LAMINAR-FLOW OF A LIQUID RIVULET DOWN A VERTICAL SOLID-SURFACE

Conditions for an energy minimum of a liquid rivulet flowing down a vertical solid surface have been considered. The solution of the equation may yield a constant value equal to the maximum rivulet thickness and the curve z(x) representing the shape of the rivulet cross section (profile). The profile describes the smallest rivulet which may be formed for a given system. "Composed" solutions correspond to wider rivulets, e.g. finite films. Numerical integration has been performed over a wide range of the parameter characterizing the liquid, at contact angles ranging from 5-degrees-C to 90-degrees-C. The minimum rivulet concept, which makes it possible to describe a finite-width laminar film of minimum thickness, extends the Nusselt theory.