Bernard Knaepen

Most fluid flows encountered in real life fall into the category of turbulent flows. As such, they are characterised by very complex motions that can be qualified as chaotic and random. The prediction of the evolution of turbulent flows is a complex but important task as such flows are essential ingredients in many physical systems and industrial applications.

In this research, the focus is placed on the study of turbulent conductive flows in the limit of a vanishing magnetic Reynolds(*) number. In this limit, the motion of the conductive flow can be significantly influenced by an electromagnetic field but cannot appreciably retroact on it.

For instance, magnetic fields are used to control flow evolution in the steel industry and the crystallisation of semiconductor crystals. Interaction of liquid metals with magnetic fields is also an essential question in the design of coolant blankets for nuclear fusion reactors. Although widely used in technological applications, the interaction of conductive flows with applied electromagnetic fields in turbulent situations still cannot be predicted in a satisfactory manner.

We will study this interaction further. Since no exact mathematical framework is available to solve turbulent flow problems, there is currently a great need for efficient numerical tools to predict them.

In order to analyze and predict the kinds of flows encountered in real-world applications, a versatile simulation code will be developed. Different approximate methods will be incorporated in this code, among them the method of large-eddy simulations in which only the large-scale structures of a flow are predicted while the influence of the small scales is taken into account through a model.

Using the numerical tools developed, we plan to study in detail the physics of this flow-magnetic-field interaction. In particular, a careful examination of the influence of wall boundaries on the core flow will be performed. Attention will also be focused on the modification by the magnetic field of the ability of the flow to transport heat and particles.

As the findings of the planned research will have a clear potential impact on different industrial activities, a particular effort will be made to find partners in industry and transfer part of the know-how gathered.

(*) Definition - Magnetic Reynolds number:
The magnetic Reynolds number, denoted Rm, provides a measure of the ability of the flow to distort magnetic field lines. For low values of Rm, the magnetic field lines are smooth and are not appreciably modified by the fluid's motion. For high values of Rm, the magnetic field lines can become very complex and twisted as they are transported by the fluid's turbulent motions. (Source: Bernard Knaepen)