A coupled CFD and observational approach to improve measurements of ocean turbulence from gliders (PALMER_UENV16NEX)
Primary supervisor: Dr Matthew Palmer
Email: rolm@noc.ac.uk
Please note that the successful applicant to this project will be registered for a PhD in the School of Environmental Sciences at the University of East Anglia.
Project rationale
Ocean turbulence is sporadic, chaotic and, therefore, difficult to understand and predict. Yet it is critical to understand and simulate turbulence, and its associated mixing, to predict ocean dynamics and the complex interactions that control the global carbon cycle and the earth’s climate. Currently, state-of-the-art models fail to replicate the complexity of turbulence and, consequently, ocean mixing is poorly simulated, which severely limits predictions by ocean and/or earth-system models.
Autonomous vehicles offer the potential for a large step-change improvement in measuring ocean turbulence. Recent developments by Palmer et al (2015) and others show that microstructure-enabled autonomous ocean gliders are a robust platform for measuring turbulence, both for extended durations and at fine resolutions, beyond the capability of traditional ship-based methods. Uncertainty still remains, however, on how the motion of buoyancy-controlled platforms, impacts the flow around the attached sensors, which measure millimeter-scale turbulence. Utilising the rapid technological advances in autonomy is, therefore, dependent on finding someone possessing the engineering skills to unravel the complexities of how turbulent flow fields interact with complex glider geometry, and scientific creativity to develop new methods of processing and interpreting ocean turbulence measurements.
Methodology
The student will employ a mixture of theoretical and empirical methods, using data from observations and computational fluid dynamics (CFD) models, to develop improved understanding of laminar and turbulent flows around ocean gliders and attached turbulence sensors. This new understanding will be applied to data from numerous field campaigns, from both available ocean glider platforms (TWR & Kongsberg), to develop improved algorithms for calculating glider motion and oceanic turbulence. To achieve these ambitious goals, the student will be advised by an expert team with a broad range of skills in shallow (Palmer) and deep (Hall) ocean turbulence measurements, in CFD realisation of turbulent flows (Moat), and in the design, development and manufacture of instrumentation for measuring turbulence (Lueck). An established LES model (Gerris) will be optimised to reveal the flow around glider-mounted microstructure probes. A variety of realistic forcing scenarios will be used to explore the impact of the glider, and its sensors, on the measurement of the microstructure turbulence. New methods and algorithms will be developed to correct the vehicle-induced distortions of turbulence, and validated using observational data, to enable reliable application to glider-based measurements. That is, to improve measurements of ocean turbulence and our understanding of ocean mixing.
Training
The NEXUSS CDT provides state-of-the-art, highly experiential training in the application and development of cutting-edge Smart and Autonomous Observing Systems for environmental sciences, alongside comprehensive personal and professional development. There will be extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial / government / policy partners. The student will be registered at the University of East Anglia, and be hosted at NOC-Liverpool with periods of training in Southampton and UEA. Specific training includes:
Processing and analysis of ocean turbulence data.
- Application of the CFD results;
- Applied and theoretical mathematical and physical analytical techniques;
- Opportunities for seagoing research and glider training;
- Participation in international workshops and conferences.
CASE partner Rockland Scientific (Lueck) will also provide up to 9 months placement in Victoria, Canada, with training collecting, processing and interpreting turbulence measurements and teaching the scientific motivation for taking these data.
References
(i) Palmer M. R., G. R. Stephenson, M. E. Inall, C. Balfour, A. Dusterhus & J. A. M. Green (2015) Turbulence and Mixing by Internal Waves In The Celtic Sea Determined From Ocean Glider Microstructure Measurements. Journal of Marine Systems, http://dx.doi.org/10.1016/j.jmarsys.2014.11.005
(ii) Lueck, R. G., F. Wolk & H. Yamazaki (2002) Ocean velocity microstructure measurements in the 20th century. Japan J. of Oceanogr., 58, 153-174.
(iii) Creed, E., W. Ross, R. Lueck, P. Stern, W. Douglas, F. Wolk & R. Hall (2015) Integration of a RSI microstructure sensing package into a Seaglider. Proceedings of OCEANS’15 MTS/IEEE Washington.
Entry requirements
First degree subjects: Oceanography, marine science, meteorology, geophysics, environmental sciences, physics, mathematics, engineering, any physical science.
Minimum entry requirement: Undergraduate degree with a classification of 2:1 (or international equivalent).
Start date: September 2016
Programme: PhD
Mode of Study: Full-time
Studentship Length: 3 years, 8 months
Application deadline: 1 June 2016