The
construction of the 'Total Environment Simulator'
by Armfield Limited on behalf of the Geography Department at the
University of Hull is set to make a major contribution to modelling
and managing our river and coastal resources. It is a large scale
physical modelling facility that can simulate the effects of changing
patterns of rainfall, flow and waves and their impact on sediment
and biota. It was officially opened by Professor John Lawton in
June 2002 and is managed by Lynne Frostick and Stuart McLelland
of the University of Hull with support from a distinguished advisory
group drawn from the Universities of Bristol, Cambridge, East
Anglia, Leeds, Loughborough and Southampton.
The Total Environment Simulator was made possible through grants
from the Millennium Commission, the Higher Education Funding Council
through the Joint Research Equipment Initiative and the Science Research
Investment Fund. The latter funds being used to purchase state-of-the-art
flow measurement equipment including a submersible 3D particle image
velocimetry (PIV) system (below) and a three-dimensional laser Doppler
anemometer (LDA). The Total Environment Simulator is housed on the
ground floor of the award winning submarium, The Deep, a Millennium
Commission funded project that has broken all records as a visitor
attraction.
For
many experiments this will be a mixture of sediment and water
which will be used together to model different types of environments.
The flume was constructed using a steel frame which allows space
to install instruments beneath the experimental area. The working
section is constructed from marine plywood with a protective layer
of stainless steel on the floor. One side of the flume is designed
for viewing experiments and is constructed from 18 mm thick toughened
glass. The inlet and outlet tanks and associated pipework are
constructed of stainless steel and plastic so that they are resistant
to corrosion from salt water. A gantry spans across the flume
width for mounting instruments and can be moved along the length
of the working section.
To enable a wide variety of environmental scenarios to
be modelled the Total Environment Simulator has three different
flow driving mechanisms:
> Two giant pumps located in a pit beneath the flume
tank recirculate water. Each pump delivers up to 500 litres of
water per second and when operated together can deliver 1000 litres
per second. As well as recirculating water in the flume, the pumps
can also recirculate sediment up to coarse sand size through the
system.
> At one end of the flume tank is a wave generator.
The wavemaker consists of 8 paddles across the channel width which
generate regularly or irregularly shaped waves of up to 0.5m in
height. The waves can be generated either parallel to the flume
sides or at oblique angles to simulate the effect of different
wind directions.
> An array of over 50 sprinklers above the flume can
generate rainfall over the experimental surface. Rainfall rates
of 100mm per hour can be simulated and the rainfall can be distributed
across different zones of the modelling area (shown below left).
Each
flow driving mechanism can be operated either separately or simultaneously,
depending on the type of environment being simulated.
The flow systems are all computer controlled so that operators
can run whole experiments from outside the flume tank.
Instruments
for measuring flow and sediment movement are also computer operated
remotely.
How is the flume unique?
The Total Environment Simulator is designed to provide a flexible
modelling environment that can be configured to simulate a wide
variety of environmental conditions, including:
> Turbulent boundary layer flows up to 1m deep with
either fixed or mobile boundaries.
> Studies of sediment transport to investigate controls
on transport rates and/or spatial patterns of erosion and deposition.
> Combined wave and unidirectional flows and their effects
on sediment transport over sand or mud bed material.
> Rainfall effects on surface erosion and subsurface
hydrology.
Setting
up the PIV |
There is no similar facility in the world. Some experimental
flow tanks are bigger in volume, but there is no facility
that combines
all three flow driving mechanisms which make this one
unique. A particular advantage of the Total Environment
Simulator is the depth of flow
it can accommodate. This is useful since it allows
environments with marked depth contrasts to be modelled
successfully, such as the interface
between deep tidal channels and shallow mudflats. This
also allows deep river channels to be simulated so
that models can be made close
to real-scale. Another advantage is the volume of water
that can be pumped round the flume. Some facilities
divert natural river water
to create larger flows, but few facilities can recirculate
flow and sediment at rates of 1000 litres per second.
Instrumentation
A suite of high resolution monitoring equipment has been integrated
with the physical modelling capabilities of the flume itself.
This equipment is designed to quantify spatial patterns of flow
and the dynamics of sediment transport during experiments.
This
monitoring equipment includes:
> Seven acoustic Doppler velocimeters that measure the
spatial distribution of three-dimensional flow velocities at frequencies
of up to 100Hz.
> Two-camera Particle Image Velocimetery (PIV) system
to map three-dimensional flow vectors in areas up to 0.5 x 0.5m
in size with an automated traverse for mapping flow volumes. Images
can be captured at up to 15Hz for periods of up to 8 minutes
> Laser Doppler Anemometry (LDA) using a large (112mm)
5-beam probe for non-intrusive three- dimensional flow measurements
and also two miniature (14mm) probes for three-dimensional flow
measurements in confined spaces.
> Six miniature current meters with continuous recording
to monitor inlet and outlet flow conditions.
> A distributed array of 24 pressure sensors for monitoring
flow depths throughout the model space.
> Laser and acoustic distance measurers for quantifying
bed topography. These instruments can be linked to an automated
traverse system for automated scanning of bed morphology.
> Digital video and still cameras for monitoring change
during experiments.
What type of research will be carried out in the Total
Environment Simulator?
The need for physical modelling facilities like the Total Environment
Simulator has never been greater. Global climate models predict,
at continental scale, changes in the patterns of temperature,
rainfall and wind. For the UK there is a prediction of increased
storminess, indeed many of the recent adverse weather events which
have caused widespread flooding in many of our major towns and
cities have been interpreted as the consequences of global climate
change. In spite of the growing evidence of the reality of climate
change and our increasing ability to produce well calibrated predictive
models at a global scale, we are far from translating these models
into local and regional scale predictions. Yet this is the scale
at which individuals and societies are beginning to feel the adverse
effects. In addition, the impact of mankind on the aquatic environment
is increasing as population grows. Water is central to sustainable
development and managing water resources effectively and efficiently
is a growing imperative.
The Total Environment Simulator will offer a unique opportunity
to physically model areas of aquatic systems at the scale of the
natural environment and thereby derive data to calibrate and validate
the mathematical models that are the foundation of future prediction.
Although the facility is owned and run by the University of Hull,
it is available for both research and developmental projects to
both industry and academia.
The following research projects are examples of the type
of work already underway or planned:
> Modelling the behaviour of quasi-steady turbidity
currents which are generated at river mouths and are believed
to deliver significant volumes of sediment to the oceans. These
phenomena are obviously difficult to study in the natural world
and experimental studies are an essential tool to understand their
development.
> Rogue waves have been intensively studied in deep
water environments, however relatively little is known about the
development of rogue waves in shallow water. Experiments will
be used to help understand the mechanisms of rogue wave development
in shallow water and the impact of rogue waves on near-shore sediment
transport.
> Understanding the fluxes of effluents through estuaries
is important for effective pollution control and environmental
management. The Total Environment Simulator offers a unique opportunity
to investigate the movement of mud under controlled conditions
by subjecting artificial deposits to different combinations of
intensities of wind waves and rainfall.
The
Deep seen through the barrier across the River Hull |
University of Hull Staff at the Total Environment Simulator:
Prof. Lynne Frostick, Dr. Stuart McLelland, Brendan
Murphy and Mark Anderson
Contact Details:
Department of Geography
University of Hull, Hull, HU6 7RX
Tel: 01482 465385 " Fax: 01482 466340
Email: S.J.McLelland@hull.ac.uk
University of Hull Research Facility
The Deep. Hull, HU1 4DP
Tel: 01482 381050
www.hull.ac.uk/geog
