PhD position: hydro-/morpho-dynamic instabilities of thin films on soluble rockbeds

Mission

We are offering a challenging position as a full-time (100%) PhD Student at the School of Engineering at EPFL, Lausanne. Our laboratory (LFMI) is focused on the study of hydrodynamic instability applied to separated flows, coaxial jets and droplet formation, as well as droplet-based microfluidics. You will be working on a SNSF-funded project whose goal is to understand the role of transient instabilities and nonlinearities in the formation of patterns in of spatially developing thin films on soluble rockbeds.

Thin film flows are omnipresent in both natural and industrial settings. Understanding the dynamics and stability of thin films is essential to technological applications such as nano-lithography. Recently, the natural regularity of coating flow has been exploited to design an inexpensive and rapid fabrication technique of hemispherical elastic shells. By coating a curved surface with a polymer solution, a nearly uniform shell is obtained, upon polymerization of the resulting thin film. The natural instabilities of these films can also be harnessed to produce well controlled soft lenses.

In the context of natural thin-film flows along soluble rock, the presence of a free surface may serve as a canvas to the formation of spectacular patterns. A viscous liquid layer on the underside of a horizontal plate, for example, destabilizes into an array of drops, which transforms into a comb of rivulets when the plate is inclined. Coupled to a deposition process, this hydrodynamic instability can imprint patterns in limestone caves. Reciprocally, dissolution is the sculptor of equally impressive patterns forming on upward-pointing rock faces with a remarkable regularity, rillenkarren. Open questions concern the pattern’s wavelength selection given environmental conditions but also the basic hydrodynamic and physical mechanisms behind the phenomenon. 

The rillenkarren formation falls within the general question of pattern formation and morphodynamics. Examples range from the hexagonal cells on salt lakes to the dendritic structure of snowflakes, suggesting the existence of robust mechanisms underpinning the genesis of such patterns. We will investigate the pattern forming role of the hydrodynamic instabilities of thin film coating flows coupled to the calcite dissolution in karst structures overrun by water flow.

The present project continues our past efforts to understand the role of transient instabilities and nonlinearities in the formation of anisotropic patterns in lubricating coating flows by focusing on two important but still unexplored facets : the non-parallelism of the flow and its rigorous coupling to substrate deformation. We will in particular analyze the origin of the anisotropy in the more complex case of flows above the substrate where inertia, streamwise diffusion of momentum and solute all matter equally. The suggested approach is a combination of numerical and analytical techniques, which shall allow to determine pattern selection in these spatially varying flows. The fundamental hypothesis to be investigated in this project is that nonparallel and nonlinear mechanisms govern pattern selection in these geomorphogenetic coating flows. Special care will be taken in exploiting depth-averaged models, wherever possible. Finally, we will strive to reconcile the competing views on rillenkarren formation by continuous film flow and discrete raindrop impacts dissolution.

Main duties and responsibilities

As a PhD Student, you will be expected to:

• Have full responsibility for your own dissertation
• Derive equation-based models
• Design, implement and execute numerical simulations
• Analyze and interpret results
• Write scientific articles for publication in peer-reviewed journals
• Present at international conferences
• Supervise student projects and basic administrative support

Profile

• A M.Sc. degree in the fields of Engineering, Physics or Applied Maths
• Good communication skills and willingness to work as part of a team
• Enthusiasm, scientific curiosity, eager to learn, good organizational skills, rigor
• High level of motivation for academic research work in general, and specfically for theoretical/numerical aspects of fluid mechanics
• Experience with flow stability, dynamical systems, weakly nonlinear analysis, reduced-order modeling, stochastic analysis, numerical methods, physico-chemistry, lubrication
  equations, etc.
• Fluency in English

We offer

• 4 years to complete your PhD with a competitive remuneration
• You will be part of the EDME doctoral program
• An opportunity to develop a scientific career in fluid mechanics
• A world-class research and training environment with access to state-of-the-art research facilities
• A multi-cultural and stimulating work environment
• Term of employment: 1-year fixed-term contract (CDD), renewable for 4 years

Informations

Only applications submitted through the online platform are considered. Your application should contain:

• Motivation Letter
• Detailed CV
• Contact information
• At least 2 references willing to write a recommendation letter. Letters of recommendation should be sent back by the same deadline

For more information, please contact: francois.gallaire@epfl.ch

CDD for 1 year, renewable for 4 years

If you are successful, you will need to enroll in one of the EPFL doctoral school programs. Please check this page for additional information. Please note that this is a separate application process necessary to be eligible to complete your PhD at EPFL.