- Reference
- SCI2089
- Closing Date
- Friday, 30th September 2022
- Department
- Mathematical Sciences
Modeling vibroacoustic energy distributions in submerged structures at high frequencies
Duration:
3 years, earliest start date Sept 2022
Locations:
- University of Nottingham, United Kingdom
- Naval Group, Ollioules, France
- Matelys Research Lab, Vaulx-en-Velin, France
Context:
Predicting the vibro-acoustic behavior of structures in contact with water is of primary interest for the naval industry: the noise level on-board must satisfy regulations and should be kept low for comfort of crew and passengers. The radiated noise into water must be controlled to reduce the impact on the marine fauna. Prediction methods typically used in the industry such as the Finite Element Method (FEM) [1] require a mesh to discretize the dynamical equations. To properly describe the physical phenomena, this mesh needs to be refined as frequency increases, leading to prohibitive calculation cost above several hundreds of Hertz for a full-scale surface ship. Over the last decades, novel methods have been developed to propose an alternative at high frequencies. Among those methods, the Dynamical Energy Analysis (DEA) has been successfully applied to various model and full-scale industrial structures [2,3]. The method calculates the vibrational energy flow within structures and is based on a reformulation of ray-tracing algorithms, where boundary operators describe the energy transfer between elements of the structure. Compared to more classical high frequency methods such as Statistical Energy Analysis (SEA), the DEA has a wider range of applications due to less limiting assumptions [4].
Objectives of the PhD:
The DEA has so far only been applied to the description of energy propagation within structures in-vacuo. In the naval industry, the coupling with surrounding water must be modeled: it has an important impact on the response of the structure and there is interest in understanding and predicting the radiated energy into the water.
The DEA is so far limited to mechanical excitation, meaning that energy is directly injected into the structure. Internal machinery (engines for instance) produces noise that can be transmitted through
air-borne propagation to the hull, and then tends to radiate noise into water. The energy flow from an internal acoustic source needs thus to be modeled.
Finally, to reduce the underwater radiated noise (URN), decoupling materials can be introduced between the structure and the fluid. These materials, classically made of viscoelastic with micro-voids or cavities, have the ability to isolate the structure from the surrounding fluid or reduce the scattering from incoming waves. The modeling of these materials in the high frequency range is still a challenge [5].
The main tasks of the PhD consist in extending the DEA formulation by:
- modeling the energy exchanges between the structure and the internal and external fluid;
- adding the possibility to excite the structure by an acoustic source, located in the internal or external fluid;
- accounting for external coatings. The coatings can be applied on the hull (air on one side, water on the other side) or on a light structure (water on both sides).
The developments will be implemented into an additional module of the existing DEA software. Results will be validated through comparison to analytical, numerical and if possible experimental results.
Profile
- Holding a MsC in Acoustics, Mechanical Engineering, Physics or Applied Mathematics
- Experience in programming (preferably Python and C++)
- Working independently and as a member of the team
- Good command of the English language
How to apply:
Send a resume, a cover letter and MsC transcripts to:
- Prof Gregor Tanner, University of Nottingham, [email protected]
- Valentin Meyer, Naval Group Research, [email protected]
- Fabien Chevillotte, Matelys Research Lab, [email protected]
References:
[1] N. Atalla, F. Sgard, Finite Element and Boundary Methods in Structural Acoustics and Vibration, CRC Press, 2015.
[2] G. Tanner, Dynamical Energy Analysis –Determining wave energy distributions in vibro-acoustical structures in the high frequency regime, Journal of Sound and Vibration, 320:1023–1038, 2009.
[3] T. Hartmann, S. Morita, G. Tanner and D. J. Chappell, High-frequency structure- and air-borne sound transmission for a tractor model using Dynamical Energy Analysis, Wave Motion 87:132-150, 2019.
Similar Positions
-
Ph D Studentship: Using Next Generation Nitrogen Sources For Producing Spring Malting Barley And Its Impact On Yield And Grain Malt Quality , ;, United Kingdom, about 15 hours ago
Supervisor: Dr John Foulkes (Brewing Science) Secondary Supervisor: Dr Guillermina Mendiondo (Brewing Science), Joe Bevan (Technical Innovation Manager, Molson Coors Beverage Company) Research Des...
-
Ph D Studentship: Technology Solutions To Monitor Activity For In Patient Stroke Rehabilitation , ;, United Kingdom, 10 days ago
Location: UK Other An exciting opportunity has arisen to undertake a PhD as part of the National Rehabilitation Centre (NRC) Training Academy. The student will be based at University of Nottingham...
-
Ph D Studentship: Contribution Of Permafrost Thaw To Arctic Methane Emissions From Peatland Systems , ;, United Kingdom, 13 days ago
Supervisor: Roseanna Mayfield Secondary Supervisor: Sofie Sjögersten Research Description Arctic and Subarctic peatlands are rich in carbon and account for c. 20% of permafrost (layers of frozen s...
-
Ph D Studentship: Understanding And Enhancing The Physiological Resilience Of Older Adults To Improve Health Span: A Focus On Skeletal Muscle , ;, United Kingdom, 8 days ago
Funded by the Dunhill Medical Trust (dunhillmedical.org.uk), we have three fully-funded (stipend at UKRI rates (£19,327 per annum), PhD fees (for UK nationals only) and research costs) three-year...