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A model for the shapes of advected triangles

Pumir, Alain and Wilkinson, Michael (2013). A model for the shapes of advected triangles. Journal of Statistical Physics, 152(5) pp. 934–53.

DOI (Digital Object Identifier) Link: https://doi.org/10.1007/s10955-013-0789-6
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Abstract

Three particles floating on a fluid surface define a triangle. The aim of this paper is to characterise the shape of the triangle, defined by two of its angles, as the three vertices are subject to a complex or turbulent motion. We consider a simple class of models for this process, involving a combination of a random strain of the fluid and Brownian motion of the particles. Following D.G. Kendall, we map the space of triangles to a sphere, whose equator corresponds to degenerate triangles with colinear vertices, with equilaterals at the poles. We map our model to a diffusion process on the surface of the sphere and find an exact solution for the shape distribution. Whereas the action of the random strain tends to make the shape of the triangles infinitely elongated, in the presence of a Brownian diffusion of the vertices, the model has an equilibrium distribution of shapes. We determine here exactly this shape distribution in the simple case where the increments of the strain are diffusive.

Item Type: Journal Item
Copyright Holders: 2013 Springer Science+Business Media
ISSN: 1572-9613
Keywords: diffusion; advection
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Mathematics and Statistics
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 41297
Depositing User: Michael Wilkinson
Date Deposited: 10 Nov 2014 16:51
Last Modified: 07 Dec 2018 10:26
URI: http://oro.open.ac.uk/id/eprint/41297
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