| 1. |
- Scapin, Nicolo, et al.
(author)
-
Finite-size evaporating droplets in weakly compressible homogeneous shear turbulence
- 2022
-
In: Journal of Fluid Mechanics. - : Cambridge University Press (CUP). - 0022-1120 .- 1469-7645. ; 934
-
Journal article (peer-reviewed)abstract
- We perform interface-resolved simulations of finite-size evaporating droplets in wealdy compressible homogeneous shear turbulence. The study is conducted by varying three dimensionless physical parameters: the initial gas temperature over the critical temperature T-g,T-0/T-c, the initial droplet diameter over the Kolmogorov scale d(0)/eta and the surface tension, i.e. the shear-based Weber number, We(S). For the smallest We(S), we first discuss the impact on the evaporation rate of the three thermodynamic models employed to evaluate the gas thermophysical properties: a constant property model and two variable-properties approaches where either the gas density or all the gas properties are allowed to vary. Taking this last approach as reference, the model assuming constant gas properties and evaluated with the '1/3' rule is shown to predict the evaporation rate better than the model where the only variable property is the gas density. Moreover, we observe that the well-known Frossling/Ranz-Marshall correlation underpredicts the Sherwood number at low temperatures, T-g,T-0/T-c = 0.75. Next, we show that the ratio between the actual evaporation rate in turbulence and the one computed in stagnant conditions is always much higher than one for wealdy deformable droplets: it decreases with T-g,T-0/T-c without approaching unity at the highest T-g,T-0/T-c considered. This suggests an evaporation enhancement due to turbulence also in conditions typical of combustion applications. Finally, we examine the overall evaporation rate and the local interfacial mass flux at higher Wes, showing a positive correlation between evaporation rate and interfacial curvature, especially at the lowest T-g,T-0/T-c.
|
|
| 2. |
- Wang, Jietuo, et al.
(author)
-
Modelling the direct virus exposure risk associated with respiratory events
- 2022
-
In: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 19:186, s. 20210819-20210819
-
Journal article (peer-reviewed)abstract
- The outbreak of the COVID-19 pandemic highlighted the importance of accurately modelling the pathogen transmission via droplets and aerosols emitted while speaking, coughing and sneezing. In this work, we present an effective model for assessing the direct contagion risk associated with these pathogen-laden droplets. In particular, using the most recent studies on multi-phase flow physics, we develop an effective yet simple framework capable of predicting the infection risk associated with different respiratory activities in different ambient conditions. We start by describing the math- ematical framework and benchmarking the model predictions against well-assessed literature results. Then, we provide a systematic assessment of the effects of physical distancing and face coverings on the direct infection risk. The present results indicate that the risk of infection is vastly impacted by the ambient conditions and the type of respiratory activity, suggesting the non-existence of a universal safe distance. Meanwhile, wearing face masks provides excellent protection, effectively limiting the transmission of pathogens even at short physical distances, i.e. 1 m.
|
|
