The Coalescence of Drying Droplets
Lead Research Organisation:
University of Bristol
Department Name: Chemistry
Abstract
Abstract:
The Weber number (We), a dimensionless number used to describe the ratio of a fluid's inertia to its surface tension, is often plotted as a function of the impact parameter (B), a measure of how head-on a collision is, as a way of mapping collisional outcomes of two fluid droplets. These regime maps, as they are known, have been studied experimentally and models have been suggested for predicting the collisional outcome. However, the focus of previous work has been the collisions of submillimetre droplets. The initial experiment proposed here will focus on the collisions of water-water droplets of ~ 30-80 um radius. This novel size makes the proposed work relevant to the research of aerosols and their microphysical properties. A comparison can be made with existing collisional regime maps of water to determine whether droplet size, and the shift in the kinetic regime, influences the collisional outcome. This will be investigated using two microdroplet dispensers to collide droplets, imaged by a stroboscopic imaging technique. Following this, the effect of viscosity on the regime map can be determined using the same method, with varying concentrations of aqueous sucrose droplets. This is likely to be limited by the ability of the dispensers to eject high viscosity droplets (> 20 mPa.s), which may lead to the use of an electrodynamic trap in order to have control over droplet drying time prior to coalescence. Both instrumentations have the potential to be combined with cavity enhanced Raman spectroscopy to determine droplet composition and heterogeneity.
The Weber number (We), a dimensionless number used to describe the ratio of a fluid's inertia to its surface tension, is often plotted as a function of the impact parameter (B), a measure of how head-on a collision is, as a way of mapping collisional outcomes of two fluid droplets. These regime maps, as they are known, have been studied experimentally and models have been suggested for predicting the collisional outcome. However, the focus of previous work has been the collisions of submillimetre droplets. The initial experiment proposed here will focus on the collisions of water-water droplets of ~ 30-80 um radius. This novel size makes the proposed work relevant to the research of aerosols and their microphysical properties. A comparison can be made with existing collisional regime maps of water to determine whether droplet size, and the shift in the kinetic regime, influences the collisional outcome. This will be investigated using two microdroplet dispensers to collide droplets, imaged by a stroboscopic imaging technique. Following this, the effect of viscosity on the regime map can be determined using the same method, with varying concentrations of aqueous sucrose droplets. This is likely to be limited by the ability of the dispensers to eject high viscosity droplets (> 20 mPa.s), which may lead to the use of an electrodynamic trap in order to have control over droplet drying time prior to coalescence. Both instrumentations have the potential to be combined with cavity enhanced Raman spectroscopy to determine droplet composition and heterogeneity.
Organisations
- University of Bristol (Lead Research Organisation)
- Fortius Clinic (Collaboration)
- Wexham Park Hospital (Collaboration)
- Guy's and St Thomas' NHS Foundation Trust (Collaboration)
- Royal Brompton Hospital (Collaboration)
- Chelsea and Westminster Hospital (Collaboration)
- IMPERIAL COLLEGE LONDON (Collaboration)
- University of Bristol (Collaboration)
People |
ORCID iD |
Jonathan Reid (Primary Supervisor) | |
Lauren McCarthy (Student) |
Publications
Archer J
(2022)
Comparing aerosol number and mass exhalation rates from children and adults during breathing, speaking and singing.
in Interface focus
Gregson F
(2021)
Comparing aerosol concentrations and particle size distributions generated by singing, speaking and breathing
in Aerosol Science and Technology
McCarthy L
(2021)
Aerosol and droplet generation from performing with woodwind and brass instruments
in Aerosol Science and Technology
McCarthy LP
(2022)
Dynamics and outcomes of binary collisions of equi-diameter picolitre droplets with identical viscosities.
in Physical chemistry chemical physics : PCCP
Description | Vocalization (speaking or singing) generates more aerosol than breathing and louder sound volume increases the amount of aerosol generated. A new technique has been developed to observe the oscillations of a sessile droplet (droplet on a surface) after falling and impacting with the surface. Picolitre sessile droplet oscillations can be modelled in the same way as larger droplets. The technique has been developed further to investigate droplet drying on a surface. |
Exploitation Route | Sessile droplet oscillations can be studied further with more complex systems including dried respiratory droplets (or surrogates) in order to probe fomite formation and pathogen survival |
Sectors | Agriculture, Food and Drink,Healthcare,Leisure Activities, including Sports, Recreation and Tourism,Pharmaceuticals and Medical Biotechnology |
Description | Policy implications for DCMS (social distancing and singing restrictions) |
First Year Of Impact | 2020 |
Sector | Leisure Activities, including Sports, Recreation and Tourism |
Impact Types | Policy & public services |
Description | Data shared with DCMS regarding aerosol emissions from respiratory activities |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
Impact | Policy decisions regarding social distancing and singing |
Description | COVID-19 3 month extension |
Amount | £3,902 (GBP) |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 10/2021 |
End | 12/2021 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | Chelsea and Westminster Hospital |
Country | United Kingdom |
Sector | Hospitals |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | Fortius Clinic |
Country | United Kingdom |
Sector | Hospitals |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | Guy's and St Thomas' NHS Foundation Trust |
Country | United Kingdom |
Sector | Public |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | Imperial College London |
Department | Department of Bioengineering |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | Imperial College London |
Department | National Heart & Lung Institute (NHLI) |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | Royal Brompton Hospital |
Country | United Kingdom |
Sector | Hospitals |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | University of Bristol |
Department | School of Education |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | ParticulatE Respiratory matter to inForm guidance for the safe distancing of perfOrmeRs in a COVID-19 pandeMic (PERFORM) |
Organisation | Wexham Park Hospital |
Country | United Kingdom |
Sector | Hospitals |
PI Contribution | Our research team conducted the aerosol sampling measurements and analysis of the data |
Collaborator Contribution | Other partners within the collaboration provided specialist clinical knowledge as well as equipment and facilities |
Impact | 10.1098/rsfs.2021.0078 10.1080/02786826.2021.1947470 10.1080/02786826.2021.1883544 Yes this is a multi-disciplinary collaboration between our research group (physical sciences) and clinicians (medicine) |
Start Year | 2020 |
Description | Black Death Documentary |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | For a Channel 5 documentary on the Black Death, my supervisor Jonathan Reid was interviewed about his thoughts on the airborne transmission of the disease. In order to highlight some of the key concepts, we carried out a demonstration showing the emission of particles from breathing and vocalising. I was involved in the design and execution of the demonstration. The documentary will be aired in Spring 2023. |
Year(s) Of Engagement Activity | 2022 |
Description | Royal Institution Christmas Lectures |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | 500 secondary school age pupils attended the live recording of the Royal Institution Christmas Lecture (2) in which my PhD supervisor Professor Jonathan Reid presented a demonstration of an aerodynamic particle sizer. This recording was broadcast on BBC4 and subsequently added to BBC iPlayer. I was involved in the design of the demo, and was unfortunately at the last minute unable to join due to COVID. |
Year(s) Of Engagement Activity | 2021 |
URL | https://www.bbc.co.uk/iplayer/episodes/b00pmbqq/royal-institution-christmas-lectures |