Wirth Research OpenAir

The droplets containing Coronavirus are so small and light that their path is primarily determined by the direction of their surrounding airflow – and some types of airflow can completely defeat the benefits of social distancing.

Wirth Research use high resolution Computational Fluid Dynamics (CFD) analyses to identify key airflow mechanisms which promote viral transport, and how these can be changed to minimise viral transport. This has been termed the OpenAir process. Wirth also design and develop innovative airflow solutions, that minimise viral transport for various high-risk location types such as: Lifts, airports, aircrafts, hospital wards, supermarkets.

 

Coronavirus Transport

During normal speech, or coughing, the most common average water droplet size emitted by a human is seven microns in diameter (less than a tenth of the thickness of human hair – about the size of common pollen) and these droplets can contain and transmit Coronavirus.

Evaporation of these droplets kills the coronavirus within them, hence conditions that encourage quick evaporation is favourable. Equally conditions where droplet evaporation isn’t favourable can increase transmission. Such as low temperature/high humidity environments, as has been seen in low temperature food processing plants worldwide.

In still air and ambient conditions, these droplets typically evaporate within 2m, hence why the 2m social distancing rule is so effective.

In enclosed spaces such as offices, supermarkets or any work facility, the moving airflow caused by HVAC can have a major effect on the chance of Coronavirus transmission, as the environment is no longer “still air”.

 

Social Distancing

Social distance distancing is designed to limit the amount of person-to-person airborne Coronavirus transmission.

The greater the person-to-person social distance – in still air – the lower the risk of Coronavirus transmission, as greater social distance allows the airborne virus to disperse into a greater volume of air, reducing its concentration, before it can be is ingested by another person nearby:-

 

The OpenAir process

Using Wirth Research’s high-resolution and validated Computational Fluid Dynamics (CFD) technology, the airflow surrounding people in any indoor environment (such as a shop, food manufacturing plant or office) can be assessed for its occupant safety to help Clients determine and immediately implement mitigation strategies to avoid transmission of Coronavirus by either changing the occupied spaces usage, or by introducing physical airflow mitigation by modifying the HVAC to improve safety

The OpenAir is process is carried out in the following stages:

  1. Create CFD digital twin of occupied zone
  2. Analyse viral dwell time and viral trajectory when air is released in a particular location
  3. Repeat this process for viral release across an entire grid of multiple locations (every 1m in any direction) across the entire occupied zone to form maps of virus dwell time and trajectory
  4. Analyse these dwell time and trajectory maps, taking into account occupant behaviour (occupant movements, fixed occupant location, queue positioning) to help client identify high risk areas.
  5. Help client recommend immediate occupant behaviour mitigation strategies:-
    • Cordoning-off high-risk zones
    • Limiting use of high risk zones
    • Both of the above will immediately improving occupant safety
    • If required, and working with the client and the OpenAir results, WR agree and simulate a range of physical HVAC modification options to reduce either reduce viral dwell time or improve airflow direction
    • Present the costs and benefits of the range of options tested above for the Client downselect and implement

The below movie shows an output from an analysis of a supermarket. The complex airflow movement around and through a supermarket has been modelled, allowing measures to be put in place to minimise viral transmission.

Example Results Output

The following image shows an example heat map from a generic store which shows the viral lifetime profile within the store. The red areas show high viral life time, and it is these areas which we would aim to minimise/remove.

 

The OpenAir Vertical airflow solution

There are some types of airflow that can not only compliment and reinforce the benefits of social distancing, but can either significantly reduce or even entirely eliminate the need for social distancing altogether:-

Such a safe area is called an OpenAir Vertical Airflow Zone (OVAZ) and is created by a combination of both:-

Vertical airflow: Fresh, virus-free airflow, which flows in a direction that is perpendicular to the floor (i.e. airflow that either is goes either straight up or straight down in the region where people are present) will naturally carry the airborne virus away from a virus emitting person – wherever they are.  As the airflow direction isn’t horizontal, the virus is immediately removed from the occupied zone without reaching anyone else, therefore the risk of transmission is significantly reduced or even eliminated:-.

Fresh airflow:

OVAZ will significantly reduce/eliminate the risk of airborne virus transmission.

OVAZ will also significantly reduce/eliminate the chance of surfaces becoming contaminated by airborne virus settling on them.

 

Wirth Research OpenAir overview

A confined space – such as a passenger lift – can be made safe by retrofitting OpenAir Technology to give vertical airflow, which is recirculated and continuously cleansed by the Continuous Autoclaving System:

 

Further reading on coronavirus airborne transmission can be found at the following links:

https://aip.scitation.org/doi/10.1063/5.0011960

https://www.globaltimes.cn/content/1182008.shtml

https://www.bbc.co.uk/news/uk-england-northamptonshire-53762233

 

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