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Title: Importance of Body Stance in Fog Droplet Collection by the Namib Desert Beetle

Abstract

The fog-basking behavior of the Onymacris unguicularis, a beetle species living in the coastal regions of the Namibian desert, has recently caught the attention of the engineering community, as suggesting a viable biomimetic approach to address the problem of harvesting water in arid regions of the globe. Previous research has focused on observation and analysis of the beetle’s elytron properties and how these affect fog-collection rates. The head stance taken by the Onymacris unguicularis when fog basking is well documented. However, how this stance affects droplet collection has not been studied up to now. The present paper addresses this problem from a computational fluid dynamics perspective, where three-dimensional numerical simulations are used to characterize the fog flow properties around a simplified geometry mimicking the beetle’s body. The simulations employ two-way coupling between the gas flow and the dispersed fog phase to account for feedback effects of fog droplets on the carrier fluid (air), and assume that droplets are captured after hitting the elytron surface. The study considers several combinations of free-stream velocity and droplet volume fraction. The analysis reveals that there is a range of head-stance angles, corresponding to an inclination of the beetle between 35 deg and 45 degmore » with respect to the horizon, that maximizes water collection on the beetle’s back, in qualitative agreement with observations in nature and laboratory experiments. A rationale is proposed to explain this phenomenon, finding that the specific head stance corresponds to the maximum residence time of fluid particles above the beetle’s elytron surface. This, in turn, designates the maximum likelihood for water droplets to be captured in the boundary layer developing over the beetle and subsequently hit the surface where they get captured. The results reveal the importance of the fluid flow pattern around the beetle’s body in addition to the microphysical properties of the elytron when reliable predictions of the water droplet collection efficiency are sought.« less

Authors:
; ORCiD logo; ; ORCiD logo
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1559074
Grant/Contract Number:  
#ANL 4J-30361-0030A
Resource Type:
Published Article
Journal Name:
Biomimetics
Additional Journal Information:
Journal Name: Biomimetics Journal Volume: 4 Journal Issue: 3; Journal ID: ISSN 2313-7673
Publisher:
MDPI AG
Country of Publication:
Country unknown/Code not available
Language:
English

Citation Formats

Chakrabarti, Unmeelan, Paoli, Roberto, Chatterjee, Souvick, and Megaridis, Constantine M. Importance of Body Stance in Fog Droplet Collection by the Namib Desert Beetle. Country unknown/Code not available: N. p., 2019. Web. doi:10.3390/biomimetics4030059.
Chakrabarti, Unmeelan, Paoli, Roberto, Chatterjee, Souvick, & Megaridis, Constantine M. Importance of Body Stance in Fog Droplet Collection by the Namib Desert Beetle. Country unknown/Code not available. doi:10.3390/biomimetics4030059.
Chakrabarti, Unmeelan, Paoli, Roberto, Chatterjee, Souvick, and Megaridis, Constantine M. Wed . "Importance of Body Stance in Fog Droplet Collection by the Namib Desert Beetle". Country unknown/Code not available. doi:10.3390/biomimetics4030059.
@article{osti_1559074,
title = {Importance of Body Stance in Fog Droplet Collection by the Namib Desert Beetle},
author = {Chakrabarti, Unmeelan and Paoli, Roberto and Chatterjee, Souvick and Megaridis, Constantine M.},
abstractNote = {The fog-basking behavior of the Onymacris unguicularis, a beetle species living in the coastal regions of the Namibian desert, has recently caught the attention of the engineering community, as suggesting a viable biomimetic approach to address the problem of harvesting water in arid regions of the globe. Previous research has focused on observation and analysis of the beetle’s elytron properties and how these affect fog-collection rates. The head stance taken by the Onymacris unguicularis when fog basking is well documented. However, how this stance affects droplet collection has not been studied up to now. The present paper addresses this problem from a computational fluid dynamics perspective, where three-dimensional numerical simulations are used to characterize the fog flow properties around a simplified geometry mimicking the beetle’s body. The simulations employ two-way coupling between the gas flow and the dispersed fog phase to account for feedback effects of fog droplets on the carrier fluid (air), and assume that droplets are captured after hitting the elytron surface. The study considers several combinations of free-stream velocity and droplet volume fraction. The analysis reveals that there is a range of head-stance angles, corresponding to an inclination of the beetle between 35 deg and 45 deg with respect to the horizon, that maximizes water collection on the beetle’s back, in qualitative agreement with observations in nature and laboratory experiments. A rationale is proposed to explain this phenomenon, finding that the specific head stance corresponds to the maximum residence time of fluid particles above the beetle’s elytron surface. This, in turn, designates the maximum likelihood for water droplets to be captured in the boundary layer developing over the beetle and subsequently hit the surface where they get captured. The results reveal the importance of the fluid flow pattern around the beetle’s body in addition to the microphysical properties of the elytron when reliable predictions of the water droplet collection efficiency are sought.},
doi = {10.3390/biomimetics4030059},
journal = {Biomimetics},
number = 3,
volume = 4,
place = {Country unknown/Code not available},
year = {2019},
month = {8}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.3390/biomimetics4030059

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