Thin liquid films: Where hydrodynamics, capillarity, surface stresses and intermolecular forces meet

Ephemeral Antibubbles: Spatiotemporal Evolution from Direct Numerical Simulations

“…Clearly, an antibubble is unstable in the presence of gravity, and, if the inner core of the antibubble is denser than the outer core, the antibubble rises under gravity; because of hydrostatic pressure in the outer core, the fluid rises from the bottom to the top, resulting in a thinning, and subsequent collapse, of the outer shell. Although there have been a number of experimental investigations of the spatiotemporal evolution of an antibubble [7][8][9][10][11][12][13][14][15] and drops [16][17][18][19][20] to name a few, over the past few decades, theoretical studies of antibubble evolution have been initiated only recently [15,[21][22][23][24][25] and they have not, attempted, hitherto, to address the spatiotemporal evolution of antibubbles in detail. The number of experimental studies of the complete spatiotemporal evolution of antibubbles is also limited, partly because great care has to be exercised to stabilise antibubbles; often, surfactant molecules have to be introduced into the highdensity liquid phase for such stabilization.…”

Breakup Dynamics of Thin Liquid Sheets With Viscous Interfaces

“…Thus, the presence of molecular assemblies along interfaces may influence how hydrodynamic stresses are transmitted in the system, as viscous, viscoelastic and Marangoni stresses arise from the interaction between the fluid molecules and the complex microstructures [55]. Interface diffusion and Marangoni convection opposes to surfactant concentration variations over the interface, whereas surface viscous stresses reduce the surface velocity gradients [56].…”

“…A rheologically complex interface is often modeled through interfacial constitutive models that account the extra and deviatoric contributions to the interfacial stress from the interfacial microstructure. A general expression for the interfacial stress σ s of a complex interface is given by Eq 2-1 [61,55].…”

“…Hence, interfacial shear and dilatational viscosities can have a significant effect on the flow behavior, and effects caused by these properties can strongly influence the dynamics of thin liquid films and other high interface materials [63]. In most practical applications, thin film stabilisation is caused by a blend of surface-active components of different sizes that yield extra viscous and viscoelastic stresses that are strongly coupled with the steric intermolecular interactions [55].…”

“…in which à is the Hamaker constant and h is the thickness of the liquid film. The disjoining pressure is often modelled by assuming equilibrium van der Waals attraction between two unbounded parallel interfaces, albeit the free interfaces generally not being flat [55,9]. The bottom boundary 2, as in Figure 3.1, is a symmetry line, where there is no flux across it and the tangential stress is null.…”