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These seminars (unless otherwise stated) will take place on Wednesdays at 4pm in Maths Room 707 (25 Gordon Street) on a bi-weekly basis - see the map for further details.
31 January 2018
Speaker: Alexander Chamolly (University of Cambridge)
Title: Stochastic dynamics of active microswimmers
Abstract:
The design and behaviour of artificial microswimmers has garnered significant research interest in recent years. Potential applications such as controlled drug-delivery make them a very promising tool once perfected. However, the vast majority of current designs suffers from a common problem: the swimmers remain in the fluid indefinitely, posing risks of clogging and damage. Inspired by recent design proposals, we investigate the dynamics of a degradable microswimmer. In this seminar, we will give an introduction to the stochastic calculus necessary for the description of a colloid with slowly varying diffusivity, and use this to present and compare three models of the decay of a swimmer, taking into account the nature of the chemical reaction at its surface. From this we can draw valuable conclusions about the practicability of a wide range of materials for the design of such a colloid.
14 February 2018
Speaker: Natasha Senior (University of East Anglia)
Title: Eddy-mean-flow interactions in geostrophic turbulence
Abstract:
Owing to its similarity with the 2D vorticity equation, the quasi-geostrophic equation permits the existence of a dual cascade in energy and enstrophy. This is accompanied by the formation of large scale structures as a consequence of energy being transported to successively larger scales through interactions between eddies of similar wavenumber. Spontaneously forming zonal jets in the oceans could be explained as intermediate or final states in the evolution of an inverse energy cascade. Jets have been known to be supported by a negative viscosity, where the divergence of the Reynolds' stress pattern reveals eddies tilting in a manner to flux momentum into the mean flow. What is unclear is how these eddy-mean-flow interactions fit in to the picture of geostrophic turbulence. Using a channel model forced at intermediate scales and dissipated through Rayleigh friction, the relationship between eddy-tilts and the formation of turbulence zonal jets is investigated.