Papers by Georges Jourdan
Physical Review E, 2013
When solid particles are impulsively dispersed by a shock wave, they develop a spatial distributi... more When solid particles are impulsively dispersed by a shock wave, they develop a spatial distribution which takes the form of particle jets whose selection mechanism is still unidentified. The aim of the present experimental work is to study particle dispersal with fingering effects in an original quasi two-dimensional experiment facility in order to accurately extract new information. Shock and blast waves are generated in the carrier gas at the center of a granular medium ring initially confined inside a Hele-Shaw cell and impulsively accelerated. With the present experimental set-up, the particle jet formation is clearly observed. From fast flow visualizations, we notice, in all instances, that the jets are initially generated inside the particle ring and thereafter expelled outward. This point was never observed before in the three-dimensional spherical explosion experiments. We highlight that the number of jets is unsteady and decreases with time. For a fixed configuration, considering the very early times following the initial acceleration, the jet size selection is independent of the particle diameter. Moreover, the influence of the initial overpressure and the material density on the particle jet formation have been studied. It is shown that the wave number of particle jets increases with the overpressure and with the decrease of the material density. The normalized number of jets as a function of the initial ring acceleration shows a power law valid for all studied configurations involving various initial pressure ratios, particle sizes and particle materials.
Physics of Fluids, 2012
ABSTRACT This paper addresses post detonation modelling in spherical explosions. One of the chall... more ABSTRACT This paper addresses post detonation modelling in spherical explosions. One of the challenges is thus related to compressible turbulent mixing layers modelling. A one-dimensional flow model is derived consisting in a reduced two-phase compressible flow model with velocity drift. To reduce the number of model parameters, the stiff velocity relaxation limit is considered. A semi-discrete analysis is used resulting in a specific artificial viscosity formulation embedded in the diffuse interface model of Kapila et al. [Phys. Fluids 13(10), 3002–3024 (2001)]10.1063/1.1398042. Thanks to the velocity non-equilibrium model and semi discrete formulation, the model fulfils the second law of thermodynamics in the global sense and uses a single parameter. Multidimensional mixing layer effects occurring at gas-gas unstable interfaces are thus summarized as artificial viscosity effects. Model's predictions are compared against experimental measurements of mixing layer growth in shock tubes at moderate initial pressure ratios as well as fireball radius evolutions in air explosions at high initial pressure ratios. Also, pressure signals recorded at various stations are compared, showing excellent agreement for the leading shock wave as well as the secondary one. With the help of various experiments in the low and high initial pressure ratios bounds, estimates for the interpenetration parameter are given.
Applied Physics Letters, 2015
Dynamic stabilization by simultaneous primary and superharmonic resonances for high order nonline... more Dynamic stabilization by simultaneous primary and superharmonic resonances for high order nonlinearity cancellation is demonstrated with an electrostatically-actuated, piezoresistively-transduced nanomechanical resonator. We prove experimentally how the combination of both the third-order nonlinearity cancellation and simultaneous resonances can be used to linearly drive a nanocantilever up to very large amplitudes compared to fundamental limits like pull-in occurrence, opening the way towards resonators with high frequency stability for high-performance sensing or time reference. PACS numbers: 85.85.+j, 05.45.-a, 46.40.Ff, 46.15.Ff 1 arXiv:1504.07533v1 [cond-mat.mes-hall]
29th International Symposium on Shock Waves 2, 2015
Experiments in Fluids, 2015
ABSTRACT We propose to experimentally study, in cylindrical geometry, the interaction of an initi... more ABSTRACT We propose to experimentally study, in cylindrical geometry, the interaction of an initially perturbed cylindrical gaseous interface with a converging shock wave. This interaction is commonly referred as the Richtmyer–Meshkov instability (RMI) which, in the present case, is in a cylindrical geometry. In order to achieve this goal, we use a conventional shock tube which is adapted to this geometry through a specifically designed convergent test section. Here, the first results are presented for an incident planar shock wave of Mach number 1.15 propagating through an adequately elliptical air/SF 6 interface. It curves into a cylindrical transmitted shock wave and then accelerates a second sinusoidally perturbed SF 6 /air interface. From analyzing schlieren photos and pressure histories, we validate this original approach and exhibit the great potential of this experimental method for studying the RMI induced by focusing shock waves.
28th International Symposium on Shock Waves, 2012
Volume 1: Fora, Parts A and B, 2002
ABSTRACT The aim of the present work is to determine experimental drag coefficients for spherical... more ABSTRACT The aim of the present work is to determine experimental drag coefficients for spherical particles accelerated in shock-tube. Then, validations of two phase flow calculations dealing with solid propulsion rocket in supersonic flight are undertaken. First, experiments in the multi-phase vertical-horizontal shock-tube have been set up at IUSTI in Marseille. The drag coefficient is determinated for particle Reynolds numbers less than 50000 and for particle Mach numbers less than 1.14 and is compared with those found in literature. Second, calculation of two phase flow in solid rocket plume has been performed. The particles are tracked with a stochastic one-way coupling lagrangian method.
2012 IEEE 25th International Conference on Micro Electro Mechanical Systems (MEMS), 2012
ABSTRACT We present a completely new concept of miniaturized gyroscopes based on Si nanowire piez... more ABSTRACT We present a completely new concept of miniaturized gyroscopes based on Si nanowire piezo-resistive detection. This concept enables to realize extremely compact single-chip 3D gyroscopes while maintaining high performances: performances for consumer applications are obtained with a size of the mechanical part of 0.5mm2/axis, which is 2 to 4 times smaller than state of the art gyroscopes. Moreover the extremely high sensitivity obtained with this concept enables to implement designs with high frequency mismatch between drive and sense mechanical modes, which implies high linear range in open-loop detection, large bandwidth, lower sensitivity to technological variations and low resolution dependency on sense quality factor. We present more precisely first results obtained for Z gyroscopes which have resolution below 0.05°/s/√Hz.
Physical Review E, 1995
ABSTRACT Shock tube experiments have been undertaken in which a shock wave accelerates normally t... more ABSTRACT Shock tube experiments have been undertaken in which a shock wave accelerates normally to an interface separating two gases of different densities leading to the formation of a three-dimensional mixing zone between the two gases. Assuming the mixing zone to be homogeneous and weakly dependent on the wall effects, an integrated monodirectional absorption technique had been previously carried out and average temperature and density evolutions were determined within it. But the mixing zone is really deformed by the wall effects and in consequence it is not homogeneous. Thus, to improve the diagnostic technique, the experimental setup has been modified so that the mixing zone is divided into nine identical homogeneous imaginary regions. Temperature and species concentration are determined through each region of the mixing zone by a multidirectional laser absorption technique in order to have some new information on the influence of the wall effects on the Richtmyer-Meshkov instability study in square-cross-section shock tubes. Furthermore, a better accuracy in the measurements of the mixing zone thickness is obtained from a discussion of the concentration profiles. The consequence is that previous results achieved with integrated techniques such as global Schlieren, shadograph, or monodirectional absorption methods seem to be strongly overestimated.
2011 IEEE SENSORS Proceedings, 2011
ABSTRACT This paper presents the design of a CMOS integrated circuit dedicated to the hybrid inte... more ABSTRACT This paper presents the design of a CMOS integrated circuit dedicated to the hybrid integration of a three-axis inertial smart-sensor with digital interface. Inertial sensing is achieved with an innovative low-cost technology that implements piezoresistive detection in MEMS devices with single-crystal silicon nanowires. The circuit includes a custom-designed analog front-end that achieves the bias and readout of the sensor, and an analog-to-digital converter with oversampling and integrated digital decimation. The obtained smart-sensor features a reduced output data rate that is suitable for a wireless sensor network with direct transmission of the raw data to a remote base station.
28th International Symposium on Shock Waves, 2012
Physical Review E, 2014
The dispersion of a cylindrical particle ring by a blast or shock wave induces the formation of c... more The dispersion of a cylindrical particle ring by a blast or shock wave induces the formation of coherent structures which take the form of particle jets. A blast wave, issuing from the discharge of a planar shock wave at the exit of a conventional shock tube, is generated in the center of a granular medium ring initially confined inside a Hele-Shaw cell. With the present experimental setup, under impulsive acceleration, a solid particle-jet formation is observed in a quasi-two-dimensional configuration. The aim of the present investigation is to observe in detail the formation of very thin perturbations created around the external surface of the dispersed particle layer. By means of fast flow visualization with an appropriate recording window, we focus solely on the first instants during which the external particle ring becomes unstable. We find that the critical area of the destabilization of the external ring surface is constant regardless of the acceleration of the initial layer. Moreover, we observe in detail the external front perturbation wavelength, rendered dimensionless by the initial ring perimeter, and follow its evolution with the initial particle layer acceleration. We report this quantity to be constant regardless of the evolution of the initial particle layer acceleration. Finally, we can reasonably assert that external front perturbations depend solely on the material of the particles.
2014 IEEE 27th International Conference on Micro Electro Mechanical Systems (MEMS), 2014
ABSTRACT
Shock Waves, 1997
We describe a laser absorption technique to obtain reasonably accurate density profiles within a ... more We describe a laser absorption technique to obtain reasonably accurate density profiles within a shock-induced Richtmyer-Meshkov mixing zone. Assuming a small temperature variation through the probed region, a single wavelength absorption experiment only is needed. When this criterium is satisfied, the technique described represents a considerable simplification over the more generally required dual wavelength experiments.
Shock Waves, 2005
Because of the lack of fluid-structure interaction FSI test cases, particularly for transient com... more Because of the lack of fluid-structure interaction FSI test cases, particularly for transient compressible flows, the present paper deals with a numerical and experimental study of the behaviour of a cantilever panel submitted to a shock tube flow. Our purpose is to confront our numerical model to an unsteady FSI problem. This study hopes to initiate a reference data bank in this domain. After a description of FSI numerical model, experimental device and diagnostic, a comparison is presented through the fluid flow structure and the panel deformations. A good agreement between numerical results and the experiments is obtained.
Shock Waves, 2014
The behavior of an aluminum door hanging at the exit of an opened shock tube at different angles,... more The behavior of an aluminum door hanging at the exit of an opened shock tube at different angles, from 5$^\circ$ to 85$^\circ$, and thereby providing partially open space for the exiting flow, was investigated experimentally. Experiments were conducted with an incident shock wave Mach number of M$_{is}$=1.1 impinging on the partially opened door. Both pressure measurements in the vicinity of the door, on its center and inside the shock tube and schlieren visualization were undertaken for studying the door movement and its maximum opened angle relative to its initial position. It was found that for an initial opening angle smaller than 25$^\circ$ the door opened completely while for angles larger its motion is marginal. In addition, for an initial door opening angle of about 10$^\circ$ the lowest pressures were recorded inside the shock tube behind the evolving waves after exiting of the incident shock wave. The present experimental results may be useful to numerical studies of fluidstructure interactions, e.g., in designing safety valves in jet engines.
Shock Waves, 1999
We present an overview of the diagnostic methods used in shock-tube investigations of mixing indu... more We present an overview of the diagnostic methods used in shock-tube investigations of mixing induced by Richtmyer-Meshkov instability. The different diagnostic techniques are first briefly presented, and then reviewed in a simple single table, which lists their advantages and disadvantages, their technological characteristics and domain of validity, the physical parameters measured, the laboratory in which they were developed and an assessment of their mean cost.
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Papers by Georges Jourdan