Burst Location Research Articles

Near Real-time Leak Location by Inverse Analysis Integrating Measurement Uncertainty

AbstractThis paper presents a novel model-based method for near real-time pipe burst location in water distribution networks by integrating measurement uncertainty into inverse analysis. The method accounts for expected errors between measured and computed values, providing a pipe burst location area whose size varies according to the expected error level and the burst size. The proposed method is demonstrated and compared with the traditional inverse approach using a real case study with artificial bursts of different sizes and with different pressure signal noise levels. The performance of both methods is also assessed and discussed considering the effect of seasonal water demands. The traditional inverse analysis fails to accurately locate the pipe burst events, and depending on the expected error level and pipe burst size, the obtained locations may be significantly further away from the real burst location. Conversely, the proposed method does not point to the exact burst location but provides an approximated area in which step-testing can be carried out to pinpoint the exact burst location; the size of this area can be larger or smaller depending on the burst flow rate and signal uncertainty.

Multi-Stage Burst Localization Based on Spatio-Temporal Information Analysis for District Metered Areas in Water Distribution Networks

Burst events in Water Distribution Networks (WDNs) pose a significant threat to the safety of water supply, leading people to focus on efficient methods for burst localization and prompt repair. This paper proposes a multi-stage burst localization method, which includes preliminary region determination and precise localization analysis. Based on the hydraulic model and spatio-temporal information, the effective sensor sequences and monitoring areas of the nodes are determined. In the first stage, the preliminary burst region is determined based on the monitoring region of sensors and the alarm sensors. In the second stage, localization metrics are used to analyze the dissimilarity degree between burst data from the hydraulic model and the monitoring data from the effective sensors at each node. This analysis helps identify candidate burst nodes and determine their localization priorities. The localization model is tested on the C-Town network to obtain comparative results. The method effectively reduces the burst region, minimizes the search region, and significantly improves the efficiency of burst localization. For precise localization, it accurately localizes the burst event by prioritizing the possibilities of the burst location.

Scattered M3–4 Slip Bursts Within Creep Events on the San Andreas Fault

AbstractScientists have observed the surface expression of creep events along the San Andreas Fault since the 1960s. However, the evolution of slip at depth has been examined relatively little. So here we probe that deep slip by analyzing strain observations just before and during hours‐ to day‐long creep events at the northern end of the creeping section of the San Andreas Fault. We identify 71 strain offsets that are likely produced by few‐hour bursts of slip at depth. Then, we grid search to determine the location, depth, and magnitude of these slip bursts. We find that the slip bursts occur at a range of along‐strike locations, from 0 to 7 km away from the surface slip observations. Slip occurs at depths from 0 to 10 km; 42%–55% of the bursts are likely below 4 km depth. The bursts typically have moments equivalent to Mw 3.2–4.1 earthquakes. These findings suggest that creep events are not just small shallow events; they are relatively large events that nucleate at significant depths and could play a prominent role in the slip dynamics of the creeping section.

Thermal-fluid-structure coupling progressive failure analysis for the type III composite cylinder under localized fire

Predicting the failure characteristics of composite cylinders under fire is the key to improve the fire resistance and safety of cylinders. However, the current thermal-mechanical coupled failure analysis methods for composite cylinders under fire have several limitations such as oversimplification of the cylinder dome's geometric model and the fire source. To solve these problems, a comprehensive three-dimensional thermal-fluid-structure coupling progressive failure analysis method is developed. This method encompasses a fully coupled conjugate heat transfer model, a FLUENT-ABAQUS data transfer method, and a progressive failure analysis model integrates the Hashin failure criterion and nonlinear damage evolution for fiber reinforced composites. The method is adopted to analyze the fire-resistant performance of a type Ⅲ cylinder to obtain the fire-resistant time, failure pressure and burst location of the cylinder, finding that the pattern of failure pressure depreciation correlates with the burst location of cylinder under localized fire. Besides, the influence of the glass-fiber/epoxy layer on the fire-resistant performance of the cylinder is discussed, demonstrating that even a thin layer of glass-fiber epoxy can significantly increase the fire resistance time of the cylinder.

Numerical simulation of rock bursts triggered by blasting disturbance for deep-buried tunnels in jointed rock masses

Frequent dynamic disturbances, such as explosions, vibrations, and earthquakes, may trigger the risk of rock burst disasters around neighbouring deep-buried tunnels. In this study, the PFC software was used to simulate rock bursts triggered by blasting stress waves (dynamic disturbance) to determine their effects on deep-buried tunnels in jointed rock masses. This study investigated the effects of different ground stress values and joint angles on rock bursts in tunnels under intense dynamic disturbance. An analysis of different ground stress values and joint angles revealed the changes in the ejection velocities of damaged rocks and kinetic energy under intense dynamic disturbance. The results show that higher ground stress can alter the proportion of stress waves converted into strain energy and kinetic energy. Joint angles affect the location of the rock burst. The closer the joint angle is to 90°, the greater the damage to surrounding rocks caused by stress waves. Higher ground stress and joint angles increase the risk and intensity of rock bursts, causing significant damage to surrounding rocks, which makes existing tunnels more vulnerable to impact. The findings of this research have important guiding significance to ensure the secure protection of tunnels against rock bursts.

Deep learning-based burst location with domain adaptation across different sensors in water distribution networks

This study proposes a domain adaption method for pipe burst location based on deep learning. Multi-scale feature extractors are designed to extract pipe burst features, then three classifiers are trained by pipe burst features with different scales, and adversarial training is introduced during the edge domain fusion. Finally, the probability ranking of each pipeline is obtained according to the classification results of the three classifiers. In this study, a Net3 pipe network hydraulic model was used as an example to carry out related research. The pressure monitoring data of three sensors were used to train and test the model, and different scenarios of one, two and three sensors were considered at the same time. The results showed that the overall prediction accuracy of the three scenarios was over 90% when considering the five pipelines with the highest pipe burst probability.

Approach for Near-Real-Time Pipe Burst Detection and Location Estimation Utilizing Any Sequence of Harmonics of the Transient Pressure Signal

The purpose of the paper is to present an approach for real-time pipe burst detection and location estimation, based on the changes in the harmonics and analysis of the corresponding damping that is caused by the burst. The amplitude of each resonance response of the transient pressure wave caused by the burst is damped differently due to the occurrence of the burst. However, utilizing higher order harmonics beyond the first few fundamental frequencies has not previously been possible as it leads to an increasing number of possible solutions to the burst location, which limits the application of the method. An algorithm for damping analysis has been developed which overcomes this limitation, and is able to exclude most of the incorrect solutions when utilizing the information contained in higher order harmonics. Additionally, the gap between data windows can be set so that it enables the real-time data analysis by letting the window gap equal the reciprocal of the sampling rate. Therefore, this algorithm makes utilizing any sequence of harmonics of the signal be possible for real-time burst detection and location estimation. The approach has been verified both numerically and experimentally with acceptable accuracy.

Hyperparameter Optimization of a Convolutional Neural Network Model for Pipe Burst Location in Water Distribution Networks

The current paper presents a hyper parameterization optimization process for a convolutional neural network (CNN) applied to pipe burst locations in water distribution networks (WDN). The hyper parameterization process of the CNN includes the early stopping termination criteria, dataset size, dataset normalization, training set batch size, optimizer learning rate regularization, and model structure. The study was applied using a case study of a real WDN. Obtained results indicate that the ideal model parameters consist of a CNN with a convolutional 1D layer (using 32 filters, a kernel size of 3 and strides equal to 1) for a maximum of 5000 epochs using a total of 250 datasets (using data normalization between 0 and 1 and tolerance equal to max noise) and a batch size of 500 samples per epoch step, optimized with Adam using learning rate regularization. This model was evaluated for distinct measurement noise levels and pipe burst locations. Results indicate that the parameterized model can provide a pipe burst search area with more or less dispersion depending on both the proximity of pressure sensors to the burst or the noise measurement level.

Solar Radio Spikes and Type IIIb Striae Manifestations of Subsecond Electron Acceleration Triggered by a Coronal Mass Ejection

Understanding electron acceleration associated with magnetic energy release at subsecond scales presents major challenges in solar physics. Solar radio spikes observed as subsecond, narrow-bandwidth bursts with Δf/f ∼ 10−3–10−2 are indicative of a subsecond evolution of the electron distribution. We present a statistical analysis of frequency- and time-resolved imaging of individual spikes and Type IIIb striae associated with a coronal mass ejection (CME). LOFAR imaging reveals that the cotemporal (<2 s) spike and striae intensity contours almost completely overlap. On average, both burst types have a similar source size with a fast expansion at millisecond scales. The radio source centroid velocities are often superluminal and independent of frequency over 30–45 MHz. The CME perturbs the field geometry, leading to increased spike emission likely due to frequent magnetic reconnection. As the field restores itself toward the prior configuration, the observed sky-plane emission locations drift to increased heights over tens of minutes. Combined with previous observations above 1 GHz, the average decay time and source size estimates follow a ∼1/f dependence over three decades in frequency, similar to radio-wave scattering predictions. Both time and spatial characteristics of the bursts between 30 and 70 MHz are consistent with radio-wave scattering with a strong anisotropy of the density fluctuation spectrum. Consequently, the site of the radio-wave emission does not correspond to the observed burst locations and implies acceleration and emission near the CME flank. The bandwidths suggest intrinsic emission source sizes <1″ at 30 MHz and magnetic field strengths a factor of two larger than average in events that produce decameter spikes.

Computational Tools for Supporting the Operation and Management of Water Distribution Systems towards Digital Transformation

This paper presents a set of computational tools specially developed for supporting the operation and management of water distribution systems towards digital transformation of water services. These tools were developed in the scope of two R&amp;D projects carried out in Portugal, DECIdE and WISDom, during 2018–2022. The DECIdE project focused on the development of tools for importing cadastral and operational data, as well as on the three operational tools for supporting the performance assessment: the first allows the calculation of different key performance indicators, both at a global and sectorial level, which is an annual requirement of the water regulator, and the other two allow the calculation of the water and the energy balances and a set of complementary indices. The WISDom project aimed at the implementation of applications that directly address specific water utility needs, namely, the flow rate data processing, the optimal location of pressure sensors, the identification of critical areas in the distribution network for pipe burst location, and the prioritization of pipes for rehabilitation. Implemented tools are useful to support water utilities in the daily operation and management of their systems, being a step forward towards digital transformation of the water sector.

Comparison of model-based techniques for pipe burst location in water distribution networks

The current paper compares the performance of three model-based techniques for the automatic location of pipe burst events in water distribution networks. The first technique is based on nodal pressure sensitivities, the second solves an inverse analysis problem and the third technique uses hydraulic simulation to train a classifier. A real case study is used and a set of artificial measurements is generated for a number of pipe burst scenarios, with fixed burst location and variable pressure and flowrate noise levels and burst sizes. The performance of each technique is assessed based on the determined burst distance to the real burst location. Obtained results are discussed and the most relevant conclusions are drawn.

Solar Coronal Density Turbulence and Magnetic Field Strength at the Source Regions of Two Successive Metric Type II Radio Bursts

We report spectral and polarimeter observations of two weak, low-frequency (≈85–60 MHz) solar coronal type II radio bursts that occurred on 2020 May 29 within a time interval ≈2 minutes. The bursts had fine structures, and were due to harmonic plasma emission. Our analysis indicates that the magnetohydrodynamic shocks responsible for the first and second type II bursts were generated by the leading edge (LE) of an extreme-ultraviolet flux rope/coronal mass ejection (CME) and interaction of its flank with a neighboring coronal structure, respectively. The CME deflected from the radial direction by ≈25° during propagation in the near-Sun corona. The estimated power spectral density and magnetic field strength (B) near the location of the first burst at heliocentric distance r ≈ 1.35 R ⊙ are ≈2 × 10−3 W2m and ≈1.8 G, respectively. The corresponding values for the second burst at the same r are ≈10−3 W2m and ≈0.9 G. The significant spatial scales of the coronal turbulence at the location of the two type II bursts are ≈62–1 Mm. Our conclusions from the present work are that the turbulence and magnetic field strength in the coronal region near the CME LE are higher compared to the corresponding values close to its flank. The derived estimates of the two parameters correspond to the same r for both the CME LE and its flank, with a delay of ≈2 minutes for the latter.

Combined Usage of Hydraulic Model Calibration Residuals and Improved Vector Angle Method for Burst Detection and Localization in Water Distribution Systems

This paper proposes a combined usage of the hydraulic model calibration residuals and an improved vector angle method for the Battle of the Leakage Detection and Isolation Methods (BattLeDIM). The proposed method starts with the hydraulic model decomposition and followed by data partition, with both procedures aimed at simplifying the BattLeDIM problem. Next, a calibration residuals–based burst detection approach is used, in which the nodal demands of the hydraulic model are calibrated in real-time using a newly developed algorithm based on prior information. The burst detection is achieved by identifying the anomalous calibration residuals. Finally, the locations of pipe bursts are approximated by an improved vector angle method, which compares the angle between each pipe’s sensitivity vector and the vector of calibration residuals. Application results to the BattLeDIM problem indicate the proposed method is effective and efficient in burst detection and localization, with nearly all abrupt bursts (9 out of the total 19 bursts) in 2019 being successfully detected within 5–10 min after their occurrence, and 7 out of 10 detected bursts being localized with a spatial difference less than 300 m from the true burst pipes. Performance comparisons with the Kalman filtering–based burst detection method have been conducted, and the obtained results indicate the proposed method has better performance under both consistent and varying operation conditions, as well as in detectability for small bursts. Lessons learned from this battle and future works are summarized towards the development of a more effective and robust burst detection and localization method.

Flowrate Time Series Processing in Engineering Tools for Water Distribution Networks

AbstractThe current paper presents a comprehensive methodology for processing unevenly (and evenly) spaced flowrate time series for subsequent use in engineering tools, such as the calibration of hydraulic models or the detection and location of leaks and bursts. The methodology is a four‐step procedure: (a) anomaly identification and removal, (b) short‐duration gap reconstruction, (c) time step normalization, and (d) long‐duration gap reconstruction. The time step normalization is carried out by a numerical procedure prior to the reconstruction process. This reconstruction process uses a pattern model coupled with regression techniques (i.e., autoregressive integrated moving average and exponential smoothing). The methodology is calibrated using Monte Carlo simulations applied to a water utility flowrate time series and validated with two additional time series from different water utilities. Obtained results demonstrate that the proposed methodology can process flowrate time series from water supply systems with different characteristics (e.g., consumption pattern, data acquisition system, transmission settings) both for normal operating conditions and during the occurrence of abnormal events (e.g., pipe bursts). This methodology is a very useful tool for the daily management of water utilities, preparing the time series to be used in different engineering tools, namely, hydraulic simulation, model calibration or online burst detection.

Multi-objective optimization of pressure sensor location for burst detection and network calibration

This paper proposes a methodology to determine the optimal location of pressure sensors for the simultaneous calibration of the hydraulic network model and the detection of pipe bursts. The methodology considers a search space reduction process and aims at maximizing nodal pressure sensitivities to both pipe roughness coefficients and pipe burst sizes. A multi-objective optimization problem is formulated for a given number of sensors and multiple optimal configurations of pressure sensors are obtained. Three different optimal configurations are selected and compared: one solution that individually maximizes each objective function (two solutions) and one trade-off solution. The methodology is applied to a real water distribution network with hourly consumption data. Results demonstrate that (i) the optimal location of pressure sensors hardly changes with the perturbation values used to numerically compute the sensitivities and (ii) minor differences can be found in the performance of pipe roughness calibration and pipe burst location by using either a solution that individually maximizes each objective function or the trade-off solution considering the high number of pressure sensors (26) and the oversized pipe diameters to comply with firefighting conditions, being pressure less sensitive to friction and flow rate changes.

LOFAR Observations of Lightning Initial Breakdown Pulses

AbstractThis paper reports an observational study of lightning initial breakdown pulses (IBPs) using the low‐frequency array radio telescope and a broadband magnetic field sensor. The data show that the overall spatiotemporal evolution of the electrical breakdown causing an IBP is rather complex. During an IBP, spatially and temporally separated bursts of very high frequency (VHF) electromagnetic radiation occur in a volume on the order of 1003 m3, and they are coincident with brief magnetic field pulses, indicating that the location of the active breakdown region can change suddenly. Furthermore, recurrent breakdown activity is observed, especially at the location of the VHF burst. Interpreting each VHF burst as being generated by a corona burst, an IBP pulse appears to start off from an initial corona burst and subsequent corona bursts enhance it. We further suggest that the generation of IBPs likely involves multiple space stems/leaders and connections between them.

A Review of Cluster Wideband Data Multi‐Spacecraft Observations of Auroral Kilometric Radiation

AbstractWe review important advances in the understanding of auroral kilometric radiation (AKR) resulting from observations by the Wideband Data instruments on the four Cluster spacecraft. AKR is an intense radio emission originating in the Earth's auroral regions with frequencies typically in the range 50–700 kHz, usually observed from space. It is now widely accepted that AKR is generated by the cyclotron maser instability (CMI) in density cavities in the auroral acceleration region. Multi‐point observations by the Cluster spacecraft with a time delay of arrival technique have allowed the source locations of many individual AKR bursts to be determined. The position uncertainty is around 500 km at the source region or about 200 km when mapped on to the auroral zone. AKR is emitted in a narrow beam close to the tangent to the magnetic field vector in the source region. This has important implications for the possible generation mechanisms, being incompatible with filled or hollow cone beaming models. It also implies that an observer at a given location can only see AKR from a fraction of possibly active source regions. The complex frequency time structure of AKR sometimes shows regular striations or pulsations. Cluster observations of these phenomena have been interpreted as modulation of the CMI by disturbances propagating through the generation region. Exceptionally, AKR can sometimes be observed from low altitude spacecraft or even on the ground. Recent work has involved simultaneous observations of AKR on the Cluster spacecraft and on the ground at the South Pole.

Burst characteristics of advanced accident-tolerant FeCrAl cladding under temperature transient testing

Assessment of burst characteristics of accident-tolerant fuel (ATF) claddings is essential to evaluate the safety margins of nuclear reactors, and better understanding can enable accelerated licensing for reactor concepts that include the new materials. Therefore, this study investigated the burst behavior of an ATF candidate of C26M, which is an iron–chromium–aluminum alloy (FeCrAl) under transient testing like the simulated loss-of-coolant accident (LOCA) conditions, except the water-quenching phase, in light-water reactors (LWRs).The effect of LOCA specimen length was assessed in terms of post-burst tube parameters. No critical length effect was determined on the burst pressure, burst location, and burst size measurements. Burst temperature showed larger variation likely due to its measurement approach used in this study. The post-test diametral strain was identified as the critical parameter to reduce the specimen length as compared to tube burst length or width. Postmortem optical metrology and digital image correlation were employed to determine the local strain-state during the simulated LOCA, which showed the loading path was close to equibiaxial conditions in regions away from the burst location, rather than internally pressurized conditions (or “plane-strain” tension).Pst-test microstructural characterizations of the FeCrAl revealed that ductile damage was present at the edge of the outer radial surface while the rest of the material was ruptured via cleavage at LOCA burst temperatures. Furthermore, internal grain boundary cracks were observed at locations away from the tube burst region. This behavior was considered to occur during the cooling down period of the simulated LOCA test. Overall, this study aimed to provide essential data for fuel performance code development by considering micromechanics of the deformation and failure.

Tracking the Source of Solar Type II Bursts through Comparisons of Simulations and Radio Data

Abstract The most intense solar energetic particle events are produced by coronal mass ejections (CMEs) accompanied by intense type II radio bursts below 15 MHz. Understanding where these type II bursts are generated relative to an erupting CME would reveal important details of particle acceleration near the Sun, but the emission cannot be imaged on Earth due to distortion from its ionosphere. Here, a technique is introduced to identify the likely source location of the emission by comparing the dynamic spectrum observed from a single spacecraft against synthetic spectra made from hypothesized emitting regions within a magnetohydrodynamic (MHD) numerical simulation of the recreated CME. The radio-loud 2005 May 13 CME was chosen as a test case, with Wind/WAVES radio data being used to frame the inverse problem of finding the most likely progression of burst locations. An MHD recreation is used to create synthetic spectra for various hypothesized burst locations. A framework is developed to score these synthetic spectra by their similarity to the type II frequency profile derived from the Wind/WAVES data. Simulated areas with 4× enhanced entropy and elevated de Hoffmann–Teller velocities are found to produce synthetic spectra similar to spacecraft observations. A geometrical analysis suggests the eastern edge of the entropy-derived shock around (−30°, 0°) was emitting in the first hour of the event before falling off, and the western/southwestern edge of the shock centered around (6°, −12°) was a dominant area of radio emission for the 2 hr of simulation data out to 20 solar radii.

Speckle Noise Detection and Removal for Laser Speech Measurement Systems

Laser speech measurement is a new sound capture technology based on Laser Doppler Vibrometry (LDV). It avoids the need for contact, is easily concealed and is ideal for remote speech acquisition, which has led to its wide-scale adoption for military and security applications. However, lasers are easily affected by complex detection environments. Thus, speckle noise often appears in the measured speech, seriously affecting its quality and intelligibility. This paper examines all of the characteristics of impulsive noise in laser measured speech and proposes a novel automatic impulsive noise detection and removal method. This method first foregrounds noise using decorrelation based on a linear prediction (LP) model that improves the noise-to-signal ratio (NSR) of the measured signal. This makes it possible to detect the position of noise through a combination of the average short-time energy and kurtosis. The method not only precisely locates small clicks (with a duration of just a few samples), but also finds the location of longer bursts and scratches (with a duration of up to a hundred samples). The located samples can then be replaced by more appropriate samples whose coding is based on the LP model. This strategy avoids unnecessary processing and obviates the need to compromise the quality of the relatively large fraction of samples that are unaffected by speckle noise. Experimental results show that the proposed automatic speckle noise detection and removal method outperforms other related methods across a wide range of degraded audio signals.