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Use of air curtains for creating safe areas in bodybuilding salons for controlling the spread of SARS-CoV-2-carrying respiratory droplets

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Abstract

In this study, the spreading of cough droplets emitted by an infected person in a bodybuilding salon in the presence of an air curtain system was investigated using computational fluid dynamics (CFD) simulations. The RNG k-ε model was used to simulate turbulent airflows in the bodybuilding salon. The Eulerian–Lagrangian model was used for cough droplet dispersion simulation. This study introduced various innovative elements that contributed to advancing the field. First, it presented a groundbreaking air curtain flow pattern designed for bodybuilding salons. Second, the study employed user-defined functions (UDFs) to model airflow containing cough droplets and their evaporation, providing a comprehensive understanding of droplet behavior. Third, the risk of infection was evaluated using the Wells–Riley equation and then the effect of relative humidity on droplet evaporation in bodybuilding salons. Air curtain flow pattern, requiring no structural changes to the building while optimizing energy consumption, preventing the spread of viruses and dust, and ensuring fresh air circulation throughout the salon, can be implemented in various public and private spaces. The air curtains were generated using two narrow inlets at the ceiling with floor-level outlets to separate the indoor environments into compartments with limited mass transfers but unlimited access through the opening between these spaces. The simulation results showed that when the air curtain ventilation system was used, 60s after the cough, the average cough droplet concentrations in some areas are at nearly 5%. There were no droplets in the bodybuilding salon after the 90s and the virus-carrying droplets stayed in the space between the air curtains and did not spread in the salon. The study evaluates the risk using the Wells–Riley equation of infection for individuals in the bodybuilding salon, providing valuable insights into the potential vulnerabilities and the need for precautions in this setting. The infection risk of a healthy person in areas A1, A4, and A7 is 21%, 33%, and 25%, respectively, but in areas A2, A3, and A5–A9, the infection risk is less than 1%. The reason is that the airflow pattern created by the air curtain reduces or prevents the spread of virus-carrying droplets to the other compartment generated by the air curtains and also makes the environment safer. These findings significantly enhanced safety measures and controlled droplet spread in these indoor spaces.

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Data availability

No new experimental data are provided in this manuscript.

Abbreviations

A :

Surface area (m2)

A C :

Average droplet concentration (Kg/m3)

A i :

I-The area (i = 1,2,..,8)

A N :

Number of particles

V A :

Velocity average in domain solving flow (m/s)

v(x, t):

Droplet concentration

C C :

Cunningham coefficient (-)

C i,s :

Vapor concentration at the particle surface (kg mol/m3)

C i,∞ :

Vapor concentration in the bulk gas (kg mol/m3)

C p :

Specific heat capacity (J/kg K)

cp:

Quanta number density in droplets (-)

d :

Droplets diameter (μm)

D i,m :

Diffusion coefficient of vapor (m2/s)

F B :

Brownian force (-)

F D :

Drag factor (-)

FTH :

Thermophoretic force (-)

F L :

Saffman lift force (-)

f(t):

Viability of the virus

ṁp:

Flow rate (kg/s)

G :

Gravity (m/s2)

g :

Gravitational acceleration components (m/s2)

h :

Convective heat transfer coefficient (W/m2-K)

h fg :

Latent heat (J/kg)

I :

Number of infectors (-)

I I :

Injection time (s)

K T :

Fluid thermal conductivity (W/m K)

k C :

Mass transfer coefficient (m/s)

M w,i :

The molecular weight of species i (kg/kg mol)

m :

Mass (kg)

N :

Number of droplets (-)

Nu:

Nusselt number (hl/ka)

N i :

Molar flux of vapor (kg mol/m2-s)

N T :

Total number of droplets (-)

N t :

Droplets at each time (-)

\(N\) Tn :

Droplets remaining in the dental clinic (-)

\({N}_{{\text{m}}}\) :

Number of meshes (-)

Ns:

Total number of quanta (-)

P :

Pressure (Pa)

PRT:

Particle residence time (s)

P op :

Operating pressure (pa)

ρ :

Breathing rate per person (m3/s)

\({\rho }_{{\text{d}}}\) :

Density of droplets

Q :

Air supply rate (m3/s)

q :

Quantum generation rate (quanta/s)

R :

Universal gas constant (J/kg.K)

Re:

Reynolds number (-)

RH:

Relative humidity (-)

P rt :

Particle removal time (s)

m :

Mass (kg)

S :

Number of susceptible (-)

Sc:

Schmidt number (-)

S T :

Source term (C)

t :

Time (s)

T :

Temperature conditions (C)

u, v, w :

Velocity components (m/s)

G k, S ε, S k, α k, α ε, R ε, \({C}_{1\varepsilon }\) , \({C}_{2\varepsilon }\) :

Turbulent kinetic energy and model constants (-)

V v :

Ventilation velocity (m/s)

V :

Velocity vector (m/s)

W :

Water mass fraction (Kg/mol)

X, Y :

Non-dimensional Cartesian coordinates (-)

α :

Thermal diffusivity (m2/s)

ε :

Dissipation rate of the turbulent energy (-)

μ T :

Dynamic viscosity (m2/s)

η :

Particle removal efficiency (-)

ρ :

Density (kg/m3)

sat:

Saturation (-)

T:

Total (-)

x,y,z :

Cartesian directions (-)

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Acknowledgements

This research was supported by the Brain Pool program funded by the Ministry of Science and ICT through the National Research Foundation of Korea (grant number). (NRF-2022H1D3A2A02090885).

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Authors and Affiliations

  1. Center of Computational Energy, Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran

    Shahram Karami & Esmail Lakzian

  2. Department of Mechanical Engineering, Andong National University, Andong, South Korea

    Esmail Lakzian

  3. Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699-5725, USA

    Goodarz Ahmadi

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  1. Shahram Karami
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Correspondence to Esmail Lakzian.

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Karami, S., Lakzian, E. & Ahmadi, G. Use of air curtains for creating safe areas in bodybuilding salons for controlling the spread of SARS-CoV-2-carrying respiratory droplets. Eur. Phys. J. Plus 139, 87 (2024). https://doi.org/10.1140/epjp/s13360-024-04899-5

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