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This content will become publicly available on August 26, 2018

Title: Coherent structures in wind shear induced wave–turbulence–vegetation interaction in water bodies

Flume experiments with particle imaging velocimetry (PIV) were conducted recently to study a complex flow problem where wind shear acts on the surface of a static water body in presence of flexible emergent vegetation and induces a rich dynamics of wave–turbulence–vegetation interaction inside the water body without any gravitational gradient. The experiments were aimed at mimicking realistic vegetated wetlands and the present work is targeted to improve the understanding of the coherent structures associated with this interaction by employing a combination of techniques such as quadrant analysis, proper orthogonal decomposition (POD), Shannon entropy and mutual information content (MIC). The turbulent transfer of momentum is found to be dominated by organized motions such as sweeps and ejections, while the wave component of vertical momentum transport does not show any such preference. Furthermore, by reducing the data using POD we see that wave energy for large flow depths and turbulent energy for all water depths is concentrated among the top few modes, which can allow development of simple reduced order models. Vegetation flexibility is found to induce several roll type structures, however if the vegetation density is increased, drag effects dominate over flexibility and organize the flow. The interaction between waves andmore » turbulence is also found to be highest among flexible sparse vegetation. But, rapidly evolving parts of the flow such as the air–water interface reduces wave–turbulence interaction.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [4]
  1. Karlsruhe Inst. of Technology (KIT) (Germany). Inst. of Meteorology and Climate Research (IMK-IFU)
  2. Freie Univ., Berlin (Germany). Dept. of Mathematics and Computer Sciences
  3. Univ. of Iowa, Iowa City, IA (United States). Dept. of Civil and Environmental Engineering
  4. Univ. of Houston, TX (United States). Dept. of Mechanical Engineering
Publication Date:
Report Number(s):
LA-UR-17-27299
Journal ID: ISSN 0168-1923
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Agricultural and Forest Meteorology
Additional Journal Information:
Journal Volume: 255; Journal ID: ISSN 0168-1923
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 54 ENVIRONMENTAL SCIENCES; Earth Sciences; Coherent structures; Flexible emergent vegetation; PIV; POD; Quadrant analysis; Shannon entropy; Wave–turbulence interaction; Wind induced flow
OSTI Identifier:
1394989