Boiling is a process widely used in industrial and scientific applications to 
promote heat transfer because of high heat transfer coefficients associated to 
the phase change. It can be mentioned, for instance, the heat exchangers in 
nuclear power reactors. Safety and design guidelines of such equipment rely on 
the fundamental understanding of heat transfer and fluid mechanics phenomena 
that occur near the heating wall where the bubbles grow. In particular, we are 
interested in the wall drying (i.e. triple liquid-vapor-solid contact line 
dynamics) which is a key phenomenon to understand the boiling crisis. Another 
feature of interest is a formation of a few microns thick liquid layer (named 
``microlayer'') between the wall and the liquid-vapor interface of the bubble. 
The microlayer is a desired feature in boiling-based equipment. It acts as a 
heat transfer bridge, allowing a heat flux in the order of MW/m2 to be 
transferred from the wall to the liquid-vapor interface, promoting an efficient 
cooling of the wall. The microlayer contribution to the overall bubble growth 
can be up to 50%. The dynamics of microlayer and dry spots and the related heat 
transfer phenomena are therefore an active research topic within the boiling 
community.

At the Paris-Saclay center of the French Alternative Energies and Atomic Energy 
Commission, STMF (French abbreviation for Division of thermal hydraulics and 
fluid mechanics) experiments performed at the recently developed installation 
``Dynabulle''. It employs novel optical techniques (fast and synchronized 
shadowgraphy, white light interferometry and infra-red thermography, IRT) to 
investigate the single bubble growth under different conditions of surface 
properties, input power and subcooling. In particular, IRT allows us to obtain 
the data on the temperature distribution over the heater wall. From this data, 
one can reconstruct, among other things, the heat flux distribution over the 
wall by using the temperature as a boundary condition [1]. To solve the 
transient heat conduction in the solid, the TrioCFD open source code (used 
extensively at STMF) is employed. Such a problem is however ill-posed 
mathematically and should be regularized [2]. The postdoc will collaborate with 
both the simulation and experimental groups to couple the regularization 
algorithm with TrioCFD and process the experimental data. The submission of one 
or two scientific papers within the postdoctoral period is expected.

The expertize in C++ (TrioCFD is the object oriented code), and knowledge of 
inverse problems is required.

References
[1] C. Tecchio, Experimental study of boiling: characterization of near-wall 
phenomena and bubble
dynamics, Ph.D. thesis, Paris-Saclay University, 2022. URL: 
https://theses.hal.science/tel-03859592.
[2] L. Cattani, F. Bozzoli, V. Ayel, C. Romestant, Y. Bertin, Experimental 
estimation of the local
heat transfer coefficient for thin liquid film evaporation in a capillary tube, 
Appl. Therm. Eng.
219 (2023) 119482. doi:10.1016/j.applthermaleng.2022.119482.