Runepal Singh Sørensen Dhaliwal

• Dhaliwal, Runepal Singh Sørensen; Liu, Jingbang & Carlson, Andreas (2025). Stochastic elastohydrodynamics of contact and coarsening during membrane adhesion. Journal of Fluid Mechanics. ISSN 0022-1120. 1024. doi: 10.1017/jfm.2025.10872. Full text in Research Archive Show summary

  Contact between fluctuating, fluid-lubricated soft surfaces is prevalent in engineering and biological systems, a process starting with adhesive contact, which can give rise to complex coarsening dynamics. One representation of such a system, which is relevant to biological membrane adhesion, is a fluctuating elastic interface covered by adhesive molecules that bind and unbind to a solid substrate across a narrow gap filled with a viscous fluid. This flow is described by the stochastic elastohydrodynamic thin film equation, which incorporates thermal fluctuations into the description of viscous nanometric thin-film flow coupled to elastic membrane deformation. The average time it takes the fluctuating elastic membrane to adhere is predicted by the rare event theory, increasing exponentially with the square of the initial gap height. When the forces arising from spring-like adhesive molecules are included in the simulations, thermal fluctuations initiate phase separation of domains of bound and unbound molecules. The coarsening process of these unbound pockets displays close similarities to classical Ostwald ripening; however, the inclusion of hydrodynamics affects power-law growth. In particular, we identify a new bending-dominated coarsening regime, which is slower than the well-known tension-dominated case.

• Dhaliwal, Runepal Singh Sørensen; Pedersen, Christian; Kadri, Kheireddin; Miquelard-Garnier, Guillaume; Sollogoub, Cyrille & Peixinho, Jorge [Show all 8 contributors for this article] (2024). Instability and rupture of sheared viscous liquid nanofilms. Physical Review Fluids. 9(2). doi: 10.1103/PhysRevFluids.9.024201. Full text in Research Archive Show summary

  Liquid nanofilms are ubiquitous in nature and technology, and their equilibrium and out-of-equilibrium dynamics are key to a multitude of phenomena and processes. We numerically study the evolution and rupture of viscous nanometric films, incorporating the effects of surface tension, van der Waals forces, thermal fluctuations, and viscous shear. We show that thermal fluctuations create perturbations that can trigger film rupture, but they do not significantly affect the growth rate of the perturbations. The film rupture time can be predicted from a linear stability analysis of the governing thin film equation, by considering the most unstable wavelength and the thermal roughness. Furthermore, applying a sufficiently large unidirectional shear can stabilize large perturbations, creating a finite-amplitude traveling wave instead of film rupture. In three dimensions, unidirectional shear does not inhibit rupture, as perturbations are not suppressed in the direction perpendicular to the applied shear. However, if the direction of shear varies in time, then the growth of large perturbations is prevented in all directions, and rupture can be impeded.

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