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Life-cycle of streaks in the buffer layer of wall-bounded turbulence

Bae, H. Jane and Lee, Myoungkyu (2021) Life-cycle of streaks in the buffer layer of wall-bounded turbulence. . (Submitted)

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Streaks in the buffer layer of wall-bounded turbulence are tracked in time to study their life-cycle. Spatially and temporally resolved direct numerical simulation data is used to analyze the strong wall-parallel movements conditioned to low-speed streamwise flow. The analysis of the streaks shows that there is a clear distinction between wall-attached and detached streaks, and that the former can be further categorized into streaks that are contained in the buffer layer and the ones that reach the outer region. The results reveal that streaks are born in the buffer layer, coalescing with each other to create larger streaks that are still attached to the wall. Once the streak becomes large enough, it starts to meander due to the large streamwise to the wall-normal aspect ratio, and consequently the elongation in the streamwise direction, which makes it more difficult for the streak to be oriented strictly in the streamwise direction. While the continuous interaction of the streaks allows the super-structure to span extremely long temporal scales and streamwise dimensions, individual streak components are relatively small and short-lived. Tall-attached streaks eventually split into wall-attached and wall-detached components. These wall-detached streaks have a strong wall-normal velocity away from the wall, similar to ejections or bursts observed in the literature. Conditional averaging of flow fields to these split events show that the detached streak has not only a larger wall-normal velocity compared to the wall-attached counterpart, it also has a larger (less negative) streamwise velocity, similar to the velocity field at the tip of a vortex cluster.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper
Bae, H. Jane0000-0001-6789-6209
Additional Information:Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0). The authors thank N. Hutchins for his insightful comments on the manuscript. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.
Funding AgencyGrant Number
Department of Energy (DOE)DE-NA0003525
Record Number:CaltechAUTHORS:20210315-141739187
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108435
Deposited By: Tony Diaz
Deposited On:19 Mar 2021 00:40
Last Modified:19 Mar 2021 00:40

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