Thèse Etude de la Croissance d'Une Bulle de Vapeur en Microgravité H/F - Doctorat.Gouv.Fr

Établissement : Institut National Polytechnique de Toulouse École doctorale : MEGEP - Mécanique, Energétique, Génie civil, Procédés Laboratoire de recherche : IMFT - Institut de Mécanique des Fluides de Toulouse Direction de la thèse : Catherine COLIN ORCID 0000000199859488 Début de la thèse : 2027-10-01 Date limite de candidature : 2026-11-23T23:59:59 Boiling liquid-vapor flows are encountered in a wide range of industrial applications, including steam generation in nuclear power plants, cooling of electronic components, and thermal management systems such as heat pumps and air-conditioning systems. Boiling liquid-vapor flows are also present in space applications, for example in two-phase flow loops used to cool electronic equipment in telecommunications and Earth observation satellites. In space launch vehicles, cryogenic tanks are exposed to solar radiation, which can induce boiling inside the tanks and lead to overpressure, requiring venting to maintain safe operating conditions. The limited understanding of boiling physics under microgravity conditions remains a major obstacle to the development of space technologies, particularly in the context of space exploration.
Understanding boiling under microgravity conditions is the primary objective of the Multiscale Boiling Experiment (RUBI), which was conducted aboard the International Space Station between 2019 and 2021. A large experimental database was collected and can be used to validate theoretical models and numerical simulations. Improving modelling and numerical simulation tools is a key challenge for the development of future space technologies.
To investigate boiling on isolated bubbles using advanced diagnostic techniques, the Multiscale Boiling (RUBI) experiment was developed over more than a decade by several European research teams within the framework of the ESA BOILING project. The experiment was operated aboard the International Space Station (ISS) between 2019 and 2021. Experiments were conducted on an isolated nucleation site under pool boiling conditions, as well as in the presence of external forces induced by an electric field and/or a shear flow. Side-view visualization was performed using a high-speed black-and-white (BW) camera operating at 500 fps (frames per second) to capture bubble growth and departure. A high-speed, high-resolution infrared (IR) camera was also used to record the temporal and spatial evolution of the wall temperature and compute the heat flux at the bubble foot on the heater surface.
The PhD project will be carried out under the joint supervision of Univ. Toulouse IMFT and TU Darmstadt. Both institutions have extensive expertise in experiments, modelling and direct numerical simulation of boiling. Both teams have actively contributed in the development of the RUBI experiment, participated in monitoring the experiments in orbit and post-process the data.
The PHD thesis will be devoted to the analysis and modelling of the bubble dynamics and heat transfer in a shear flow. Unlike in pool boiling (in stagnant liquid), in flow boiling the bubble will grow on its nucleation site and depart under the effect of the flow and slide along the heated wall. BW images have been processed at IMFT to determine the bubble growth rate and radius of detachment. The time evolution of the bubble radius evolves as R(t)=kt^n, with k and n dependent on the experimental parameters such as heat flux, flow rate, and subcooling. A careful modeling of the bubble growth rate requires estimating the heat flux from the wall, especially close to
the contact line and the heat flux around the bubble. The methodology will be based on complementary approaches: data processing of infrared temperature (IRT) measurements to obtain the local heat flux, modeling of the evaporation heat flux in the contact line vicinity and numerical simulations of flow and temperature field around the growing bubble to estimate the interfacial mass flux.
The expected outcomes of the project include a detailed comparison between the numerical simulation results and the experimental data obtained from the RUBI experiment.
The results will be published in peer-reviewed journals and presented in international conferences. To investigate boiling on isolated bubbles using advanced diagnostic techniques, the Multiscale Boiling (RUBI) experiment was developed over more than a decade by several European research teams within the framework of the ESA BOILING project. The experiment was operated aboard the International Space Station (ISS) between 2019 and 2021. Experiments were conducted on an isolated nucleation site under pool boiling conditions, as well as in the presence of external forces induced by an electric field and/or a shear flow. Side-view visualization was performed using a high-speed black-and-white (BW) camera operating at 500 fps (frames per second) to capture bubble growth and departure. A high-speed, high-resolution infrared (IR) camera was also used to record the temporal and spatial evolution of the wall temperature and compute the heat flux at the bubble foot on the heater surface. The experimental setup and operating procedures are described in detail by Sielaff et al. [2]. BW images of the bubble growth have been post-processed by the different teams to assess the image processing technics and determine the evolution of the bubble shape during their growth [3]. These data and some temperature measurements with IR thermography have also been used to validate numerical simulations in pool boiling (axisymmetrical configuration) by the team of Darmstadt [4] and Toulouse [5, 6]. These simulations shows that the contribution of the evaporation at the contact line is significant in the bubble growth rate. Since this phenomenon occurs at nanometric scale, some sub-grid models have to be developed and implemented in the numerical simulations.
Beyond its relevance to space applications, microgravity provides a unique environment for observing bubble growth and heat transfer with significantly enhanced spatial and temporal resolution, enabling much more accurate measurements, especially close to the contact line. Boiling liquid-vapor flows are encountered in a wide range of industrial applications, including steam generation in nuclear power plants, cooling of electronic components, and thermal management systems such as heat pumps and air-conditioning systems. Boiling liquid-vapor flows are also present in space applications, for example in two-phase flow loops used to cool electronic equipment in telecommunications and Earth observation satellites. In space launch vehicles, cryogenic tanks are exposed to solar radiation, which can induce boiling inside the tanks and lead to overpressure, requiring venting to maintain safe operating conditions [1]. The limited understanding of boiling physics under microgravity conditions remains a major obstacle to the development of space technologies, particularly in the context of space exploration.
Understanding boiling under microgravity conditions is the primary objective of the Multiscale Boiling Experiment (RUBI), which was conducted aboard the International Space Station between 2019 and 2021. A large experimental database was collected and can be used to validate theoretical models and numerical simulations. Improving modelling and numerical simulation tools is a key challenge for the development of future space technologies.
The PhD project will be carried out under the joint supervision of Univ. Toulouse IMFT and TU Darmstadt. Both institutions have extensive expertise in experiments, modelling and direct numerical simulation of boiling. Both teams have actively contributed in the development of the RUBI experiment, participated in monitoring the experiments in orbit and post-process the data.
The PHD thesis will be devoted to the analysis and modelling of the bubble dynamics and heat transfer in a shear flow. Unlike in pool boiling (in stagnant liquid), in flow boiling the bubble will grow on its nucleation site and depart under the effect of the flow and slide along the heated wall. BW images have been processed at IMFT to determine the bubble growth rate and radius of detachment. The time evolution of the bubble radius evolves as R(t)=ktn, with k and n dependent on the experimental parameters such as heat flux, flow rate, and subcooling. A careful modeling of the bubble growth rate requires estimating the heat flux from the wall, especially close to the contact line and the heat flux around the bubble. The methodology will be based on complementary approaches: data processing of infrared temperature (IRT) measurements to obtain the local heat flux, modeling of the evaporation heat flux in the contact line vicinity and numerical simulations of flow and temperature field around the growing bubble to estimate the interfacial mass flux.
Technical University of Darmstadt has a strong expertise in infrared temperature measurements and data processing to compute the heat flux at the wall [7, 8]. The same technics will be used to evaluate the heat flux in the shear flow experiments. The two teams have also developed numerical simulations. At IMFT, the DIVA solver is based on a finite-volume approach and is capable of simulating boiling two-phase flows using a Level-Set method for interface tracking and deformation. Its development, led by Sébastien Tanguy, began at IMFT in 2009. DIVA has already demonstrated its capability to reproduce a wide range of multiphase phenomena, including droplet collisions, bubble growth with conjugate heat transfer at the wall and a microregion model [5]. At TU Darmstadt, the OpenFOAM code has been successfully used to simulate bubble growth under microgravity conditions. Significant efforts of the group are devoted to further development and improvement of the microregion model for predicting evaporation at the contact line [4, 9, 10], which include the effect contact line velocity. Technical University of Darmstadt has also a long-standing expertise in experimental investigation of small-scale evaporation phenomena near contact lines [11, 12]. Similar experimental and numerical methods are used at TU Darmstadt to investigate the impact of single and multiple drops on heated surfaces [13, 14]
During the PhD project, the existing two-dimensional axisymmetric simulations will be extended to fully three-dimensional simulations with the DIVA code. From a theoretical perspective, the microregion model will be extended to include the contact-angle hysteresis, to enable modelling the contact-line pinning. Because three-dimensional simulations are computationally demanding, they will be performed selectively. IMFT will benefit from access to the regional high-performance computing center CALMIP and the national computing facilities provided by GENCI.

Master of Science in Fluid Mechanics with a good knowledge in thermodynamics, thermal science. Skills in data processing, image processing, modelling and numerical simulations

Application link : https://edd-projets.utoulouse.fr/