Repository: Freie Universität Berlin, Math Department

Lagrangian hairpins in atmospheric boundary layers

Harikrishnan, Abhishek P. and Ansorge, Cedrick and Klein, Rupert and Vercauteren, Nikki (2021) Lagrangian hairpins in atmospheric boundary layers. Gallery of Fluid Motion .

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Official URL: https://doi.org/10.1103/APS.DFD.2021.GFM.P0018

Abstract

In this poster, we have shown beautiful direct volume renders of finite-time Lyapunov exponent (FTLE) fields applied to a highly stratified Ekman flow. This flow describes the atmospheric boundary layer (ABL) over a smooth flat plate driven by a uniform pressure gradient and experiencing steady rotation in the wall-normal direction. An interesting result can be observed here. We note that hairpins extracted from different regions in the flow field are oriented in a similar direction i.e., the head of the hairpins point to a similar direction. These results are in-line with our previous observation with the Eulerian Q-criterion [1, 2]. For further details on FTLE, please refer to the work of [3, 4]. FTLE is sometimes referred in literature as direct Lyapunov exponent (DLE). The Reynolds number is described in terms of the geostrophic wind velocity (G), the laminar Ekman-layer depth (D) and the kinematic viscosity (ν) as Re = GD/ν.

Item Type:Article
Additional Information:Dfd 2021 74th Annual Meeting of the APS Division of Fluid Dynamics Phoenix, AZ - November 21, 2021 — November 23, 2021 Videos Now Available Videos for the 2021 Gallery of Fluid Motion are now available to view.
Subjects:Mathematical and Computer Sciences > Mathematics > Applied Mathematics
Divisions:Department of Mathematics and Computer Science > Institute of Mathematics
ID Code:2744
Deposited By: Monika Drueck
Deposited On:15 Feb 2022 18:37
Last Modified:15 Feb 2022 18:37

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