Multiphase flow instabilities in fusion reactor environments

Abstract: Free-surface metal flows may occur on the wall of magnetic confinement fusion devices, either due to unintended transient melting during high-energy events, or as an integral part of liquid wall concepts which are considered as a potential alternative design route for future nuclear fusion reactors. Due to the extreme thermomechanical loads involved, a wide variety of hydrodynamic instabilities may develop, potentially leading to significant wall damage via liquid displacement and splashing.
While the main scenarios of interest in fusion research can be linked to well-studied configurations like open-channel flows and droplet-surface impacts, their analysis is complicated by several atypical features: time-varying bathymetry and body forces, temperature-dependent heat loads, strong evaporation. Furthermore, CFD modelling of such systems is made challenging by the large density ratios involved (up to 10¹¹) and the need to impose specific boundary conditions at the liquid’s surface.
Recent numerical efforts to model accidental wall melting under high-energy transients will be used as a basis to showcase how prototypical instabilities, such as Rayleigh-Taylor or Marangoni flows, may manifest and interact in fusion environments. The case of the Hickman instability due to differential vapor recoil will also be considered, along with its potential implications for liquid wall concepts.

Bio: Ladislas Vignitchouk is a researcher at KTH with an interest in multi-physics modelling. Following his PhD and postdoctoral work on simulating the behavior of metallic dust particles in fusion plasma devices, he was trained in multiphase computational fluid dynamics by Andrei Khodak at the Princeton Plasma Physics Laboratory.