are examined to improve large-eddy simulations (LESs) of flow parameters relevant to wind energy applications, during relatively simple but unsteady meteorological conditions. Nesting of an LES domain directly within a mesoscale simulation, wherein the LES receives time-varying lateral boundary forcing from the mesoscale simulation at each mesoscale time step, is compared with use of a traditional LES using periodic lateral boundary conditions, augmented with internal forcing extracted from a precursor mesoscale simulation. The application of stochastic inflow perturbations to improve parameter predictions within the nested LES is also examined. Case studies representing a diurnal cycle and a frontal passage, over relatively flat and uniform terrain, are utilized to evaluate each approach. The use of stochastic inflow perturbations leads to improved parameter values within nested LES, especially during near-neutral to stable conditions. While application of internal mesoscale forcing can improve the performance of traditional periodic LES, preparation of appropriate mesoscale forcing in the presence of nontrivial synoptic-scale meteorological variability requires further investigation. Recommendations in light of our results are presented.