PhD Studentship: Computational Modelling of Nonlinear Infrasound Propagation through the Atmosphere

Engineering & the Environment

Location: Highfield Campus

Closing Date:  Wednesday 20 December 2017

Reference: 821816F2

Project Reference:NGCM-0093

Infrasound waves can travel hundreds of miles and even interact with the outer reaches of the atmosphere. They are particularly useful to detect and characterise powerful events, either natural (volcanic eruptions) or man-made (explosions). In fact monitoring infrasound waves in the atmosphere is an important technique used to enforce international bans on nuclear tests. The scientific challenges result from the nonlinear radiation of the initial large-amplitude waves, and the variations of temperature and wind speed/direction in the atmosphere, which affect the propagation of the infrasound waves. Much of the existing knowledge on the infrasound propagation has been based on linear or quasi-linear models. The consequence of discarding the nonlinear components is currently unknown. Furthermore, physical understanding of the relationship between the initial strength of the infrasonic pressure at explosion and the subsequent evolution of the acoustic signals is currently underdeveloped. It is believed that the physical understanding can only be achieved by studying the full nonlinear processes of the infrasound propagation.

Supported by AWE, this PhD project aims to achieve extensive knowledge of the nonlinear effects on the long-range propagation of infrasound waves through the atmosphere. In order to achieve the goal, we will develop an efficient computational model based on fully nonlinear compressible Navier-Stokes equations. The computational model will enable us to accurately simulate the long-range propagation of infrasound waves through realistic wind conditions and temperature gradients across the atmosphere. We will develop the new model based on an existing in-house code CANARD (Computational Aerodynamics & Aeroacoustics Research coDe) that has successfully been used for various aeroacoustic problems at the University of Southampton [1-3]. In this project, significant effort will go into precisely modelling the event of explosion and creating the Infrasound waves can travel hundreds of miles and even interact with the outer reaches of the atmosphere. They are particularly useful to detect and characterise powerful events, either natural (volcanic eruptions) or man-made (explosions). In fact monitoring infrasound waves in the atmosphere is an important technique used to enforce international bans on nuclear tests. The scientific challenges result from the nonlinear radiation of the initial large-amplitude waves, and the variations of temperature and wind speed/direction in the atmosphere, which affect the propagation of the infrasound waves. Much of the existing knowledge on the infrasound propagation has been based on linear or quasi-linear models. The consequence of discarding the nonlinear components is currently unknown. Furthermore, physical understanding of the relationship between the initial strength of the infrasonic pressure at explosion and the subsequent evolution of the acoustic signals is currently underdeveloped. It is believed that the physical understanding can only be achieved by studying the full nonlinear processes of the infrasound propagation.

In addition, new theoretical analysis of nonlinear wave propagation will be undertaken to provide a complementary, low-fidelity efficient prediction method. This will be used to support validation of the computational simulations, as well as to provide further understanding of the physical mechanisms.

We are looking for an applicant with a strong background in physics, applied mathematics or aerospace engineering. An interest in theoretical modelling is important and experience with scientific computing is a distinct advantage. The studentship will cover full tuition fees and stipend at the standard EPSRC levels. More information on the PhD programme and structure can be found at: http://ngcm.soton.ac.uk.

Please note that working with AWE normally requires that the student is either a UK national or has been a resident of the UK for the last ten years at least. The student will also be required to undergo security clearance. Successful completion of the project could lead to employment at AWE.

[1] http://eprints.soton.ac.uk/399809

[2] http://eprints.soton.ac.uk/400758

[3] http://eprints.soton.ac.uk/387135

[4] http://cmg.soton.ac.uk/iridis

[5] http://www.archer.ac.uk/about-archer

If you wish to discuss any details of the project informally, please contact Dr Jae-Wook Kim, Email: J.W.Kimsoton.ac.uk, Tel: +44 (0) 2380 594886.

This project is run through participation in the EPSRC Centre for Doctoral Training in Next Generation Computational Modelling (http://ngcm.soton.ac.uk). For details of our 4 Year PhD programme, please see http://www.findaphd.com/search/PhDDetails.aspx?CAID=331&LID;=2652

For a details of available projects click here http://www.ngcm.soton.ac.uk/projects/index.html

Further details:

• Job Description and Person Specification