Impact of the Wetting Length on Flexible Blade Spreading

We study the spreading of a Newtonian fluid by a deformable blade, a common industrial problem, characteristic of elastohydrodynamic situations. Here, we consider the case of a finite reservoir of liquid, emptying as the liquid is spread. We evidence the role of a central variable: the wetting length l_{w}, which sets a boundary between the wet and dry parts of the blade. We show that the deposited film thickness e depends quadratically with l_{w}. We study this problem experimentally and numerically by integration of the elastohydrodynamic equations, and finally propose a scaling law model to explain how l_{w} influences the spreading dynamics.