Moulay Saïd El Youssoufi researcher at LMGC, University of Montpellier.
Published the 15/10/2018 at 08:37
Changed the 17/10/2018 at 06:59
Sciences and techniques, Montpellier, france
Professor El Youssoufi is a specialist in mechanics of soil non-saturated with water.
Who is there in common between the Salins of Aigues-Mortes, the weightlessness and the LMGC, University of Montpellier (Laboratory of mechanics and civil engineering) ? To schematize, we could say : the professor Moulay Saïd El Youssoufi.
This researcher, “specialist in géomatériaux”, as he defines himself, is studying within the LMGC, the reactions of the soil non-saturated with water (sand, for example), the subject of “the complex demands on the plan thermal, mechanical and water”. The aim of these experiments is to investigate at microscopic level the behaviour of these environments subject to the variations of stresses mentioned above.
The impact block of sand
Everyone has experienced in his youth. It is impossible to make a block of sand that stands with sand sec. By hand, adding a little water, no problem, the block becomes consistent. What creates this physical consistency induced by the presence of water, these are the forces generated by the capillary action.
In soil not saturated with water, it is the capillary action is at work : “as Soon as we add a little water to this type of environment, a change in the internal stresses. The bridges capillaries generated between the grains exert then forces that provide the cohesion of the community,” says the researcher.
Then, in a second time, to extrapolate the mechanical behavior at the macroscopic level to develop simulation software. Examples of applications ? The modeling of avalanches, landslides, flow of grain into a silo, etc., But one of the applications, the most telling, for the common man, for the pellets of salt for water softeners.
Developed since the 90s by the Salins of Aigues-Mortes, in collaboration with LMGC, “the quality of a pellet of salt lies in its resistance. It should not crumble when in contact with water as it may clog filters and pipes”. Thanks to the results of its research, the team of the laboratoire montpelliérain was “capable of accurately determining the granularity, water content and the pressure to be applied to produce each dot according to the criteria of quality required”.
And weightlessness in all of this ? For Moulay Saïd El Youssoufi, the fact of being in zero gravity “allows you to validate the models of computer simulation developed in collaboration with the Asia (Laboratory of engineering sciences for the environment of La Rochelle) and that does not take into account the earth’s gravity”.
A first campaign of flight experiment has been performed in 2015, in the aircraft zero G the Cnes (Centre national d’études spatiales). A necessity, because, according to the researcher, this avoids the need to perform experiments with very small distances between the granular particles and water volumes significantly reduced”. The experimental conditions that walking away researchers “of the actual conditions of the study materials and soil”.
In 2015, the first campaign of experimentation in weightlessness has enabled us to verify the relevance of the models developed”. The flight campaign of 2017 helped to refine the results. And after the resolution of some problems, the new campaign is to be conducted in the spring of 2019.
To find himself in weightlessness (zero gravity ), there is no need to mount it in the ISS as the French astronaut Thomas Pesquet. Since 1988, the Cnes (national space studies Centre), with its plane of zero G, the scientists carry out their experiments in a “state of weightlessness”.
An Airbus A310 performs during each flight thirty of the trajectories are parabolic. During those portions of the flights, in the shape of a bell, scientists, and their experiments are in complete weightlessness, during 22 seconds. It is short, but sufficient to validate a number of scientific experiments, including those of the LMGC.