Killing coronavirus indoors with CFD simulation

Designed fully with Simcenter computational fluid dynamics (CFD) simulation, part of the Xcelerator portfolio from Siemens, Soluva, a new UV-C purifier kills 99.99% of coronavirus in the air. The device from Heraeus Noblelight is already in operation in buses, classrooms and hospitals.

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Indoors – the most dangerous place to be during a global pandemic.


How do you minimize airborne virus transmission in indoor spaces? How do we reopen the world safely? Are we resigned to a future of lockdowns, empty buildings, social distancing and avoiding indoors altogether? The global Coronavirus (Covid-19) pandemic has upended lives, destroyed livelihoods and has made indoors the most dangerous place to be today.


While doctors and healthcare workers are fighting Covid-19 on the frontlines, others have their attention on a different challenge: How do we make the indoors safer?


The answer is a new device by a company started in 1660, based on a phenomenon discovered in 1896 and fully designed with the best of 21st century digital simulation from Siemens. The answer is Soluva, an Ultraviolet (UV) air purifier that kills 99.99% of the SARS-CoV-2 coronavirus in the air.  

(UV-C) Light at the end of the (lockdown) tunnel

The aptly named Heraeus Noblelight is the maker of Soluva. Starting as a pharmacy in 1660, Heraeus is known worldwide for their lamps, emitters and disinfection products. Light, whether UV, infrared or middle wave range, is at the heart of everything they do. When COVID-19 hit Europe and countries shut down, Heraeus immediately knew their UV expertise could help. The question was how?


“UV light has been used for killing bacteria and viruses since Nobel Prize winner Niels Finsen discovered the phenomenon in 1896,” says Larisa von Riewel, Group Leader Computer Aided Engineering (CAE) at Heraeus Noblelight. “We usually make customer-specific UV systems. But fighting COVID transmission indoors needed a completely new device. A device that could harness UV-C light to kill the virus.”


UV-C light (200 – 280 nm) from the sun, unlike its counterparts UV-A and UV-B, never gets past the atmosphere. It’s no wonder that UV-C radiation, artificially produced, is the most effective at killing viruses, destroying their structure and inactivating living cells. This UV-C light (at 254 nm wavelength) is at the heart of Soluva.

Simulation mastered safety challenge

Heraeus Noblelight put together a team of 60 – engineers, designers and simulation experts – to design the new device for rooms, offices, transportation and public spaces. The timeline? Six months from idea to delivery. The UV-C lamp in Soluva sits inside a housing. A fan pulls air in from one side and UV-C radiation kills the virus before the air flows out.


“Our biggest challenge was safety. UV-C is harmful to humans, so our device had to contain it within the system,” adds Dörte Eggers, Simulation Engineer at Heraeus Noblelight. “Also, the air has to be in the system long enough for the UV-C dose to kill the virus. If it flows out too soon, the virus remains active.”


To design a safe, efficient, noise-free device, Heraeus Noblelight turned to multiphysics computational fluid dynamics (CFD) simulation with Simcenter. Before building any product – be it a plane, car, ship, even baby incubators – engineers use CFD simulation to virtually predict fluid, thermal, structural and other product performance. The team at Heraeus Noblelight used Simcenter STAR-CCM+, the Multiphysics CFD simulation software, to optimize the device performance and analyze airflow and droplet transmission with the UV-C purifier. They also used CAD-embedded Simcenter FLOEFD to quickly analyze airflow inside a bus where the device is fitted.

From idea to operation in six months

“CFD simulation with Simcenter STAR-CCM+ software was the backbone of developing Soluva,” says Larisa von Riewel. “It is much easier to model the performance in the virtual world. Thanks to precise simulation with Simcenter STAR-CCM+, we saved many production steps and brought Soluva to life in six months.”


“Simcenter STAR-CCM+ helped us find the best housing and fan design, simulate performance for various rooms and wall positions, optimize the noise level and ensure the air and particle stay in the system long enough,” adds Dörte Eggers. “A Monte-Carlo probability method then showed the device had enough UV-C dose to inactivate 99.99% of the virus.”


Dörte Eggers even simulated cough droplets from an infected person in an office and classroom to test Soluva’s efficiency. Within six months, the team delivered seven different Soluva products in operation, all designed virtually with CFD. 

Modeling cough virtually

“We were under heavy time pressure,” adds Larisa von Riewel. “Modeling cough virtually was a new area to us. But Siemens gave a webinar with Airbus on the joint research into cough modeling. This research gave us clues to calculate transmission probability in the room.”


The role of Siemens Sales and Support was crucial too. “What makes Simcenter STAR-CCM+ exceptional is the support we receive. Our Dedicated Support Engineer, Paco Ezquerra, helped us immensely in modeling the cough physics correctly,” adds Dörte Eggers. 

Keeping indoors safe with Soluva

The real ‘test’ of the virtual design, of course, was in physical testing. The Heraeus Noblelight team tested Soluva in experimental testing by the University of Tübingen, the Hygienic Institute biotec GmbH and the Frauenhofer Institute. Using both surrogates and a real virus, the tests confirmed the effectiveness of the UV-C device. In five to six minutes, Soluva eliminated 99.99% of viruses in an empty room with no residue of harmful ozone detected.


The device can be installed and be operational in under two hours. The city of Hanau, Germany became the first city to use Soluva in its public buses. Here, Heraeus Noblelight used Simcenter FLOEFD to quickly analyze air flow in the bus before fitting the device. “I find Simcenter FLOEFD to be very handy for fast calculations which we needed to integrate the device quickly in the bus,” says Larisa von Riewel. 

With handheld, wall-mounted and ceiling-mounted variants among others, Soluva is now offering effective, flexible UV disinfection for public transport, hospitals, offices, schools and more.


The standard safety precautions of masks, distancing and handwashing are still needed. But in six months, Heraeus Noblelight, aided by Simcenter STAR-CCM+, has brough us one-step closer to what we are all longing for: safer indoors and a semblance of normalcy in our lives. 

The simulations were time-critical and needed huge computing power. Our Support Engineer, Paco, helped us at every step. The Siemens team gave us trial Power licenses for two months to speed up the results. This is something special about Simcenter and Siemens.
Dörte Eggers, Simulation Engineer, Heraeus Noblelight

Prashanth Shankara Shastrigal
April 2021

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