Software TU Delft for determining contamination risk for specific locations

Delft aerodynamics professor Fulvio Scarano, together with fluid dynamics expert Lorenzo Botto and simulation expert Wouter van den Bos, developed software to calculate the risk of infection with the coronavirus for a specific location. The model virtually places a sick person in the space and simulates how quickly the virus particles spread. The TU Delft researchers hope that designers and engineers will use the software to make predictions to determine whether, for example, sitting in an airplane, classroom or restaurant is safe. The plugin will probably be available in February.

Addition to CFD software

“The purpose of the model is to estimate the risk of a virus infection for a specific location,” says Van den Bos. “Instead of setting up a large and ambitious CFD (Computational Fluid Dynamics) project, which takes a very long time, our strategy was to create an add-on for already existing CFD software. CFD engineers use this program to simulate the airflows in a room with doors, windows and ventilation.”

Visualizing the spread of virus particles

The model is a plugin that virtually places a sick person in that space and simulates how quickly that person’s virus particles spread, based on breathing, talking or coughing. That speed increases as the person is taller, has a larger lung capacity and sneezes or coughs harder. To make sure the simulations match real-world conditions, the team validates them using quantitative visualization experiments.

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“I make visible the invisible,” says Scarano. He gets up from his chair, coughs in front of a screen with dots and a camera pointed at it, then shows on his computer screen how the droplets of his cough spread. “I then compare whether this is correct with our simulations. This cross-check is crucial to verify that the simulation captures all aspects of reality.”

Predicting risk of infection

Once all existing data has been added to the software, the researchers can then predict what the risk of infection will be. “Then you can try out on your computer, so in a safe way, what happens if, for example, you put a hundred students together in a lecture hall for an hour and a half and one of them has corona. The model also becomes more accurate as more is known about the virus, such as information about the lifespan of the virus and how many virus particles make someone sick,” says Van den Bos.

Read more in the Story of Science: 'Is it dangerous to sit in a cinema with 30 people for two hours?'