ORGANISATION/COMPANYUniversité Gustave Eiffel
RESEARCHER PROFILEFirst Stage Researcher (R1)
APPLICATION DEADLINE21/03/2022 17:00 - Europe/Brussels
LOCATIONFrance › Nantes
TYPE OF CONTRACTTemporary
HOURS PER WEEK35
OFFER STARTING DATE01/10/2022
EU RESEARCH FRAMEWORK PROGRAMMEH2020 / Marie Skłodowska-Curie Actions COFUND
MARIE CURIE GRANT AGREEMENT NUMBER101034248
Context. Granular materials (powders, grains) are ubiquitous in industrial processes but often problematic to handle as they are intrinsically polydisperse in size and composition. This intrinsic polydispersity may induce selective spatial transport according to particle size and other particle properties. This phenomenon, commonly referred to as segregation, is very problematic for process control, and is one of the main reasons for which processes associated to granular flows are often characterized by excessive energy and resource demands.
As a first example of an industrial process relevant for the sustainable city, the biomass gasification by means of fluidized beds has become one of the most reliable and sustainable processes to produce energy, thanks to the low-impact by-products developed during the process. For this reason, many countries have recently decided to invest on this particular technology. Being able to optimize solid-fuel conversion systems entails the capability to correctly model the particle motion under the fluidization regime. Although fluidized beds for gasification purposes have been widely studied from the chemical and thermal points of view, their fluid dynamic behaviour is still partially unknown.
Another example is the recycling of Construction and Demolition Waste (C&DW) that accounts for nearly 30% of all EU waste. As a result, C&DW is one of the priority waste streams in the EU, as detailed in the Waste Framework Directive. Recycling requires to sort of the types of materials present in the building (e.g. plaster, concrete, wood…). Better understanding particle transport in, polydisperse systems will lead to a better optimization of the latter sorting process and improve the efficiency of C&DW recycling.
This PhD thesis offer is addressed to the theoretical and experimental analysis of the particle motion and of the segregation problem in industrial processes (reactors, mixers, recycling equipment), with the goal of controlling segregation phenomena and maximizing the process efficiency. This project is part of an ongoing international collaboration between two laboratories, which has started on the determination of diffusion terms for segregation models (Artoni et al, 2021).
For investigating the particle scale phenomena, the project will profit from the use of discrete element models (DEM) for the numerical simulation of granular materials. These methods, originating from the work of Cundall & Strack (1979), are numerical techniques in which a granular medium is simulated as a collection of distinct individuals interacting through laws accounting for impenetrability of matter, friction, cohesion, etc. They are necessary for tracking the micro-macro relation, due to the possibility of obtaining particle-level information, which can be coarse grained to obtain continuum like constitutive laws. DEM simulations of polydisperse materials will be carried out first in a gravity-free homogeneous shear configuration (in order to quantify the local rheology), then in a flow configuration with gravity. The latter simulations will allow to quantify diffusive and segregating fluxes as a function of shear, pressure, and particle size. The relation between self diffusion and gradient diffusion in homogeneous and heterogeneous granular flows will be particularly addressed from the theoretical and numerical point of view.
For investigating process scale phenomena, the PhD thesis will mobilize the expertise of both research groups on the experimental analysis of confined 3D flows of polydisperse systems. For UGE, an annular shear cell (Artoni et al. (2018)) will be used to study flow profiles of polydisperse granular materials and will be equipped by torque sensors and multi-axis wall force sensors. At UniBZ, two distinct fluidization cells will be employed: the first one using a gas as interstitial fluid and polydisperse sediments, which will be imaged through the transparent sidewall using a set of synchronized high-speed cameras. Particle Tracking Velocimetry (PTV) developed with the participation of the research group (Spinewine et al. 2003, 2011) will allow velocity, velocity fluctuations (granular temperature) and solid fraction measurements and permit a comparison with the results of DEM simulations and with the predictions of kinetic theory, which provides a physically based framework for understanding granular segregation (Larcher & Jenkins 2015). In the second reactor bi-disperse transparent particles will be used in combination with a liquid interstitial fluid, matching the refractive index of the particles. In this way it will be possible to use the high-speed cameras together with a laser source in order to measure particle motion also in the interior of the reactor, while Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) will be used to measure the fluid flow.
The experimental and numerical investigation on the coupling between size segregation and the flow rheology performed during this PhD thesis will allow the two research groups to construct models for spatial transport of polydisperse granular materials, which will be applicable to the optimization of industrial processes, with a particular attention towards solid-fuel conversion systems and technologies for the recycling of construction and demolition waste.
Artoni, R., Soligo, A., Paul, J. M., & Richard, P. (2018). Shear localization and wall friction in confined dense granular flows. Journal of Fluid Mechanics, 849, 395-418.
Artoni, R., Larcher, M., Jenkins, J. T., & Richard, P. (2021). Self-diffusion scalings in dense granular flows. Soft Matter, 17(9), 2596-2602.
Cundall, P. A., & Strack, O. D. (1979). A discrete numerical model for granular assemblies. geotechnique, 29(1), 47-65.
Larcher, M., Jenkins, J.T. (2015). The evolution of segregation in dense inclined flows of binary mixtures
of spheres. Journal of Fluid Mechanics, 782, 405-429.
Spinewine, B., Capart, H., Fraccarollo, L., Larcher, M. (2011). Laser stripe measurements of near-wall solid fraction in channel flows of liquid-granular mixtures. Experiments in Fluids, 50(6), 1507-1525.
Spinewine, B., Capart, H., Larcher, M., Zech, Y. (2003). Three-dimensional Voronoï imaging methods for the measurement of near-wall particulate flows. Experiments in Fluids, 34, 227-241."
This thesis will be in cosupervision with Free University of Bolzano, Faculty of Science and Technology (Italy). For more information, contact the PhD thesis supervisor.
- High-quality doctoral training rewarded by a PhD degree, delivered by Université Gustave Eiffel
- Access to cutting-edge infrastructures for research & innovation.
- Appointment for a period of 36 months based on a salary of 2 700 € (gross salary per month).
- Job contract under the French labour legislation in force, respecting health and safety, and social security: 35 hours per week contract, 25 days of annual leave per year.
- International mobility will be mandatory
- An international environment supported by the adherence to the European Charter & Code.
- Access to dedicated CLEAR-Doc trainings with a strong interdisciplinary focus, together with a Career development Plan.
- At the time of the deadline, applicants must be in possession or finalizing their Master’s degree or equivalent/postgraduate degree. At the time of recruitment, applicants must be in possession of their Master’s degree or equivalent/postgraduate degree which would formally entitle to embark on a doctorate.
At the time of the deadline, applicants must be in the first four years (full-time equivalent research experience) of their research career (career breaks excluded) and not yet been awarded a doctoral degree. Career breaks refer to periods of time where the candidate was not active in research, regardless of his/her employment status (sick leave, maternity leave etc). Short stays such as holidays and/or compulsory national service are not taken into account.
At the time of the deadline, applicants must not have resided or carried out their main activity (work, studies, etc.) in France for more than 12 months in the 3 years immediately prior to the call deadline.
Applicants must be available to start the programme on schedule (around 1st October 2022).
- Please refer to the Guide for Applicants available on the CLEAR-Doc website.
- The First step before applying is contacting the PhD supervisor. You will not be able to apply without an acceptation letter from the PhD supervisor.
- Please contact the PhD supervisor for any additional detail on job offer.
- There are no restrictions concerning the age, gender or nationality of the candidates. Applicants with career breaks or variations in the chronological sequence of their career, with mobility experience or with interdisciplinary background or private sector experience are welcome to apply.
- Support service is available during every step of the application process by email: firstname.lastname@example.org
Web site for additional job details
REQUIRED EDUCATION LEVELPhysics: Master Degree or equivalentChemistry: Master Degree or equivalentMathematics: Master Degree or equivalentEngineering: Master Degree or equivalent
REQUIRED LANGUAGESENGLISH: ExcellentFRENCH: Good
- At the time of the deadline, applicants must be in possession or finalizing their Master’s degree or equivalent/postgraduate degree.
- At the time of recruitment, applicants must be in possession of their Master’s degree or equivalent/postgraduate degree which would formally entitle to embark on a doctorate.
- Applicants should hold a degree of Master in Physics, energy engineering, mechanical engineering, chemical engineering, civil engineering or applied mathematics.
EURAXESS offer ID: 716908
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