scholarly journals Mathematical Modeling and Associated Numerical Simulation of Fusion/Solidification Front Evolution in the Context of Severe Accident of Nuclear Power Engineering

Mathematics ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 116
Author(s):  
Adrien Drouillet ◽  
Guillaume Bois ◽  
Romain Le Tellier ◽  
Raphaël Loubère ◽  
Mathieu Peybernes

Considering transient processes where liquid/solid phase change occurs, this paper focuses on the associated modeling and numerical treatment in the frame of “Computational Fluid Dynamics” simulations. While being of importance in many industrial applications involving solidification and melting of mixed materials, including power and manufacturing engineering, the first application of this work pertains to the analysis of severe accidents in a nuclear reactor. Indeed, in this context, the molten core materials (a.k.a. corium) can form a high-temperature multiphase liquid pool at the boundary of which fusion and solidification phenomena are of prime importance. In this context, even if materials at play are treated as pure components, it is mandatory to distinguish two different phase change temperatures with a solid fusion temperature and a liquid solidification temperature. Accordingly, in the frame of a sharp interface representation, the paper introduces non-classical heterogeneous conditions at the liquid/solid boundary in such a way that both moving interface (through Stefan conditions associated with fusion or solidification) and static interface (imposing heat flux continuity) are supported at the same time on different spatial locations along this boundary. Within a monolithic resolution of Navier–Stokes and heat conduction equations, this interface is explicitly tracked with combined Front-Tracking and VOF methods. In order to ensure zero velocity in the solid phase, an Immersed Boundary Method and a direct forcing penalization are also introduced. The main relevant features of this combination of numerical methods are discussed along with their implementation in the TrioCFD code taking advantage of the pre-existing code capabilities. Numerical simulations including both verification tests and a case of interest for our industrial application are reported and demonstrate the applicability of the proposed triptych model+methods+code to treat such problems. The numerical tools and the simulation code developed in this work could be used not only in the several accident context but also to simulate melting, solidification and fusion processes occurring in aerodynamics, hypersonic reentry vehicles and laser applications to cite but a few.

Author(s):  
Gregory J. Kowalski ◽  
Richard A. Whalen

A numerical simulation code is developed to study the significance of refraction effects (beam self-focussing or defocussing) of a laser during a laser welding process. Relationships between the size of the heat affected zone (HAZ), the melt zone and the laser beam parameters are investigated for a short pulsed laser welding process. The solution method includes the thermally stimulated nonlinear optical effects caused by the temperature dependent index of refraction, as well as the step change in surface reflection that occurs due to the liquid and solid phase change. The interaction of these parameters is investigated to better control the laser manufacturing processes. Difficulties of numerical modeling and the tradeoff between using small nodes to reduce the sawtooth behavior in the phase change model and computer run times that are consistent with real time control are discussed. The results indicate that there are no significant refraction affects of the laser beam and that the heat affected zone is approximately 6% larger for a collimated beam input as compared to a gaussian beam input. Peak temperatures are lower for the collimated beam.


2018 ◽  
Author(s):  
Ryohei Gotoh ◽  
Tsuyoshi Totani ◽  
Masashi Wakita ◽  
Harunori Nagata

2021 ◽  
Vol 6 (24) ◽  
pp. 6280-6285
Author(s):  
Burcu Oktay ◽  
Nilhan Kayaman‐Apohan

2021 ◽  
Vol 129 (7) ◽  
pp. 075103
Author(s):  
Matt Jacobs ◽  
Xinran Zhou ◽  
Edgar Olivera ◽  
Ryan Sheil ◽  
Shu Huang ◽  
...  

Author(s):  
Stefan Puttinger ◽  
Mahdi Saeedipour

AbstractThis paper presents an experimental investigation on the interactions of a deflected submerged jet into a liquid pool with its above interface in the absence and presence of an additional lighter liquid. Whereas the former is a free surface flow, the latter mimics a situation of two stratified liquids where the liquid-liquid interface is disturbed by large-scale motions in the liquid pool. Such configurations are encountered in various industrial applications and, in most cases, it is of major interest to avoid the entrainment of droplets from the lighter liquid into the main flow. Therefore, it is important to understand the fluid dynamics in such configurations and to analyze the differences between the cases with and without the additional liquid layer. To study this problem, we applied time-resolved particle image velocimetry experiments with high spatial resolution. A detailed data analysis of a small layer beneath the interface shows that although the presence of an additional liquid layer stabilizes the oscillations of the submerged jet significantly, the amount of kinetic energy, enstrophy, and velocity fluctuations concentrated in the proximity of the interface is higher when the oil layer is present. In addition, we analyze the energy distribution across the eigenmodes of a proper orthogonal distribution and the distribution of strain and vortex dominated regions. As the main objective of this study, these high-resolution time-resolved experimental data provide a validation platform for the development of new models in the context of the volume of fluid-based large eddy simulation of turbulent two-phase flows.


2020 ◽  
Vol 2 (3) ◽  
pp. 167-177 ◽  
Author(s):  
Junwen Huang ◽  
Houyong Yu ◽  
Somia Yassin Hussain Abdalkarim ◽  
Jaromir Marek ◽  
Jiri Militky ◽  
...  

2018 ◽  
Vol 25 (6) ◽  
pp. 1157-1165
Author(s):  
Taoufik Mnasri ◽  
Adel Abbessi ◽  
Rached Ben Younes ◽  
Atef Mazioud

AbstractThis work focuses on identifying the thermal conductivity of composites loaded with phase-change materials (PCMs). Three configurations are studied: (1) the PCMs are divided into identical spherical inclusions arranged in one plane, (2) the PCMs are inserted into the matrix as a plate on the level of the same plane of arrangement, and (3) the PCMs are divided into identical spherical inclusions arranged periodically in the whole matrix. The percentage PCM/matrix is fixed for all cases. A comparison among the various situations is made for the first time, thus providing a new idea on how to insert PCMs into composite matrices. The results show that the composite conductivity is the most important consideration in the first case, precisely when the arrangement plane is parallel with the flux and diagonal to the entry face. In the present work, we are interested in exploring the solid-solid PCMs. The PCM polyurethane and a wood matrix are particularly studied.


2015 ◽  
Vol 52 (8) ◽  
pp. 617-624 ◽  
Author(s):  
Siyang Mu ◽  
Jing Guo ◽  
Chunfang Yu ◽  
Yuanfa Liu ◽  
Yumei Gong ◽  
...  

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