Fluid Dynamics Lab

Overview of PhD Research

I undertook my PhD in the Fluid Dynamics Laboratory where I investigated the flushing of embayments.

Layman's version!

You can download my thesis here.

I have written an article about my research called A Current Problem for Plus magazine (an online maths magazine aimed at 14-18 year-olds).

Flushing of Embayments

This research examines the flow of sea water in an embayment (coastal bay). The flow external to this embayment is tidal, and flows back and forth across the embayment mouth. The exchange between the embayment and external flow is an important mechanism for the transport and dispersion of pollutants, and also substances such as nutrients and sediments. Entrapment, where pollutants are retained in the embayment for some time, is of particular interest. Understanding the flow patterns in and around an embayment may enable the prediction of substance transport and dispersion in its locality.


With the help of staff from the Brixham Environmental Laboratory, velocity measurements were taken in Blackpool Sands (Devon) in July 2002 and 2003. These measurements showed tidal driven circulation in the bay. More details of the 2002 fieldwork are given here.

Laboratory Experiments

Laboratory experiments were designed and conducted in a bi-directional flume tank where the effects of varying embayment and tidal parameters were investigated.

The experiments included particle tracking, qualitative observations from dye visualisation and the extension of the synthetic schlieren technique to measure water surface deformations.

lab experiment

A synthetic schlieren experiment shows the water surface deformation indicating the presence of primary and secondary eddies, as well as the shear layer.


I developed a code which models an oscillating freestream flow past an embayment. This is a 2D, inviscid code where vorticity is injected at the embayment corners (to satisfy the Kutta condition) and is advected downstream.

Dipole generated by reversing flow.

A dipole is generated when the freestream flow reverses. The gyre which developed in the bay is swept out and joins with a gyre being generated at the corner.


In September 2002 I attended the Challenger Society Centenary Conference in Marine Science where I presented both a poster and a talk on my work on simple models for embayment flows. In April 2003 I attended the EGS-AGU-EUG Joint Assembly in Nice where I presented a poster.


My research was sponsored by the NERC (Natural Environment Research Council) and the Brixham Environmental Laboratory which is part of AstraZeneca.

useful science links
Last updated: 5th April 2005
F.C. Elwell

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