Phd Studentship- The Dynamics of Droplet Condensation and Coalesence



Faculty of Engineering

The project:  This project aims to better understand the lifecycle of a droplet, from nucleation through to precipitation. Airborne water droplets form on aerosol particles, normally originating from dust or pollution, and their growth is determined by the balance of heat diffusion outwards and vapour diffusion inwards. This simple balance appears to persist only until droplets reach ~10μm diameter. Thereafter, lies a mystery.

This mechanism for growth could not produce raindrop-sized droplets in the life-time of a typical cloud. Though it is unclear exactly how, we believe droplets become large enough to have their own relative inertia, and start colliding with one another, coalescing to form progressively larger droplets. While the collision dynamics of two droplets are relatively simple to model, the collective dynamics of large ensembles of droplets is poorly understood, and where the focus of this PhD position will lie.

Droplets remain in a self-generated suspension until they have become too large to be supported by drag forces arising from relative motion through the gaseous phase. At this point, they precipitate out as rain. We will model this transition and use nonlinear dynamics techniques to test the models. One of the key aims of this project is to characterise the time-scales over which this life-cycle occurs, ultimately improving our modelling of anthropogenic weather events.

End applications: Sooty combustion products, both by aircraft in the high atmosphere and by general pollution in urban environments produce aerosol particles on which droplets nucleate. Better understanding of the time-scales between aerosol deposition and local rainfall is one of several important outcomes from this project. Droplet dynamics strongly influence system performance in other engineering contexts, eg. LIDAR measurement technology, pharmaceutical distillation, cooling systems for power generation, and fuel supply in direct injection engines.

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Implementation: This project involves analysis of the fluid mechanics of droplet ensemble behaviour, mapping local interactions to a network-based model of the system, statistical interpretation of this model and its computational implementation. Depending on the preferences of the candidate, the option is offered to pursue some aspects of the project through laboratory experiment.

Candidate requirements: Competitive applicants will hold a first-class honours degree in Mathematics, or a physical science with strong mathematical content. A good understanding of nonlinear dynamics and fluid mechanics will be considered highly desirable; applicants with equivalent industrial experience are encouraged.

Funding: Studentship covers full UK/EU (EU applicants who have been resident in the UK for 3 years prior to application) PhD tuition fees and a tax-free stipend at the current RCUK rate (£13,726 in 2013/14). EU nationals resident in the EU may also apply and will qualify only for PhD tuition fees

How to apply: Please make an online application for this project at http://www.bris.ac.uk/pg-howtoapply. Please select The Dynamics of Droplet Condensation and Coalesence on the Programme Choice page and enter details of the studentship when prompted in the Funding and Research Details sections of the form.

Contacts: In the first instance qualified, eligible applicants should seek further information about the project from supervisors Dr. Robert Szalai or Dr. Andrew Lawrie by contacting [email protected] before making a formal application

Deadline for applications: until filled

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