Mar 11, 2022 
New fluid dynamics provide the flying robotics of the future (w/video)

(Nanowerk News) The first professional robotic birds – like UT and Clear Flight Solutions’ Robird® – have been in the air for a few years now. Yet, the physics of the bird’s flight is not yet completely clear.

“We only had some rough explanations based on some experimental data”, says Prof.Dr.Ir. Stefano Stramigioli. Thanks to his work, we are now on the way to a better understanding of the complex physics surrounding wings, bringing us one step closer to robotic birds, that take off, fly and land like real birds.


PortWings – Decoding the Nature of Flapping Flight by portHamiltonian System Theory. (Image: University of Twente)

Leonardo da Vinci dreamed of machines that could fly as easily as birds. Mimicking the movements of birds’ wings is extremely complicated. The Robird®, with its flapping wings, was already a major step forward. Unfortunately, this was still nowhere near a realistic bird. In 2018, Stramigioli received an ERC Advanced Grant of 2.8 million euros to further understand and develop robotic birds.

Theoretical insights

The first novelty the researchers presented was an understanding of the precise role of advection in the NavierStokes equations, which are used to, for example, forecast the weather but also model the complex fluid dynamics of aeroplanes. Using the socalled portHamiltonian model, they found an elegant description, that resulted in a twopart paper in the Journal of Geometry and Physics ("PortHamiltonian modeling of ideal fluid flow: Part I. Foundations and kinetic energy" and "PortHamiltonian modeling of ideal fluid flow: Part II. Compressible and incompressible flow").

“The two publications were quickly accepted and led to an invitation from the Editor in Chief of the journal Physics of Fluids to submit our future work to the journal”, says Stramigioli.


Prof. Stefano Stramiglioni is invoking math and engineering to make robotic birds that fly like a real bird.

First major milestone

Stramigioli and his team were on to something with their use of the portHamiltonian model. After publishing their invited paper in Physics of Fluids ("Geometric and energyaware decomposition of the Navier–Stokes equations: A portHamiltonian approach"), they went back to the biggest problem so far and the reason they started the project in the first place. The team managed to use the portHamiltonian model to couple the mechanics of the deformations of the wings to the 3D flow dynamics of the ‘fluids’ around those wings.

This resulted in another publication in the Journal of Geometry and Physics and is the first major milestone of the project.

Engineering the bird

Now, the team will start working on the experimental part: “We are building setups and measuring systems in order acquire data to learn from it and eventually to test our models and look at the control challenges”, says Stramigioli, “Once we have good experimental data we will be a step closer to building a new robotic bird which would exploit the physics at its best.”

This next phase in the project means Stramigioli is one step closer to making his dream come true.

“We have also just submitted a new fundamental paper which presents a way to discretize partial differential equations. This allows varying boundaries and at the same time conserves all physical quantities of the problem. I am very proud of this strong advance in the computational side of the project”, says Stramigioli

Multidisciplinary team

In 2018, Stefano Stramigioli set up a multidisciplinary team for his project ‘PortWings – Decoding the Nature of Flapping Flight by portHamiltonian System Theory’.

The initial team included Prof. Frederic Schuller, Dr. Federico Califano and Dr. Ramy Rashad Hashem and a number of collaborators. In the meanwhile, this team has been extended with Riccardo Sneep (Engineering PhD Student), Luuk Groot Koerkamp (Wind tunnel experiments lead), Alexander Dijkshoorn (Intelligent Materials PhD Student) and Andrea Brugnoli (PortHamiltonian numerics postdoc). In February 2022, Stramigioli has been awarded a Proof of Concept grant for the PORTWINGS project.
