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Emmanuel Motheau

Research Scientist, Computational Research Division

Fluid Dynamics, High-Performance Computing, Applied Deep Learning


Contact Information

Emmanuel Motheau
MS 50A-3111
Lawrence Berkeley National Lab
1 Cyclotron Rd.
Berkeley, CA 94720

510-486-7286 (office)
510-486-6900 (fax)

EMotheau@lbl.gov


Affiliation and Research Interests

I am a Research Scientist in the Center for Computational Sciences and Engineering (CCSE) in the Computational Research Division of the Computing Sciences Area at the Lawrence Berkeley National Laboratory.

My research aims to develop robust and innovative numerical tools to perform simulations and analysis of multi-scale and multi-physics applications that are encountered in practical industrial configurations. More specifically, I am interested in the areas of clean energy and efficient propulsion for aeronautical and automotive industries.

Currently, my research activities focus on several different topics:

Machine Learning: I am interested in applying deep learning techniques to practical Computational Fluid Dynamics (CFD) simulations. More specifically, I am actively involved in the NESAP FlowGAN team to develop super-resolution techniques based on deep convolutional neural networks, with a focus on realistic 3D turbulent flows (see [arxiv]).

Applied Mathematics: I am interested in the study of the dynamics of turbulent flames, and more specifically combustion instabilities in industrial applications. Currently, I am investigating the properties of numerical schemes to accurately capture the stability of flames together with a correct spectral representation of turbulence in reactive flows. I am trying to go beyond the debate between low-order and high-order methods to focus on the actual restitution of the physics of reactive turbulent flows.

High Performance Computing (HPC): I am working actively for the DOE Exascale Computing Project on the development of the Pele suite of codes, which consist on the two AMR (Adaptive Mesh Refinement) combustion modeling codes PeleC (compressible) and PeleLM (Low-Mach) designed for exascale computing. In that context, I have implemented in the PeleLM code the Embedded Geometry feature to impose complex geometries, as well as a hybrid MPI/OpenMP strategy together with full support for GPU computing. In PeleC, I have developed and implemented the Ghost-Cells Navier-Stokes Characteristic Boundary Conditions (GC-NSCBC, see [AIAA J. 2017]) as well as the hybrid PPM/WENO strategy to accurately capture compressible turbulence spectra (see [CAMCOS 2020]).


Previous works and background

I joined Lawrence Berkeley National Laboratory in January 2016 as a Postdoctoral Research Fellow in the CCSE team. During that time I worked with Ann Almgren and John B. Bell on the development of a hybrid strategy to couple the fully-compressible and the low-Mach-number approaches, based on multigrids and AMR (Adaptive Mesh Refinement) methods (see [JCP 2018]). Also, I was involved in the development of high-order methods for AMR, such as the Adaptive Multi-Level Spectral Deferred Correction (AMLSDC) method, which employs an Implicit/Explicit treatment suitable for combustion applications (see [CTM 2019]).

Before joining Lawrence Berkeley National Laboratory, I was a Research Associate (ARC Level B) at the University of Adelaide (Australia) and collaborated with Prof. John Abraham (Purdue University, USA). During two years (2014-2015), I have developed a DNS code named HOLOMAC (High-Order LOw MAch Combustion) to perform numerical simulations of reactive flows with detailed chemistry and under the low-Mach-number assumption.
The algorithm uses high-order numerical methods and reaches sixth-order accuracy with quasi-spectral accuracy. For detailed informations, please see Motheau and Abraham, JCP 2016. HOLOMAC is currently used in the group of Prof. John Abraham to assess petro/bio-diesel performances.

In 2013, I graduated from the Institut National Polytechnique of the University of Toulouse, France. I did my Ph.D. thesis at CERFACS (European Center for Research and Formation in Scientific Computation) under the supervision of Prof. Thierry Poinsot and Prof. Franck Nicoud. Snecma Motors (SAFRAN group) has funded the thesis. The subject of my Ph.D. thesis is the study of combustion instabilities in realistic aeronautical gas turbines, and more specifically instabilities resulting from the coupling between acoustic and entropy modes of fluctuation.

Large-Eddy Simulations (LES) were performed to reproduce stable and unstable operating points. However, despite a great agreement with the experimental results provided by the industry, LES results come at a tremendous computational cost and do not explain all the physics and why the system is unstable. An alternative approach has been developed, based on mixed numerical and analytical models. It relies on the use of a zero-Mach-number thermoacoustic Helmholtz solver together with a Delayed Entropy Coupled Boundary Condition (DECBC). Coupled with a Dynamic Mode Decomposition (DMD) analysis, such methodology is able to construct a reduced-order model so as to extract the underlying instability mechanism. The mixed acoustic-entropy nature of the mechanism has then been demonstrated. During my Ph.D. I participated in 2012 at the Summer Program of the Center for Turbulence Research, Stanford University, USA. For details, please see Motheau et al., JFM 2014 and Motheau et al., JSV 2014.

In 2010, I earned a M.Sc. in Acoustics from the Engineering School of the Conservatoire National des Arts et Metiers, Paris, France. Between 2005 and 2010, I did several internships in academic and industrial research labs: musical acoustics at the LAM (Laboratory of Musical Acoustics) in the Pierre and Marie Curie University in Paris, France; fluid-structure interactions and underwater acoustics at DCNS in Nantes, France; Large-Eddy-Simulations of multiperforated plates of gas turbine combustion chambers at Turbomeca (SAFRAN group) in Pau, France.


Refereed Journal Publications

E. Motheau and J. Wakefield, "On the numerical accuracy in finite-volume methods to accurately capture turbulence in compressible flows", Int. J. Numer. Methods Fluids, In press, 2021. [doi]

J. Pathak, M. Mustafa, K. Kashinath, E. Motheau, T. Kurth, M. Day, "Using Machine Learning to Augment Coarse-Grid Computational Fluid Dynamics Simulations", Under Review, 2021. [arxiv]

E. Motheau and J. Wakefield, "Investigation of finite-volume methods to capture shocks and turbulence spectra in compressible flows", Commun. in Appl. Math. and Comput. Sci, 15-1 (2020), 1--36. [arxiv]

M. Emmett, E. Motheau, W. Zhang, M. Minion and J. B. Bell, "A Fourth-Order Adaptive Mesh Refinement Algorithm for the Multicomponent, Reacting Compressible Navier-Stokes Equations", Combustion Theory and Modelling 23:4, 592-625, 2019. [arxiv]

E. Motheau, M. Duarte, A. Almgren, J. Bell, "A Hybrid Adaptive Low-Mach-Number/Compressible Method: Euler Equations", Journal of Computational Physics, Volume 372, Pages 1027-1047, 2018. [arxiv][pdf]

Emmanuel Motheau, Ann Almgren, John Bell, "Navier-Stokes Characteristic Boundary Conditions Using Ghost Cells", AIAA J., Vol. 55, No. 10 : pp. 3399-3408, 2017. [pdf]

Z. Wang, E. Motheau and J. Abraham, "Effects of equivalence ratio variations on turbulent flame speed in lean methane/air mixtures under lean-burn natural gas engine operating conditions", Proc. Combust. Inst., Volume 36, Issue 3, 3423-3430, 2017. [pdf]

E. Motheau, J. Abraham, "A high-order numerical algorithm for DNS of low-Mach-number reactive flows with detailed chemistry and quasi-spectral accuracy", Journal of Computational Physics, Volume 313, 430-454, 2016. [pdf]

E. Motheau, F. Nicoud and T. Poinsot, "Mixed acoustic-entropy combustion instabilities in gas turbines", Journal of Fluid Mechanics, 749, 542-576, 2014. [pdf]

E. Motheau, L. Selle and F. Nicoud, "Accounting for convective effects in zero-Mach-number thermoacoustic models", Journal of Sound and Vibration, 333(1), 246-262, 2014. [pdf]

E. Motheau, Y. Mery, F. Nicoud, and T. Poinsot, "Analysis and modelling of entropy modes in a realistic aeronautical gas turbine", Journal of Engineering for Gas Turbines and Power, 135(09):092602, 2013. [pdf]

E. Motheau, F. Nicoud, and T. Poinsot, "Using boundary conditions to account for mean flow effects in a zero-Mach-number acoustic solver", Journal of Engineering for Gas Turbines and Power, 134(11):111502, 2012. [pdf]

E. Motheau, T. Lederlin, Juan Florenciano, and P. Bruel, "LES investigation of the flow through an effusion-cooled aeronautical combustor model", Flow, Turbulence and Combustion, 88(March):169-189, 2012. [pdf]

Refereed Conference Proceedings

E. Motheau, A. Almgren and J.B. Bell. "Navier-Stokes Characteristic Boundary Conditions Using Ghost Cells", 23rd AIAA Computational Fluid Dynamics, Denver, CO, USA, June 6 2017. [pdf]

E. Motheau, M. Duarte, A. Almgren and J.B. Bell. " A Hybrid Adaptive Low-Mach-Number/Compressible Method for the Euler Equations", 23rd AIAA/CEAS Aeroacoustics Conference, Denver, CO, USA, June 5 2017. [pdf]

Z. Wang, E. Motheau and J. Abraham, "Equivalence Ratio Effects on Turbulent Premixed Flames in Lean Methane/Air Mixtures", Australian Combustion Symposium 2015, Melbourne (Australia), December 7-9 2015. [pdf]

E. Motheau, Y. Mery, F. Nicoud and T. Poinsot, "Analysis and modelling of entropy modes in a realistic aeronautical gas turbine", ASME Turbo Expo 2013, San Antonio (Texas, USA), June 3-7 2013, Selected for journal publication.

E. Motheau, F. Nicoud and T. Poinsot, "Using boundary conditions to account for mean flow effects in a zero-Mach-number acoustic solver", ASME Turbo Expo 2012, Copenhagen (Denmark), June 11-15 2012, Selected for journal publication.

E. Motheau, T. Lederlin, and P. Bruel, "LES investigation of the flow through an effusion-cooled aeronautical combustor model", ETMM8: 8th International ERCOFTAC Symposium, Marseille, France, June 9-11 2010, Selected for journal publication.

Peer-reviewed Conference Publications

E. Motheau, L. Selle, Y. Mery, T. Poinsot, and F. Nicoud, "A mixed acoustic-entropy combustion instability in a realistic gas turbine", Center for Turbulence Research, Proceedings of the Summer Program, Stanford University, 2012. [pdf]

Presentations

E. Motheau, A. Almgren and J.B. Bell. "Navier-Stokes Characteristic Boundary Conditions Using Ghost Cells", 23rd AIAA Computational Fluid Dynamics, Denver, CO, USA, June 6 2017.

E. Motheau, M. Duarte, A. Almgren and J.B. Bell. " A Hybrid Adaptive Low-Mach-Number/Compressible Method for the Euler Equations", 23rd AIAA/CEAS Aeroacoustics Conference, Denver, CO, USA, June 5 2017.

E. Motheau, A. Almgren and J.B. Bell. "A Hybrid Adaptive Compressible/Low-Mach-Number method", SIAM-CSE17, Atlanta, USA, February 27 2017.

E. Motheau, "Towards a Hybrid Adaptive Compressible/Low-Mach-Number method", Invited talk, BASCD 2016, Stanford University, USA, December 3 2016.

Z. Wang, E. Motheau and J. Abraham, "Equivalence Ratio Effects on Turbulent Premixed Flames in Lean Methane/Air Mixtures", Australian Combustion Symposium 2015, Melbourne (Australia), December 7-9 2015.

E. Motheau, "Using Mach-number assumptions to derive CFD methods: application to reactive flows and combustion instabilities", Invited seminar, University of New South Wales, Sydney, Australia, June 3 2015.

E. Motheau, Y. Mery, F. Nicoud and T. Poinsot, "Analysis and modelling of entropy modes in a realistic aeronautical gas turbine", ASME Turbo Expo 2013, San Antonio (Texas, USA), June 3-7 2013.

E. Motheau, F. Nicoud, and T. Poinsot, "Analysis and modelling of entropy modes in a realistic aeronautical gas turbine", Journee des Doctorants, Snecma Motors, Safran Group, Villaroche, France, May 2013.

E. Motheau, F. Nicoud and T. Poinsot, "Using boundary conditions to account for mean flow effects in a zero-Mach-number acoustic solver", ASME Turbo Expo 2012, Copenhagen (Denmark), June 11-15 2012.

E. Motheau, F. Nicoud, and T. Poinsot, "Using boundary conditions to account for mean flow effects in a zero-Mach-number acoustic solver", Journee des Doctorants, Turbomeca, Safran Group, Bordes, France, December 2011.

E. Motheau, F. Nicoud, and T. Poinsot, "Using boundary conditions to account for mean flow effects in a zero-Mach-number acoustic solver", Journee des Doctorants, Groupe Francais de Combustion, Ecole Centrale Paris, Paris, France, December 15 2011.

E. Motheau, F. Nicoud, and T. Poinsot, "Using boundary conditions to account for mean flow effects in a zero-Mach-number acoustic solver", 3rd INCA Colloquim, Toulouse, France, November 17-18 2011.

E. Motheau, T. Lederlin, and P. Bruel, "LES investigation of the flow through an effusion-cooled aeronautical combustor model", ETMM8: 8th International ERCOFTAC Symposium, Marseille, France, June 9-11 2010.

Other academic activities

Reviewing activities for Combustion Science and Technology, Combustion and Flame, Journal of Fluids Engineering, Journal of Fluid Mechanics, International Journal of Aeroacoustics, Journal of Sound and Vibration, AIAA Journal, Engineering with Computers.