Vortex dynamics and scalar transport in the wake of a bluff body driven through a steady recirculating flow

Poussou, Stephane B.; Plesniak, Michael W.

doi:10.1007/s00348-012-1325-1

Cited by 9 publications

(2 citation statements)

References 80 publications

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“…Smaller droplets (diameters of the order of 10 μm or smaller) fall so slowly through the air that they have time to evaporate [ 38 ]. These very light, desiccated particles, or aerosols, can then remain suspended in the air, potentially for several hours [ 18 , 19 ], and can travel long distances on air flows before eventually landing [ 17 , 19 , 20 ]. Studies conducted following the 2003 SARS outbreak provided evidence consistent with aerosolised transmission within buildings, influenced by the effects of ventilation and plumbing systems [ 21 - 25 ].…”

Section: Resultsmentioning

confidence: 99%

Which factors influence the extent of indoor transmission of SARS-CoV-2? A rapid evidence review

et al. 2021

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Background This rapid evidence review identifies and integrates evidence from epidemiology, microbiology and fluid dynamics on the transmission of SARS-CoV-2 in indoor environments. Methods Searches were conducted in May 2020 in PubMed, medRxiv, arXiv, Scopus, WHO COVID-19 database, Compendex & Inspec. We included studies reporting data on any indoor setting except schools, any indoor activities and any potential means of transmission. Articles were screened by a single reviewer, with rejections assessed by a second reviewer. We used Joanna Briggs Institute and Critical Appraisal Skills Programme tools for evaluating epidemiological studies and developed bespoke tools for the evaluation of study types not covered by these instruments. Data extraction and quality assessment were conducted by a single reviewer. We conducted a meta-analysis of secondary attack rates in household transmission. Otherwise, data were synthesised narratively. Results We identified 1573 unique articles. After screening and quality assessment, fifty-eight articles were retained for analysis. Experimental evidence from fluid mechanics and microbiological studies demonstrates that aerosolised transmission is theoretically possible; however, we found no conclusive epidemiological evidence of this occurring. The evidence suggests that ventilation systems have the potential to decrease virus transmission near the source through dilution but to increase transmission further away from the source through dispersal. We found no evidence for faecal-oral transmission. Laboratory studies suggest that the virus survives for longer on smooth surfaces and at lower temperatures. Environmental sampling studies have recovered small amounts of viral RNA from a wide range of frequently touched objects and surfaces; however, epidemiological studies are inconclusive on the extent of fomite transmission. We found many examples of transmission in settings characterised by close and prolonged indoor contact. We estimate a pooled secondary attack rate within households of 11% (95% confidence interval (CI) = 9, 13). There were insufficient data to evaluate the transmission risks associated with specific activities. Workplace challenges related to poverty warrant further investigation as potential risk factors for workplace transmission. Fluid mechanics evidence on the physical properties of droplets generated by coughing, speaking and breathing reinforce the importance of maintaining 2 m social distance to reduce droplet transmission. Conclusions This review provides a snap-shot of evidence on the transmission of SARS-CoV-2 in indoor environments from the early months of the pandemic. The overall quality of the evidence was low. As the quality and quantity of available evidence grows, it will be possible to reach firmer conclusions on the risk factors for and mechanisms of indoor transmission.

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Section: Resultsmentioning

confidence: 99%

Which factors influence the extent of indoor transmission of SARS-CoV-2? A rapid evidence review

et al. 2021

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“…To visualise the vortex structures inside the wake, the Q-criteria or k 2 methods have been widely used to identify vortex cores in the wake region. 30,39 However, this method can be challenging to distinguish the actual rotational motion of the vortex. 40 The selection of the vorticity value in either the Q-criteria or k 2 methods for vortex identification is threshold value-dependent, where inappropriate values can lead to strong vortices being captured and weak vortices skipped.…”

Section: Vortex Identification Methodsmentioning

confidence: 99%

Vortex structures and wake flow analysis from moving manikin models

Tao

Inthavong

Petersen

et al. 2020

Indoor and Built Environment

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Vortex shedding in the wake flow generated by moving bodies exerts considerable influence on pollutant dispersion. This study investigated the effects of different body shapes using scaled models 1/5th of realistic size, including thin and wide shapes, standing and walking poses. The airflow from moving bodies was simulated using computational fluid dynamics (CFD) with dynamic meshing to account for the manikin movement. Experimental data from a smoke visualisation technique provided validation data for computational simulations which included flow separation angle over the head computed through image processing. Vortex structures were visualised using an Omega vortex identification method and compared with experimental visualisations. The main objective of this study is to verify the CFD simulations with smoke visualisation in terms of predicting motion-induced vortex structures, thus helping identify contaminant transport around different shaped bodies during walking and when coming to a stop. The results showed matching locations and patterns of vortex structures between the smoke visualisation and CFD simulations. After the manikin came to a stop, the flow induced by the larger body was characterised by a longer residence time for airborne contaminants in the breathing region while a reduced flow residence time for the thinner bodied manikin.

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Flow field in the wake of a bluff body driven through a steady recirculating flow

Poussou

Plesniak

2015

Exp Fluids

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Vortex dynamics and scalar transport in the wake of a bluff body driven through a steady recirculating flow

Cited by 9 publications

References 80 publications

Which factors influence the extent of indoor transmission of SARS-CoV-2? A rapid evidence review

Which factors influence the extent of indoor transmission of SARS-CoV-2? A rapid evidence review

Vortex structures and wake flow analysis from moving manikin models

Flow field in the wake of a bluff body driven through a steady recirculating flow

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