Nico Gray

Nico Gray

Prof

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Biography

[Granular jets and hydraulic jumps on an inclined plane] [Multi-component particle-size segregation in shallow granular avalanches] [Gravity-driven granular free-surface flow around a circular cylinder] [Asymmetric breaking size-segregation waves in dense granular free-surface flows][Segregation-induced finger formation in granular free-surface flows] Multiple solutions for granular flow over a smooth two-dimensional bump [Formation of levees, troughs and elevated channels by avalanches on erodible slopes] Self-channelisation and levee formation in monodisperse granular flows [Particle-size segregation in dense granular avalanches] [Underlying Asymmetry within Particle Size Segregation]

Nico Gray is Professor of Applied Mathematics and Deputy Director of the Manchester Centre for Nonlinear Dynamics a joint Institute formed by the School of Mathematics and the School of Physics & Astronomy to study nonlinear phenomena through a combined approach of theory, numerical computation and laboratory experiment.

He graduated with a first class degree in Mathematics from The University of Manchester in 1988 and was awarded a PhD on sea-ice dynamics by Cambridge University in 1992. He also holds a Habilitation in Continuum Mechanics and Geophysical Mechanics from the the Technical University of Darmstadt, Germany.

Following postdoctoral research positions at the School of Mathematics, University of East Anglia and the Institute of Mechanics, Technical University of Darmstadt he was appointed to a Lectureship in Mathematics at Manchester in 1998. He was subsequently promoted to Senior Lecturer (2003), Reader (2004) and to a personal chair in 2006.

In 2003 Nico was one of the main international organizers of a four month research programme on Granular and Particle-Laden Flows at the Isaac Newton Institute in Cambridge. From 2004-2009 he held an EPSRC Advanced Research Fellowship on particle size segregation, mixing and pattern formation in rapid granular avalanches. He currently holds an  EPSRC Established Career Fellowship on particle-size segregation in chutes, silos, conveyor belts and rotating drums, a Royal Society Wolfson Research Merit Award and a  NERC grant on self-organization and run-out behaviour of geophysical mass flows.

Research interests

Nico Gray is an expert on the flow of avalanches over complex natural terrain. This is of importance for understanding the dynamics of hazardous geophysical flows (e.g. snow avalanches, debris-flows, pyroclastic flows and lahars) for planning and risk assessment in alpine, mountainous and volcanic regions. Recent work has focussed on how avalanches flow pastdeflecting dams and obstacles, that are used to slow the flow, or steer it into less harmful areas. Nico uses a novel combination of theory, numerical computation, small scale laboratory experiment and field observations to investigate how obstacles generate shock waves, expansion fans and zero thickness regions[Catherine wheel pattern]  

Avalanches are part of a much wider class of gravity-driven granular free-surface flows that frequently occur in industrial processes as well as in foodstuffs in our kitchens! Indeed, small avalanches are responsible for the transport of our cereal grains from the box into a bowl at breakfast!

Over recent years Nico has become particularly interested in particle-size segregation that takes place within the flowing avalanche and the patterns that are formed as the grains are subsequently deposited. An example of a Catherine wheel pattern formed in a partially filled rotating drum is shown on the right. Most of the grains are in slow solid body rotation, but there is a rapid thin avalanche just near the surface, in which the large (white) grains rise to the top and small (dark) grains fall towards the base. Dependent on whether the grains are brought to rest by the passage of a shock wave, or, by basal deposition from the avalanche, different patterns are formed. Nico is developing simple theoriesfor the segregation process and investigating the complex patterns that are generated in heaps and rotating containers.

In some situations the segregation can have a direct feedback on the bulk velocity of the avalanche. Nico Gray and Peter Kokelaar (Liverpool University) have a joint NERC project to investigate the dynamic feedbacks that give rise to the spontaneous formation of coarse grained lateral levees, that channelize the flow and enhance the run-out of hazardous geophysical grain flows.

Further details of Nico's research including pictures and movies of some of the flows can be found at his personal webpage and in his publication list.

My group

Opportunities

Students interested in pursuing research in the exciting area if granular flows should contact Professor Nico Gray who is a world leading expert on the flow of avalanches.

Try clicking on the images below to find out more about some recent PhD projects on particle-size segregation and granular rheology that have direct application to both geophysical and industrial problems.

[Granular jets and hydraulic jumps on an inclined plane] [Multi-component particle-size segregation in shallow granular avalanches] [Gravity-driven granular free-surface flow around a circular cylinder] [Asymmetric breaking size-segregation waves in dense granular free-surface flows] [Segregation-induced finger formation in granular free-surface flows] Multiple solutions for granular flow over a smooth two-dimensional bump[Formation of levees, troughs and elevated channels by avalanches on erodible slopes] Self-channelisation and levee formation in monodisperse granular flows [Particle-size segregation in dense granular avalanches] [Underlying Asymmetry within Particle Size Segregation]

 

Details of the application procedure for postgraduate study can be found at the Department of Mathematics website.

Expertise related to UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This person’s work contributes towards the following SDG(s):

  • SDG 3 - Good Health and Well-being
  • SDG 13 - Climate Action
  • SDG 14 - Life Below Water

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