Detailed simulation of viral propagation in the built environment
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ORIGINAL PAPER
Detailed simulation of viral propagation in the built environment Rainald Löhner1 · Harbir Antil2 · Sergio Idelsohn3,4 · Eugenio Oñate4 Received: 18 June 2020 / Accepted: 29 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A summary is given of the mechanical characteristics of virus contaminants and the transmission via droplets and aerosols. The ordinary and partial differential equations describing the physics of these processes with high fidelity are presented, as well as appropriate numerical schemes to solve them. Several examples taken from recent evaluations of the built environment are shown, as well as the optimal placement of sensors. Keywords Covid-19 · Particle methods · Finite elements · Computational fluid dynamics
1 The Covid-19 crisis
2 Virus infection
Starting in Wuhan, China, in the fall of 2019, the Covid-19 pandemic has claimed and will continue to claim millions of infected patients and hundreds of thousands of deaths. The lockdowns that followed its outbreak have led to mass unemployment, stalled economic development and loss of productivity that will take years to recover. Some changes in habits and lifestyles may be permanent: in the future, working from home or in a ‘socially distanced manner’ may be the prevalent modus operandi for large segments of society. The present paper gives a short description of computational techniques that can elucidate the flow and propagation of viruses or other contaminants in built environments in order to mitigate [31] or avoid [47] infections.
Before addressing the requirements for the numerical simulation of virus propagation a brief description of virus propagation and lifetime are given. Covid-19 is one of many corona-viruses. The virus is usually present in the air or some surface, and makes its way into the body either via inhalation (nose, mouth), ingestion (mouth) or attachment (eyes, hands, clothes). In many cases the victim inadvertedly touches an infected surface or viruses are deposited on its hands, and then the hands touch either the nose, the eyes or the mouth, thus allowing the virus to enter the body. An open question of great importance for all that will follow is how many viruses it takes to overwhelm the body’s natural defense mechanism and trigger an infection. This number, which is sometimes called the viral load or the infectious dose will depend on numerous factors, among them the state of immune defenses of the individual, the timing of viral entry (all at once, piece by piece), and the amount of hair and mucous in the nasal vessels. In principle, a single organism in a favourable environment may replicate sufficiently to cause disease [86]. Data from research performed on biological warfare agents [33] suggests that both bacteria and viruses can produce disease with as few as 1–100 organisms (e.g. brucellosis 10–100, Q fever 1–10, tularaemia 10–50, smallpox 10–100, viral haemorrhagic fevers 1–10 organisms, tuberculosis 1). Compare these numbers and consider that as many as 3,000
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