Study Reveals How Porous Walls Alter Stability of Particle-Laden Flows
Researchers have conducted a three-dimensional linear stability analysis of particle-laden Couette-Poiseuille flow between parallel plates, where one wall is coated with a porous medium. The study finds that porous boundaries introduce a permeability-dependent destabilizing mechanism that overrides classical stability trends seen in flows over solid walls. These results have implications for engineering and industrial systems involving particle suspensions flowing over or through porous substrates.
A new preprint posted to arXiv examines how a porous lower wall affects the stability of Couette-Poiseuille flow carrying suspended particles in a Newtonian fluid. Using a two-domain formulation, the researchers modeled the particle-laden suspension with the dusty-gas framework and the porous layer with volume-averaged Navier-Stokes equations, keeping particles confined to the fluid region. A key finding is that while particle inertia can either stabilize or destabilize flow over impermeable walls depending on parameters, the addition of a porous layer introduces a permeability-driven destabilizing effect that can lower the critical Reynolds number even when particles would otherwise stabilize the flow. The analysis also reveals new disturbance branches arising from fluid-particle coupling near the permeable interface; these modes remain stable but reshape the eigenspectrum and influence which instability dominates. Additionally, the study shows that increasing the Couette (wall-driven) component of the flow, which typically stabilizes impermeable-wall configurations, instead monotonically decreases the critical Reynolds number in the porous-wall case. Collectively, the results demonstrate that porous boundaries can qualitatively change established stability behavior in particle-laden shear flows.
What's missing
The study is a theoretical linear stability analysis and does not include experimental validation or direct numerical simulations to confirm the predicted instability thresholds. The dusty-gas framework assumes dilute suspensions and point-like particles, which may limit applicability to denser or finite-size particle systems.
What different sources said
- arXiv physicsCenter
Linear stability analysis of particle-laden Couette-Poiseuille flows: effect of porous walls
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