• Sujet encadré par GautierVerhille (IRPHE) & HenriLhuissier (IUSTI)

This project tackles the challenging problem of the turbulent mixing of liquids with non uniform viscosity. It will focus on the idealized case of the mixing of an initially spherical blob, which is more viscous than the surrounding fluid, in a uniform isotropic turbulent flow. The objective is to understand (1) the history of the blob deformation, (2) the mixing time, (3) the mechanisms and dependences of the process on the relevant parameters: viscosity ratio between the blob and the flow (⌫/⌫0), Reynolds number of the flow (ReT), blob size relative to the flow (Kolmogorov) microscale (d/`K), and relative mass di↵usivity (inverse Schmidt number D/⌫0). The project launches a new collaboration between IRPH´ E (G.Verhille) and IUSTI (H.Lhuissier). It will leverage on the experimental facilities and expertise of IRPH´ E on turbulent flows, and on the model materials and expertise of IUSTI on laminar heteroge neous flows, to tackle an essentially unexplored field of research.

 The project will benefit from the experience and involvement of the high-level postdoc candidate, Julie Deleuze, on mixing in non-uniform high-Reynolds number flows.

• Sujet encadré par Bruno LOMBARD (LMA)

By structuring materials, it is possible to control waves and obtain surprising effects: high-resolution lenses, directional antennas, invisibility cloaks, etc. This is the paradigm of metamaterials, a field of research that has been very active since the early 2000s and which promises many technological developments, for example improving Wi-Fi coverage or insulating buildings against seismic waves. However, the properties accessible with these materials also have limits, given by the usual laws of physics. Reciprocity is one of these laws [4]. In the linear regime and without flow, a wave transmitted between two points remains the same when the source and receiver are interchanged. Breaking the reciprocity makes it possible to control the waves in a novel way by making directional band gaps possible. Applications include wave filtering, diode design and logic gates in elastodynamics.(...)

• Sujet encadré par Martin BRANDENBOURGER (IRPHE) & Joel MARTHELOT (IUSTI)

Inspired by nature, pneumatic soft robots use vascular networks and external pumps to twist, deform, move and bend in ways that traditional hard robots cannot. So far, these soft robots lack autonomy compared to organisms, which control fluid transport in vascular networks in much more advanced ways. From animals to fungi, one of the most efficient fluid transport mechanism is based on vessels that can actively contract upon local sensing of stimuli. This adaptative fluid transport enables advanced functionalities in organisms such as autonomous locomotion toward objectives. The main goal of the proposed research is to design self-contracting vascular networks to study active solids that deform upon sensing.(...)

• Sujet encadré par Carine GUIVIER-CURIEN (IRPHE), Cécile BARON (IRPHE), Philippe LASAYGUES (LMA)

Bone is a mechanosensitive living tissue subjected to constant remodeling in response to mechanical constraints. Bone remodeling is a skillful balance between the action of bone-forming cells (osteoblasts), and bone-resorbing cells (osteoclasts) orchestrated by bone-mechanosensing cells (osteocytes). However, this natural process is insufficient to address numerous bone disorders such as complex bone fracture or bone cancer, in which bone reconstruction must be assisted. As mechanical waves, ultrasound can provide additional local mechanical stimulation and potentially restore the balance of bone remodeling. (...)