Experimental and Numerical Study of Geometrically Driven Drop Motion

Pr. Marie-Christine NÉEL


Avignon University, France.

Some organisms living in arid environment harvest water on own skin, on which liquid drops move spontaneously in a privileged direction. Here the word « spontaneous » means that no pressure difference or external force is needed. In view of copying such motion in industrial process we consider it on materials possessing properties like robustness or electric conductivity.

Spontaneous directed drop motion on horizontal flat surface may be caused by heterogeneous wettability whose gradient points toward some specific direction. It also occurs on flat surface of uniform physico-chemical properties decorated by sequences of identical micrometric obstacles forming like channels. Measuring drop motion on such device, here made of steel, evidences patterns that promote directed transport. Observed motion is fragmented into successive stages of uneven velocity . Numerical simulation investigates the flow regimes observed during these stages. It also gives us a flexible tool to optimize channel design in order to enhance motion.


Pr. Marie Christine NÉEL : Professor Emerita at Avignon University, where she teached mechanics and physics since 1998. Her research covered diverse themes in the field of fluid mechanics, with special attention to liquid flowing through porous material. She developped theoretical and numerical methods to predict fluid flow instability caused by thermal gradient or magnetic field. She also studied diffusion equations including derivatives of non-integer order that reveal molecular motion represented by stochastic process more general than Brownian motion. Considering that Nuclear Magnetic Resonance measures the increment characteristic function of such process she is investigating molecular motions on the basis of such data complemented by tracer test. Marie-Christine Néel is moreover presently working on fluid flow in non saturated porous material.