Improved acoustic methods for leak detection in buried plastic water distribution pipes
Notice bibliographique
Résumé
This thesis is concerned with a theoretical and experimental investigation into the enhancement of acoustic methods used to detect leaks in buried plastic water distribution pipes. Although acoustic methods have been successfully used for leak detection in metallic pipes, they are less effective in plastic pipes due, for example, to the high attenuation of leak noise signals. Two specific problems investigated in this thesis. They are the uncertainty involved in the calculation of the time delay in arrival times between two leak signals, and the variation of speed at which the leak noise propagates in the pipe. This is done in both the time and frequency domains. A new way to estimate the wave speed from measurements made in the presence of a leak is also proposed, together with a way of estimating the attenuation of leak noise as it propagates in the pipe. A bespoke test-rig was designed and built specifically for this project by South Staffs Water plc, so that leaks could be simulated and investigated in controlled conditions.<br/>Following the characterisation of the test rig, two specific correlators were investigated, one using the basic cross-correlation (BCC) function and other using the phase transform (PHAT). It is shown that the BCC is more suitable for leak detection, when the pipe exhibits resonance behaviour. It is further shown that the bandwidth over which the analysis is conducted is crucial to locate the leak accurately. To determine this bandwidth a procedure is developed to determine automatically low and high frequency cut-off frequencies of a band-pass filter. This method uses both the coherence and the modulus of the cross-spectral density (CSD) function between two leak noise signals.<br/>A new technique is also proposed to calculate the time delay estimate using both the modulus and phase of the CSD function, and this is validated using a wide range of<br/>data from the bespoke test-rig and also from a Canadian test-rig. Moreover, an expression for the variance of the time delay estimate is determined based on frequency domain data, and this is shown to give the same result as that previously determined in the time domain. Using the variance and statistical analysis a range of values that the time delay estimate can assume is calculated. This range of values is related to the 95% confidence interval of the time delay estimate calculated using the weighted least squares fit. The confidence interval can also be applied to the wave-speed estimate. The time delay and wavespeed estimates can be combined to determine a region where a leak is likely to be located in a pipe rather than giving an exact position as provided by commercial correlators. Measured data is used to validate the approach using the bespoke test-rig.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».