# Who am I ?

My name is Vivien Denis. I graduated from INSA Lyon (Mechanical Engineering Design branch) and obtained a PhD in acoustics, at the Laboratory of Acoustics of the University of Le Mans (LAUM), in France. Currently I'm a postdoctoral researcher working on the Acoustic Black Hole effect, which is a strategy of vibration damping in thin structures.

# Research

My PdD work was about the so-called Acoustic Black Hole (ABH) effect, used in the context of passive vibration damping. Vibration damping is a major concern in today's engineering structures, and it is also important to keep an eye on the weight aspect. The Acoustic Black Hole effect aims to be both passive and light. It is based on the idea that flexural wave speed and wave length are related to the thickness in a thin medium (plates, beams). A theoretical work predict that a wave can propagate infinitely without being reflected in a medium whose thickness decreases to zero with a power-law profile, at least quadratic (Mironov, Soviet Physics: Acoustics 34, 1988). The practical realisation is always of non-zero thickness at the end, nevertheless a condition of low reflection for an incident wave can be obtained adding a small piece of damping material to the power-law profile, as shown in Krylov, 2004.

The research focused on two axes : what is the effect of the such a termination on the whole structure, and what about the reflective properties of a practical termination, which always exhibits imperfections ? The first question is answered doing experimental and numerical modal analysis of a simple one-dimensional structure with an ABH termination. It shows an increase of the modal density, the modal loss factor and the modal overlap factor of the whole structure, a localization of the energy in the termination and an intrinsic plate behavior at the extremity. To answer the second question, we measure reflection coefficients and model an imperfectly made extremity.

I recently defended my PhD thesis. Here are the manuscript and the presentation. A not-so-recently-made poster about this work can be found here and conferences acts and papers are given below.

My current post-doc focuses on nonlinearities in the ABH extremity.

# Publications & conferences

- V. Denis, L. Maxit :
*Prediction of ﬂow induced sound and vibration of periodically stiffened plates*, Proceedings of NOVEM 2012, Sorento, April 2012. - L. Maxit, V. Denis :
*Prediction of ﬂow induced sound and vibration of periodically stiffened plates*, J. Acoust. Soc. Am. 133 (1), 146-160 (2013). - V. Denis, F. Gautier, A. Pelat :
*Simulation of vibrations of a 2D acoustic black hole placed in an infinite plate using the Finite Difference Time Domain method*, conference given at Acoustics 2012 Nantes on april 25th, 2012. - V. Denis, F. Gautier, A. Pelat :
*Increasing the modal overlap of a beam using the acoustic black hole effect*, Proceedings of MEDYNA 2013, Marrakech, April 2013. - V. Denis, F. Gautier, A. Pelat :
*Increasing the modal overlap of a beam using the acoustic black hole effect*, Proceeding of ICOVP 2013, Lisboa, September 2013. - V. Denis, F. Gautier, A. Pelat, B. Elie :
*Modal Overlap Factor of a Beam with an Acoustic Black Hole termination*, J. Sound Vib. 333, 2475-2488 (2014). [pdf] - V. Denis,
*Vibration damping in beams using the Acoustic Black Hole effect*, PhD thesis, Université du Maine, 2014. [pdf] - V. Denis, F. Gautier, A. Pelat, J. Poittevin,
*Measurement and modelling of the reflection coefficient of an Acoustic Black Hole termination*, J. Sound Vib. 349, 67-79 (2015). [pdf] - V. Denis, J. Poittevin, F. Gautier, A. Pelat, P. Picart, C. Pézerat,
*Characteristics of the vibratory field inside an acoustic black hole placed on a beam*, Proceedings of ICEDyn 2015, Lagos, June 2015. - V. Denis, A. Pelat, F. Gautier,
*Scattering effects induced by imperfections on an Acoustic Black Hole placed at a structural waveguide termination*, J. Sound Vib. 362, 56-71 (2016). [pdf] - V. Denis, A. Pelat, C. Touzé, F. Gautier,
*Effet des non linéarités géométriques sur l'amortissement par effet Trou Noir*, Proceedings of CFA 2016, Le Mans, April 2016. [pdf]

# Teaching

Teaching can be one of the task assigned to PhD students. I was a teaching assistant in the engineering school ENSIM. From 2011 to 2015, I gave tutorials in vibro-acoustics and tutorials and practical work in engineering design, which was my main interest in INSA Lyon.

# Other interests

My other interests are mainly music and bikes. I play the clarinet (at Fanfare Takasouffler), the accordion and I conduct the ENSIM'phonic orchestra (every tuesday evening, C05, ENSIM !). I'm also fond of bicycles and their simple yet interesting mechanics.

# Contact

My office is in the engineering school ENSIM. Feel free to write me an email.

# Useful links

My ResearchGate profile

Laboratoire d'Acoustique de l'Université du Maine, the laboratory I work in.

Université du Maine

ENSIM

INSA Lyon, the school I'm from.