Ecole Superieure de Plasturgie, France
In many industrial processes, one is faced with high velocity coating flows, i.e. the spreading of a thin liquid layer on a moving solid substrate. This three phase (liquid/solid/air) problem is classically reduced to a two phase (liquid/solid) one. However, increasing the coating speed induces air phenomena which cannot be neglected. After a short bibliographical survey of the experimental work in that domain, a novel theoretical model is presented. The spatial stability of the contact line is studied within the framework of linear stability analysis. The temporal stability of this line is also considered by studying the response of the contact line to fluctuations generated upstream. It is shown that there is a subcritical Hopf bifurcation, which seems to be in a good qualitative agreement with experimental observations done separately.
[ Spring 2001]