Energy transfer and dissipation tensor anisotropy in atmospheric turbulence

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Abstract

Turbulence in the atmosphere is generally affected by rotation and stratification. The combination of these two effects endows the atmosphere with wavelike motions, which are particularly relevant for the mixing processes in the middle and upper atmosphere. Gravity-waves, for instance, can transfer energy over large distances, carrying energy from where they are created to regions thousands of kilometers away (Fritts and Alexander (2003)). Due to wave instabilities, they break and induce small scale turbulence in the overall large scale flow, thus contributing to the mixing process. In current general circulation models, however, small scale motion is not resolved and instead only parametrized. Hence, understanding the breaking process can potentially lead to improved parametrization models and predictions. Depending on their frequency, gravity-waves can be classified as high-frequency gravity-waves (HGWs) and low-frequency inertia-gravity waves (IGWs). The breaking behavior of IGWs differs fundamentally from HGWs and must be investigated separately (Dunkerton (1997), Achatz and Schmitz (2006), Fruman et al. (2014)). Given that the wave breaking event leads to small scale three-dimensional turbulence, computational investigations must resolve a very large range of dynamic scales of motions (Lelong and Dunkerton (1998) and Fritts et al. (1994)). For HGWs, three-dimensional high resolution Direct Numerical Simulations (DNS) have already been performed, for example, by Fritts et al. (2009) and Remmler et al. (2015). For IGWs, fully threedimensional investigations of a IGW breaking in the upper mesosphere were first presented by Remmler et al. (2012) and Fruman et al. (2014). The present work focuses on turbulence induced by the breaking events of IGWs. We extend the work of Remmler et al. (2012) and Fruman et al. (2014) by performing DNS of an IGW breaking at a lower altitude and correspondingly higher Reynolds number typical of the middle mesosphere. Additionally, we explain the turbulent energy transfer during breaking events and analyze the structure of the turbulence dissipation tensor. Finally, we perform Large-Eddy Simulations (LES) using different models. We compare LES results to our DNS and asses if these models can be used to qualitatively predict breaking events.
Original languageEnglish
Title of host publicationProceedings of the ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurement (ETMM12)
Subtitle of host publication26-28 September 2018, Montpellier, France
Number of pages6
Publication statusPublished - 2018
Event12th International ERCOFTAC Symposium on Engineering Turbulence Measurement and Modelling - Le Quetzal Hotel and Le Prose Hotel, Montpellier, France
Duration: 26 Sep 201828 Sep 2018
Conference number: 12
https://www.ercoftac.org/events/new_etmm12/

Conference

Conference12th International ERCOFTAC Symposium on Engineering Turbulence Measurement and Modelling
Abbreviated titleETMM12
CountryFrance
CityMontpellier
Period26/09/1828/09/18
OtherThe 12th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements aims to provide a bridge between researchers and practitioners in Flow, Turbulence and Combustion by reporting fundamental and application-oriented progress in all areas of turbulence research.
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