IMPACTING DROPS · Impact and rebound of liquid drops: from fundamental to technological aspects
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2006-02-01 → 2008-01-31
- EU contribution
- €167,664
- Participants
- 1
- Scheme
- EIF
Lines connect the coordinator with its partners.
Results in brief
Final Activity Report Summary - IMPACTING DROPS (Impact and rebound of liquid drops: from fundamental to technological aspects)
The project has yielded various results in the field of free surface flows, with direct impact for technological applications. First, we have explained a long-standing controversy on the dynamics of bubble pinch-off. This fundamental problem in singularities focuses on the final instances when an elongated bubble breaks up into two smaller bubbles. This breakup also happens for drop impact on a hydrophobic substrate, where it leads to the formation of violent jets. The fluid mechanical equations become singular at this point and existing experimental and numerical results disagreed on the precise dynamics. We developed a theory that shows that there is a universal dynamics, but that this regime is approached very slowly, explaining the apparent non-universal behaviour in the literature. Second, we found a new solution to the classical problem of dip-coating, a common technique to cover a thin film of liquid onto a hydrophobic surface. It has been thought since the work by Landau and Levich in the 1940s that the thickness of the coated film is uniquely determined by the speed of withdrawal of the solid. We found a new set of mathematical solutions that allow for a range of thicknesses. Our colleagues from the ESPCI in Paris have confirmed that these new films are easily generated experimentally, providing a way to obtain coatings that are much thicker than the Landau-Levich films. We furthermore showed how this coating is closely related to the stability of the moving contact line. Third, we studied drops that are levitated by an air cushion. The most famous realization of this phenomenon is encountered in the Leidenfrost-effect for which water drops can 'float' above a hot plate. This principle is also used in the production of lenses, where molten glass is cooled by an air cushion. We identified the mechanism of instability that is observed in these systems, which is particularly hindering the lens production. By computing for the first time the detailed shape of the drops, we found the critical volume at which drops become unstable.
Data: CORDIS, © European Union
Project objective
The goal of the project is to unravel fundamental aspects of the impact and rebound of liquid drops, a problem highly relevant to technological applications ranging from inkjet printing to deposition of pesticides on plant leaves.We develop a theoretical description of the singular small-scale structures that emerge upon impact, and numerical simulations of the dynamics on high-tech surfaces engineered for technological purposes. When a liquid drop hits a wall, it does not deform to a simple pancake-like structure, but instead exhibits a variety of remarkable morphologies.This drop subsequently retracts and often rebounds from the surface: for most applications this effect is extremely unwelcome. The dynamics and singular morphologies of impacting drops have only recently been characterized experimentally, while there exists no theory based on the underlying fluid mechanics.The problem brings together fundamental problems such as free surface flows, high Reynolds numbers and moving contact lines, and hence forms a theoretical challenge of timely interest. Revealing these fundamental mechanisms is extremely valuable for technological applications, which are often based on trial and error" solutions.The project will greatly contribute through numerical simulations of impact on micro-patterned substrates, such as "superhydrophobic" surfaces. This directly connects to cutting-edge experimental research via collaborations with the groups of Daniel Bonn (ENS), David Quere (College de France), and a recent major UK initiative on inkjet technology. The project thus provides a unique opportunity to combine recent advances in hydrodynamics with rapidly evolving technology-based research.For the applicant, the project allows to work with the pioneer of singularity research in fluid mechanics, within an international effort of leading European institutes. As such, the Fellowship provides a crucial step towards professional maturity."
Original text from CORDIS.
Participants
- UNIVERSITY OF BRISTOL · BRISTOL, CLIFTONCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union