A selective literature review of transient-based leak detection methods

Pipe system diagnosis and leak detection by unsteady-state tests. 1. Harmonic analysis

Un nouveau modele mathematique a ete developpe pour calculer les regimes transitoires hydrauliques des systemes de conduites pressurisees en polyethylene (PE). Ce modele hydraulique (nomme HTS) integre des termes additionnels pour simuler la friction pendant le regime transitoire et l'effet de la viscoelasticite de la conduite. Les resultats numeriques obtenus ont ete compares avec la solution classique du coup de belier et avec les resultats experimentaux collectes a partir d'un systeme de conduites simples en PE construit au Imperial College (Londres, Royaume Unit). Contrairement au modele classique, le modele HTS est capable de predire rigoureusement les fluctuations transitoires de pression dans la conduite de PE ainsi que l'extension de la circonference des parois de la conduite. Le grand challenge de ce travaille est la distinction entre l'effet dynamique de la friction transitoire et l'effet mecanique de la deformation retardee de la conduite. Dans un premier temps, le modele HTS a ete calibre et teste en considerant les deux effets separement. Lorsque la friction en regime transitoire est consideree seule, de grandes differences entre les resultats experimentaux et numeriques sont observees. Si l'effet viscoelastique de la conduite est considere seul, meme avec une bonne correlation entre les resultats experimentaux et numeriques, les fonctions des fluage calibrees varient avec le flux initial. Dans un deuxieme temps, la combinaison de ces deux effets a ete analysee et une bonne correspondance entre les resultats experimentaux et numeriques a ete observee. Enfin, le modele HTS a ete verifie avec succes en utilisant la fonction de fluage mesuree lors d'un test mecanique negligeant la friction en regime transitoire.

The dynamic effect of pipe-wall viscoelasticity in hydraulic transients. Part II—model development, calibration and verification

The mechanical behaviour of the pipe material determines the pressure response of a fluid system during the occurrence of transient events. in viscoelastic pipes, typically made of polyethylene (pe), maximum or minimum transient pressures are rapidly attenuated and the overall pressure wave is delayed in time. this is a result of the retarded deformation of the pipe-wall. this effect has been observed in transient data collected in a high-density pe pipe-rig, at imperial college (london, uk). several transient tests were carried out to collect pressure and circumferential strain data. the pipe material presented a typical viscoelastic mechanical behaviour with a sudden pressure drop immediately after the fast valve closure, a major dissipation and dispersion of the pressure wave, and transient mechanical hysteresis. the creep-function of the pipe material was experimentally determined by creep tests, and, its order-of-magnitude was estimated based on pressure-strain data collected from the pipe-rig. a goo...

The dynamic effect of pipe-wall viscoelasticity in hydraulic transients. Part I—experimental analysis and creep characterization

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Fluid transients and fluid-structure interaction in flexible liquid-filled piping

An effective numerical method is presented to compute transients in piping systems in which frequency-dependent parameters influence the response. Frequency-dependent friction is utilized as the parameter-of-concern herein, however, the procedure can accommodate other factors such as frequency-dependent wavespeed equally well. The method, a variation in the impulse response method, is developed from the frequency response analysis and incorporates the fast Fourier transform

Impulse Response Method for Frequency-Dependent Pipeline Transients

The classic formula for waterhammer wavespeed is extended to calculate the complex-valued, frequency-dependent wavespeed in a viscoelastic pipe, which takes into account the effect of viscoelasticity of pipe wall material on wave propagation. With the complex wavespeed, the standard impedance or transfer matrix is directly used to analyze resonating conditions in systems including viscoelastic pipes, and the impulse response method presented previously by the authors is applied to compute nonperiodic transients. Numerical results are compared with experimental data and good agreement is observed.

Complex wavespeed and hydraulic transients in viscoelastic pipes

Matched impedance to control fluid transients.

Analyse numerique des problemes d'ecoulements lents transitoires bidimensionnels. La methode s'apparente a la methode des caracteristiques

E. B. Wylie

Papers

Impulse Response Method for Frequency-Dependent Pipeline Transients

Complex wavespeed and hydraulic transients in viscoelastic pipes

Matched impedance to control fluid transients.

Linearized Two-Dimensional Fluid Transients

Multidimensional Fluid Transients by Latticework