A study of the dispersion of expiratory aerosols in unidirectional downward and ceiling‐return type airflows using a multiphase approach
Identifieur interne : 000F79 ( Istex/Checkpoint ); précédent : 000F78; suivant : 000F80A study of the dispersion of expiratory aerosols in unidirectional downward and ceiling‐return type airflows using a multiphase approach
Auteurs : C. Y. H. Chao [République populaire de Chine] ; M. P. Wan [République populaire de Chine]Source :
- Indoor Air [ 0905-6947 ] ; 2006-08.
English descriptors
- Teeft :
- Actual dispersion distance, Aerosol, Aerosol generator, Aerosol response time, Aerosol size, Aerosol size distribution, Airborne infection, Airborne transmission, Building ventilation applications, Bulk stream, Carrier phase, Ceiling exhaust vent, Chamber measurements, Change rate, Chao, Clean room, Clean room chamber, Computational, Computational cell, Computational geometry, Computational resources, Considerable dispersion distance, Discrete matters, Discrete phase, Disease transmission, Dispersion, Dispersion characteristics, Dispersion coefficient, Dispersion mechanisms, Dispersion patterns, Displacement system, Downward pattern, Droplet, Droplet nuclei, Eddy, Eddy lifetime, Entire life span, Entire width, Eulerian, Eulerian frame, Eulerian integral length scale, Eulerian time scale, Evaporation, Evaporation rate, Exhaust vent, Exhaust vents, Experimental results, Expiratory, Expiratory aerosol, Expiratory aerosols, Form droplet nuclei, Glare points, Graham james, Gravitational force, Health care facilities, Heat transfer, Higher level, Hong kong, Hong kong university, Human expirations, Indoor, Indoor environments, Infection pattern, Infectious aerosols, Infectious diseases, Initial size, Initial sizes, Injection, Injection point, Instantaneous velocity, Instantaneous velocity components, Integral length scale, Isotropic turbulence, Lagrangian, Large aerosols, Large particles, Laser, Laser source, Lateral, Lateral dispersion, Lateral dispersion characteristics, Mass transfer, Mechanical engineering, Multiphase flow, Nominal time, Numerical model, Numerical results, Numerical simulation, Numerical simulations, Original sizes, Overall dispersion, Particle image velocimetry, Practical applications, Present study, Pressure source, Previous section, Rans equations, Reasonable agreement, Response time, Riley, Schematic diagram, Seeding machine, Short time, Shortest time, Simulation, Size bins, Size distribution, Size distributions, Size reduction, Small aerosols, Smaller aerosols, Smallest aerosols, Smallest size, Square displacement, Square displacements, Stokes drag, Time frame, Time frames, Time scales, Time series, Transport mechanisms, Tting curves, Turbulence, Turbulence dispersion, Turbulence intensity, Turbulence quantities, Turbulent, Turbulent dispersion, Uctuating component, Unidirectional, Ventilation, Ventilation patterns, Ventilation system, Ventilation systems, Vertical position, Vertical position trajectory, Vertical positions, Volatile fraction, Water aerosols, Water vapor.
Abstract
Abstract Abstract Dispersion characteristics of expiratory aerosols were investigated in an enclosure with two different idealized airflow patterns: the ceiling‐return and the unidirectional downward. A multiphase numerical model, which was able to capture the polydispersity and evaporation features of the aerosols, was adopted. Experiments employing optical techniques were conducted in a chamber with downward airflow pattern to measure the dispersion of aerosols. Some of the numerical results were compared with the chamber measurement results. Reasonable agreement was found. Small aerosols (initial size ≤45 μm) had settling times of below 20 s in downward flow but increased to 32–80 s in ceiling‐return flow. Lateral dispersion was limited to around 0.3 m in downward flow, in which only turbulent dispersion was significant. It increased to over 2 m in ceiling‐return flow, which had a combination of both turbulant dispersion and bulk flow transport mechanisms. The significance of aerosol transport by bulk flow was about an order of magnitude stronger than that by turbulent dispersion. However, results also show that aerosols could be dispersed for considerable distances solely by turbulence if they were suspended longer. Large aerosols settled within very short time due to heavy gravitational effects. The results provided new insights in designing proper bed spacing in hospital ward environments.
Url:
DOI: 10.1111/j.1600-0668.2006.00426.x
Affiliations:
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H." last="Chao">C. Y. H. Chao</name><affiliation wicri:level="1"><country xml:lang="fr">République populaire de Chine</country><wicri:regionArea>Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong</wicri:regionArea><wicri:noRegion>Hong Kong</wicri:noRegion></affiliation></author><author><name sortKey="Wan, M P" sort="Wan, M P" uniqKey="Wan M" first="M. P." last="Wan">M. P. Wan</name><affiliation wicri:level="1"><country xml:lang="fr">République populaire de Chine</country><wicri:regionArea>Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong</wicri:regionArea><wicri:noRegion>Hong Kong</wicri:noRegion></affiliation></author></analytic><monogr></monogr><series><title level="j" type="main">Indoor Air</title><title level="j" type="alt">INDOOR AIR</title><idno type="ISSN">0905-6947</idno><idno type="eISSN">1600-0668</idno><imprint><biblScope unit="vol">16</biblScope><biblScope unit="issue">4</biblScope><biblScope unit="page" from="296">296</biblScope><biblScope unit="page" to="312">312</biblScope><biblScope unit="page-count">17</biblScope><publisher>Blackwell Publishing Ltd</publisher><pubPlace>Oxford, UK</pubPlace><date type="published" when="2006-08">2006-08</date></imprint><idno type="ISSN">0905-6947</idno></series></biblStruct></sourceDesc><seriesStmt><idno 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mechanisms</term><term>Dispersion patterns</term><term>Displacement system</term><term>Downward pattern</term><term>Droplet</term><term>Droplet nuclei</term><term>Eddy</term><term>Eddy lifetime</term><term>Entire life span</term><term>Entire width</term><term>Eulerian</term><term>Eulerian frame</term><term>Eulerian integral length scale</term><term>Eulerian time scale</term><term>Evaporation</term><term>Evaporation rate</term><term>Exhaust vent</term><term>Exhaust vents</term><term>Experimental results</term><term>Expiratory</term><term>Expiratory aerosol</term><term>Expiratory aerosols</term><term>Form droplet nuclei</term><term>Glare points</term><term>Graham james</term><term>Gravitational force</term><term>Health care facilities</term><term>Heat transfer</term><term>Higher level</term><term>Hong kong</term><term>Hong kong university</term><term>Human expirations</term><term>Indoor</term><term>Indoor environments</term><term>Infection pattern</term><term>Infectious aerosols</term><term>Infectious diseases</term><term>Initial size</term><term>Initial sizes</term><term>Injection</term><term>Injection point</term><term>Instantaneous velocity</term><term>Instantaneous velocity components</term><term>Integral length scale</term><term>Isotropic turbulence</term><term>Lagrangian</term><term>Large aerosols</term><term>Large particles</term><term>Laser</term><term>Laser source</term><term>Lateral</term><term>Lateral dispersion</term><term>Lateral dispersion characteristics</term><term>Mass transfer</term><term>Mechanical engineering</term><term>Multiphase flow</term><term>Nominal time</term><term>Numerical model</term><term>Numerical results</term><term>Numerical simulation</term><term>Numerical simulations</term><term>Original sizes</term><term>Overall dispersion</term><term>Particle image velocimetry</term><term>Practical applications</term><term>Present study</term><term>Pressure source</term><term>Previous section</term><term>Rans equations</term><term>Reasonable agreement</term><term>Response time</term><term>Riley</term><term>Schematic diagram</term><term>Seeding machine</term><term>Short time</term><term>Shortest time</term><term>Simulation</term><term>Size bins</term><term>Size distribution</term><term>Size distributions</term><term>Size reduction</term><term>Small aerosols</term><term>Smaller aerosols</term><term>Smallest aerosols</term><term>Smallest size</term><term>Square displacement</term><term>Square displacements</term><term>Stokes drag</term><term>Time frame</term><term>Time frames</term><term>Time scales</term><term>Time series</term><term>Transport mechanisms</term><term>Tting curves</term><term>Turbulence</term><term>Turbulence dispersion</term><term>Turbulence intensity</term><term>Turbulence quantities</term><term>Turbulent</term><term>Turbulent dispersion</term><term>Uctuating component</term><term>Unidirectional</term><term>Ventilation</term><term>Ventilation patterns</term><term>Ventilation system</term><term>Ventilation systems</term><term>Vertical position</term><term>Vertical position trajectory</term><term>Vertical positions</term><term>Volatile fraction</term><term>Water aerosols</term><term>Water vapor</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Abstract Abstract Dispersion characteristics of expiratory aerosols were investigated in an enclosure with two different idealized airflow patterns: the ceiling‐return and the unidirectional downward. A multiphase numerical model, which was able to capture the polydispersity and evaporation features of the aerosols, was adopted. Experiments employing optical techniques were conducted in a chamber with downward airflow pattern to measure the dispersion of aerosols. Some of the numerical results were compared with the chamber measurement results. Reasonable agreement was found. Small aerosols (initial size ≤45 μm) had settling times of below 20 s in downward flow but increased to 32–80 s in ceiling‐return flow. Lateral dispersion was limited to around 0.3 m in downward flow, in which only turbulent dispersion was significant. It increased to over 2 m in ceiling‐return flow, which had a combination of both turbulant dispersion and bulk flow transport mechanisms. The significance of aerosol transport by bulk flow was about an order of magnitude stronger than that by turbulent dispersion. However, results also show that aerosols could be dispersed for considerable distances solely by turbulence if they were suspended longer. Large aerosols settled within very short time due to heavy gravitational effects. The results provided new insights in designing proper bed spacing in hospital ward environments.</div></front></TEI><affiliations><list><country><li>République populaire de Chine</li></country></list><tree><country name="République populaire de Chine"><noRegion><name sortKey="Chao, C Y H" sort="Chao, C Y H" uniqKey="Chao C" first="C. Y. H." last="Chao">C. Y. H. Chao</name></noRegion><name sortKey="Wan, M P" sort="Wan, M P" uniqKey="Wan M" first="M. P." last="Wan">M. P. Wan</name></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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