Motion of a Mِbius band in free fall

A Möbius band is a three-dimensional surface with the particular feature of having only one side and one edge. A simple geometrical model consists of a circular centreline, and surface elements which are locally tangent to this line and continuously twist around it, completing one-half turn going once around the circle. From an aerodynamic perspective, such a Möbius strip presents a profile that is locally a flat plate with an angle of attack smoothly varying between - 90 ∘ and 90 ∘ , and this regardless of the orientation of the object. We here present results from an experimental study of Möbius bands in free fall, focussing on the trajectory, body motion and wake dynamics. Free-fall experiments were carried out at low Reynolds numbers in a water tank, with Möbius bands made of different plastic materials, having an aspect ratio (perimeter/width) of 14. The bands are found to rapidly adopt a bluff leading edge orientation and to follow a spiral path, with an independent frequency of pitching.