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The Mesoscale to Microscale Coupling team, part of the U.S. Department of Energy Atmosphere to electrons (A2e) initiative, has studied various important challenges related to coupling mesoscale models to microscale models for the use case of wind energy development and operation. Several coupling methods and techniques for generating turbulence at the microscale that is subgrid to the mesoscale have been evaluated for a variety of cases. Case studies included flat terrain, complex terrain, and offshore environments. Methods were developed to bridge the terra incognita, that scale from about 100 m through the depth of the boundary layer. The team used wind-relevant metrics and archived code, case information, and assessment tools and are making those widely available. Lessons learned and discerned best practices are described in the context of the cases studied for the purpose of enabling further deployment of wind energy.

Microscale flow descriptions are often given in terms of mean quantities, turbulent kinetic energy, and/or stresses. Those metrics, while valuable, give limited information about turbulent eddies and 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. We calculate spatial correlations over entire planes of velocity fluctuations, from which we can evaluate 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–microscale coupled scenario with time-varying conditions and examine nuances in spatial correlations that are often overlooked. Through these analyses and results, this work highlights important differences observed in terms of coherence when comparing large-eddy simulation data to simpler models and suggests ways to improve these simpler models. We note that such differences are important for disciplines like wind energy structural dynamic analysis, in which blade loading and fatigue depend strongly on the structure of the turbulence. 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.

In the present work, unsteady effects present in a ship airwake are further analyzed. The effort is performed in the context of simulation of helicopter launch and recovery operations under a reali...

The influence of a neutral atmospheric boundary layer on a one-way coupled dynamic interface simulation is evaluated. The effort is performed within the context of time-accurate large-eddy simulati...

A methodology for solving three-dimensional topology optimization problems through a two-level mesh representation approach is described and evaluated. Structural topology optimization problems are executed on a polytope-based mesh, which carries the design variable (and subsequently the density). Displacement field is determined using tetrahedron elements, embedded within the polytopes. The proposed mapping-based framework decouples the analysis routine and optimization algorithm from the specific choice of topology optimization formulation. The mapping-based formulation allows easy applicability of features such as regularization and density filters and symmetry through a mapping matrix. The embedding approach is demonstrated on minimum compliance problems and solid–void solution is obtained by employing continuation on the solid isotropic material with penalization penalty parameter. We show that the proposed approach is able to achieve solutions free of numerical anomalies (e.g., checkerboard pattern and one-node connections) without the application of any explicit regularization scheme nor filtering. Our solutions approach the theoretical solution as mesh size increases.