Preprints
https://doi.org/10.5194/acp-2022-76
https://doi.org/10.5194/acp-2022-76
 
17 Mar 2022
17 Mar 2022
Status: this preprint is currently under review for the journal ACP.

Impact of Turbulence on Aeolian Sand and Dust Entrainment: Results from Wind-tunnel Experiment

Jie Zhang1,, Guang Li1,2,3,, Li Shi1, Ning Huang1, and Yaping Shao4 Jie Zhang et al.
  • 1Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000, China
  • 2College of Atmospheric Science, Lanzhou University, Lanzhou 730000, China
  • 3College of Architecture Civil and Environmental Engineering, Ecole Polytechnique Federal de Lausanne, Lausanne 1015, Switzerland
  • 4Institute for Geophysics and Meteorology, University of Cologne, Germany
  • These authors contributed equally to this work.

Abstract. We hypothesize that large eddies play a major role in the entrainment of aeolian sand and dust particles. To test this, wind-tunnel experiments are carried out to measure the entrainment rate of various particle sizes under different flow conditions. Wind tunnel flows are usually neutrally stratified with no large eddies which typically develop in convective atmospheric boundary layers. Here, a novel technique is applied by deploying a piece of randomly fluttering cloth to generate large eddies similar to convective eddies in atmospheric boundary layers, which we call quasi-convective turbulence. The characteristics of quasi-convective turbulence are analyzed with respect to neutral turbulence in the Monin-Obukhov similarity framework, and the probability distributions of surface shear stress are examined. We show that for given mean flow speed and in comparison with neutral flow conditions, quasi-convective turbulence increases the surface shear stress and alters its probability distribution, and hence substantially enhances the entrainment of sand and dust particles. Our hypothesis is thus confirmed by the wind-tunnel experiments. We also explain why large eddies are important to aeolian entrainment and transport.

Jie Zhang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • AC1: 'Comment on acp-2022-76', Guang Li, 17 Mar 2022
  • RC1: 'Comment on acp-2022-76', Gilles Bergametti, 29 Mar 2022
  • RC2: 'Comment on acp-2022-76', X.-L. Cheng, 02 Apr 2022
  • RC3: 'Comment on acp-2022-76', Cheryl McKenna Neuman, 13 Apr 2022

Jie Zhang et al.

Jie Zhang et al.

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Short summary
Sand and dust emission are usually investigated by wind tunnel experiments. However, the wind tunnel flows are usually neutrally stratified without large eddies, which typically develop in convective atmospheric boundary layers. Here we proposed a novel technique by deploying a piece of randomly fluttering cloth in a wind tunnel to generate the large eddies and found them enhancing the entrainment of sand and dust particles, which explains why large eddies are important to aeolian entrainment.
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