








key: cord-334413-h6n36jei
authors: Bhattacharyya, Suvanjan; Dey, Kunal; Paul, Akshoy Ranjan; Biswas, Ranjib
title: A Novel CFD Analysis to Minimize the Spread of COVID-19 Virus in Hospital Isolation Room
date: 2020-09-17
journal: Chaos Solitons Fractals
DOI: 10.1016/j.chaos.2020.110294
sha: 
doc_id: 334413
cord_uid: h6n36jei

The COVID-19 is a severe respiratory disease caused by a devastating coronavirus family (2019-nCoV) has become a pandemic across the globe. It is an infectious virus and transmits by inhalation or contact with droplet nuclei produced during sneezing, coughing, and speaking by infected people. Airborne transmission of COVID-19 is also possible in a confined place in the immediate environment of the infected person. Present study investigates the effectiveness of conditioned air released from air-conditioning machines to mix with aerosol sanitizer to reach every point of the space of the isolation room so as to kill the COVID-19 virus which will help to protect the lives of doctors, nurses and health care workers. In order to numerically model the laminar-transitional flows, transition SST k-ε model, which involves four transport equations are employed in the current study. It is found from the analysis that high turbulent fields generated inside the isolation room may be an effective way of distributing sanitizer in entire volume of isolation room to kill the COVID-19 virus.

The COVID-19 is a severe respiratory disease originated from the devastating coronavirus family (2019-nCoV) (Zhou et al., 2020; Zu et al., 2020) and has become a pandemic across the globe. It is a contagious virus and transmits by inhalation or contact with droplet nuclei of size Φ < 5μm produced during sneezing, coughing and even speaking by infected persons.

Exhaled droplets from confirmed COVID-19 patients or an active carrier of the virus can deposit in the mucosae of noses, mouths, and conjunctiva of eyes of people in close contact. The virus may be transmitted through personal contact with the COVID-19 patient or indirect contact with fomites such as clothes, utensils, furniture, surface etc. used, touched or in the immediate environment of the infected person. Generally, fever, breathlessness, cough, throat pain, weakness are traditional symptoms at the initial stage of the disease (Huang et al., 2020) . The disease causes respiratory illness such as pneumonia and acute respiratory distress syndrome resulting in rapid death of those affected, depending on their age, condition of lungs, immunity and sociodemographic profile. A study (Bukhari et al. 2020) showed that the COVID 19 is highly harmful and transmitted the infection throughout the world. Total of 212 countries and territories around the world are infected by the disease and became a pandemic as declared by the World Health Organization (WHO) (Peng et al., 2020; WHO, 2020a; WHO, 2020b) . It has also been reported (WHO, 2020c ) that airborne transmission of COVID-19 is also possible in specific circumstances like aerosol therapy performed during treatment of pulmonary critical illness such as asthma, bronchoscopy, chronic obstructive pulmonary disease (COPD), tracheostomy and other related diseases. In addition to cough, the droplets produced by sneeze produced aerosols, the droplets containing virus present in the air also constitute a substrate for viruses which transmit the disease through air in an isolated space (Setti et al., 2020; WHO, 2020c) . Furthermore, relative humidity, temperature, rainfall etc. are recognized as factors affecting the infectivity of the virus in the respiratory system (Ahmadi et al., 2020; Bashir et al., 2020; Prata et al., 2020; Monserrate et al., 2020; Taylor, 2019; Xie and Zhu 2020; Qi et al., 2020; Sahin 2020; Shi et al., 2020) .

As the characteristics of COVID-19 virus is still not fully understood, there is no particular treatment, medication, therapy or vaccine approved by the medical authorities till date. The mortality rate of the patients affected by this virus is 2 to 3%, but it can be fatal for aged people and children and those with a prolonged illness with less immunity. The medical boards and health administration has implemented travel ban, complete lockdown, containment zone identification, home quarantine of all citizens, strict monitoring of movement of citizens etc. to combat the spread of COVID-19. The transmission can also be reduced by controlling indoor dust level, temperature, humidity, ventilation, improved hygiene, sanitization, wearing mask, using personal protective equipment (PPE) by the healthcare and sanitary personnel etc.

It is indispensable to accommodate the confirmed COVID-19 patients and patients with symptoms in isolated rooms or separate ICUs in hospitals for treatment so that spread of this disease can be prevented. These isolated rooms are designated as "Airborne Infection Isolation Rooms (AII)". Also, exhaust air released from AIIs is likely to carry virus particles and hence an effective strategy should be employed to arrest the spread of infections. Recent COVID-19 outbreak in Wuhan province of China found the evidence of COVID-19 virus genetic material in the air about 4 metres from the affected persons in two ICU wards of Huoshenshan Hospital in Wuhan, risking to healthcare personnel (Guo et al., 2020) . Care should therefore be taken to disinfect the exhaust air through various available treatments such as HEPA filtration, sanitization, heating, UV irradiation etc. (European Centre for Disease Prevention and Control, 2020; Ministry of Health & Family Welfare, Government of India, 2020; WHO, 2006; WHO, 2020d ). Very few researchers have however studied the design aspects of an effective ventilation system and influencing factors for room ventilation to reduce the spread of the virus (Li et al., 2007) . The healthcare personnel working in hospitals are at greater risk of getting infected due to outbreak of airborne or droplet contact diseases.

Many researchers used Computational Fluid Dynamics (CFD) based models (Memarzadeh et al., 2000) to study air quality inside a room, comfort level, performance of HVAC systems etc. in different types of buildings. It is a very robust and efficient tool to investigate the airflow and contaminant dispersion in rooms where many parameters involved. CFD analysis using complex particle tracking methodologies (Cole et al., 1998; Kowalski et al., 1998; Memarzadeh, 2011; Zhang et al., 2008) with dynamic process variables like velocity, movement, path lines followed by the air in order to determine control strategy for the trajectory of infectious particles moving in air, may be considered and simulated to control the spread the huge number of infectious droplets generated from patients cough, sneeze. As the medical treatments are often inaccurate, besides precautionary measures and supports, it is therefore reasonable to investigate the possibilities to sanitize the confined volume of air to mitigate the spread of COVID-19 virus inside the airborne infection isolation rooms, and ICUs of a hospital. This can be accomplished by designing an aerosolized sanitization system which effectively can sanitize the air inside the room to be used for the treatment of confirmed COVID-19 patients. This is essential to protect the lives of doctors, nurses and health care workers. However, no work is reported in literature on this topic till date. Hence, the present paper depicts aerosol sanitizer delivery systems focusing the effectiveness of conditioned air released from air-conditioning machine to mix with aerosol sanitizer and enabling every corner of the isolation room killing the COVID-19 virus, thereby achieving complete sanitization. Also, results obtained from the research work could be used to help flatten the infection curve of COVID-19. A CFD analysis is carried out considering factors affecting aerosol sanitizer delivery system such as temperature, turbulent kinetic energy and flow dynamics. Tetrahedral and hexahedral elements are used to generate these meshes ( Fig. 2 (b) ). Hexahedral meshing is used to fill the intricate parts, while tetrahedral meshes are used in the remaining parts of the control volumes. On each computational element, governing equations, like mass, momentum and energy equations are solved using finite volume based CFD technique. Boundary conditions constitute an important criterion for any CFD simulation and the present study is of no difference. Inlet conditions are specified at the ceiling of the isolation room with a velocity of 3.91 m/s applied uniformly with an inlet temperature of 24C. With a mass flow rate of 29.97 kg/s. No-slip, no-temperature jump conditions are applied at the exit of the ducting system.

Similarly, inlet conditions are specified at the sanitizing machine of the isolation room with a velocity of 1.5 m/s applied uniformly with an inlet temperature of 30C, with a mass flow rate of 1.854 kg/s. Numerical solution to any governing equation which is expressed in a partial differential equation requires discretization. Second-order upwind schemes with Boussinesq approximation (Bhattacharyya et al. 2020 ) are used for this purpose. The purification of air in the isolation room with chemical diffusion requires simulating the diffusion as well as the natural ventilation process, which involves pressure forces, buoyant forces and elements of forced-convection, and conductive as well as convective heat transfer. An unsteady CFD analysis is carried out to get more insight into the flow physics of the system.

In order to numerically model the laminar-transitional flows, transition SST k model, which involves four transport equations are employed in the current study (Bhattacharyya et al. 2017 ).

This special transition SST k model is formed by a combination of the SST k model along with two additional transport equations-one designed for the transition onset criteria while the other for flow separation induced transition, in terms of momentum thickness Reynolds number (Bhattacharyya et al. 2017 , Rajnath et al., 2020 . (Menter 1994) 

CFD simulation is carried out in a 16-core IBM HPC with 64 GB RAM and 27 CPU seconds of processing time (51 days).

The CFD models are well accepted and used to investigate thermal comfort, indoor air quality, load of the room, HVAC performance, etc. in numerous buildings. CFD is one of the most resourceful and capable tools to study fluid flow (air as the working fluid) and pollutant spreading in the comfort area. So, computational technique is used in this particular study.

This particular study is to computational investigate the flow characteristics of the sanitizer-laden conditioned air inside the room, which is essential for disinfection of the room air and thereby protecting the lives of doctors, nurses and healthcare workers. The inlet and outlet of the portions are shown in Fig. 3 .

Before investigating the fluid dynamics/pattern of hospital isolation room geometry, the current numerical model and methodology are validated against published experimental and numerical works (Chung and Hsu 2001, Jacob et al. 2019) . Fig. 4 (a) and Fig. 4 subsequently spreads towards the walls. Another view (seen from the top) is presented in Fig. 6 showing the ever-changing streamlines. It is understood from these figures that the fluid flow which influences the isolation hospital room has originated from the clean air openings (vents) positioned at the top of the isolation room (ceiling) irrespective of the direction of observation. together. It is evident from Fig. 8 (refer to the right side the image) that the sanitizing machine releases sanitizer at relatively higher temperature, which mixes with the cool air coming from the air-conditioning vent. Better mixing is ensured due to velocity as well as the temperature gradient available between the flows of the sanitizing machine and the air-conditioning vent. The cool air coming from the air-conditioning machine from the top of the isolation room exhibits asymmetric pattern due to the influence of the velocity and temperature gradient maintained by the sanitizing machine.

An effect with Fig. 8 is demonstrated in Fig. 9 . The velocity vectors are shown in Fig. 9 . with the other flow (sanitizer, horizontal flow). It is also found that both the flows slow a bit when striking the walls. Flow circulation and large scale eddies found due to the mixing of flows between cool air and sanitizer and also due to bounding walls. Due to thorough mixing between cool air and sanitizer it is expected that the entire isolation room air will be sanitized, and due to this sanitizing by volume, it is also expected that the isolation room is fully virus free and the occupants (patients) can stay comfortably. This results and novel idea could be used to help flatten the curve of COVID-19. Moreover, these results could be used to design the effective layout of the air-conditioning ducts.

In the context of COVID-19, since there is no specific treatment or established medical protocol, medication and vaccine, the objective should be to control and prevent the transmission of this virus as far as possible. It is absolutely essential to reduce the risk of airborne infection transmission to the lowest possible level in hospital isolation rooms to protect the lives of doctors, nurses and other health care workers, and simultaneously, flatten the curve of COVID-

This particular investigation was performed to offer understanding the airflow patterns in the isolation room. The study has been carried out to investigate the effectiveness of conditioned air released from air-conditioning machines to mix with aerosol sanitizer so as to reach every corner of the isolation room and kill the COVID-19 virus. A CFD analysis has been carried out considering factors affecting aerosol sanitizer delivery systems such as temperature, turbulent kinetic energy and flow dynamics. In order to numerically model the laminar-transitional flows, transition SST k model, which involves four transport equations are employed in the current study. It is found from the analysis that high turbulent fields generated inside the isolation room may be an efficient way of distributing sanitizer in a volume of confined isolation room to kill or minimize the COVID-19 virus.

G k = generation of turbulent kinetic energy (k) 

Comprehensive review and study of the buoyant air flow within positive-pressure hospital operating rooms

Investigation of effective climatology parameters on COVID-19 outbreak in Iran

Correlation 186 between climate indicators and COVID-19 pandemic

Infuence of Inlet Turbulence Intensity on Transport Phenomenon of Modifed Diamond Cylinder: A Numerical Study

Computational investigation of heat transfer enhancement by alternating inclined ribs in tubular heat exchanger. Progress in Computational Fluid Dynamics

Characterization of infectious aero-sols in health care facilities: an aid to effective engineering controls and preventive strategies

Effect of ventilation pattern on room air and contaminant distribution

Disinfection of environments in healthcare and no healthcare settings potentially contaminated with SARS-CoV-2

Aerosol and surface distribution of severe acute respiratory syndrome Coronavirus 2 in hospital wards

Design and simulation of isolation room for a hospital

Airborne Respiratory Diseases and mechanical systems for control of microbes

Role of ventilation in airborne transmission of infectious agents in the built environment-a multidisciplinary systematic review

Improved Strategy to Control Aerosol-Transmitted Infections in a Hospital Suite

Methodology for minimizing risk from airborne organisms in hospital isolation rooms

Two-equation eddy-viscosity turbulence models for engineering applications

COVID 19: Guidelines on disinfection of common public places including offices

Indirect effects of COVID-19 on the environment

Temperature significantly changes COVID-19 transmission in (sub) tropical cities of Brazil

Outbreak of a new coronavirus: what anaesthetists should know

COVID-19 transmission in Mainland China is associated with temperature and humidity: A time-series analysis

Effects of flow control in the presence of asymmetric inflows in twin air-intake. Aircraft Engineering and Aerospace Technology

Impact of weather on COVID-19 pandemic in Turkey

Impact of temperature on the dynamics of the COVID-19 outbreak in China

Evaluation of the Potential Relationship between Particulate Matter (PM) Pollution and COVID-19 Infection Spread in Italy

Optimize Occupant Health, Building Energy Performance and Revenue through Indoor-Air Hydration

High Temperature and High Humidity Reduce the Transmission of COVID-19

Collecting, preserving and shipping specimens for the diagnosis of avian influenza A(H5N1) virus infection : guide for field operations

WHO, 2020a. Coronavirus Disease 2019 (COVID-19) Situation Report -51

WHO Characterizes COVID-19 as a Pandemic

Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations, Scientific brief

Severe acute respiratory infections treatment centre: practical manual to set up and manage a SARI treatment centre and SARI screening facility in health care facilities

Association between ambient temperature and COVID-19 infection in 122 cities from China

Study on biological contaminant control strategies under different ventilation models in hospital operating room

The authors would like to gratefully acknowledge Birla Institute of Technology and Science, Pilani, Pilani Campus and Motilal Nehru National Institute of Technology Allahabad for this research.

The authors declared that they have no conflict of interests.

