Levitating Herringbones in motion

Levitating Herringbones in motion
H. de Maleprade, D. Soto, C. Clanet, D. Quéré
Physique et Mécanique des Milieux Hétérogènes – ESPCI, Paris, France
Laboratoire d’Hydrodynamique de l’X – École polytechnique, Palaiseau, France
helene.de-maleprade@espci.fr
1. Introduction
Controlling objects motion without contact is an major application issue as it ensures uncontaminated materials and low friction. Levitation can be induced by blowing air from below, through a porous medium, to create a thin air cushion squeezed by the object. “Air tables” have been developed to optimise the motion of different objects [1]. By controlling independently the pressure of each air jet of the table, the map of pressure can be controlled thus the object can be manipulated. Another recently developed method offers to control the object motion by rectifying the flow of escaping air [2]. Asymmetry is introduced through microscopic textures on the top of the porous medium; viscous entrainment of air enables drops, rigid plastic or even glass cards to self-­‐propel. 2. Materials and methods
In this work, we consider the symmetric case where textures are not on the porous media, but are engraved on the moving object itself. Varying parameters are plate geometry and wall depth.
Figure: Herringbone micro-textures: walls are 200 µm thick and spaced every 1 mm, they form a 90° angle. Air is
blown vertically from below through 50 µm holes. The long arrow indicates the horizontal direction of the plate.
3. Results and conclusion
We experimentally observe propulsion of the objects in the opposite direction than in previous scenario [2] which is interpreted as a rocket effect. Weight and geometry of the objects as well as characteristics of the micro-­‐textures are critical parameters that can be explored and offer insight to model the physical parameters.
4. References
[1] Laurent, G. J. and Delettre, A. and Le Fort-Pilat, N., “A New Aerodynamic Traction Principle for Handling
Products on an Air Cushion”, IEEE Transactions on Robotics Vol. 27, 2 (2011).
[2] Soto, D. and Lagubeau, G. and Clanet, C. and Quéré, D., “Surfing on a Herringbone”, in prep. (2014).