Roland Liebe from SIEMENS Power Generation in Germany gave a lecture on Design & Nature. He focused on “The key role of vortices to generate thrust and lift in Nature”.

First, typical closed-loop steps in engineering were compared with those followed by Nature to arrive at continuous improvement. Then the main chapters of a new WIT book were outlined: “FLOW PHENOMENA IN NATURE – A Challenge to Engineering Design”. They covered:

• Swimming and flying in Nature. Diversity of propulsion
• Laws of similarity and optimum design (Reynolds-, Strouhal-number etc)
• Unsteady flow mechanisms. Low Reynolds-number flight
• Kinematics of wings and fins. Models for simulation
• The natural vortex. The concept of the Finite Vortex Model
• Applications in engineering and medicine
• Numerical methods and experimental techniques

Special concern was put on the edge flow mechanism, the roll-up of large attached/bound vortices, giving rise to an efficient way of generating lift and thrust forces. New insights were addressed, ie the stability and interaction between the trailing edge (TE), as well as the leading edge (LE), vortex of oscillating wings/fins.

Selected applications were on flapping airfoils, birds’ flight, hovering etc. Summarising conclusions stressed the key role of vortex generation both in Nature and engineering. Finally several future activities were mentioned.