Ultrasound Testing of Metallic Structures using a Dual Symmetric Path Inspection and a Matched Filter-based Method

International audienceIn this paper, we present a new technique for detecting and localising defects in metallic structures, using ultrasound non-destructive inspection. This technique consists in applying a dual path inspection and the matched filter to a stepped frequency-type signal. This new technique is compared with classical non-destructive testing approaches. An experimental setup is presented that allows us to validate the proposed method

Underwater Object Tracking Using Time Frequency Signatures of Acoustic Signals

International audienceDetecting underwater objects is an important ap plication in marine applications. Most of the techniques are based on the amplitude related techniques, whereby the amplitude of the received echo is used to detect objects within specified bounds. Amplitude techniques however are prone to interference and attenuation, thus limiting the capabilities of such systems. Hence, the aim of this paper is to propose a new technique that detect and track underwater moving objects usingthe turbulence generated by the object. Wideband signals have proven to be a very efficient alternative for merging turbulent flow characteristics and waveform design in order to describe and explain the behavior of turbulence, both artificial and natural. Therefore, constructing adapted waveforms to the natural turbulence embedded in the flow, as well as to the artificial turbulence created by an unknown underwater moving object may hold the key for a new technique for underwater object tracking. When acoustic signals with a particular Instantaneous Frequency Law traveling into underwater environment will hit a moving object, their Instantaneous Frequency Law will capture the object's artificial turbulence, as well as the natural turbulence embedded in the flow. Experimental results carried out in our reduced scale facility provide the validation of the technique

On the vortex parameter estimation using wide band signals in active acoustic system

International audienceThis paper proposes a new method for detection of the vortex presence in fluid flow based on an active acoustic system. The experiment that validates the theory was done on a reduced scale facility using ultrasonic transceivers. The main objective was to highlight the effect of a cavitation vortex on an applied wide band signal. In order to accomplish that, the Recurrence Plot Analysis (RPA) was investigated which emhasizes similar states of a dynamic process. The Tests were done from no vortex cavitation flow to vortex cavitation flow and backward

Zernike ultrasonic tomography for fluid velocity imaging based on pipeline intrusive time-of-flight measurements

International audienceIn this paper, we propose a novel ultrasonic tomography method for pipeline flow field imaging, based on the Zernike polynomial series. Having intrusive multipath time-offlight ultrasonic measurements (difference in flight time and speed of ultrasound) at the input, we provide at the output tomograms of the fluid velocity components (axial, radial, and orthoradial velocity). Principally, by representing these velocities as Zernike polynomial series, we reduce the tomography problem to an ill-posed problem of finding the coefficients of the series, relying on the acquired ultrasonic measurements. Thereupon, this problem is treated by applying and comparing Tikhonov regularization and quadratically constrained l1 minimization. To enhance the comparative analysis, we additionally introduce sparsity, by employing SVD-based filtering in selecting Zernike polynomials which are to be included in the series. The first approach - Tikhonov regularisation without filtering, is used because it is the most suitable method. The performances are quantitatively tested by considering a residual norm and by estimating the flow using the axial velocity tomogram. Finally, the obtained results show the relative residual norm and the error in flow estimation, respectively, ~0.3% and ~1.6% for the less turbulent flow and ~0.5% and ~1.8% for the turbulent flow. Additionally, a qualitative validation is performed by proximate matching of the derived tomograms with a flow physical model

On the distributed acoustic sensing based on local time-frequency coherence analysis

International audienceThis paper outlines novel approaches to design a new generation of distributed networks of acoustic sensors. The key-concept is marked by the use of time-frequency signal analysis tools directly embedded at the sensor node. The general framework for analysis at the acoustic sensor level is based on spectrogram which is very simple and easy to implement. The choice of the detection threshold in time-frequency domain is always a difficult task, even more complicated in the embedded computing configurations where eventual threshold adaptive selection algorithms might not have the required complexity. That is, the performances in terms of probability of detection classification and localization accuracy are generally strongly depending of the operational conditions. As such, this paper proposes a novel approach of local signal processing based on phase coherence criterion, designed to track the time-frequency multi-components and which is implemented in a distributed network with a minimum number of acoustic sensors

Passive acoustic inversion to estimate bedload size distribution in rivers

International audienceThe main subject of our research is the analysis of quality of water in rivers by measuring the bedload transport. The bedload transport is defined by a particle moving close to the river bed, by sliding, saltation and rolling. We have adopted the Passive Acoustic Monitoring to listen to the river soundscape using a submerged hydrophone. These sources are due to surface waves, to turbulence and to inter-particular collisions. Inter-particular collision is the noise that we study because it is generated by the bedload phenomenon. In this study, we developed a Least Square procedure to inverse the spectra of noise recorded. The result represents an estimation of the transported grain size distribution

Inversion de Signaux d'Acoustique Passive pour Estimer la Granulométrie des Sédiments Transportés dans une Rivìère

National audienceLe contexte de notre contribution est la mesure par acoustique passive du transport sédimentaire dans les rivières. A partir d'une mesure du spectre acoustique des sons générés par les chocs entre particules sur le lit de la rivière, nous proposons un schéma d'inversion permettant d'estimer la granulométrie (i.e distribution des diamètres de particules mises en mouvement). Pour cela, nous modélisons le spectre acoustique comme la somme des spectres individuels des chocs obtenus pour un diamètre donné et pondérés par la proportion relative de chaque diamètre (i.e la granulométrie). L'estimation de la granulométrie est obtenue par une minimisation de l'erreur quadratique (E.Q) entre spectre mesuré et spectre modélisé. Une minimisation directe de l'E.Q produit une inversion instable puisque les spectres individuels des chocs ont des formes similaires. Ce problème inverse mal posé est régularisé en introduisant la contrainte de positivité de la granulométrie lors de la minimisation de l'E.Q. La méthode régularisée est comparée avec l'état de l'art sur des données simulées réalistes, elle améliore considérablement l'estimation de la granulométrie

Flow Rate Computation of Highly Turbulent Pipe Flows using Wide-Band Signals and Matched Filter-Based Approach in Ultrasonic Multi-Element Configuration

International audienceFlow profile analysis and flow rate estimation with ultrasound Non-Destructive Testing (NDT) tools were performed in a pipe flow varying the Reynolds number from 4.33x10E5 to 1.67x10E6. This study investigated the flow rate computation right downstream a 90 deg curvature pipe with a clamp-on multi-path ultrasonic flow meter (UFM) and a compensation scheme for the time-of-flight (TOF) errors due to the asymmetrical flow profile. The challenge is to model through the CFD analysis the separation region in the intrados of the pipe's elbow and its influence on the flow velocity profile, in order to calibrate the flow rate computations. The use of the matched filtering technique improves the performances in terms of measurement precision, which is validated by the numerical models. The experimental measurements on TOF differences in the pipe's elbow prove the interest of such approach for the improvement of the flow rate computations in the case of relative high turbulent flows

Advanced signal processing techniques for detection and localization of electrical arcs

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