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Transport characteristics of TVOC in cockpits of commercial airliners have not been carefully studied relative to passenger cabins, and VOC emissions are currently not well regulated by the standards (e.g. ASHRAE, FAA, etc.). This study numerically performed a comprehensive assessment of cockpit environment using the developed all-in-one model, for the first time, integrating a full-scale A320 cockpit model and detailed manikins with 3D-rebuilt nasal cavity models. A generalised total volatile organic compound (TVOC) was selected as one representative gaseous contaminant and two representative emission scenarios in the cabin environment (aged and new aircraft) were analysed. Potential risky regions of the nasal system after inhaling the given contaminants were further evaluated. The outcomes demonstrated that windshield inlets were the key determinant of yielding the strong local vortex in the pilot's near field, which could potentially promote the contaminant lock-up. For aged aircraft, the average contaminant concentration in the pilots' breathing zone was nearly half of that in a brand-new aircraft, while TVOC concentrations were significantly higher in the human upper respiratory system than those detected in the breathing zones for both cases, particularly for vestibule, olfactory, sinus and nasopharynx regions. Olfactory regions were the most affected region in two cases, with an approximately 20% increase in the case of brand-new aircraft compared to an aged one. This study enlightened a novel pathway to assess indoor environment, from tracing the pollutants from the release source to ultimately quantifying the contaminant distribution characteristics in human upper respiratory system. [Display omitted] • Cockpit environment is analysed with manikin model including CT-rebuilt nasal cavity. • TVOC transport characteristics in aged and brand-new aircraft are investigated. • TVOC inhalation characteristics in pilots' upper respiratory systems are quantified. • TVOC concentration is 132%–171% higher in nasal cavity than those in breathing zone. • Olfactory region is the most affected region of inhaled TVOC. [ABSTRACT FROM AUTHOR]

Escalating demands of assessing airborne disease infection risks had been awakened from ongoing pandemics. An inhalation index linked to biomedical characteristics of pathogens (e.g. TCID 50 for coronavirus delta variant) was proposed to quantify human uptake dose. A modified Wells–Riley risk-assessment framework was then developed with enhanced capability of integrating biological and spatiotemporal features of infectious pathogens into assessment. The instantaneous transport characteristics of pathogens were traced by Eulerian–Lagrangian method. Droplets released via speaking and coughing in a conference room with three ventilation strategies were studied to assess occupants' infection risks using this framework. Outcomes revealed that speaking droplets could travel with less distance (0.5 m) than coughing droplets (1 m) due to the frequent interaction between speaking flow and thermal plume. Quantified analysis of inhalation index revealed a higher inhalation possibility of droplets with nuclei size smaller than 5 μ m , and this cut-off size was found sensitive to ventilation. With only 60-second exposure, occupants in the near-field of host started to have considerable infection risks (approximately 20%). This risk was found minimising over distance exponentially. This modified framework demonstrated the systematic analysis of airborne transmission, from quantifying particle inhalation possibility, targeting specific disease's TCID 50 , to ultimate evaluation of infection risks. [Display omitted] • An novel inhalation index (ID) was proposed based on droplet inhalability. • The biological attributes of airborne pathogen were integrated into modelling. • A modified Wells–Riley model integrating ID and Tissue Culture Infectious Dose. • Exposure over 60 s within 2 m of host could have considerable infection risk. • 5 μ m is cut-off size of sensitive ID and could increase with enabled ventilation. [ABSTRACT FROM AUTHOR]

This study numerically investigated the impact of ambient conditions on the evaporation process of full-range cough expelled droplets. The multi-component Eulerian-Lagrangian framework was adopted to simulate droplet evaporation within the inhomogeneous humidity fields. The results found that effect of ambient relative humidity (RH) on droplet evaporation was more pronounced than that of temperature. When the ambient relative humidity was higher than 40 % R H , the evaporation of droplets with a diameter smaller than 100 μ m would be significantly decelerated. Meanwhile, in normal indoor environments, 175 μ m could be a marginal diameter, in which droplets with larger initial diameters would probably not be fully evaporated before settling to the ground. Moreover, a novel cost-efficient approach, representing the instantaneous droplet diameter by functions of d t = φ (R H , t , T) , was developed to fulfil the time-dependent dynamic size distributions of evaporated droplets under various ambient conditions directly from the data by this study. The implementation of this approach into User Defined Function (UDF) was demonstrated and it would significantly reduce the computational resource on simulating droplet-related scenarios as it does not require costly calculations on the evaporation processes of each droplet repeatedly in every simulation. This development is limited to cough droplets so far and further fulfilment on droplets database regarding other respiratory behaviours would be highly suggested. • Evaporation of full-size cough droplets under various indoor conditions is analysed. • A cost-efficient method is developed to omit repeat recalculation of evaporation. • RH over 40% could vastly decelerate evaporation rate of droplets under 100 μm. • Droplet of 175 μm is a cut-off size to distinguish non-fully evaporated droplets. [ABSTRACT FROM AUTHOR]

Airflow in the cockpits of commercial airliners could be substantially different and more complex than it in passenger cabins, while simply referring to the standard of passenger cabin may not effectively achieve optimum ventilation or ensure a comfortable working environment for pilots. This study numerically investigated the ventilated Boeing 737 cockpit by analysing its airflow and thermal distribution inside, especially in pilots' micro-environments, under various in-flight conditions (number of personalised jet-inlets, window heat exchange, etc.). Gaseous contaminant CO 2 released from pilots was analysed in relation to its concentration distribution and potential lock-up phenomena in pilots' micro-environments, followed by quantitative analysis of pilots' thermal comfort and air quality. The outcomes demonstrated that the window heat exchange had significant impacts on pilots' thermal sensation and could induce severe thermal stratification around pilots' head level. The most effective CO 2 removal rate was achieved by initiating windshield inlets in combination of the side diffusers. Further adding personal gaspers did not significantly alleviate the CO 2 concentration in pilots' micro-environment but may potentially compromise their thermal comfort. Also, the overwhelming numbers of personalised inlets could hardly provide superior ventilation performance or ensure consistent air quality and could be impractical to use sometimes. It is suggested that future optimisation of the environmental control system could rely more on the global airflow circulations induced by larger or wider diffusers rather than the local complex jet flows from high number of personal gaspers. [Display omitted] • Pilots' micro-environments in terms of thermal comfort and air quality are assessed. • Window heat exchange is a vital factor and may propel thermal stratification. • Air change efficiency and age of air in the upper region is seemingly unsatisfactory. • Contaminants removal is ineffective in pilots' breathing zone with diffuser open only. • Adding windshield inlets significantly improve air exchange and contaminants remove. [ABSTRACT FROM AUTHOR]

Urgent demands of assessing respiratory disease transmission in airliner cabins had awakened from the COVID-19 pandemics. This study numerically investigated the cough flow and its time-dependent jet-effects on the transport characteristics of respiratory-induced contaminants in passengers' local environments. Transient simulations were conducted in a three-row Boeing 737 cabin section, while respiratory contaminants (2 μm–1000 μm) were released by different passengers with and without coughing and were tracked by the Lagrangian approach. Outcomes revealed significant influences of cough-jets on passengers' local airflow field by breaking up the ascending passenger thermal plumes and inducing several local airflow recirculation in the front of passengers. Cough flow could be locked in the local environments (i.e. near and intermediate fields) of passengers. Results from comparative studies also revealed significant increases of residence times (up to 50%) and extended travel distances of contaminants up to 200 μm after considering cough flow, whereas contaminants travel displacements still remained similar. This was indicating more severe contaminate suspensions in passengers' local environments. The cough-jets was found having long and effective impacts on contaminants transport up to 4 s, which was 8 times longer than the duration of cough and contaminants release process (0.5 s). Also, comparing to the ventilated flow, cough flow had considerable impacts to a much wider size range of contaminants (up to 200 μm) due to its strong jet-effects. • Cough-jets could break up thermal plume and induce local air recirculation. • Contaminant residence time and travel distance increase with cough flow. • More severe contaminant suspensions are caused by strong cough-jet effects. • Cough-jets has long impacts on contaminants transport up to four seconds. • Cough flow has considerable impacts to large contaminants up to 200 μm. [ABSTRACT FROM AUTHOR]