Fluid Mechanics of Complex Flows

About the Group

Led by Professor Alban Potherat, the Fluid Mechanics of Complex Flows group gathers mathematicians and experimentalists to tackle fundamental problems in fluid mechanics arising in natural and industrial processes. The group's expertise lies in stability theory, turbulence, convection, magnetohydrodynamics, plasmas, particulate and free surface flows, as well as advanced numerical methods. A large part of the group’s research is concerned with astro- and geophysical flows (in particular in planetary interiors), metallurgical and nuclear engineering, and flow measurement.

The research carried out by its members is supported by partners including the Royal Society, the Leverhulme Trust, EPSRC, as well as a number of industrial partners.

Meet the Team

Alban Potherat

Alban Potherat (Group Leader)

Magnetohydrodynamics, geophysical flows, nuclear fusion, electromagnetic processing of materials and metallurgy

aa4111@coventry.ac.uk

Michael Dallaston

Michael Dallaston

Mathematical modelling of viscous interfacial fluid dynamics, and the analysis and numerical computation of partial differential equation (PDE) systems that arise from such modelling

ac7047@coventry.ac.uk

Paul Griffiths

Paul Griffiths

Boundary layer flow, shear thinning and mathematics

ac7972@coventry.ac.uk

Abhishek Kumar

Abhishek Kumar

Hydrodynamic stability, buoyancy-driven turbulence, Rayleigh-Bénard convection, geostrophic turbulence

ac7600@coventry.ac.uk

Janis Priede

Magnetohydrodynamics, heat and mass transfer, boundary integral methods, free surface instabilities, electromagnetic velocimetry, computational electrodynamics, magnetorotational instability and applied mathematics

aa2371@coventry.ac.uk

Daniel Olvera

Couette flow and phase space

ac7701@coventry.ac.uk

Chris Pringle

Turbulence, pipe flow and dynamic systems

ab5838@coventry.ac.uk

Bogdan Teaca

Turbulence, Plasma Physics, Kinetic Theory, Mathematical Physics, Magnetohydrodynamics, Theoretical Astrophysics and Magnetic Confinement Fusion.

ab5422@coventry.ac.uk

Jonathan Brons

ac2002@coventry.ac.uk

Alex Pedcenko

aa3025@coventry.ac.uk

Michail Akritidis

akritidm@coventry.ac.uk

Sanjay Singh

Gerasimos Politis

Kelig Aujogue

Honourary researcher, Bast Inc Ltd Uk

Brahim Moudjed

Honourary researcher, Laboratoire National des Champs Magnétiques Intenses - CNRS, Grenoble

Binod Sreenivasan

Honourary researcher, Indian Institute of Science, Bangalore

Projects

Feature Project: Transition to Turbulence in Complex Fluids

Pumping fluids through pipes is an important part of many industrial processes. Turbulence during pumping greatly reduces its efficiency. In theory avoiding turbulence is achievable as a disturbance over a certain minimum size is needed to trigger it. Knowledge of this minimum size tells us how smooth the pipe needs to be in order to avoid turbulence. However, it has recently been shown with classical fluids, such as oil and water, that this minimum size is very low indeed – so low that in practice it may be entirely impossible to avoid turbulence for anything above moderate flow rates. 

A potential solution would be to change the characteristics of the observed turbulence. Adding small quantities of polymers to a fluid can change its fundamental properties. In this way it is possible to create a shear thinning fluid – one which becomes less viscous as it is forced through a pipe. Although for classical fluids reducing the viscosity actually increases the chances of turbulence, shear thinning fluids exhibit two types of turbulence. Along with the problematic turbulence observed for water or oil, there is also an intermediate ‘weak turbulence’ that has a much smaller impact on pumping efficiency. This proposal seeks to explore and understand the ‘weak state’ and to find conditions for holding off turbulence to improve pumping efficiency.

Kinetic turbulence in magnetised plasmas

The generation of electrical power through magnetic confinement fusion has the potential to provide an abundant, safe and reliable source of energy. It offers a viable alternative to fossil fuels as a way to tackle global environmental challenges. Magnetic confinement fusion uses strong magnetic fields to confine the fusion plasma fuel. Turbulence in plasma represents a key impediment to this, leading to the eventual loss of plasma confinement that stops the fusion reaction.

This project is tackling plasma turbulence at the smallest of scales from a kinetic perspective, addressing fundamental questions pursued in multiple academic fields such as astrophysics, mathematical physics and magnetic confinement fusion. For instance, the identification of the dynamical route used for the dissipation of small scale turbulence energy represents an important question in the solar wind community. At the same time, the project looks to develop practical solutions in the form of new knowledge-based turbulence modes that will directly aid fusion research, as a promising long-term industrial goal.

This work was initiated and is led by Dr. Bogdan Teaca, in collaboration with national institutions (Culham Centre for Fusion Energy and The University at Warwick) and international partners (Max-Planck Institute for Plasma Physics, Germany and The University of Texas at Austin, US) and has received financial support from the EPSRC.

Characterising the Earth’s liquid core

Much of the mystery surrounding the Earth's dynamics (its magnetic field, plate tectonics) lies in the nature of the convective patterns within its liquid core, and in particular in the region called the “Tangent Cylinder (TC).

This Leverhulme Trust-sponsored project , led by Prof. Alban Potherat, aims at characterising the state of the liquid core of the Earth- a 2200km thick region between the solid iron inner core and a thick rocky mantle. Heat and solute elements released from here drive thermal and compositional convection, which is in turn shaped by both the planet's fast rotation and its magnetic field. These complex phenomena directly determines the global dynamics of the planet: how fast it cools, how much energy it dissipates, how much energy drives the movement of the large pieces of the Earth's crust and upper part of the mantle, referred to as plate tectonics, and how much its rotation slows down. It also sustains the Earth’s magnetic field through the ‘dynamo’ process.

Because the core lies beyond reach, the very nature of flow within it is unclear so progress towards a physical and computational interpretation is impeded by insufficient insight into the state of convection in the core. A number of forces, sometimes competing, are also involved: extremely large buoyancy forces that drive convection, opposing damping forces, Coriolis forces due to the Earth’s rotation and electromagnetic force.

This project combines the most up-to-date numerical techniques from nonlinear hydrodynamic stability theory with geophysical insight and understanding. By initially focussing on the Tangent Cylinder reduces the complexity of the geometry to more manageable levels with two decisive advantages: first, the magnetic field there is predominantly axial and similar to that of solenoidal magnets, enabling us to visualise the nonlinear states found theoretically in an experimental model of the TC obtained by rotating a heated cylinder filled with a weakly conducting but transparent electrolyte inside very high magnetic fields. Second, convection is around 10 times less critical inside the TC than outside it, thus more amenable to numerical and experimental analysis.

The main goals of the project are to:
  1. Create a complete stability diagram for the states of magneto-convection in a rotating cylinder;
  2. Experimentally observe nonlinear magneto-convective states predicted theoretically for the first time;
  3. Among these states, to identify and characterise those consistent with flow patterns inferred from satellite measurements of the Earth magnetic field (flow intensity, topology, heat transferred).

Doctoral Opportunities

FCS PhD Opportunities

If you think you have what it takes to study for a PhD with us then take a look at the current PhD opportunities that are available within the Centre. We also welcome applications from suitably qualified self-funded or sponsored PhD candidates if they are in areas directly relevant to our research themes. The next step, once you have identified the research area of interest, is to contact the relevant academic and have an informal discussion with them. The academic can then advise you whether to proceed with a formal application.

Newton Institutional Links
FCS Engineering Doctorate Opportunities

Our Engineering Doctorate in Fluid and Complex Systems is a PhD-level qualification aimed at individuals who have a career, or wish to pursue a career, as an active researcher in industry. Typically, the Engineering Doctorate qualification is undertaken part-time, whilst working in industry. For employers it provides an opportunity to raise the level of skills of their research staff, allowing them to support the on-going developing of their own experts, who can influence and inspire those working around them. For individuals it provides the relevant technical, business and personal development required to become one of the senior technical managers of the future. For more information on our Engineering Doctorate Programme take a look at the course specification or contact us on research.eec@coventry.ac.uk

View current PhD opportunities