Sonic Characterisation of Water Surface Waves, Turbulence, Mixing and Bed Friction in Shallow Water Flows

Lead Research Organisation: University of Bradford
Department Name: Sch of Engineering Design and Technology

Abstract

Flows found in many situations including gravel bed rivers, overland flows, and in partially filled pipes are turbulent. Such depth-limited flows always have patterns of small waves on the air/water boundary. We believe that the dynamic behaviour of these small waves carries information about the turbulent mixing and energy losses within that flow. Normally in engineering calculations the water surface is assumed to be flat and so this source of potentially very valuable information is ignored. This project will use laboratory observations and a complex 3D numerical model to study and predict the turbulent flow structures that are created by turbulent flows over rough solid boundaries. These flow structures then rise to the water surface and cause it to oscillate and create a distinct pattern of small waves. The numerical model will be able to predict the generation, growth and transport of these flow structures in 3D, and capture their effect on the water surface pattern. It is believed that by measuring the wave pattern it will be possible to predict the mixing and energy losses within the flow. The numerical model will be used to simulate this process for a wide range of physical scales, bed roughness types and flow depth to width ratios, so that a very wide range of flow regimes will have been examined.The wave pattern on a water surface can be measured using a number of methods; e.g. optical, eletromagnetic and acoustic. Acoustic measurements are particularly suited to hydraulic applications because they are fast, low-cost, non-invasive, and can be easily used at both small and large scales. An airborne acoustic sensor that can project sound energy onto the moving water surface pattern will be placed above the water surface in a channel or pipe. By examining the acoustic reflections, the behaviour of the air-water boundary will be measured. New methods of acoustic signal analysis and sound propagation theory are needed to re-construct the fine detail of the water surface patterns from the measured acoustic reflections. The processed acoustic data will then be combined with the knowledge gained from the laboratory and 3D numerical studies to provide engineers with relationships to estimate energy losses and turbulent mixing solely from measurements of the air-water boundary. Information on energy losses and turbulent mixing is needed to predict water levels for flood studies and to predict the mixing of pollutants and sediments accidentally released into rivers and pipes. This system will be able to improve flood prediction and warning, so providing better protection for people and their property. Better assessment of turbulent mixing in water bodies will help to protect better the natural environment and sensitive habitats. In the final part of the project, a prototype sensor system will be manufactured and tested at full scale in the River Taff, at an Environment Agency test facility. The results will be used to demonstrate the practical applicability of the concept and the technology to end users.

Publications

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Horoshenkov K (2013) The pattern of surface waves in a shallow free surface flow FREE SURFACE WAVES in Journal of Geophysical Research: Earth Surface

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Kazemi E (2017) SPH modelling of depth-limited turbulent open channel flows over rough boundaries. in International journal for numerical methods in fluids

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Krynkin A (2013) An eigenvalue correction due to scattering by a rough wall of an acoustic waveguide. in The Journal of the Acoustical Society of America

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Nichols A (2013) A non-invasive airborne wave monitor in Flow Measurement and Instrumentation

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Nichols A (2016) A model of the free surface dynamics of shallow turbulent flows in Journal of Hydraulic Research

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Nichols A (2013) Low cost on-line non-invasive sewer flow monitoring in Water Practice and Technology

 
Description The results of the work on this grant have shown that there are two types of surface waves created in shallow turbulent flows. The first is caused by the underlying turbulent structures and the second are simple gravity waves. By being able to understand the behavior of the two types of waves, measurment of the water surface is able to be sued to measure the underlying flow propertites. Non-contact flow measurement is extremely useful to measure environmental flows such as in rivers, drainage channels and sewers. The project also produced a novel acoustic array able to measure the water surface behaviour in a non-contact manner. It was tested in a sewer pipe and in an inlet channel to a waste water treatment works and performed well. This work has led to an industrial sponsored PhD student, who has recently completed and whose work has provided a more complete description of water surface waves. In particular his work has demonstrated the dominance of gravity waves especially at flow regimes above a critical Froude number.
Exploitation Route The finding may be used to develop non-contact flow measurement instrumentation. The understanding of the link between turbulent structures and the water surface behaviour would help in the understanding of the transfer of heat and gas at such an interface. These findings have led to a further industrial funded studentship.
Sectors Environment,Other

 
Description The findings from this project were used to develop a high level of understanding of the dynamic air-water interface in turbulent shallow water flow. This enabled us to develop new underpinning theory and a new type of acoustic sensor which can be used to monitor the flow velocity and mixing processes in open channel flows non-invasively. This sensor was tested successfully at Yorkshire Water's Esholt Wastewater Treatment Plant and in a foul water sewer. Its technology has been patented and subject to further investment via an EPSRC IAA award at the University of Sheffield. It was intended to further develop this technology via an EA award but that did not prove possible due to IP issues. The underpinning theory has been published in the academic literature.
First Year Of Impact 2012
Sector Environment,Other
Impact Types Societal,Economic

 
Description Acoustic Scattering by Dynamically Rough Surfaces
Amount $60,000 (USD)
Organisation Applied Dynamic Solutions (ADS) LLC 
Sector Private
Country United States
Start 01/2013 
End 12/2016
 
Description Development of Novel Acoustic Instrumentation for Non-invasive Monitoring of Water Flows
Amount £50,000 (GBP)
Funding ID X/140064 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 08/2014 
End 07/2015
 
Description EPSRC - Pennine Water Group (PWG); Urban Water Systems for a Changing World
Amount £1,201,720 (GBP)
Funding ID EP/I029346/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 05/2011 
End 04/2016
 
Description Rapid monitoring of river hydrodynamics and morphology using acoustic holography
Amount £521,877 (GBP)
Funding ID EP/R022275/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 07/2018 
End 12/2021
 
Description ADS LLC 
Organisation ADS LLC
Country United States 
Sector Private 
PI Contribution The research funded by the EPSRC EP/G015341/1 grant led to the development of a new acoustic wave monitor technology which paves the way to new instruments which can be used to measure hydraulic characteristics of a shallow water flow. This technology appeared attractive to our industry partner, ADS LLC (USA), who make and sell ultrasonic flow meters which operate on the Doppler principle. The existing commercial instruments have some limitations which the new acoustic technology developed as a part of the EPSRC project offered an improvement to the existing instrument.
Collaborator Contribution The company funded a PhD studentship. Mr. Giulio Dolcetti was appointed to work with the University of Sheffield to develop this technology toward the commercial end.
Impact A laboratory instrument prototype was constructed. The University of Sheffield carried out an extensive testing programme for the instruments provided by ADS LLC and alternative products available on the market.
Start Year 2010
 
Title Device and method for measuring the depth of media 
Description This invention relates to a device and method for measuring the depth of water and sediment deposition in pipes, channels, overland flows and tidal beaches. Sediment deposition may be detrimental to flood control in sewer systems. The invention is specifically concerned with measuring an electrical property such as the conductivity or capacitance in different mediums and therefore quantifying the depths of the different mediums. The measurement of an electrical property such as conductance or capacitance of the medium may also indicate the nature of the medium such as sediment structure, water salinity, and the presence of pollutants. The device includes an array of elongate, substantially mutually parallel electrodes each having a predetermined length, the lengths being incremented stepwise from a shortest electrode to a longest electrode. The device includes electronic circuitry to apply a potential difference across selected pairs of electrodes and to measure a resulting electrical property between each selected pair of electrodes, the measured electrical property providing an indication of a submersion depth of the pair of electrodes in the at least one medium. 
IP Reference WO2014027208 
Protection Patent application published
Year Protection Granted 2012
Licensed Yes
Impact This invention relates to a device and method for measuring the depth of water and sediment deposition in pipes, channels, overland flows and tidal beaches. Sediment deposition may be detrimental to flood control in sewer systems. The invention is specifically concerned with measuring an electrical property such as the conductivity or capacitance in different mediums and therefore quantifying the depths of the different mediums. The measurement of an electrical property such as conductance or capacitance of the medium may also indicate the nature of the medium such as sediment structure, water salinity, and the presence of pollutants. The device includes an array of elongate, substantially mutually parallel electrodes each having a predetermined length, the lengths being incremented stepwise from a shortest electrode to a longest electrode. The device includes electronic circuitry to apply a potential difference across selected pairs of electrodes and to measure a resulting electrical property between each selected pair of electrodes, the measured electrical property providing an indication of a submersion depth of the pair of electrodes in the at least one medium.
 
Title Acoustic wave monitor 
Description This is a new device which makes used of airborne acoustic waves and measures the instantaneous water surface level in an open channel flow. 
Type Of Technology Detection Devices 
Year Produced 2012 
Impact There is a general lack or reliable airborne laboratory or in-situ methods which can be used to measure non-invasively characteristics of a dynamically rough free surface of a shallow water flow such as the flow velocity, turbulence intensity and hydraulic energy losses. This work presents an alternative, much more accurate airborne acoustical method of roughness height measurement which is being developed in collaboration with ADS LLC (USA) and Yorkshire Water Services. 
URL http://www.adsenv.com/
 
Description Attendance at Yorkshire Water Services (YWS) Innovation event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact YWS decided to invest in the development of two acoustic technologies: acoustic inspection of underground pipes; (ii) acoustic flow metering.
Year(s) Of Engagement Activity 2011