Zhao Li

Measurement and analysis of wave propagation in water-filled steel pipeline using iterative quadratic maximum likelihood algorithm

Acoustic wave propagation (up to 50 kHz) within a water-filled steel pipeline is studied using laboratory experiments. The experiments were carried out in a 6 m length of cylindrical stainless steel pipeline using acoustic transducers to acquire signals from 100 locations uniformly spaced along the longitudinal axis of the pipe. By applying the iterative quadratic maximum likelihood algorithm (IQML) to the experimental results, parameters such as wave numbers, attenuations and mode amplitudes were accurately extracted for individual modes from the measurement data. We found that the IQML algorithm could extract these parameters more accurately in situations where the measurement data had low signal to noise ratio as compared to other algorithms such as Prony’s method. A very good match was obtained between the experimental results and predictions from an analytical waveguide model for the wave number dispersion curves, attenuations and acoustic power characteristics of the axisymmetric and non-axisymmetric modes. Additional physical explanations of the propagation phenomena in the pipeline waveguide were obtained using the experimental results and analytical model.Acoustic wave propagation (up to 50 kHz) within a water-filled steel pipeline is studied using laboratory experiments. The experiments were carried out in a 6 m length of cylindrical stainless steel pipeline using acoustic transducers to acquire signals from 100 locations uniformly spaced along the longitudinal axis of the pipe. By applying the iterative quadratic maximum likelihood algorithm (IQML) to the experimental results, parameters such as wave numbers, attenuations and mode amplitudes were accurately extracted for individual modes from the measurement data. We found that the IQML algorithm could extract these parameters more accurately in situations where the measurement data had low signal to noise ratio as compared to other algorithms such as Prony’s method. A very good match was obtained between the experimental results and predictions from an analytical waveguide model for the wave number dispersion curves, attenuations and acoustic power characteristics of the axisymmetric and non-axisymmetri...

An approximate inverse scattering technique for reconstructing blockage profiles in water pipelines using acoustic transients

An approximate inverse scattering technique is proposed for reconstructing cross-sectional area variation along water pipelines to deduce the size and position of blockages. The technique allows the reconstructed blockage profile to be written explicitly in terms of the measured acoustic reflectivity. It is based upon the Born approximation and provides good accuracy, low computational complexity, and insight into the reconstruction process. Numerical simulations and experimental results are provided for long pipelines with mild and severe blockages of different lengths. Good agreement is found between the inverse result and the actual pipe condition for mild blockages.

Experimental measurement and analysis of acoustic wave propagation in water-filled steel pipeline using the iterative quadratic maximum likelihood algorithm

Acoustic wave propagation (up to 50 kHz) within a water-filled steel pipeline is studied using laboratory experiments. The experiments were carried out in a 6 m length of cylindrical stainless steel pipeline using acoustic transducers to acquire signals from 100 locations uniformly spaced along the longitudinal axis of the pipe. By applying the iterative quadratic maximum likelihood algorithm (IQML) to the experimental results, parameters such as wavenumbers, attenuations, and mode amplitudes were accurately extracted for individual modes from the measurement data. We found that the IQML algorithm could extract these parameters more accurately in situations where the measurement data had low signal to noise ratio as compared to other algorithms such as Prony’s method. A very good match was obtained between the experimental results and predictions from an analytical waveguide model for the wavenumber dispersion curves, attenuations, and acoustic power characteristics of the axisymmetric and non-axisymmetric modes. Additional physical explanations of the propagation phenomena in the pipeline waveguide were obtained using the experimental results and analytical model.Acoustic wave propagation (up to 50 kHz) within a water-filled steel pipeline is studied using laboratory experiments. The experiments were carried out in a 6 m length of cylindrical stainless steel pipeline using acoustic transducers to acquire signals from 100 locations uniformly spaced along the longitudinal axis of the pipe. By applying the iterative quadratic maximum likelihood algorithm (IQML) to the experimental results, parameters such as wavenumbers, attenuations, and mode amplitudes were accurately extracted for individual modes from the measurement data. We found that the IQML algorithm could extract these parameters more accurately in situations where the measurement data had low signal to noise ratio as compared to other algorithms such as Prony’s method. A very good match was obtained between the experimental results and predictions from an analytical waveguide model for the wavenumber dispersion curves, attenuations, and acoustic power characteristics of the axisymmetric and non-axisymmetri...

Corrections to “Utilizing the Born and Rytov Inverse Scattering Approximations for Detecting Soft Faults in Lossless Transmission Lines”

Following publication of [1] , the first three authors realized their IEEE membership acronyms were incorrect. Therefore, the IEEE membership in the byline and in the biographies should have appeared as follows: Wenjie Wang, Student Member, IEEE , Liwen Jing, Student Member, IEEE , and Zhao Li, Member, IEEE .

Experimental study of acoustic channel characteristics of rigid and elastic pipelines

In this work we describe an experimental investigation into wideband channel models for acoustic wave propagation in rigid and elastic pipelines operating over the 1∼50 kHz frequency band. We provide frequency domain transfer function measurements for both rigid and elastic pipes, from which time domain responses of the pipeline channel can be calculated. Narrowband impulse responses are studied to illustrate the frequency selectivity of the channel. We extend the narrowband impulse responses to a spectrogram representation to further highlight the channel characteristics. Signal attenuation is investigated experimentally. Preliminary results of channel noise characterization are also provided in the water pipe channel consisting of noise power spectrum density (PSD) in a laboratory environment. It is shown that the pipeline channels exhibit three major characteristics: (a) wave travels in modes and the cutoff frequency of two modes are found to be zero in the elastic pipe, in comparison with only one plane wave mode existing in the rigid pipe; (b) the signal dispersion is obvious in the pipeline channel, but the delay spread is only insufferable when the wave speed changes dramatically within the signal bandwidth; (c) it is also observed that acoustic waves up to 50 kHz can propagate through both water pipes but exhibit distinctive average power loss per meter (1 dB/m for acrylic-air channel, and 3 dB/m for HDPE-water channel). In addition to the effect of pipe material, signal attenuation is also found to be mode and frequency dependent in experiments. We hope the channel characterization can be utilized to develop communication and imaging systems for pipeline channels.

Propagation of monopole source excited acoustic waves in a cylindrical high-density polyethylene pipeline

Acoustic wave propagation (up to 50u2009kHz) within a water-filled high-density polyethylene (HDPE) pipeline is studied using laboratory experiments and theoretical analysis. Experiments were carried out in a 15u2009m length of cylindrical HDPE pipeline using acoustic transducers to acquire signals uniformly spaced along the axis of the pipe. By proposing the use of the iterative quadratic maximum likelihood algorithm to this experimental configuration, wavenumbers, attenuations, and mode amplitudes could be accurately extracted from the measurement data. To allow comparisons with theoretical analysis, dispersion curves of the wavenumbers, attenuations, and acoustic power characteristics of the axisymmetric and nonaxisymmetric modes are predicted by extending an existing waveguide model. The model extensions included the introduction of a monopole acoustic source into the water medium so that amplitude variations with respect to individual modes and frequencies could be investigated in detail. In addition, stiffness coefficients of HDPE material are carefully used to account for viscoelastic effects. The comparisons between the theoretical predictions and experimental results demonstrate a very good match and are a validation of the theoretical model.

Utilizing the Born and Rytov Inverse Scattering Approximations for Detecting Soft Faults in Lossless Transmission Lines

We apply and experimentally verify inverse scattering techniques based on the Born and Rytov approximations for detecting soft faults in lossless transmission lines. The advantages of these approximate approaches compared with exact formulations such as those based on the Zakharov–Shabat equations are that they are straightforward to apply and provide intuitive insight into the reconstruction process. The formulations are also well-posed so the effects of noise and measurement errors on the reconstructions are also well behaved. The approaches are well suited for the detection of soft faults since they are based on the assumption that the medium is weakly scattering. We demonstrate the techniques with both experimental and numerical results. In addition, the application to lossy transmission lines is also investigated to determine the approximations usefulness in realistic settings. These show that surprisingly accurate results can be obtained for a wide range of characteristic impedance distributions even when the transmission lines have loss.