Soft Matter and Complex Systems Seminar
2006/2007 | 2007/2008 | 2008/2009 | 2009/2010 | 2010/2011 | 2011/2012 | 2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025 | 2025/2026
2025-12-05 (Piątek)
Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 09:30 
Antoine Sellier (LadHyX, Ecole Polytechnique, Palaiseau, France)Stokes flow about a collection of slip solid bodies
A boundary efficient and accurate method is proposed and numerically worked out to calculate, in the creeping flow regime, the resistance matrix of a cluster made of N arbitrarily-shaped slip solid bodies. The slip on each body curved surface is modeled using the widely-employed Navier slip condition and there is no restriction on the number N of bodies. Moreover, the task reduces to the treatment of 6N boundary-integral equations on the cluster surface and it is no use calculating the Stokes flow about the moving particles. Comparisons with the literature for one sphere (singularity method) and for two-interacting spheres (multipole method) will be presented. Finally, some numerical results for slip ellipsoids and the gravity-driven motion of two slip interacting spheres will be given and discussed.
2025-11-07 (Piątek)
Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 09:30
Tomasz Szawełło (IFT UW)Diffusive transport in network models of dissolution in porous media
Dissolution in porous media emerges from the interplay of fluid flow, reactant transport, chemical reactions, and evolving structure. Reactant transport combines advection and diffusion: advection promotes channeling instabilities, whereas diffusion stabilizes fronts. Pore network models provide an efficient framework to simulate dissolution, but often assume advection-dominated axial transport in pores—an assumption frequently violated in natural and industrial systems such as groundwater flows or catalytic reactors.
In this seminar I first motivate the need to include axial diffusion in pore network models and derive the classical Graetz solution for advection–reaction in a cylindrical pore with reactive walls. I next show how retaining axial diffusion modifies the solution structure, inducing additional dependence on Damköhler and Péclet numbers. Building on this, I present a solution to the 1D advection–diffusion–reaction problem for pores in the network that incorporates axial diffusion. Finally, I map dissolution outcomes on Damköhler–Péclet phase diagrams, highlighting transitions in morphology and comparing them with laboratory benchmarks.
In this seminar I first motivate the need to include axial diffusion in pore network models and derive the classical Graetz solution for advection–reaction in a cylindrical pore with reactive walls. I next show how retaining axial diffusion modifies the solution structure, inducing additional dependence on Damköhler and Péclet numbers. Building on this, I present a solution to the 1D advection–diffusion–reaction problem for pores in the network that incorporates axial diffusion. Finally, I map dissolution outcomes on Damköhler–Péclet phase diagrams, highlighting transitions in morphology and comparing them with laboratory benchmarks.
2025-10-24 (Piątek)
Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 09:30
Akash Unnikrishnan (IFT UW)Taylor-Couette flow: from table-top experiments to planetary patterns
The Taylor-Couette system-the flow between two concentric rotating cylinders, has served as a model problem for studying flow instabilities and transitions to turbulence. In the first part of this seminar, I will briefly trace its historical importance and discuss how simple variations in rotation rates and geometry give rise to a hierarchy of flow states, from steady Taylor vortices to complex wavy and turbulent regimes. Extending the problem to non-circular enclosures introduces additional confinement effects and even Moffatt-like vortices, enriching the dynamics further.
In the second part, I will outline how meshless numerical methods can be employed to simulate such flows efficiently without requiring structured grids. Finally, I will present results from simulations, some using these meshless methods, that exhibit vortex patterns, including one reminiscent of the hexagonal jet observed in Saturn’s atmosphere. While not being an exact planetary model, the similarity highlights the universality of pattern-forming mechanisms in rotating shear-driven flows.
In the second part, I will outline how meshless numerical methods can be employed to simulate such flows efficiently without requiring structured grids. Finally, I will present results from simulations, some using these meshless methods, that exhibit vortex patterns, including one reminiscent of the hexagonal jet observed in Saturn’s atmosphere. While not being an exact planetary model, the similarity highlights the universality of pattern-forming mechanisms in rotating shear-driven flows.
2025-10-17 (Piątek)
Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 09:30
Jenna Poonoosamy (Forschungszentrum Jülich)Deciphering interface coupled mineral dissolution and precipitation processes: experiments and modelling
Interface-coupled dissolution and precipitation (ICDP) processes control the evolution of reactive mineral/fluid systems in many subsurface environments, from CO₂ sequestration and concrete carbonation to steel corrosion in nuclear waste repositories and natural hydrogen generation. ICDP involves the dissolution of a primary mineral and the precipitation of a secondary phase directly on its surface, forming a rim. This rim may facilitate complete replacement of the parent phase or lead to passivation or mineral armoring. Despite its importance, the mechanisms governing mineral passivation and the fate of co-evolving gas phases remain poorly understood.
To address these gaps, we combined controlled column and microfluidic experiments with advanced microstructural characterization and pore-scale modelling. Using a model system which is redox- and pH-insensitive with the primary mineral celestine (SrSO4) covered with secondary barite (BaSO4), we quantified the role of barite nucleation dynamics, barite porosity, and the heterogeneity of celestine surface reactivity in driving mineral armoring. Three-dimensional FIB-SEM and HAADF-STEM analyses revealed nanoporosity in the secondary barite rim, while microfluidic experiments coupled with in-situ Raman and AFM imaging demonstrated how spatial variations in surface reactivity govern localized dissolution–precipitation patterns. Pore-scale modelling further showed that selective ion diffusion and electric double layer effects contribute to mineral passivation.
We extended this framework to ICDP systems involving gas generation. Using witherite (BaCO3) dissolution in sulfate-rich acidic solutions, we observed that the concomitant precipitation of barite and CO₂ exsolution forms distinctive “cauliflower-like”, mineral precipitates encrusting gas bubbles. These textures arise from electrostatic enrichment of ions around gas bubbles, promoting barite nucleation and trapping water droplets within mineral shells. When precipitation outpaces dissolution, these structures inhibit further mineral reaction and clog pore spaces, potentially impeding CO₂ storage, hydrogen recovery, and metal corrosion processes.
Together, our results reveal the coupled roles of surface chemistry, microstructure, and fluid dynamics in controlling ICDP kinetics and the evolution of reactive interfaces, key to predicting the long-term reactivity and permeability of subsurface systems.
To address these gaps, we combined controlled column and microfluidic experiments with advanced microstructural characterization and pore-scale modelling. Using a model system which is redox- and pH-insensitive with the primary mineral celestine (SrSO4) covered with secondary barite (BaSO4), we quantified the role of barite nucleation dynamics, barite porosity, and the heterogeneity of celestine surface reactivity in driving mineral armoring. Three-dimensional FIB-SEM and HAADF-STEM analyses revealed nanoporosity in the secondary barite rim, while microfluidic experiments coupled with in-situ Raman and AFM imaging demonstrated how spatial variations in surface reactivity govern localized dissolution–precipitation patterns. Pore-scale modelling further showed that selective ion diffusion and electric double layer effects contribute to mineral passivation.
We extended this framework to ICDP systems involving gas generation. Using witherite (BaCO3) dissolution in sulfate-rich acidic solutions, we observed that the concomitant precipitation of barite and CO₂ exsolution forms distinctive “cauliflower-like”, mineral precipitates encrusting gas bubbles. These textures arise from electrostatic enrichment of ions around gas bubbles, promoting barite nucleation and trapping water droplets within mineral shells. When precipitation outpaces dissolution, these structures inhibit further mineral reaction and clog pore spaces, potentially impeding CO₂ storage, hydrogen recovery, and metal corrosion processes.
Together, our results reveal the coupled roles of surface chemistry, microstructure, and fluid dynamics in controlling ICDP kinetics and the evolution of reactive interfaces, key to predicting the long-term reactivity and permeability of subsurface systems.
2025-10-03 (Piątek)
Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 09:30
Jordan Orchard (IFT UW)Anomalous diffusion in billiard channels
Polygonal billiard channels are examples of pseudo-chaotic dynamics, a combination of integrable evolution and sudden jumps due to singular points that arise from the corners of the polygon. Such pseudo-chaotic behaviour, often characterised by an algebraic separation of nearby trajectories, is believed to be linked to the wild dependence that particle transport has on billiard geometry. Borrowing ideas from the Zemlyakov-Katok construction, we derive an exact expression of a scattering map of the cell connecting the outgoing flow of trajectories to the unconstrained incoming flow.