Researchers at the University of Warwick have developed a new method that makes it possible to predict how irregularly shaped nanoparticles move through the air. These particles are a major category of air pollution and have long been difficult to model accurately. The new approach is the first that is both simple and predictive, allowing scientists to calculate particle motion without relying on overly complex assumptions.
Each day, people inhale millions of microscopic particles, including soot, dust, pollen, microplastics, viruses, and engineered nanoparticles. Some of these particles are so small that they can penetrate deep into the lungs and even enter the bloodstream. Exposure has been linked to serious health problems, including heart disease, stroke, and cancer.
Most airborne particles do not have smooth or symmetrical shapes. However, traditional mathematical models usually assume these particles are perfect spheres because spherical shapes make equations easier to solve. This simplification limits scientists’ ability to accurately track how real-world particles behave, especially those with irregular shapes that may pose greater health risks.
Reviving a Century-Old Equation for Modern Science
A researcher at the University of Warwick has now introduced the first straightforward method that can predict how particles of virtually any shape move through air. The study, published in Journal of Fluid Mechanics Rapids, updates a formula that is more than 100 years old and addresses a major gap in aerosol science.
The paper’s author, Professor Duncan Lockerby, School of Engineering, University of Warwick said: “The motivation was simple: if we can accurately predict how particles of any shape move, we can significantly improve models for air pollution, disease transmission, and even atmospheric chemistry. This new approach builds on a very old model — one that is simple but powerful — making it applicable to complex and irregular-shaped particles.”
Correcting a Key Oversight in Aerosol Physics
The breakthrough came from taking a fresh look at one of the foundational tools in aerosol science, known as the Cunningham correction factor. First introduced in 1910, the correction factor was designed to explain how drag forces on tiny particles differ from classical fluid behavior.
In the 1920s, Nobel Prize winner Robert Millikan refined the formula. During that process, a simpler and more general correction was overlooked. Because of this, later versions of the equation remained restricted to particles that were perfectly spherical, limiting their usefulness for real-world conditions.
Professor Lockerby’s work restructures Cunningham’s original idea into a broader and more flexible form. From this revised framework, he introduces a “correction tensor” — a mathematical tool that accounts for drag and resistance acting on particles of any shape, including spheres and thin discs. Importantly, the method does not rely on empirical fitting parameters.
Professor Duncan Lockerby added: “This paper is about reclaiming the original spirit of Cunningham’s 1910 work. By generalizing his correction factor, we can now make accurate predictions for particles of almost any shape — without the need for intensive simulations or empirical fitting.
“It provides the first framework to accurately predict how non-spherical particles travel through the air, and since these nanoparticles are closely linked to air pollution and cancer risk, this is an important step forward for both environmental health and aerosol science.”
What This Means for Pollution, Climate, and Health Research
The new model offers a stronger foundation for understanding how airborne particles move across a wide range of scientific fields. These include air quality monitoring, climate modeling, nanotechnology, and medicine. The approach could improve predictions of how pollution spreads through cities, how wildfire smoke or volcanic ash travels through the atmosphere, and how engineered nanoparticles behave in industrial and medical applications.
To expand on this work, Warwick’s School of Engineering has invested in a new state-of-the-art aerosol generation system. The facility will allow researchers to create and closely study a broad variety of non-spherical particles under controlled conditions, helping validate and refine the new predictive method.
Professor Julian Gardner, School of Engineering, University of Warwick, who is collaborating with Professor Lockerby, said: “This new facility will allow us to explore how real-world airborne particles behave under controlled conditions, helping translate this theoretical breakthrough into practical environmental tools.”