From laboratory innovation to industrial impact: complex flows in rheology
Coen van der Gracht defended his PhD thesis at the Department of Mechanical Engineering on May 12th.
At the heart of the thesis of lies a deceptively simple idea: by carefully controlling fluid flows and analyzing how the surface of a liquid deforms, it becomes possible to determine key properties such as viscosity, surface tension, and even density. This approach is made powerful by combining precise, well-designed experiments with advanced numerical modeling鈥攕howing that even everyday actions like blowing on a liquid can reveal complex material behavior when understood through the right scientific lens.
Puff Technology: a contactless leap forward
The first major innovation presented is Puff Technology, a novel, non-invasive measurement technique that uses short, controlled bursts of air to deform a fluid's surface. These deformations are measured with a high-precision 2D laser sensor and then analyzed using computational simulations. By comparing measured and simulated results, both surface tension and viscosity can be accurately determined. The method is also effective for characterizing viscoelastic fluids, broadening its application range.
What sets Puff Technology apart is its practicality: the technique requires no direct contact with the fluid, keeping samples clean and reusable. It demands minimal preparation, little training, and lends itself to automation. As such, it holds strong potential not only for laboratory environments but also for integration into manufacturing lines for real-time quality control.
Understanding complex climbing
In a parallel study, Van der Gracht explored swirling viscoelastic flows through the rodless Weissenberg effect, where certain fluids climb along rotating objects due to internal stress differences. By developing the Weissenberg Effect Analyzer, which uses a rotating disk instead of a rod, he was able to generate and study these normal stress differences in a controlled way. Two distinct climbing behaviors were identified, depending on the Weissenberg number: linear climbing at lower values, and a non-linear regime at higher values following a power law. This offers new insight into the dynamics of complex fluids in confined, rotating systems.
From academic insight to industrial application
Perhaps the most impactful conclusion of the thesis is that through a combination of controlled yet simple experiments鈥攕uch as blowing on a liquid鈥攁nd sophisticated numerical modeling, it is indeed possible to extract detailed material information. This includes rheological properties, surface tension, and density鈥攑arameters that are essential in many industries but traditionally difficult to measure quickly and accurately.
This realization is already making its way from academia to the industrial sector. Van der Gracht鈥檚 research is being translated into practical tools through Puform, a startup focused on modernizing liquid quality control in production environments. Especially in sectors facing a retiring skilled workforce, innovations like Puff Technology offer a way to maintain precision and reliability while simplifying the measurement process.
In doing so, the thesis not only advances the scientific field of rheometry but also directly addresses pressing industrial challenges鈥攂ridging the gap between laboratory innovation and real-world impact.
Want to find out more about Puff Technology, have a look at the .
Title of PhD thesis: . Supervisors: Prof. Ruth Cardinaels, and Dr. Nick Jaensson.