Field Stereoscopic Particle Image Velocimetry (FSPIV) system for high-resolution in-situ studies of freshwater and marine ecosystems

Lead Research Organisation: University of Aberdeen
Department Name: Engineering

Abstract

Field stereoscopic particle image velocimetry (FSPIV) will enable 3-component high-resolution instantaneous velocity measurements in natural aquatic environments with measurement fields covering an area up to 1.0 m by 0.5 m and sampling rates up to 200 Hz. In addition to recording flow fields, FSPIV can simultaneously capture information on biota in the sampling region using the same hardware, for example, the motion of aquatic plants, or the trajectories of swimming fish. There are no international analogues to the proposed system; it will be a world-first of its kind.
Key concepts of this technology have been developed and successfully tested by the research group in Aberdeen (Cameron 2011; Cameron et al., 2013; Biggs et al. 2019). The new system will be assembled based on this experience and will substantially enhance current capability in terms of portability, flexibility in operating conditions, and key performance characteristics such as field-of-view, spatial and time resolution, and measurement accuracy.
The new FSPIV system will consist of a lightweight submersible head unit containing eight digital cameras and light-sheet-forming optical components connected by a 30m long umbilical to a control station consisting of a pulsed laser, image capture and storage device, and a portable electric generator. The control station may be mounted, for example, on a river bank, a beach, or in a boat. The umbilical connecting the head unit with the control station will protect the power and data cables for the cameras along with a bundle of fibre optic cables to deliver the laser energy to the measurement region. The head unit may be used in a number of configurations maximising deployment flexibility, e.g. skimming the water surface in shallow rivers or fully submersed in deeper rivers, estuaries or marine environments. The high sensitivity of modern sCMOS cameras allows a relatively low intensity light sheet to be used which is completely harmless and non-invasive to wildlife.
The proposed FSPIV system surpasses the capabilities of conventional field measurement techniques in that the instantaneous measurement region covers a large 2-dimensional flow area while maintaining approximately 1 mm spatial resolution, whereas more commonly deployed techniques have comparatively coarser resolution and are limited to 1-D (along a line) or single point measurements. With eight cameras covering the FSPIV measurement domain, redundant estimates of velocity components allow low noise statistical estimates with uncertainties comparable to the best available laboratory devices. The additional capability provided by FSPIV is vital for 'next generation' research studies in freshwater and coastal environments. The FSPIV system will, for example, be used to study interactions between turbulence and aquatic plants or the flow fields around swimming fish in their natural environment. Such studies are inherently cross-disciplinary and bridge the established fields of aquatic ecology, biomechanics, and environmental fluid mechanics (e.g. Nikora 2010). The combination of a multi-disciplinary approach drawing on the collective experience of a national management group and international advisory panel with state-of-the-art world-leading technology should secure transformative changes in current understanding of the natural environment.

Biggs, H., Nikora, V., Gibbins, C., Cameron, S. et al., 2019. Journal of Ecohydraulics, 1-18.
Cameron, S., 2011. Journal of Hydro-Environment Research, 5(4), 247-262.
Cameron, S., Nikora, V. et al., 2013. Journal of Fluid Mechanics, 732, 345-372.
Nikora, V. 2010. River Research and Applications, 26, 367-384.
Nikora, V., Cameron, S., et al., 2012. Environmental Fluid Mechanics: Memorial Volume in Honour of Prof. Gerhard H. Jirka, 217-235.

Planned Impact

The proposed FSPIV system will enable unique data sets to be obtained on flow-biota interactions in natural environments such as rivers, estuaries, and coastal areas. The high resolution (mm or sub-mm) velocity fields recorded over 1.0 m by 0.5 m domains coupled with synchronous measurements of biota such as aquatic plant motion or swimming fish trajectories promise insights into dynamics of the natural environment at organism-related scales which has not yet been possible with any previous technology. Our target output during the 10 year design life of the system is: (1) to make 250 field deployments of FSPIV; (2) to use FSPIV in conjunction with our collaborative partners within at least 5 projects funded by UK funding bodies for studies of freshwater and marine ecosystems; (3) to report scientific findings from FSPIV in 20 papers in leading international journals; (4) to report outcomes from FSPIV at 10 international conferences; and (5) report outcomes obtained from FSPIV at 10 workshops or engagement events for key beneficiaries (government bodies, public and private agencies and consultancies, and members of the public).

The key social and economic benefits of FSPIV relate to: (1) improved management of freshwater and coastal/marine resources and (2) bio-inspired design. Specifically, it is expected that insights gained from FSPIV will contribute to the design of cost effective strategies aimed at preserving and recovering biodiversity in natural aquatic ecosystems which are under threat due to industrial pollution, overfishing, climate change, and invasive species. In addition, FSPIV should contribute to realising some of the vast potential for bio-inspired design of, for example, low environmental impact hydraulic structures such as dams or offshore windfarms, and design of aquafarms utilising symbiotic relationships between plant and animal species.

The direct beneficiaries of the data and research findings from FSPIV therefore include: (1) central and local government bodies responsible for the management of aquatic ecosystems (e.g., Environment Agency [EA], Marine Management Organization [MMO], Joint Natural Conservation Committee [JNCC], Scottish Environment Protection Agency [SEPA], and Marine Scotland Science [MSS] ); (2) energy companies, environmental and engineering consultancies designing water-related infrastructure such as dams or offshore wind-farms; (3) owners and designers of aquafarms for fish and shellfish; and (4) recreational users of aquatic resources including sport-fisherman and nature enthusiasts. In addition, we will expose this state-of-the-art equipment and its application to groups of students from nearby school(s) by organising tours to the deployment sites, allowing students to experience the excitement of scientific research through personal involvement.

Publications

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