Better simulations for aerospace

When building lightweight aircraft, engines, or wind turbines, engineers need to understand physical forces and predict them accurately. However, current simulation methods are unable to achieve this. Malte Krack, professor at the University of Stuttgart, is developing new simulations to make damping calculable and propulsion systems for aerospace safer. International talent will support his team in this endeavor. As Henriette Herz Scout, he nominates three Humboldt scholarship recipients.

To prevent aircraft fairings from tearing off or engine blades from breaking, engineers must keep extreme physical forces, known as oscillations, under control. The solution to this is damping.

"We need to understand how large the oscillations are and how we can dampen them in a targeted manner through friction and shocks. This is the only way we can build stable and reliable aircraft," explains Malte Krack. The professor at the Institute of Aircraft Propulsion Systems at the University of Stuttgart focuses on the structural mechanics and dynamics of engines for aerospace designs. His focus is on contact processes and how their oscillation and damping behavior can be predicted in simulations. "We are also researching future methods for oscillation testing. Our goal is to provide new theories and methods and demonstrate that they work."

The challenge lies in the details: “Most damping occurs at joints, for example, so-called contact points, where parts are assembled by friction or form fit,” says Krack. The movements within these joints are usually a hundred times smaller than the thickness of a human hair. In contrast, the oscillations that must be damped often occur in the millimeter range – making them 1,000 to 10,000 times larger. “We are dealing with a multi-scale problem here,” explains Krack. “Accurate predictions require that all these different length scales be represented within a single model. However, conventional simulation and measurement techniques have so far been unable to accomplish this.”

Krack and his team are therefore developing new simulation methods. One of these tools is already being used in industry, for example to build better engines or gas and steam turbines. Precise predictions play a particularly important role in lightweight construction. “The thinner and lighter a structure is, the more prone it becomes to oscillations – and the more pronounced nonlinear effects become,” explains Krack. In other words, physical phenomena that cannot be represented using linear approximations. However, the simulation and measurement methods used are based on linear approaches. “It's like trying to push a square peg through a round hole.”

To solve this problem, Krack has nominated three international early career researchers for his team. Awarded the Henriette Herz Scout by the Alexander von Humboldt Foundation, he is now looking for young talents with expertise in friction physics, fluid mechanics, or energy harvesting. The latter offers a promising research approach for storing energy released through friction and using it, for example, to operate microsensors. “That would complement our work perfectly and ultimately enable research that would otherwise be inconceivable,” says Krack. In addition to technical expertise, one thing is particularly important to him: "What excites me most is working with young people who are passionate about their field. I hope that we can learn a lot from each other."

The Henriette Herz Scouting Program is aimed at researchers at various career stages and from all disciplines in Germany. The prerequisite for the role of scout is a (junior) professorship or comparable management position, for example a group leader, as well as an international cooperation network. Scouts identify outstanding young researchers from abroad and can nominate up to three international scientific talents for a two-year research fellowship. After a formal review, up to 100 scholarships are awarded annually through a direct selection process.

In 2020, the University of Stuttgart received the Henriette Herz Prize - an award for the strategic recruitment and retention of highly qualified international early career researchers.