Hydraulic Transients in Viscoelastic Branched Pipelines

Evangelista, Stefania; Leopardi, Angelo; Pignatelli, Roberto; Marinis, Giovanni de

doi:10.1061/(asce)hy.1943-7900.0001030

Cited by 44 publications

(28 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first kind of test cases regard three different Riemann problems, solved only for the elastic case, hence using the Laplace law, for which a quasi-exact solution is available [17]. Secondly, two water hammer problems in HDPE tubes are presented, for which experimental data already used by Pignatelli [38] and Evangelista et al [20] were provided and assumed as reference. For this kind of tests, visco-elastic parameters calibration is also discussed.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…In Fig. 8 it is possible to observe the trend of the calibrated creep functions adopted for this work compared against those used by Evangelista et al [20], neglecting the unsteady friction effects with a 5 KV elements model, and Covas et al [13,12], neglecting the unsteady friction effects or considering them with a 5 KV elements model or using the creep data experimentally determined in mechanical tests. It has to be mentioned that Covas et al [12] creep function is referred to a PE pipe and an average pressure wave speed of 395 m/s, corresponding to an instantaneous Young modulus E 0 = 1.43 GPa.…”

Section: Water Hammer Problemsmentioning

confidence: 99%

“…The instantaneous elastic modulus E 0 is estimated accordingly to the reference elastic wave speed value of each test. As a matter of fact, knowing the mean value of the wave speed, estimated by observing the oscillation period on the basis of experimental measurements, and using the definition (56), it is possible to obtain the proper value of E 0 [20]. Concerning the rest of the visco-elastic parameters, for a multi-parameter model, while τ k are fixed as in references [12,20], E k are calibrated by minimizing the least square error (LSE) between numerical and experimental pressure at the downstream end.…”

Section: Calibration Of the Visco-elastic Parametersmentioning

confidence: 99%

“…Meniconi et al [33,34] analyzed the effect of water hammer pressure waves in case of sudden contraction or expansion of the cross-sectional area or with an in-line valve in the pipeline. Evangelista et al [20] also investigated the behavior of more complex hydraulic systems, with a Y-shaped configuration.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Numerical methods for hydraulic transients in visco-elastic pipes

Bertaglia

Ioriatti

Valiani

et al. 2018

Journal of Fluids and Structures

View full text Add to dashboard Cite

In technical applications involving transient fluid flows in pipes the convective terms of the corresponding governing equations are generally negligible. Typically, under this condition, these governing equations are efficiently discretised by the Method of Characteristics (MOC). Only in the last years the availability of very efficient and robust numerical schemes for the complete system of equations, such as recent Finite Volume Methods (FVM), has encouraged the simulation of transient fluid flows with numerical schemes different from the MOC, allowing a better representation of the physics of the phenomena. In this work, a wide and critical comparison of the capability of Method of Characteristics, Explicit Path-Conservative Finite Volume Method (DOT solver) and Semi-Implicit (SI) Staggered Finite Volume Method is presented and discussed, in terms of accuracy and efficiency. To perform the analysis in a framework that properly represents real-world engineering applications, the viscoelastic behaviour of the pipe wall, the effects of the unsteadiness of the flow on the friction losses, cavitation and cross-sectional changes are taken into account. The analyses are performed comparing numerical solutions obtained using the three models against experimental data and analytical solutions. In particular, water hammer studies in high density polyethylene (HDPE) pipes, for which laboratory data have been provided, are used as test cases. Considering the visco-elastic mechanical behaviour of plastic materials, a 3-parameter and a multiparameter linear visco-elastic rheological models are adopted and implemented in each numerical scheme. Original extensions of existing techniques for the numerical treatment of such visco-elastic models are introduced in this work for the first time. After a focused calibration of the visco-elastic parameters, the different performance of the numerical models is investigated. A comparison of the results is presented taking into account the unsteady wall-shear stress, with a new approach proposed for turbulent flows, or simply considering a quasi-steady friction model. A predominance of the damping effect due to visco-elasticity with respect to the damping effect related to the unsteady friction is confirmed in these contexts. Moreover, all the numerical methods show a good agreement with the experimental data and a high efficiency of the MOC in standard configuration is observed. Finally, three Riemann Problems (RP) are chosen and run to stress the numerical methods, taking into account cross-sectional changes, more flexible materials and cavitation cases. In these demanding scenarios, the weak spots of the Method of Characteristics are depicted.

show abstract

Section: Numerical Resultsmentioning

confidence: 99%

Section: Water Hammer Problemsmentioning

confidence: 99%

Section: Calibration Of the Visco-elastic Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Numerical methods for hydraulic transients in visco-elastic pipes

Bertaglia

Ioriatti

Valiani

et al. 2018

Journal of Fluids and Structures

View full text Add to dashboard Cite

show abstract

“…Therefore, the reliability of the result depends heavily on the wave speed in the numerical simulation of the water hammer. Generally, the wave speed is subjected to many factors, such as the density and elastic modulus of the fluid, the material [19,20] and shape of the pipe [21][22][23], and the means of fixation of the pipe [24]. Moreover, the temperature, pressure, and gas content can also affect the wave speed in a pipe system [25,26].…”

Section: Introductionmentioning

confidence: 99%

Shock Wave Speed and Transient Response of PE Pipe with Steel-Mesh Reinforcement

Wan

Mao

2016

Shock and Vibration

View full text Add to dashboard Cite

A steel mesh can improve the tensile strength and stability of a polyethylene (PE) pipe in a water supply pipeline system. However, it can also cause more severe water hammer hazard due to increasing wave speed. In order to analyze the influence of the steel mesh on the shock wave speed and transient response processes, an improved wave speed formula is proposed by incorporating the equivalent elastic modulus. A field measurement validates the wave speed formula. Moreover, the transient wave propagation and extreme pressures are simulated and compared by the method of characteristics (MOC) for reinforced PE pipes with various steel-mesh densities. Results show that a steel mesh can significantly increase the shock wave speed in a PE pipe and thus can cause severe peak pressure and hydraulic surges in a water supply pipeline system. The proposed wave speed formula can more reasonably evaluate the wave speed and improve the transient simulation of steel-mesh-reinforced PE pipes.

show abstract