Improved hybrid model applied to liquid jet in crossflow

Fontes, Douglas; Vilela, Vitor; Meira, Lucas de Souza; Souza, Francisco José de

doi:10.1016/j.ijmultiphaseflow.2019.02.009

“…This work shows a new methodology to develop models for injection of Lagrangian droplets. Its main advantages with respect to other Lagrangian injection models [18,19] are its capability to perform full two-phase Lagrangian simulations without the need to resolve atomization once the spray state is known, allowing in the future to initialize reactive cases with evaporation and combustion; to use one numerical code for resolving atomization and another one for dispersed phase (e.g. combustion) simulations; and to model the aerodynamic field in dispersed phase simulations caused by coherent liquid structures without the need of resolving atomization.…”

Section: Discussionmentioning

confidence: 99%

Building Lagrangian injectors from resolved primary atomization simulations. Application to jet in crossflow fuel injection

Guillamón

¹

,

Janodet

²

,

Voivenel

³

et al. 2021

ICLASS

0

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This work aims at improving Lagrangian particle injectors for the simulation of sprays. In such simulations, primary atomization is not resolved and Lagrangian particles are directly injected as a dispersed phase in the flow. Two main challenges arise in such methodology: i) the prescription of the correct droplet size and velocity distributions at injection, ii) ensuring the proper coupling of the dispersed phase with the gas phase to have the correct gas flow field after the injection. The proposed approach relies on an improved Lagrangian injector model and on resolved primary atomization simulations to feed the injector model parameters. The resolved atomization simulations are performed using a sharp-interface approach (ACLS/GFM) on unstructured grids [1,2]. The validation test case is a high-pressure, non-reactive kerosene jet in crossflow (JICF) atomizer configuration [3], which is representative of complex injection systems. Resolved simulations of atomization for this configuration are performed and validated against the experimental correlation for the jet trajectory, showing good accordance. These simulations are then post-processed to feed the Lagrangian injector model. Finally, the injectors are applied to the same configuration and compared to experimental data.

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“…The present effort expands on that study using an Euler–Lagrange approach to treat the continuous air phase interacting with the dispersed liquid droplets that formed the spray generated from the sneeze event. This type of approach has been widely used to model spray formation in many configurations 35 – 40 . Given the similarities associated with physical conditions and air-droplet interactions, Euler–Lagrange approach is suitable to investigate the spray formation generated from sneeze events.…”

Section: Methodsmentioning

confidence: 99%

Effect of saliva fluid properties on pathogen transmissibility

Reyes

¹

,

Fontes

²

,

Bazzi

³

et al. 2021

Sci Rep

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With an increasing body of evidence that SARS-CoV-2 is an airborne pathogen, droplet character formed during speech, coughs, and sneezes are important. Larger droplets tend to fall faster and are less prone to drive the airborne transmission pathway. Alternatively, small droplets (aerosols) can remain suspended for long time periods. The small size of SARS-CoV-2 enables it to be encapsulated in these aerosols, thereby increasing the pathogen’s ability to be transmitted via airborne paths. Droplet formation during human respiratory events relates to airspeed (speech, cough, sneeze), fluid properties of the saliva/mucus, and the fluid content itself. In this work, we study the fluidic drivers (fluid properties and content) and their influence on factors relating to transmissibility. We explore the relationship between saliva fluid properties and droplet airborne transmission paths. Interestingly, the natural human response appears to potentially work with these drivers to mitigate pathogen transmission. In this work, the saliva is varied using two approaches: (1) modifying the saliva with colloids that increase the viscosity/surface tension, and (2) stimulating the saliva content to increased/decreased levels. Through modern experimental and numerical flow diagnostic methods, the character, content, and exposure to droplets and aerosols are all evaluated. The results indicate that altering the saliva properties can significantly impact the droplet size distribution, the formation of aerosols, the trajectory of the bulk of the droplet plume, and the exposure (or transmissibility) to droplets. High-fidelity numerical methods used and verify that increased droplet size character enhances droplet fallout. In the context of natural saliva response, we find previous studies indicating natural human responses of increased saliva viscosity from stress and reduced saliva content from either stress or illness. These responses both favorably correspond to reduced transmissibility. Such a finding also relates to potential control methods, hence, we compared results to a surgical mask. In general, we find that saliva alteration can produce fewer and larger droplets with less content and aerosols. Such results indicate a novel approach to alter SARS-CoV-2’s transmission path and may act as a way to control the COVID-19 pandemic, as well as influenza and the common cold.

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“…The air gas flow is treated as a continuous Eulerian phase, whereas each droplet is treated as discrete droplets via Lagrangian approach. This approach is widely used to model spray formation [34][35][36][37][38][39] .…”

Section: Methodsmentioning

confidence: 99%

WITHDRAWN: Effect of Saliva Fluid Properties on Pathogen Transmissibility

Reyes

¹

,

Fontes

²

,

Bazzi

³

et al. 2020

Preprint

0

View full text Add to dashboard Cite

With an increasing body of evidence that SARS-CoV-2 is an airborne pathogen, droplet character formed during speech, coughs, and sneezes are important. Larger droplets tend to fall faster and are less prone to drive the airborne transmission pathway. Alternatively, small droplets (aerosols) can remain suspended for long time periods. The small size of SARS-CoV-2 enables it to be encapsulated in these aerosols, thereby increasing the pathogen’s ability to be transmitted via airborne paths. Droplet formation during human respiratory events relates to airspeed (speech, cough, sneeze), fluid properties of the saliva/mucus, and the fluid content itself. In this work, we study the fluidic drivers (fluid properties and content) and their influence on factors relating to transmissibility. We explore the relationship between saliva fluid properties and droplet airborne transmission paths. Interestingly, the natural human response appears to potentially work with these drivers to mitigate pathogen transmission. In this work, the saliva is varied using two approaches: (1) modifying the saliva with colloids that increase the viscosity/surface tension, and (2) stimulating the saliva content to increased/decreased levels. Through modern experimental and numerical flow diagnostic methods, the character, content, and exposure to droplets and aerosols are all evaluated. The results indicate that altering the saliva properties can significantly impact the droplet size distribution, the formation of aerosols, the trajectory of the bulk of the droplet plume, and the exposure (or transmissibility) to droplets. High-fidelity numerical methods used and verify that increased droplet size character enhances droplet fallout. In the context of natural saliva response, we find previous studies indicating natural human responses of increased saliva viscosity from stress and reduced saliva content from either stress or illness. These responses both favorably correspond to reduced transmissibility. Such a finding also relates to potential control methods, hence, we compared results to a surgical mask. In general, we find that saliva alteration can produce fewer and larger droplets with less content and aerosols. Such results indicate a novel approach to alter SARS-CoV-2’s transmission path and may act as a way to control the COVID-19 pandemic, as well as influenza and the common cold.

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Improved hybrid model applied to liquid jet in crossflow

Cited by 22 publications

References 40 publications

Building Lagrangian injectors from resolved primary atomization simulations. Application to jet in crossflow fuel injection

Building Lagrangian injectors from resolved primary atomization simulations. Application to jet in crossflow fuel injection

Effect of saliva fluid properties on pathogen transmissibility

WITHDRAWN: Effect of Saliva Fluid Properties on Pathogen Transmissibility

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