BRIEF:
Numerous industrial and environmental processes involve complex fluids, flowing in conditions where heat, mass, or momentum transport need to be optimized. Examples include bioprocesses, agri-food, pharmaceutical, advanced material, or microfluidic technology sectors. When properly harnessed, hydrodynamic instabilities can generate spatiotemporal flow structures that substantially enhance mixing, scalar transport, and transfer rates, thereby improving the performance of reaction, cultivation, separation, and transfer processes.
However, the non-Newtonian behaviour of these fluids profoundly modifies the nature, onset, structure, and dynamics of flow instabilities [1], [2], making their prediction and control particularly challenging. As a result, the relationship between flow physics, mixing efficiency, and transfer performance remains insufficiently understood [3]. Addressing these challenges requires access to spatially and temporally resolved measurements of both flow and scalar fields, which can be obtained through advanced optical diagnostic techniques [4], [5], [6].
Owing to its simple and well-controlled geometry, combined with a remarkable diversity of instability mechanisms, the Taylor–Couette flow (flow generated between two concentric cylinders rotating independently) constitutes an ideal model system for investigating the links between hydrodynamic instabilities, transport phenomena, and mixing efficiency in complex fluids [2], [5], [7], while enabling the development and application of state-of-the-art optical characterization methods.
The general objectives of this postdoctoral project are to
- Develop and implement cutting edge optical methods (e.g., Laser Induced Fluorescence – see figure 1) to probe mixing dynamics and local flow properties
- Use those methods to study instabilities, flow structure, and mixing in TC flow of non-Newtonian fluids
[1] S. S. Datta et al., « Perspectives on viscoelastic flow instabilities and elastic turbulence », Phys Rev Fluids, vol. 7, no 8, p. 080701, août 2022, doi: 10.1103/PhysRevFluids.7.080701.
[2] M. A. Fardin, C. Perge, et N. Taberlet, « “The hydrogen atom of fluid dynamics” – introduction to the Taylor–Couette flow for soft matter scientists », Soft Matter, vol. 10, no 20, p. 3523‑3535, avr. 2014, doi: 10.1039/C3SM52828F.
[3] T. Burghelea et V. Bertola, Transport Phenomena in Complex Fluids, 1st ed. 2020 édition. Cham: Springer Nature Switzerland AG, 2020.
[4] C. Carré, T. Lacassagne, N. E. Hani, et S. A. Bahrani, « Mixing efficiency in Taylor-Couette flow of complex suspensions », Exp. Fluids, vol. 67, no 3, p. 30, mars 2026, doi: 10.1007/s00348-026-04187-1.
[5] T. Boulafentis, T. Lacassagne, N. Cagney, et S. Balabani, « Experimental insights into elasto-inertial transitions in Taylor–Couette flows », Philos. Trans. R. Soc. Math. Phys. Eng. Sci., vol. 381, no 2243, p. 20220131, janv. 2023, doi: 10.1098/rsta.2022.0131.
[6] T. Boulafentis, T. Lacassagne, N. Cagney, et S. Balabani, « Coherent structures of elastoinertial instabilities in Taylor–Couette flows », J. Fluid Mech., vol. 986, p. A27, mai 2024, doi: 10.1017/jfm.2024.163.
[7] C. Kang et P. Mirbod, « Flow instability and transitions in Taylor–Couette flow of a semidilute non-colloidal suspension », J. Fluid Mech., vol. 916, juin 2021, doi: 10.1017/jfm.2021.75.
