Underwater vehicle helps to explore uncharted territory

August 13, 2013 - via Australian Maritime College

The Australian Maritime College is set to play an integral role in pioneering water physics research thanks to the arrival of the autonomous underwater vehicle UBC-Gavia.
Under an agreement with the University of British Columbia, Canada, the research platform will be based at AMC for five years and used to conduct surveys on projects including seafloor mapping, mixing in the water column and under-ice flow dynamics in lakes and oceans.
The torpedo-shaped device is made of anodised aluminium, pressure rated to 500m and features a sidescan sonar and optical camera that captures images at four frames per second. It can be used to measure water column velocities, temperature, salinity, chlorophyll, turbidity and dissolved organic matter.
Dr Alex Forrest, researcher and lead on this collaboration, said the UBC-Gavia was capable of collecting data from locations that would otherwise be inaccessible such as under ice, in caves and far away from surface vessels.
Unlike remotely operated vehicles (ROVs), AUVs can be pre-programmed to profile underwater environments on both the horizontal and vertical axes, providing a three-dimensional picture of the physical processes taking place.
“AUVs are a tool to do good science even though they are predominantly used for long-range surveys such as oil and gas exploration or pipeline surveys,” Dr Forrest said.
“My specialty is examining environmental fluid mechanics – I study mixing in the water column and how different water masses interact. One of the aspects I’m interested in is how water mixes near the ice surface, forms eddies and generates turbulence.
“A lot of this is primary research to try and prove that these processes exist and to try and innovate new ways to study physical processes that we may or may not understand.”
UBC-Gavia last saw action on an international research trip to Lake Kilpisjärvi, Northern Finland in May to investigate winter limnology (the study of lakes during winter) and the impacts of climate change in temperate and polar lakes.
Traditionally it was thought that ice cover arrests all water motion in lakes, but the researchers discovered a distinct pattern of upwelling in the middle. The observed pattern indicates that the Coriolis Effect plays a potential role in ice covered lakes.
The Coriolis Effect is the term used to describe the curvature of global winds, ocean currents and everything else that moves freely across the Earth’s surface due to the planet’s rotation. It is commonly thought of in terms of the way water spins down a drain.
“This finding is quite exciting as it hasn’t been shown previously. Not only is there mixing but there’s mixing happening basin-wide in these lakes and it’s being driven by Earth’s rotation, which we’ve always assumed was negligible either under winter conditions or in lakes in general,” Dr Forrest said.
“It impacts on how we view ice break-up, how we view water quality in the winter, how lakes get reoxygenated and how nutrients are transported in the winter. I would argue that it fundamentally alters how we view lakes in terms of winter dynamics.”
The team plans to visit the same lake a month earlier next year to collect data on what drives the onset of these processes and combine it with their modelling efforts.
Meanwhile, there is potential for the UBC-Gavia to be used in cross-disciplinary projects off the East Coast of Tasmania investigating the influence of shelf break dynamics on harmful algal blooms and the seafloor mapping of urchin barrens. Negotiations are also underway for a research trip to Antarctica during 2014/15.
Dr Forrest’s AUV expertise is well utilised on campus at AMC, where he teaches classes in subsea engineering and underwater vehicle technologies to ocean engineering and naval architecture students.
This year’s final project will challenge students to design, build and test AUVs made from PVC for under $300. An AUV student club, AMC Autonomous Technologies, has also been established with the aim of participating in a national competition next year.
It was the prospect of working in a maritime engineering department that attracted Dr Forrest to join AMC from the University of California – Davis in the United States.
“And also because we have strong connections to the Institute for Marine and Antarctic Studies, CSIRO and the Australian Antarctic Division, there’s an excellent opportunity to be involved with southern ice,” he said.
“Because these (AUV) platforms are designed for the ocean, there’s immense potential to crossover the science with the engineering.”
Made of anodised aluminium
Measures: 2.8 metres long x 30cm diameter
Weight: 75kg in water
Pressure rated to 500m
Features: sidescan sonar and optical camera (4 frames per second)
Measures: water column velocities, temperature, salinity, chlorophyll, turbidity, dissolved organic matter.
Power source: lithium ion battery (3-5 hours of battery life before it needs recharging)
It is six years old and valued at $800,000

External link: https://www.amc.edu.au/news/underwater-vehicle-helps-explore-uncharted-territory

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