Investigating turbulent fluid flow and granular mechanics in rivers from laboratory seismic monitoring

Laboratoire(s) de rattachement : IGE

Encadrant : Florent Gimbert

Co-encadrant : Alain Recking (IRSTEA) et Philippe Frey (IRSTEA)

Niveau de formation & pré-requis : We seek for a student with good background in fluid mechanics or Earth science or granular physics, and with a strong interest in solving physical problems based on designing dedicated laboratory and field experiments. The student should also have the motivation to pursue as a PhD, since this internship is directly linked to a follow up as a Ph.D.

Pre-requisite : an excellent academic level, a good English level and a programming experience (matlab, python, …).

Mots-clés : experiments ; river physics ; seismology

Possible follow-up for a Ph.D. in the context of the ANR SEISMORIV* project (funding acquired).

By eroding the Earth’s crust, rivers set the pace at which mountain landscapes evolve. Fundamental processes such as turbulent fluid flow and granular sediment transport exert key control on fluvial erosion, but remain poorly constrained at the natural scale due to lacking observations. Interestingly, turbulent flow and granular solid transport generate seismic waves, such that seismic monitoring near rivers may be used as a particularly innovative technique to provide new physical constraints on these processes, and thus on fluvial erosion !
Over the past decade, numerous international research teams have demonstrated the potential of monitoring rivers seismically. First order physical models have been proposed to relate the physics of turbulent fluid flow and bedload sediment transport to the seismic signal (Tsai et al., 2012 ; Gimbert et al., 2014 ; Gimbert et al., 2018). Those models combined with dedicated observations have allowed unique characterization of river flow physics during catastrophic floods where no other technique could be used (e.g., Cook et al., 2018). However, there remains numerous open questions related to how far the seismic technique can be pushed to document the full picture of river flow physics and to invert useful river flow physical characteristics with acceptable accuracy.
The objective of this master project is to answer some of those questions by conducting laboratory flume experiments with dedicated monitoring at the micro (grain) and macro (seismic) scale. Varying turbulent fluid flow and sediment transport conditions will be investigated, along with changes in the seismic signal caused by changes in river flow physics. Specific targets will include testing existing theories when sediment transport transitions from a dilute to a highly concentrated flow, or when flow turbulence is strengthened through increasing discharge. We will also test the feasibility of using multiple sensors (a dozen) to infer the spatio-temporal intermittency of turbulent and granular flow transport. Finally, we will investigate how other river sources may affect the signal, such as for example cavitation or sound waves generated in the water column.
Work on this topic may be pursued by the applicant through a PhD thesis (funding is already secured in the context of the ANR SEISMORIV project*). The Ph.D. project will take place in the continuity of the present master project, although it will add to it field investigations based on data already being acquired in strategic places around the world (French Alps, Nepal, Taiwan, La Reunion, United States), and theoretical developments to further interpret and/or better make use of seismic observations in a fluvial context.

* For more information on the ANR SEISMORIV project, please refer to : http://www.agence-nationale-recherche.fr/Project-ANR-17-CE01-0008

Pour candidater : Adresser un CV et une lettre de motivation par email à l’adresse ci-dessous :
florent.gimbert univ-grenoble-alpes.fr