The breaking of a wave, the splashing of a drop in a myriad of droplets while impacting a solid surface, a bursting bubble are are fascinating problems of fluid mechanics with free surfaces. Indeed, the liquid is bounded by a moving surface whose determination is part of the problem. Thisincreases as much the mathematical difficulties of the solution. The team has developed an important experience in the numerical treatment of surface tracking well adapted to drops and bubbles. Thus, the numerical simulation of these problems is now possible: computational calculations allow a fair reproduction of the reality, so called "numerical experiments" can be performed, useful both for curiosity-driven and profit-driven science and engineering.
Free surface problems present manifold industrial applications as well as fundamental fluid-mechanical interest.
Atomisation processes involve the development of the instabilities at the interface of a high-speed jet. The combustion of liquid fuels requires their initial brekup into small droplets. Combustion technology thus providesa powerful incentive to study atomization. Injection devices present in both petrol and diesel car engines control the atomisation of fuels which then impact in a complex manner against the wall of the combustion chambers. This eventually determines the quality of the combustion, such as engine efficiency or pollution rate. We have therefore performed numerous calculations of atomisation.
Droplet impacts on solid or liquid surface has become a cultural icon. It is also an important issue in engineering. In agriculture, the penetration of rainwater depends strongly upon the humidity of the soil. Impact of aerosol drops, containing agricultural treatment products is also of considerable interest as well. In internal combustion engines, the rebound on combustion chamber or pipe walls disturbs the size of the droplets and changesthe combustion processes.
Bubble dynamics , has extremely varied applications, in power plant technology, chemical engineering, biology and oceanography. A striking observation discovered recently is sonoluminescence: when excited by strong acoustical waves, bubbles emits a brief light flash, visible to the naked eye. Bubbles oscillations rely in fact to numerous fundamental problems: stability of oscillating bubbles, jet formation in a cavity for instance. They concern meanwhile other applications such as damaging of hydraulic circuit or turbine vanes by cavitation.