Confrontation of Genetic Algorithm Optimization Process with a New Reference Case: Analytical Study with Experimental Validation of the Deflection of a Cantilever Beam

This paper deals with the optimization of a cantilever beam submitted to its own weight. In a first approach, we consider that the beam section can be equal to two values and we are looking for the section changing location, which minimizes the deflection. We propose an analytical model with an experimental validation that will allow us to optimize the shape of the beam. Then, we develop a numerical code based on a genetic algorithm that we validate on this case. In a last section, we use our numerical optimization code to find the best shape of the beam, where the section can now take any values in a given range, to minimize its deflection. These two study cases can serve as reference case to validate numerical approach for automatic structure optimization

Confrontation of Genetic Algorithm Optimization Process with a New Reference Case: Analytical Study with Experimental Validation of the Deflection of a Cantilever Beam

International audienceThis paper deals with the optimization of a cantilever beam submitted to its own weight. In a first approach, we consider that the beam section can be equal to two values and we are looking for the section changing location, which minimizes the deflection. We propose an analytical model with an experimental validation that will allow us to optimize the shape of the beam. Then, we develop a numerical code based on a genetic algorithm that we validate on this case. In a last section, we use our numerical optimization code to find the best shape of the beam, where the section can now take any values in a given range, to minimize its deflection. These two study cases can serve as reference case to validate numerical approach for automatic structure optimization

Richtmyer-Meshkov instability induced by shock-bubble interaction: Numerical and analytical studies with experimental validation

International audienceThis paper deals with the numerical study of the interaction of a shock wave and a bubble. The three different density ratio cases between air and bubble are investigated: light/heavy, heavy/light and close density. The numerical simulations are compared to the experiments of Layes et al. Phys. Rev. Lett. 91, 17 2003. These three cases may allow us to better understand the vortex deposition by the baroclinic terms. Moreover, the behavior differences between the deformation of a bubble and a cylinder collided by a shock wave are shown. An analytical approach to evaluate the final volume of an inhomogeneity submitted to a shock wave interaction is also presented and discussed

Simulation of a complete reflected shock tunnel showing a vortex mechanism for flow contamination

Simulations of a complete reflected shock tunnel facility have been performed with the aim of providing a better understanding of the flow through these facilities. In particular, the analysis is focused on the premature contamination of the test flow with the driver gas. The axisymmetric simulations model the full geometry of the shock tunnel and incorporate an iris-based model of the primary diaphragm rupture mechanics, an ideal secondary diaphragm and account for turbulence in the shock tube boundary layer with the Baldwin-Lomax eddy viscosity model. Two operating conditions were examined: one resulting in an overtailored mode of operation and the other resulting in approximately tailored operation. The accuracy of the simulations is assessed through comparison with experimental measurements of static pressure, pitot pressure and stagnation temperature. It is shown that the widely-accepted driver gas contamination mechanism in which driver gas jets along the walls through action of the bifurcated foot of the reflected shock, does not directly transport the driver gas to the nozzle at these conditions. Instead, driver gas laden vortices are generated by the bifurcated reflected shock. These vortices prevent jetting of the driver gas along the walls and convect driver gas away from the shock tube wall and downstream into the nozzle. Additional vorticity generated by the interaction of the reflected shock and the contact surface enhances the process in the over-tailored case. However, the basic mechanism appears to operate in a similar way for both the over-tailored and the approximately tailored conditions

Prediction of Self-Compacting Concrete homogeneity by ultrasonic

To evaluate the filling capacity of self-compacting concrete SCC without segregation, a technique based on the ultrasonic velocity has been adapted in order to estimate homogeneity and quality of concrete at very young age. To monitor local change in ultrasonic velocity, the process consists of using a pair of transducers at different depths of the concrete. The aim of our experimental study was to establish the relationship between ultrasonic velocity measured by sensors of 50 mm diameter and of 54 kHz frequency, and homogeneity of fresh concrete. Measurements of wave propagation velocity are carried out every half an hour on a vertical channel whose dimensions (in mm) are 160 × 160 × 700. These measurements have been determined with three modes of transmission: direct, semi-direct and indirect. The different mixtures were prepared with the same Water/Binder ratio (W/B) of 0.28. The amount of binder is in the order of 520 kg/m3. Comparison between ultrasonic velocity and empirical tests such as sieve stability test, slump flow test, air content, and compressive strength, at 1 day, shows that the ultrasonic velocity can also be very useful to evaluate homogeneity and quality of fresh concrete

New approach to determine the plastic viscosity of self-compacting concrete

International audienceThe rheology of concrete is best measured with the use of a rheometer. The slump flow test gives a good indication of the flowability of the mixture and is therefore still used extensively to judge the workability of SCC mixtures. However, this test presents some defects. The objective of this paper is to develop a new methodology for measuring the workability of a SCC. In this article, we have proposed a correlation between the plastic viscosity of concrete, the time and the characteristics of the flow final profile from the V-funnel coupled to a Plexiglas horizontal channel. The proposed approach, verified by experimental results, represents a simple, economical and usable tool on building site, and it allows to characterize rheologically the SCC from its flow. The comparison between our approach and the experimental values of the plastic viscosity shows that, in a laboratory or on site, instead of using a rheometer we can use our approach to characterize the rheological behavior of a SCC

Shock wave impacts on deforming panel, an application of fluid-structure interaction

International audienceBecause 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

Modelling sound production from an aerodynamical model of the human newborn larynx

International audienceConsidering on the one hand the important histological differences that exist between newborn and adult vocal folds and on the other hand the specifical subglottal pressure at birth, the sound production in a newborn larynx is studied. The laryngotracheal airflow has been numerically modelled in order to evaluate its role in voice production by the larynx in newborn. The FFT spectrum of the pressure signal acquired just above the vocal folds was calculated and compared to the spectrum of a sound generated by an excised larynx. It can be determined that first, the computed pressure signal has a fundamental frequency close to that obtained experimentally with an excised larynx, and second the FFT spectra are qualitatively similar to one another. Third, the computed pressure fluctuation is strong enough to be detected by the human ear. The conclusion is that the airflow and the aerodynamical phenomena observed in a rigid geometry are, by themselves, able to produce a sound and consequently, are one of the several elements leading to sound production in the newborn larynx.