Large eddy simulation of density current on sloping beds

We present high-fidelity numerical simulations of expiratory biosol transport during normal breathing under indoor, stagnant air conditions with and without a facile mask. We investigate mask efficacy to suppress the spread of saliva particles that is underpinnings existing social distancing recommendations. The present simulations incorporate the effect of human anatomy and consider a spectrum of saliva particulate sizes that range from 0.1 to 10 μ m while also accounting for their evaporation. The simulations elucidate the vorticity dynamics of human breathing and show that without a facile mask, saliva particulates could travel over 2.2 m away from the person. However, a non-medical grade face mask can drastically reduce saliva particulate propagation to 0.72 m away from the person. This study provides new quantitative evidence that facile masks can successfully suppress the spreading of saliva particulates due to normal breathing in indoor environments.

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“…Details of the numerical method and validation studies for jet-like flows are documented elsewhere (Refs. 32–34 ).…”

Section: The Numerical Model Of the Human Anatomy And Facile Masksmentioning

confidence: 99%

A computational study of expiratory particle transport and vortex dynamics during breathing with and without face masks

et al. 2021

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“…Owing to the complexity involved in deriving the Jacobian matrix, the Jacobian-free methods are also widely used to solve non-linear equations. Among them, the Jacobian-Free Newton Krylov (JFNK) method [30,[36][37][38][39] is well known for solving large-scale problems, which replaces fsolve in LionPower when a fine mesh is used in the battery simulation or integrated into a hybrid electric powertrain model, as the derivation of the analytic Jacobian matrix becomes inefficient in MATLAB with an increased number of state variables.…”

Section: Jacobian-free Methodsmentioning

confidence: 99%

A novel numerical implementation of electrochemical-thermal battery model for electrified powertrains with conserved spherical diffusion and high efficiency

Yuan

Zhu

Akehurst

et al. 2021

International Journal of Heat and Mass Transfer

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“…It should be acknowledged that in the published article we (1) mistakenly used the same symbols for the dynamic viscosity of water and the molecular diffusion coefficient of the scalar, (2) neglected to include the value used for the molecular diffusion, and (3) did not mention that σ * is the reciprocal of the turbulent Schmidt number. Although these details should have been included, these omissions do not change well‐established facts that in turbulent flows the mixing of the solute by molecular diffusion is many orders of magnitude less important than that induced by turbulent eddies (Chawdhary et al, ; Chou & Fringer, ; Gualtieri et al, ; Gualtieri & Bombardelli, ; Khosronejad & Sotiropoulos, ; Scalo et al, ). As we mentioned in Khosronejad et al (), the viscous sublayer in Eagle Creek was not resolved in our simulations, as the first node away from the solid boundaries in wall units was (on average) equal to z + = 45 (see Table 3 in Khosronejad et al, ).…”

Section: Response To Criticism Of Misrepresentation Of Scalar Transportmentioning

confidence: 99%

Reply to Comment by Sookhak Lari, K. and Davis, G. B. on “ ‘Large Eddy Simulation of Turbulence and Solute Transport in a Forested Headwater Stream’: Invalid Representation of Scalar Transport by the Act of Diffusion”

Khosronejad

Sotiropoulos

2018

JGR Earth Surface

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Based on the molecular diffusion coefficient used in the large eddy simulation (LES) (equation (3) of the article), one can easily infer that a molecular Schmidt number of 700 was adopted for the solute. It should be acknowledged that in the published article we omitted to include the value used for the molecular diffusion and did not mention that is the reciprocal of the turbulent Schmidt number. Although these details should have been included, these omissions do not change well‐established facts that in turbulent flows the mixing of the solute by the molecular diffusion is many orders of magnitude less important than that induced by the turbulence. As we mentioned in our article, the viscous sublayer in the Eagle Creek stream was not resolved in our simulations as the first node off the solid boundaries in wall units was (on average) equal to 45 (see Table 3 of the article). This implies that all of the computational nodes are located well outside of the viscous sublayer, where molecular diffusion becomes dominant. Moreover, since we carry out LES, we do not resolve the Kolmogorov scales in the flow the rate of dissipation of which is governed by molecular viscosity. Rather, the subgrid scale eddy viscosity of the LES acts as the model for the effect of the unresolved scales of motion. Even though all these are well‐known facts from fundamental theory of turbulent mixing, we include in this response additional simulations to address the concerns raised in this commentary.

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Large eddy simulation of density current on sloping beds

Cited by 13 publications

References 50 publications

A computational study of expiratory particle transport and vortex dynamics during breathing with and without face masks

A computational study of expiratory particle transport and vortex dynamics during breathing with and without face masks

A novel numerical implementation of electrochemical-thermal battery model for electrified powertrains with conserved spherical diffusion and high efficiency

Reply to Comment by Sookhak Lari, K. and Davis, G. B. on “ ‘Large Eddy Simulation of Turbulence and Solute Transport in a Forested Headwater Stream’: Invalid Representation of Scalar Transport by the Act of Diffusion”

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