Research Interests

My main research interests lie in the general area of soft condensed matter in general with particular interest in fluid mechanics.

Each of the pictures below links to a table describing my work in that area and preprints of relevant papers. Some tables have further links to a more detailed explanation of that work as well. The News tab (above) links to various popular science articles about my research that may be of interest.

It has become quite difficult to keep this page up to date, though I will try to rectify this soon. However, my list of publications should remain reasonably current.

To search the arxiv for things by me, click here.

To view my researcherid profile, click here.

I am also interested in some elementary problems in number theory. In particular, I have studied some properties of Fibonacci sequences and Pythagorean triples. If you are interested in these kinds of subjects then you can find more details here.

The Cheerios Effect

When two, or more, objects of the same type float on water, they attract one another because of their weight and the surface tension of the interface. This is often referred to as the 'Cheerios effect' since it is often observed in breakfast cereals but can equally be seen in a glass of sparkling water or many other situations. The dynamics of the interaction have not been studied in any detail, but we showed that a very simple model of the dynamics gives reasonably good agreement with simple experimental results.

Title	Main Idea	Published?	Co-worker(s)
The wall-induced motion of a floating flexible train	We study with theory and experiment the zippering motion of a flexible train of rods at an interface	J. Fluid Mech. 502 (2004), 89 PDF (276 KB)	H.-Y. Kim and L. Mahadevan
The 'Cheerios effect'	A pedagogical article looking at the aggregation of floating objects. We explore a series of classic calculations bearing in mind the physical picture of the Cheerios interaction.	Am. J. Phys. 73 (2005), 814 arXiv:cond-mat/0411688	L. Mahadevan

Particle Rafts

With a large number of particles floating at an air-water interface, the cheerios attraction causes a qualitative change in the behaviour of the interface: it looks more like an elastic solid than a fluid. We have quantified this idea by studying the elastic properties of the interface and have also studied how these interfaces can even fracture.

Title	Main Idea	Published?	Co-worker(s)
Elasticity of particle rafts	We characterise the elastic properties of a dense assembly of particles at an interface	Europhys. Lett. 68 (2004), 212 arXiv:cond-mat/0406723	P. Aussillous and L. Mahadevan
Dynamics of surfactant-driven fracture of particle rafts	We study how a particle raft fractures when you add a drop of surfactant to the raft.	Phys. Rev. Lett. 96 (2006), 178301 arXiv:cond-mat/0509781	H.-Y. Kim, P. Aussillous and L. Mahadevan

How to Sink Things

I am currently interested in the when floating objects cannot float and must instead sink. In particular, I am interested in to what extent surface tension makes it possible to support dense objects at an interface. This work made up the majority of my PhD Thesis.

Title	Main Idea	Published?	Co-worker(s)
The Physics of Floating	A pedagogical article outlining the generalisation of Archimedes' Principle to include surface tension. This is used to calculate the maximum density of a cylinder that can remain afloat for various values of the radius.	Eureka 57 (2005), 26 PDF (160 KB)	None
Equilibrium Conditions for the Floating of Multiple Interfacial Objects	We give conditions under which multiple objects can remain afloat at an interface. In particular, we look at two parallel strips and then generalise this to a continuum raft of strips.	J. Fluid Mech. 549 (2006), 215 arXiv:physics/0509009	P. D. Metcalfe and R. J. Whittaker
Sinking of a horizontal cylinder	This is a first attempt to model the dynamics of sinking. The model is a bit naive but is in good agreement with experiments.	Langmuir 22 (2006), 2972 Langmuir copy	D. G. Lee and H.-Y. Kim
The load supported by small floating objects	We give conditions on the density and radius of a small object for it to be able to float. In particular, we study how the hydrophobicity of the object affects the critical density at which sinking occurs.	Langmuir 22 (2006), 5979 Langmuir copy	D. G. Lee and H.-Y. Kim
Surface tension dominated impact	We study the impact of a very small object onto an interface at high Reynolds number and determine quantitatively how as the impact speed increases the maximum weight the object can have and still float decreases.	Phys. Fluids 19 (2007), 072108 Phys. Fluids copy	P. D. Metcalfe

Flow in Porous Media

More recently, I have done some work on how fluids flow in porous media. This may have applications to storing Carbon Dioxide deep underground in naturally occuring reservoirs.

Title	Main Idea	Published?	Co-worker(s)
Gravity currents in a porous medium at an inclined plane	We study how a dense fluid spreads through a porous medium along an inclined plane.	J. Fluid Mech. 555 (2006), 353 arXiv:physics/0512168	Herbert Huppert
The waterlogging of floating objects	We study how a very porous body (such as a piece of pumice) sucks water in, becomes denser and ultimately sinks. This allows to estimate how long the 'pumice rafts' formed sometime formed after volcanic eruptions should be expected to float.	J. Fluid Mech. 585 (2007), 245 JFM copy	Herbert Huppert

Adhesion

I have also spent some time thinking about the processes that occur in bond rupture. This is particularly important for understanding the way that adhesives, such as scotch tape, fail under dynamic loading.

Title	Main Idea	Published?	Co-worker(s)
A simple microscopic model for the dynamics of adhesive failure	We suggest that the second peak observed in the stress-strain curves for adhesives loaded at constant velocity may be due to finite bond length effects.	Langmuir 22 (2006), 163 arXiv:cond-mat/0506717	L. Mahadevan

This page was most recently updated on the 7^th of October, 2007.