Unstructured meshes are among the most versatile approaches for capturing non-canonical geometries in fluid dynamics simulations. Despite this, most high-fidelity first-principles phase-change models are developed and applied on structured meshes. We present a phase-change simulation method for unstructured meshes that combines the algebraic Volume-of-Fluid (VOF) technique with geometric interface reconstruction, implemented in an in-house open-source CFD code. Phase-change rates are computed from local temperature gradients evaluated at the reconstructed interface, without empirical closure models, using a reconstruction procedure that operates on arbitrary polyhedral cells. Because the method relies on the standard finite-volume framework, it can be integrated into other cell-centred codes supporting unstructured meshes. The approach is validated against the one-dimensional Stefan and Sucking problems and the three-dimensional Scriven bubble growth on both hexahedral and polyhedral meshes, showing good agreement with analytical solutions in all three cases. A detailed analysis of the Scriven problem reveals that the interface-modified least-squares gradient stencil on Cartesian meshes overestimates the interfacial temperature gradient, producing a persistent overshoot of the analytical bubble radius and a coherent four-fold anisotropy that elongates the bubble along grid diagonals. On polyhedral meshes, the irregular face orientations eliminate both effects, yielding isotropic growth and monotonic convergence. Finally, we demonstrate the framework on turbulent upward co-current annular boiling flow, where early transient results are qualitatively consistent with a previous LES study and experimental observations of wave-modulated evaporation.
This paper is devoted to studies of the mechanical deformation of the S. aureus cell wall. The bacterium is modelled as a thin elastic membrane containing cytoplasm, which is treated as an incompressible fluid. Deformation occurs via Van der Waals interactions between the bacterium and a solid metallic surface, both with and without the influence of surface plasmon resonance (SPR). Our modelling results indicate that the excitation of surface plasmons significantly increases the effective interaction area between the bacterial membrane and the nanostructured surface. The elastic and dielectric properties of the bacterium's components are uninvestigated. Therefore, theoretical calculations are performed in wide, physically meaningful ranges. Thus, the results of studies give only a qualitative estimation. However, they are novel and, with further experiments, can solve the inverse problem of obtaining physical properties. The paper highlights the potential of SPR to enhance antibacterial strategies, inspiring further research and innovation.
Cell-cell adhesion is widely hypothesised to maintain cohesion within the long streams of follower cells that trail leader subpopulations during collective migration, including in neural crest cell migration, angiogenesis, and cancer cell invasion. Mathematically, non-local advection-diffusion equations provide the canonical continuum framework within which to study such adhesive cell-cell interactions. Here, we study a minimal model of leader-follower migration within this framework, in which leaders migrate at constant velocity while followers are attracted to leaders and to one another over a finite spatial interaction range. Numerical simulations reveal that, although the model can maintain small cohorts of travelling follower cells, the size of these cohorts is limited by the adhesive interaction lengthscale, and is far below what is needed to reproduce the extended streams observed in vivo. This points to a structural limitation of the standard non-local adhesion formulation and highlights the need for the development of extended continuum models capable of sustaining long, coherent migratory streams through purely mass-conserving collective cell movement.
Rxiv mechanobio
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