Search

Contrails are condensation trails generated from emitted particles by aircraft engines, which perturb Earth's radiation budget. Simulation modeling is used to interpret the formation and development of contrails. These simulations are computationally intensive and rely on high-performance computing solutions, and the contrail structures are not well defined. We propose a visual computing system to assist in defining contrails and their characteristics, as well as in the analysis of parameters for computer-generated aircraft engine simulations. The back-end of our system leverages a contrail-formation criterion and clustering methods to detect contrails' shape and evolution and identify similar simulation runs. The front-end system helps analyze contrails and their parameters across multiple simulation runs. The evaluation with domain experts shows this approach successfully aids in contrail data investigation.

Zinc (Zn) deposition and dissolution are very important processes during the charge and discharge cycles of rechargeable Zn aqueous batteries (ZBs). During this process, an interfacial ZnO layer is formed on the surface of Zn electrode that can have profound effects on the formation and growth of Zn dendrites and ZB performance and stability. The present work seeks to understand the structure and stability of the ZnO interfacial layer and mechanisms of Zn diffusion through this layer. The density functional theory (DFT) calculations supported by the aberration-corrected scanning transmission electron microscopy (AC-STEM) are employed to understand the ZnO atomic structure and its chemo-mechanical properties. Owing to the polycrystalline nature of the ZnO layer, the Zn diffusion through the two subsystems, namely, ZnO grain and ZnO grain boundary (GB) are studied. The activation energy of Zn diffusion varies significantly depending upon the modeled structure and the number of Zn adatoms. The calculated elastic properties show the decrease of Young’s modulus with an increase of Zn adatoms. Our findings provide insights into developing mitigation strategies toward the suppression of Zn dendrites during electrodeposition.

This paper presents the results from numerical experiments of the early phase of contrail-cirrus formation using a limited set of fully three-dimensional, high-resolution large-eddy-simulations. The focus is laid on the interplay between atmospheric turbulence and the radiative transfer (and to a limited extent the ambient ice relative humidity), and how this interaction affects the contrail evolution and the characteristics of the resulting contrail-cirrus one hour after emission. Turbulence is sustained via a large-scale stochastic forcing that creates a non-uniform shear in addition to pure turbulent fluctuations. This effect manifests in the formation of vertically sheared structures of ice crystals. When radiative transfer is activated, ice tends to redistribute more uniformly along the vertical direction forming spotty vertical structures. For the conditions analyzed in this study, atmospheric turbulence, inclusive of non-uniform turbulent shear and turbulent fluctuations, affects primarily the contrail width whereas the microphysical properties such ice water path and ice mass are controlled by radiative transfer and relative humidity.

Flugzeuge sind reichhaltige Quellen von Partikeln (Ruß, flüssige Aerosole und Kondensstreifen) welche die Wolkenbildung beeinflussen und so auf den Strahlungshaushalt der Erde einwirken können. Zur Untersuchung der Bildung und des Verhaltens dieser Partikel wurde ein numerischer Ansatz entwickelt, der Large Eddy Simulation (LES) und ein detailliertes Mikrophysikmodell kombiniert. Im Allgemeinen werden Mikrophysikmodelle entlang einer einzigen, gemittelten Trajektorie angewandt, ohne Temperaturschwankungen zu berücksichtigen. Dieser Ansatz kann jedoch zu signifikanten Abweichungen führen, was Partikeleigenschaften und deren Größenverteilung betrifft, da er dynamische und mischungsbezogene Prozesse im Vergleich zu mehrdimensionalen Darstellungen der Nachlaufströmung zu stark vereinfacht. Dies kann die Initialisierung von Mesoskalenmodellen beeinflussen, wie beispielsweise die Bildung von Wolkenkondensationskeimen von beständigen Kondensstreifen sowie heterogene chemische Reaktionen. In diesem Artikel präsentieren wir die Resultate von detaillierten Berechnungen mikrophysikalischer Prozesse, die auf eine große Zahl von Fluidpartikelbahnen angewandt werden, welche von einem LES Zweiphasen-Strömungslöser generiert wurden.