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Use of Multibeam and Dual-Beam Sonar Systems to Observe Cavitating Flow Produced by Ferryboats: In a Marine Renewable Energy Perspective
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2017 (English)In: Journal of Marine Science and Engineering, Vol. 5, no 30, p. 1-14Article in journal (Refereed) Published
Abstract [en]

With the prospect to deploy hydrokinetic energy converters in areas with heavy boat traffic, a study was conducted to observe and assess the depth range of cavitating flow produced by ferryboats in narrow channels. This study was conducted in the vicinity of Finnhamn Island in Stockholm Archipelago. The objectives of the survey were to assess whether the sonar systems were able to observe and measure the depth of what can be cavitating flow (in a form of convected cloud cavitation) produced by one specific type of ferryboats frequently operating in that route, as well as investigate if the cavitating flow within the wake would propagate deep enough to disturb the water column underneath the surface. A multibeam and a dual-beam sonar systems were used as measurement instruments. The hypothesis was that strong and deep wake can disturb the optimal operation of a hydrokinetic energy converter, therefore causing damages to its rotors and hydrofoils. The results showed that both sonar system could detect cavitating flows including its strength, part of the geometrical shape and propagation depth. Moreover, the boat with a propeller thruster produced cavitating flow with an intense core reaching 4 m of depth while lasting approximately 90 s. The ferry with waterjet thruster produced a less intense cavitating flow; the core reached depths of approximately 6 m, and lasted about 90 s. From this study, it was concluded that multibeam and dual-beam sonar systems with operating frequencies higher than 200 kHz were able to detect cavitating flows in real conditions, as long as they are properly deployed and the data properly analyzed.

Place, publisher, year, edition, pages
2017. Vol. 5, no 30, p. 1-14
Keywords [en]
sonar; cavitating flow; hydrokinetic power; marine renewable energy; ferryboat
National Category
Ocean and River Engineering
Identifiers
URN: urn:nbn:se:uu:diva-327978DOI: 10.3390/jmse5030030OAI: oai:DiVA.org:uu-327978DiVA, id: diva2:1131506
Funder
EU, FP7, Seventh Framework Programme, 607656Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2018-12-10
In thesis
1. Adapting sonar systems for monitoring ocean energy technologies
Open this publication in new window or tab >>Adapting sonar systems for monitoring ocean energy technologies
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The global energy sector is under profound reforms aiming towards renewable energy sources, clean technologies and expansion of smart grids, all with the additional aim of providing affordable and dependable electricity for everyone. A reduction of carbon dioxide emissions is a priority on the global agenda, and to achieve that, cleaner energy technologies has to be more integrated into the energy mix. This thesis focus on a sustainable implementation of wave, tidal and offshore wind power, wherefore there is a need to investigate more about the prerequisites and consequences ocean energy can have on the marine environment. For that, reliable, cost effective and continuous environmental monitoring framework is necessary in order to support and safeguard ocean energy operations.

The main objectives of the research presented in this thesis are to develop a multifunctional environmental monitoring platform based on sonar systems for ocean energy applications, by adapting high resolution multibeam, dual beam and split beam sonar systems and also underwater cameras; Propose data acquisition and processing protocols capable of decipher sonar data in order to provide continuous environmental monitoring and reporting; Conduct qualitative and quantitative observations of fish and marine mammals using the built monitoring platform; And investigate the feasibility of utilizing the Uppsala University wave energy converter technology to generate electricity worldwide. As a result, a multifunctional platform was designed, built and tested. This included the hardware, the data acquisition system, and a data analysis framework comprising new algorithms necessary to process the new acoustic data. The multibeam, dual beam, and split beam sonar systems and underwater cameras produced both qualitative and quantitative data of biomass, occurrence and behavior of fish and marine mammals in the vicinity of ocean energy devices. With this platform, it was also possible to conduct seabed and structural inspections within ocean energy devices, observe cavitating flows, etc. One of the most important results of this research was the possibility of extracting visual signatures of fish and marine mammals through acoustic images. This can be valuable for training algorithms for manual or automatic identification and classification of underwater targets through imaging sonar systems, a technique that can be widely used in the offshore activities. Regarding feasibility studies and wave power resource assessment, this study concluded that mild wave climates can provide enough energy to run reverse osmosis desalination systems as well as produce sufficient electricity to integrate into a national grid.

In summary, this thesis concludes that the implementation of ocean energy can be facilitated by creating environmental monitoring, risk and resource assessment frameworks such as the presented research work that contribute to lowering the risks associated with subsea work and thereby costs of ocean energy projects.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 70
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1752
Keywords
Ocean energy, sonar systems, monitoring technologies, marine environment, wave power
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-368882 (URN)978-91-513-0523-3 (ISBN)
Public defence
2019-02-01, Room 10101, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 607656
Available from: 2019-01-08 Created: 2018-12-10 Last updated: 2019-01-21

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