CENTRALE LYON - PhD Acoustic radiation of volcanic jets emitted by Plinian eruptions

ECL and Laboratory presentation

Founded in 1857, École Centrale de Lyon is one of the top 10 engineering schools in France. It trains more than 3,000 students of 50 different nationalities on its campuses in Écully and Saint-Étienne (ENISE, in-house school): general engineers, specialized engineers, masters and doctoral students. With the Groupe des Écoles Centrale, it has three international locations. The training provided benefits from the excellence of the research carried out in the 6 CNRS-accredited laboratories on its campuses, the 2 international laboratories, the 6 international research networks and the 10 joint laboratories with companies. Its excellent research and high-level teaching have enabled it to establish double degree agreements with prestigious universities and advanced partnerships with numerous companies. With its focus on sobriety, energy, the environment and decarbonization, Centrale Lyon intends to respond to the problems faced by socio-economic players in the major transitions.

Context and motivation

Plinian eruptions are explosive volcanic eruptions characterized by the continuous ejection at high speed (150−600,m.s−1) and high temperature (∼ 1000◦C) of solid rock fragments, known as tephra, as well as gases such as water vapor, carbon dioxide, and sulfur dioxide [1]. The lowermost section of the eruptive column resembles the jet of an aircraft engine (cf. Figure 1) and generates aerodynamically-induced noise [2–5]. Due

to their large diameter (∼ 100,m), these volcanic jets emit acoustic waves with frequencies typically below the human hearing range (< 20,Hz). These waves, referred to as infrasound, can travel hundreds of kilometers through the atmosphere and carry significant information about their source [6–10]. As a result, one of the main objectives of research in volcano acoustics is to establish a correlation between specific characteristics

of volcanic eruptions, such as ejection velocity or mass flux, and the spectrum of pressure signals recorded at long range [2–5]. Understanding the mechanisms of acoustic radiation of volcanic jets is essential for improving our ability to interpret these infrasonic recordings [5].

Description of the doctoral project

A volcanic jet is a multiphase flow, typically composed of a gas phase (comprising water vapor, carbon dioxide, and sulfur dioxide) and a solid phase (tephra). These two phases may not necessarily be in mechanical and thermal equilibrium with each other [11]. However, in numerous studies concerning volcanic jets, it is assumed that the gases and tephra share the same velocity and temperature [12-14]. This assumption finds

justification in typical Plinian eruptions. In these cases, the volcanic jet can be regarded as a "pseudo-gas" (with thermodynamic properties intermediate between the two phases) that is ejected into the air [12-14]. The dynamics of the jet and the noise production can then be described by the Navier-Stokes equations for a mixture of two gases, namely the aforementioned pseudo-gas and the atmosphere.

The objective of the present doctoral project is to investigate the acoustic radiation from jets resulting from Plinian volcanic eruptions. To this end, three-dimensional large-eddy simulations will be conducted by solving the Navier-Stokes equations via high-order finite difference schemes [15]. These simulations will be performed on mesh grids containing several hundred million points, enabling the simultaneous study of

the jet dynamics and its acoustic radiation. This direct approach to calculating aerodynamically-induced noise has been developed at the Center for Acoustic Research of the LMFA and has already been successfully applied to subsonic and supersonic air jets [16-20]. An illustration of the obtained results is presented in Figure 2, and additional examples are available on the Center for Acoustic Research website https:

//acoustique.ec-lyon.fr/caaweb.php. Furthermore, the large-eddy simulations will be run on CPU and GPU (Graphics Processing Units) clusters using a code written in C/C++/CUDA.

In the scope of the thesis, the first step will be to validate the numerical approach using one-dimensional and two-dimensional test cases [21]. Subsequently, the acoustic radiation from volcanic jets will be investigated for various ejection conditions in terms of velocity, pressure, and temperature. Finally, comparisons will be made between numerical results and data recorded during recent explosive eruptions [2,4].

References

[1] R. Cioni, M. Pistolesi, & M. Rosi, “Chapter 29: Plinian and Subplinian Eruptions,” dans The Encyclopedia of Volcanoes, Academic Press, 2015.

[2] R. S. Matoza, D. Fee, M. A. Garcés, J. M. Seiner, P. A. Ramón & M. A. H. Hedlin, “Infrasonic jet noise from volcanic eruptions,” Geophysical Research Letters, 36, L08303, 2009.

[3] R. S. Matoza, D. Fee, T. B. Neilsen, K. L. Gee & D. E. Ogden, “Aeroacoustics of volcanic jets: Acoustic power estimation and jet velocity dependence,” Journal of Geophysical Research: Solid Earth, 118, 6269-6284, 2013.

[4] D. Fee, R. S. Matoza, K. L. Gee, T. B. Neilsen, & D. E. Ogden„ “Infrasonic crackle and supersonic jet noise from the eruption of Nabro Volcano, Eritrea,” Geophysical Research Letters, 40, 4199–4203, 2013.

[5] L. M.Watson, E. M. Dunham, D. Mohaddes, J. Labahn, T. Jaravel & M. Ihme, “Infrasound Radiation from Impulsive Volcanic Eruptions: Nonlinear Aeroacoustic 2D Simulations,” Journal of Geophysical Research: Solid Earth, 126 (9), 1-28, 2021.

[6] R. Sabatini, O. Marsden, C. Bailly & C. Bogey, “A numerical study of nonlinear infrasound propagation in a windy atmosphere,” The Journal of the Acoustic Society of America, 140(1), 641-656, 2016.

[7] R. Sabatini, C. Bailly, O. Marsden & O. Gainville, “Characterization of absorption and nonlinear effects in infrasound propagation using an augmented Burgers’ equation,” Geophysical Journal International, 207, 1432-1445, 2016.

[8] R. Sabatini, O. Marsden, C. Bailly & O. Gainville, “Three-dimensional direct numerical simulation of infrasound propagation in the Earth’s atmosphere,” Journal of Fluid Mechanics, 859, 754-789, 2019.

[9] R. Sabatini, J. B. Snively, C. Bailly, M. P. Hickey & J. L. Garrison, “Numerical modeling of the propagation of infrasonic acoustic waves through the turbulent field generated by the breaking of mountain gravity waves,” Geophysical Research Letters, 46, 5526-5534, 2019.

[10] R. Sabatini, J. B. Snively, M. P. Hickey & J. L. Garrison, “An analysis of the atmospheric propagation of underground-explosion-generated infrasonic waves based on the equations of fluid dynamics: ground recordings,”The Journal of the Acoustic Society of America, 146, 4576-4591, 2019.

[11] M. Cerminara, T. E. Ongaro & L. C. Berselli, “ASHEE-1.0: a compressible, equilibrium-Eulerian model for volcanic ash plumes,” Geoscientific Model Development, 9, 697-730, 2016.

[12] Y. J. Suzuki, T. Koyaguchi, M. Ogawa & I. Hachisu, “A numerical study of turbulent mixing in eruption clouds using a three-dimensional fluid dynamics model,” Journal of Geophysical Research: Solid Earth, 110, B08201, 2005.

[13] Y. J. Suzuki & T. Koyaguchi, “A three-dimensional numerical simulationof spreading umbrella clouds,” Journal of Geophysical Research: Solid Earth, 114, B03209, 1-18, 2009.

[14] Y. J. Suzuki, A. Costa, M. Cerminara, T. Esposti Ongaro, M. Herzog, A. R. Van Eaton, L. C. Denby, “Intercomparison of three-dimensional models of volcanic plumes,” Journal of Volcanology and Geothermal Research, 326, 26-42, 2016.

[15] C. Bogey & C. Bailly, “A family of low dispersive and low dissipative explicit schemes for flow and noise computations,” Journal Computational Physics , 194(1), 194-214, 2004.

[16] C. Bogey, O. Marsden & C. Bailly, “Large-Eddy Simulation of the flow and acoustic fields of a Reynolds number 105 subsonic jet with tripped exit boundary layers,” Physics of Fluids, 23, 035104, 1-20, 2011.

[17] C. Bogey & R. Sabatini, “Effects of nozzle-exit boundary-layer profile on the initial shear-layer instability, flow field and noise of subsonic jets,” Journal of Fluid Mechanics, 876, 288-325, 2019.

[18] C. Bogey, “Acoustic tones in the near-nozzle region of jets : characteristics and variations between Mach numbers 0.5 and 2,” Journal of Fluid Mechanics, 931, A3, 1-41, 2021.

[19] C. Bogey & R. Gojon, “Feedback loop and upwind-propagating waves in ideally expanded supersonic impinging round jets,” Journal of Fluid Mechanics, 823, 562-591, 2017.

[20] M. Varé & C. Bogey, “Generation of acoustic tones in round jets at a Mach number of 0.9 impinging on a plate with and without a hole,” Journal of Fluid Mechanics, 936, A16, 1-32, 2022.

[21] M. Capuano, C. Bogey & P. D. M. Spelt, “Simulations of viscous and compressible gas–gas flows using high-order finite difference schemes,” Journal of Computational Physics, 361, 56-81, 2018.

The complete list of publications from the Center for Acoustic Research team is available at the following address: https://acoustique.ec-lyon.fr/publication_fr.php.

Diplomas : a master’s degree in aerospace or mechanical engineering, physics, mathematics, or a related field

Experience : none required

Knowledge required: a strong background in fluid mechanics, acoustics, and computational fluid mechanics;

Operational skills : hands-on experience with computing in C/C++, Fortran, Python, or similar programming languages; excellent written and verbal communication skills in English.