Bio-Inspired Flying and Swimming Devices

We study archetypal types of flyers and swimmers found in nature ranging from the microscale(pollen and bacteria) to the macroscale level(birds and eels). These forms serve for inspiration of engineering devices that can be in turn optimized using bioinspired algorithms.

The Legend of the Sargasso sea
Anguilliform swimmers such as eels  travel thousands of kilometers with minimal food consumption  and biologists and engineers  have long debated on the particular form of their swimming aiming for enhanced physical understanding and the design of robotic devices.  We have employed a derandomized Evolution Strategy alomng with Direct Numerical Simulations of anguiliform swimmers to identify differnt swimming modes for these structures. Our findings indicate distinct types of swimming for distinct objectives (efficiency, speed, etc.). Please visit this link for more details.

A self-propelled deforming airship
The efficiency of fishlike swimmers has inspired Engineers at the EMPA to design a blimp (i.e. an airship) which propels itself by the deforming its hull using Electro-Active Polymers.  We simulate the propulsive fish-like swimming motions of the blimp solving for the incompressible 3D-Navier-Stokes equations coupled with the equations of motion for the propulsive part. The resulting flow patterns feature the vortex rings shedded at the tail-fin, which has also been reported in flow visualization experiments of swimming fish. We investigated the influence of different motion parameters such as maximal deflection angle of the fin, tail-beat frequency and flexible elements at the tail-fin on the swimming speed and efficiency.
 
Shedding of Vortex Rings at the tail-fin: Vorticity-Iso-Contours, coloured with y-vorticity
   
Simulation of a flapping wing at Re=200

Fluid-Structure Simulations of Flexible Flying devices
We develop particle methods for simulations of flow-structure interaction that can model arbitrary deformations. As an example for the flexibility and versatility of this approach, we have simulated the flow around a flapping wing.
  • van Rees W.M., Gazzola M., Koumoutsakos P., Optimal shapes for anguilliform swimmers at intermediate Reynolds numbers. Journal of Fluid Mechanics, 722, 2013. (pdf)
  • Gazzola M., van Rees W.M., Koumoutsakos P., C-start: optimal start of larval fish. Journal of Fluid Mechanics, 698:5–18, 2012. (Abstract)(http://dx.doi.org/10.1017/jfm.2011.558(this article is featured in the JFM series: Focus on Fluids) (Cover of JFM)
  • Gazzola M., Chatelain P., van Rees W.M., Koumoutsakos P., Simulations of single and multiple swimmers with non-divergence free deforming geometries, Journal of Computational Physics, 230(19):7093–7114, 2011. (Abstract) (pdf)
  • Kern S., Koumoutsakos P.. Simulations of optimized anguilliform swimming. J. Experimental Biology, 209, 4841-4857, 2006 (Abstract) (pdf)
  • Hieber S.E., Koumoutsakos P., An immersed boundary method for smoothed particle hydrodynamics of self-propelled swimmers, J. of Computational Physics, 227, 19, 8636-8654, 2008 (Abstract) (pdf)
  • Kern S., Koumoutsakos P., Eschler K., Optimization of anguiliform swimming, Physics of Fluids (Gallery of Fluid Motion), 19, 091102-1, 2007 (pdf)