Predicting Pollutant Spill Concentrations from Urban Drainage Schemes

Current sewer modelling software focuses on the quantity of flow within the system and is used to design for capacity. When such systems fail, spills occur and research is focusing on the spill concentrations and how these might be predicted. There is currently little information available describing the transport and mixing of soluble pollutants through urban drainage systems, specifically focussing on the effect of urban drainage structures: manholes, tanks, over flows and separators and how the mixing processes vary with size, shape, flow rate and surcharge. This project would utilize a computer controlled flow rig to undertake solute tracing studies aimed at developing algorithms to describe the mixing processes within components of urban drainage systems and spill concentrations.

For more information please contact Prof. Ian Guymer.

Effects of In-Stream Vegetation on Mixing Processes

The flow field within open channel flow is affected by the presence of vegetation which is generally not uniformly distributed in the channel. These patches of vegetation may act to either enhance or suppress the longitudinal dispersion within the flow depending on the porosity or density of the vegetation. If the vegetation is sparse, soluble material may enter the patch and be retained, causing a transient storage effects. If however the vegetation patch is very dense, then exchange from the main flow will be reduced and the flow forced around the vegetation, potentially increasing the velocity and reducing the longitudinal dispersion effects. This project will aim to undertake laboratory experiments with real vegetation to relate the vegetation density to the longitudinal mixing within an open channel.

For more information please contact Prof. Ian Guymer.

Pollution in Nearshore Waters

Coastal recreational waters should comply with the appropriate water quality standards. In Europe these standards are defined by the new EU Bathing Waters Directive (2006/7/EC). Industrial and sewage treatment works often discharge their effluent into estuarine or coastal waters. Increased awareness by both regulatory bodies and the general public has made it vital to assess the effect of pollutants within coastal waters. In numerical models of the coastal region, the flows are usually depth averaged two dimensional simulations and tidal variations are used to predict velocities. The physical dispersal of plumes from waste disposal sites in the coastal zone is then simulated using the predicted velocity distributions and an estimated mixing coefficient.

At present these models are limited in their predictive capability due to a lack of detailed understanding of the hydrodynamic processes associated with bed shear stress, turbulence and mean velocity field, resulting in an inability to distinguish between the individual contribution of wave activity and current action on the mixing processes. This proposed research will extend current research and knowledge using novel experimental techniques to elucidate physical processes and provide descriptions of the key mass exchange processes and turbulent wave velocity fields.

The provision of the new 2D wave flume facility at Warwick, together with the specialist measurement available will provide the applicants with a unique opportunity to investigate the 'finer' mixing mechanisms responsible in the nearshore region, particular emphasis would be placed on measurement of the hydrodynamics (such as the vertical variation in velocity and wave generated turbulence), which would further refine the understanding of mechanisms responsible for the mixing. The use of non-intrusive measurement systems such as a laser light sheet provides the opportunity to investigate the hydrodynamics using PIV, and the diffusion/dispersion processes using PLIF (Planar Laser Induced Fluorescence).

For more information please contact Dr Jonathan Pearson

Contamination into Beaches

The overall aims of this proposed research are to improve the understanding and descriptions of key coastal processes in the nearshore region, with particular emphasis on those exchange processes influencing contamination into beaches. The applicants previous experimental investigations showed that the depth-varying forward transport under waves was a significant contributory factor to the on-off shore dispersion coefficient (Pearson et al. 2002, 2009) within the water column. In the case of contamination into beach material it is by no means clear how the mass transport and associated bed exchange mechanisms will be developed under the influence of wave activity. This project will utilise the research grade 2D wave flume in the School of Engineering at the University of Warwick utilising the vast array of scientific measurement equipment already available at Warwick. New knowledge of hydrodynamic and exchange processes will be obtained through interpretation of unique velocity and tracer measurements.

For more information please contact Dr Jonathan Pearson

Extreme Waves at Coastal Structures

In the UK there is a significant amount of infrastructure located at or close to the coast, some of it highly vulnerable to relatively small wave events as well as extreme storm events. The performance of these structures can be classified in many different ways, usually using complex functions of wave and geometric parameters. For example, many man-made coastal structures are designed to limit overtopping, in which predictions are derived from general empirical formulae fitted to laboratory measurements. Many published coastal studies, and thus guidance documents, are based on the prediction of average quantities such as overtopping rates per hour. Whilst these structures may be efficient in overtopping, they may be subject to impulsive wave breaking giving sudden and violent overtopping flows, and very large wave impact pressures, the interactions of which are currently difficult to describe with any degree of certainty.This research topic extends current research and knowledge of extreme wave responses, using novel experimental techniques and state of the art numerical modelling techniques to elucidate the coastal processes at the wave / structure interface. The project aims to understand and model the individual largest and most damaging waves within a long random sequence of severe waves impacting on the coast; a storm consisting of thousands of individual waves. We will use the idea of localised groups of waves to model the most severe waves that arise during typical 3-hour storm duration.

For more information please contact Dr Jonathan Pearson