Paper Number
VP71 

Session
Pre-recorded Flash Presentations (virtual)

Title
Drag on a spherical particle at the air-liquid interface: Interplay between compressibility, Marangoni flow and surface viscosities

Presentation Date and Time
All Week (Asynchronous) Any Time

Track / Room
Pre-recorded Presentation / Virtual

Authors (Click on name to view author profile)

  1. Pourali, Meisam (ETH Zürich)
  2. Kröger, Martin (ETH Zürich)
  3. Vermant, Jan (ETH Zurich, Materials Departement)
  4. Anderson, Patrick D. (Eindhoven University of Technology)
  5. Jaensson, Nick O. (Eindhoven University of Technology)

Author and Affiliation Lines (in printed abstract book)
Meisam Pourali1, Martin Kröger1, Jan Vermant1, Patrick D. Anderson2 and Nick O. Jaensson2
1ETH Zürich, Zürich, Switzerland; 2Eindhoven University of Technology, Eindhoven, The Netherlands

Speaker / Presenter 
Jaensson, Nick O.

Keywords
interfacial mobility; interfacial rheology

Text of Abstract
Particles at interfaces play an important role in a large range of industrial and biological processes. In the majority of these processes the interface is complex, i.e. it exhibits a position- and time- dependent surface tension and/or rheological interfacial stresses, where the latter are possibly deviatoric. Due to the coupling of the interface to the bulk and the intricate interplay between the different physical mechanisms that induce interfacial stress, understanding and predicting the flow dynamics of a particle translating at an interface is not trivial. We numerically investigate the dynamics of a spherical particle embedded symmetrically in a planar air-liquid interface. The interface is assumed to remain planar, and the particle translates tangentially to the interface. Moreover, the interface is endowed with a concentration-dependent surface tension and viscous stresses are added using the Boussinesq-Scriven model. The finite element method is employed to solve the fully coupled set of flow- and transport-equations. We first perform a thorough analysis of the role of mesh- and domain-size for an incompressible interface. We then systematically investigate the role of a non-uniform interfacial tension and interfacial viscosities, paying special attention to interfacial compressibility. For inviscid interfaces, the motion of the particle induces a gradient in surface concentration, which in turn drives a Marangoni flow in the opposite direction, increasing the drag on particle. Our numerical method allows simulations for a large range of Marangoni and Péclet numbers, and we show how these can induce incompressiblity of the interface. We then investigate the role of interfacial shear- and dilatational viscosities, and show how incompressibility of the interface can also be introduced by a large dilatational viscosity. Finally, we systematically investigate cross effects where both Marangoni stresses and interfacial viscosities play a role, and we elucidate their intricate coupling.