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@ U S T . H K
Beneath the streets of Hong Kong lie
over 7,500 kilometers of water pipes.
In the US, there are more than 1.5
million kilometers. What is pressing
for the sustainability of urban
lifestyles and future development
is that these immense labyrinths of
pipelines in cities around the world
are often aging and inefficient.
Leaks and bursts contribute
to business losses, social
disruption, and require
expensive renewal strategies –
if they can be afforded.
(The Hong Kong
government recently
completed a 15-year project
replacing 3,000 kilometers
of pipes at a cost of over
HK$23 billion.) Globally, a staggering
30%-40% of piped urban water
is wasted annually due to system
deficiencies and World Bank estimates
place the cost of water loss at US$15
billion each year.
Pressure Wave Potential
Prof Mohamed Ghidaoui, an expert in
hydraulics and fluid mechanics, is now
The bottom plate depicts a section of a pipe system under roads and buildings; its state and condition
are unknown. Pressure waves are generated in the pipes by a pump, valve, or piezo-electric transducer
and travel rapidly through the pipelines at a speed of one kilometer per second. These pressure waves
are picked up by sensors in the pipes, and the data is wirelessly transmitted in real-time to the base-
stations, where it is transformed into sharp images showing the state of the system, providing valuable
information for analysis of pipe defects e.g. blockages, leaks, and weak pipes.
seen as detrimental to conduits and
most engineering efforts to date have
focused on ways to mitigate or suppress
them. However, from his accumulated
research findings over the past 20
years, Prof Ghidaoui is focusing on the
beneficial outcome of pressure waves –
pipeline diagnostics. In a similar way
to a doctor conducting an ultrasound
scan in a clinic, waves could be used
as tools to “image” conduits and, from
analysis of the resulting data, find and
characterize system defects, such as
leaks, blockages and pipe deterioration.
Being fast (pressure waves travel at one
kilometer per second) and non-intrusive
(waves can be sent to sample a large
area of pipeline from just one location),
such tools would also facilitate system-
wide diagnosis and be applicable to
most faults.
tackling these issues through visionary
research with the potential to take
urban water supply systems to the next
level of efficiency, cost-effectiveness,
and sustainability. Prof Ghidaoui is
seeking to harness understanding
of the propagation and reflection of
pressure waves in pipelines to build a
“smart”, pioneering real-time diagnostic
management platform. The “smart”
platform will utilize sensors in pipes and
wave-based techniques and technologies
to allow engineers to continuously
monitor the health of underground
water systems and rapidly pinpoint and
anticipate pipeline problems, in a non-
disruptive and non-intrusive manner.
In water systems, the simple action
of starting a pump, or opening and
closing a valve, causes pressure waves.
Traditionally, these waves have been
Ultrasound imaging is based on
sending waves into a patient’s
body and measuring the echoes.
We want to do that with
pipelines. We want to send
acoustic waves in the fluid
in pipes, capture the echoes,
and use them to diagnose the
health of the pipe system
PROF MOHAMED GHIDAOUI
Chinese Estates Professor of Engineering
IN THE PIPELINE
INPUT SIGNAL
HFW
INPUT SIGNAL
LFW
Smart Urban Water Supply Systems (Smart UWSS)
Using Waves as Diagnostic Tools
SERVER SIDE
LFW
Low
frequency
waves
HFW
High
frequency
waves
WAVE ANALYSIS
Pipe Condition Assessment
Using low frequency waves (LFW)
to identify possible defects,
and high frequency waves (HFW)
to pinpoint problems
Air Pocket
Leakage
(20% Flow Rate)
Blockage
(15% Pipe Area)
Smart
UWSS
