CAS Accelerator Seminars

Computational Fluid Dynamics (CFD) as efficient tool to improve experiments: Strength and drawback

by Frédéric Topin (University Aix-Marseille)




Nowadays, Computational Fluid Dynamics (CFD) is a widely used tool in mechanical, chemical and thermal control engineering. It is a powerful method for the design of new thermal components (such as compact heat exchangers) as well as an efficient way to optimize thermal systems in terms of performance, reliability (hot spot, thermal stability…), mass, or to test innovative solutions. The main uses are simulations of thermal systems (virtual twins that are far less expensive than duplication of actual experiments), test of different boundary conditions, dynamic behavior, scaling (e.g. prototype to pilot scale) and so on. CFD full models are used to explore systems and extract the main driving phenomena, thus giving access to a better design. Simplified fast models of thermal components are then derived and used for operation and large systems design.

For cryogenic applications, such as are needed for superconducting components in accelerator and fusion technology, these tools are less used due to several limitations. In this context, the large number of physics that should be included makes the tools become complex and difficult to use. Generally, the number of required data exponentially increases with the system complexity, scale, and geometry (large 3D complex objects with a necessity to encompass small scale elements). The material properties (thermodependency, barodependency, electric and magnetic fields ….) vary sharply, become highly non-linear and may be difficult to gather, thus inducing many modelling and numerical issues. In case of two-phase flow, the situation is even worse as the closure laws used in all models are not yet well known. An emblematic example is the modelling of cryogenic pulsating heat pipes as innovative alternative to solid thermal conductors that contain all difficulties when used in the accelerator context. The simulation involves many time and geometric scales as well as moving interfaces. This induces complexity in formalism and creates bottlenecks in terms of numerical stability and quality of solutions.

This talk aims to present a panorama of recent applications, trends, and drawbacks of CFD modelling. Furthermore, it briefly presents methods and good practices to achieve an efficient use of CFD.

Contact: Caroline Zoller (5619)