Suppressing van der Waals driven rupture through shear

An ultra-thin viscous film on a substrate is susceptible to rupture instabilities driven by van der Waals attractions. When a unidirectional wind shear is applied to the free surface, the rupture instability in two dimensions is suppressed when exceeds a critical value c and is replaced by a permanent finite-amplitude structure, an intermolecular-capillary wave, that travels at approximately the speed of the surface. For small amplitudes, the wave is governed by the Kuramoto-Sivashinsky equation. If three-dimensional disturbances are allowed, the shear is decoupled from disturbances perpendicular to the flow, and line rupture would occur. In this case, replacing the unidirectional shear with a shear whose direction rotates with angular speed, suppresses the rupture if 2c. For the most dangerous wavenumber, c 10² dyn cm ² at 1 rad s¹ for a film with physical properties similar to water at a thickness of 100 nm.