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A Arris S Tijsseling - One of the best experts on this subject based on the ideXlab platform.
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numerical investigations of Water Hammer with column separation induced by vaporous cavitation using a one dimensional finite volume approach
Journal of Fluids and Structures, 2018Co-Authors: Frederic Daude, A Arris S Tijsseling, Pascal GaloAbstract:Abstract Water-Hammer with column-separation induced by cavitation is investigated numerically. The vapor–Water flow is modeled using the Homogeneous Equilibrium Model in conjunction with the 1984 NBS/NRC Steam Tables. The discretization is done with the quasi 1-D Finite-Volume approach recently developed by the authors for compressible flows in pipelines. The ability of the present approach to tackle cavitating flows is first assessed. Then, comparisons with experimental results of Water-Hammer with column-separation demonstrate consistency with the present computations. Based on the obtained numerical results, focus is given to the dynamics of the liquid column-separation and to the associated physics such as cavitation, vapor growth and collapse, generation of the secondary Water-Hammer peak and the interaction of the primary and secondary pressure waves. The influence of the initial flow velocity before valve closure on the duration and size of the cavity and on the magnitude of the secondary Water-Hammer is examined.
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fluid structure interaction with pipe wall viscoelasticity during Water Hammer
Journal of Fluids and Structures, 2012Co-Authors: A Arris S Tijsseling, Alireza Kerama, Qingzhi Hou, Ahmad AhmadiAbstract:Fluid–structure interaction (FSI) due to Water Hammer in a pipeline which has viscoelastic wall behaviour is studied. Appropriate governing equations are derived and numerically solved. In the numerical implementation of the hydraulic and structural equations, viscoelasticity is incorporated using the Kelvin–Voigt mechanical model. The equations are solved by two different approaches, namely the Method of Characteristics–Finite Element Method (MOC-FEM) and full MOC. In both approaches two important effects of FSI in fluid-filled pipes, namely Poisson and junction coupling, are taken into account. The study proposes a more comprehensive model for studying fluid transients in pipelines as compared to previous works, which take into account either FSI or viscoelasticity. To verify the proposed mathematical model and its numerical solutions, the following problems are investigated: axial vibration of a viscoelastic bar subjected to a step uniaxial loading, FSI in an elastic pipe, and hydraulic transients in a pressurised polyethylene pipe without FSI. The results of each case are checked with available exact and experimental results. Then, to study the simultaneous effects of FSI and viscoelasticity, which is the new element of the present research, one problem is solved by the two different numerical approaches. Both numerical methods give the same results, thus confirming the correctness of the solutions.
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fluid structure interaction with pipe wall viscoelasticity during Water Hammer
CASA-report, 2011Co-Authors: A Arris S Tijsseling, Alireza Kerama, Qingzhi Hou, Ahmad AhmadiAbstract:Fluid-structure interaction (FSI) due to Water Hammer in a pipeline which has viscoelastic wall behaviour is studied. Appropriate governing equations are derived and numerically solved. In the numerical implementation of the hydraulic and structural equations, viscoelasticity is incorporated using the Kelvin-Voigt mechanical model. The equations are solved by two different approaches, namely the Method of Characteristics - Finite Element Method (MOCFEM) and full MOC. In both approaches two important effects of FSI in fluid-filled pipes, namely Poisson and junction coupling, are taken into account. The study proposes a more comprehensive model for studying fluid transients in pipelines as compared to previous works, which take into account either FSI or viscoelasticity. To verify the proposed mathematical model and its numerical solutions, the following problems are investigated: axial vibration of a viscoelastic bar subjected to a step uniaxial loading, FSI in an elastic pipe, and hydraulic transients in a pressurized polyethylene pipe without FSI. The results of each case are checked with available exact and experimental results. Then, to study the simultaneous effects of FSI and viscoelasticity, which is the new element of the present research, one problem is solved by the two different numerical approaches. Both numerical methods give the same results, thus confirming the correctness of the solutions. Keywords: Water Hammer; fluid transient; pressure surge; fluid-structure interaction; pipe vibration; plastic pipe; viscoelasticity
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parameters affecting Water Hammer wave attenuation shape and timing part 2 case studies
Journal of Hydraulic Research, 2008Co-Authors: A Bergant, A Arris S Tijsseling, John P Vitkovský, Didia Covas, Angus R Simpson, Martin F LambertAbstract:This two-part paper investigates parameters that may significantly affect Water-Hammer wave attenuation, shape and timing. Possible sources that may affect the waveform predicted by classical Water-Hammer theory include unsteady friction, cavitation (including column separation and trapped air pockets), a number of fluid–structure interaction effects, viscoelastic behaviour of the pipe-wall material, leakages and blockages. Part 1 of this two-part paper presents the mathematical tools needed to model these sources. Part 2 of the paper presents a number of case studies showing how these modelled sources affect pressure traces in a simple reservoir-pipeline-valve system. Each case study compares the obtained results with the standard (classical) Water-Hammer model, from which conclusions are drawn concerning the transient behaviour of real systems
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parameters affecting Water Hammer wave attenuation shape and timing part 1 mathematical tools
Journal of Hydraulic Research, 2008Co-Authors: A Bergant, A Arris S Tijsseling, John P Vitkovský, Didia Covas, Angus R Simpson, Martin F LambertAbstract:This two-part paper investigates key parameters that may affect the pressurewaveform predicted by the classical theory ofWater-Hammer. Shortcomings in the prediction of pressure wave attenuation, shape and timing originate from violation of assumptions made in the derivation of the classical WaterHammer equations. Possible mechanisms that may significantly affect pressure waveforms include unsteady friction, cavitation (including column separation and trapped air pockets), a number of fluid–structure interaction (FSI) effects, viscoelastic behaviour of the pipe-wall material, leakages and blockages. Engineers should be able to identify and evaluate the influence of these mechanisms, because first these are usually not included in standard Water-Hammer software packages and second these are often “hidden” in practical systems. Part 1 of the two-part paper describes mathematical tools for modelling the aforementioned mechanisms. The method of characteristics transformation of the classical Water-Hammer equa...
Ali Triki - One of the best experts on this subject based on the ideXlab platform.
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dual control technique for mitigating Water Hammer phenomenon in pressurized steel piping systems
International Journal of Pressure Vessels and Piping, 2019Co-Authors: Mounir Trabelsi, Ali TrikiAbstract:Abstract This paper examined a dual technique -based branching strategy to sustain the conventional technique skills in terms of limitation of wave oscillation period spreading. This technique consists in splitting the single plastic short-penstock used in the conventional one into dual plastic sub-short penstocks placed upstream each of the connections of the original steel piping system to other hydraulic parts. Numerical computations used the method of characteristics for the discretization of unconventional Water-Hammer model based on the Vitkovsky and the Kelvin-Voigt formulations. The robustness of the transient solver was evaluated by comparing the obtained numerical results with pertinent experimental results. Moreover, the efficiency of the dual technique was explored for a series of operating condition tests including up- and- down surge- initiated Water Hammer events. Additionally, two plastic material types were utilized for sub- short-penstock pipe-walls, including (HDPE) or (LDPE) plastic materials. Results demonstrated that dual technique is a useful tool to soften both first hydraulic-head peak and crest. Moreover, examination of wave oscillation periods confirmed that the dual technique could markedly improve the efficiency of the conventional one, providing acceptable trade-off between hydraulic-head peaks or crests attenuation, and wave oscillation period spreading limitation. Furthermore, results demonstrated that the amortization of pressure head -rise and -drop was sensitive to the plastic sub- short-penstocks dimensions.
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compound technique based inline design strategy for Water Hammer control in steel pressurized piping systems
International Journal of Pressure Vessels and Piping, 2019Co-Authors: Ali Triki, Mohamed Amir ChakerAbstract:Abstract The inline design strategy was recognized as being an effective tool for Water-Hammer control in pressurized-pipe flow. Principally, this strategy is based on replacing a short-section of the existing steel-piping system by another made of polymeric material. However, this strategy leads to an excessive radial-strain amplification and a large spread-out of wave oscillation period. Alternatively, an innovative compound technique -based inline design strategy was reported in this paper to enhance the foregoing limitations. The proposed technique is based on splitting the single short-section used in the conventional technique into a couple of two sub short-sections made up of two distinct material types. The materials demonstrated in this study include high- and low-density polyethylene (HDPE) and (LDPE). The transient solver was based on the 1-D unconventional Water-Hammer model embedding the Vitkovsky et al. and Kelvin-Voigt formulation, while the numerical discretization was performed using the Fixed Gird Method of Characteristics (FG-MOC). The proposed method is validated through a comparison with experimental results. Further, detailed numerical results obtained from several scenarios are presented and discussed. Results illustrated the reliability of the proposed technique in mitigating excessive high- or low-pressures, and evidenced that the (HDPE–LDPE) sub short-sections combination (where the former is attached to hydraulic parts and the latter to the steel pipe) is the most prominent configuration providing an acceptable trade-off between piezometric-head and circumferential-stress attenuation (from one side), and limitation of the excessive spreading of oscillation period and amplification of radial-strain (from the other side). The findings of a parametric study of the sensitivity of pressure wave damping and spreading to the employed short-section length and diameter resulted in estimation of the near-optimal design values of the short-section size.
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further investigation on the Water Hammer control branching strategy in pressurized steel piping systems
International Journal of Pressure Vessels and Piping, 2018Co-Authors: Ali Triki, Mohamed FersiAbstract:Abstract The branching design strategy was recognized as being a practical technique for Water-Hammer surge control in pressurized steel-piping systems. This strategy is based on adding a branched polymeric short-section at the transient sensitive region of an existing steel piping system. On the other hand, design practices require numerical solvers that are both accurate and computationally efficient. Accordingly, this paper revisited the implementation of the branching design strategy using a 1-D unconventional Water-Hammer model based upon the Ramos formulation to benefit from its simplified representations of unsteady friction effects and pipe wall behavior. The transient solver was performed using the Fixed Gird Method of Characteristics ( FG-MOC ). The transient solver effectiveness was demonstrated by comparing the obtained numerical results with pertinent experimental ones quoted in the literature; further, computational savings were significantly carried out via the selected formulation. The proposed design strategy was implemented within two kinds of boundary conditions initiating Water-Hammer up- and down-surge waves. In addition, two types of polymeric materials, including high- or low-density polyethylene ( HDPE or LDPE ), were utilized for the branched short-section. Results evidenced the potential of the branching design strategy to attenuate excessive pressure -rise and -drop, while safeguarding existing pressurized piping system configurations. Furthermore, the study of the dependency of the short-section material and size on the attenuation rate of pressure -rise and -drop evidenced that a higher wave speed of the branched short-section provided a higher attenuation rate of pressure -rise and -drop, and helped estimate near-optimal values for the short-section length and diameter.
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dual technique based inline design strategy for Water Hammer control in pressurized pipe flow
Acta Mechanica, 2018Co-Authors: Ali TrikiAbstract:A dual-technique-based inline strategy was investigated in this study as a sustainment to conventional-technique skills in terms of limitation of wave oscillation period spread-out. Instead of the single polymeric short section employed by the latter technique, the former is based on replacing an up- and downstream short section of the primitive piping system using another couple made of polymeric pipe-wall material. Numerical computations used the method of characteristics for the discretization of unconventional Water-Hammer model based on the Vitkovsky and the Kelvin–Voigt formulations. The efficiency of the dual technique was considered for two operating conditions associated with up- and downsurge frames. Moreover, two pipe-wall material types were utilized for short-section pipe wall, namely the HDPE or LDPE materials. Additionally, the conventional technique was also addressed in this study, for comparison purposes. First, analyses of pressure-head, circumferential-stress and radial-strain wave patterns, along with wave oscillation periods examination, confirmed that the dual technique could improve the efficiency of the conventional one, providing acceptable trade-off between the attenuation of pressure-head and circumferential-stress peaks (or crests), and limitation of period spreading and radial-strain amplification. Second, a parametric study of the sensitivity of the wave damping to the employed short-section dimensions was performed in terms of short-section length and diameter. This parametric study helped estimate the near-optimal values of the short-section dimensions.
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alternative design strategy for Water Hammer control in pressurized pipe flow
International Conference on Acoustics and Vibration, 2018Co-Authors: Mohamed Fersi, Ali TrikiAbstract:This paper proposed a design technique to dampen Water-Hammer surges into an existing steel piping system based on replacing a short-section of the transient sensitive region of the main piping system by another one made of polymeric material. The flow behavior was described using a one dimensional unconventional Water Hammer model based on the Ramos formulation to account for pipe-wall deformation and unsteady friction losses. The numerical solver was performed using the fixed gird Method of Characteristics. The effectiveness of the proposed design technique was assessed with regard to Water-Hammer up-surge scenario, using a high- or low-density polyethylene (HDPE or LDPE) for the replaced short-section. Results demonstrated that the utilized technique provided a useful tool to soften severe Water-Hammer surges. Additionally, the pressure surge softening was slightly more important for the case of a short-section made of LDPE polymeric material than that using an HDPE polymeric material. However, it was observed that the proposed technique induced an amplification of the radial-strain magnitude and spread-out of the period of wave oscillations. It was also found that the amortization of pressure amplitude, and reciprocally the radial strain magnitude, was strongly dependent upon the short-section size and material.
Alireza Riasi - One of the best experts on this subject based on the ideXlab platform.
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energy dissipation in unsteady turbulent pipe flows caused by Water Hammer
Computers & Fluids, 2013Co-Authors: Alireza Riasi, Ahmad Nourbakhsh, Mehrdad RaiseeAbstract:Abstract Energy dissipation and turbulent kinetic energy production and its dissipation in unsteady turbulent pipe flows due to Water Hammer phenomena are numerically studied. For this purpose, the two-dimensional governing equations of Water Hammer are solved using the method of characteristics. A k–ω turbulence model which is accurate for two-dimensional boundary layers under adverse and favorable pressure gradients is applied. The numerical results are in good agreement with the experimental data. Through an order of magnitude analysis, two dimensionless parameters have been identified which can be used for the evaluation of viscous and turbulent shear stress terms. The influence of these non-dimensional parameters on pressure oscillations, wall-shear-stress, dissipation rate as well as profiles of velocity, turbulent production and dissipation are investigated. The non-dimensional parameter P, which represents time scale ratio of turbulence diffusion in the radial direction to the pressure wave speed, is used to study the structure and strength of turbulence. It is found that for the case of P ≈ 1, for which the values of the non-dimensional groups are larger, the peaks of turbulence energy production and dissipation move rapidly away from the wall and turbulence structure is significantly changed. For the case of P ≫ 1, for which the values of non-dimensional parameters are smaller, these variations are found to be small.
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cavitating flow during Water Hammer using a generalized interface vaporous cavitation model
Journal of Fluids and Structures, 2012Co-Authors: M H Sadafi, Alireza Riasi, Seyed Ahmad NourbakhshAbstract:In a transient flow simulation, column separation may occur when the calculated pressure head decreases to the saturated vapor pressure head in a computational grid. Abrupt valve closure or pump failure can result in a fast transient flow with column separation, potentially causing problems such as pipe failure, hydraulic equipment damage, cavitation or corrosion. This paper reports a numerical study of Water Hammer with column separation in a simple reservoir-pipeline-valve system and pumping station. The governing equations for two-phase transient flow in pipes are solved based on the method of characteristics (MOC) using a generalized interface vaporous cavitating model (GIVCM). The numerical results were compared with the experimental data for validation purposes, and the comparison indicated that the GIVCM describes the experimental results more accurately than the discrete vapor cavity model (DVCM). In particular, the GIVCM correlated better with the experimental data than the DVCM in terms of timing and pressure magnitude. The effects of geometric and hydraulic parameters on flow behavior in a pumping station with column separation were also investigated in this study.
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unsteady velocity profiles in laminar and turbulent Water Hammer flows
Journal of Fluids Engineering-transactions of The Asme, 2009Co-Authors: Alireza Riasi, Ahmad Nourbakhsh, Mehrdad RaiseeAbstract:The behavior of unsteady velocity profiles in laminar and turbulent Water Hammer flows is numerically investigated. In this way, the governing equations for the quasitwo-dimensional equations of transient flow in pipe are solved by using the modified implicit characteristics method. A k-w turbulence model which is accurate for two-dimensional boundary layers under adverse and favorable pressure gradients is applied. The numerical results for both steady and unsteady turbulent pipe flows are in good agreement with the experimental data. The results indicate that both decelerating and accelerating flows are produced in a wave cycle of Water Hammer. During deceleration of the flow, a region of reverse flows and also strong gradients is formed near to the pipe wall. In case of the turbulent Water Hammer, this region is very close to the pipe wall compared with the laminar Water Hammer. Moreover, point of inflection and also point of zero velocity are formed in the unsteady velocity profile due to the Water Hammer problem. The results show that the point of zero velocity does not move very far from its initial location, while the point of inflection moves rapidly from the wall.
Mehrdad Raisee - One of the best experts on this subject based on the ideXlab platform.
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energy dissipation in unsteady turbulent pipe flows caused by Water Hammer
Computers & Fluids, 2013Co-Authors: Alireza Riasi, Ahmad Nourbakhsh, Mehrdad RaiseeAbstract:Abstract Energy dissipation and turbulent kinetic energy production and its dissipation in unsteady turbulent pipe flows due to Water Hammer phenomena are numerically studied. For this purpose, the two-dimensional governing equations of Water Hammer are solved using the method of characteristics. A k–ω turbulence model which is accurate for two-dimensional boundary layers under adverse and favorable pressure gradients is applied. The numerical results are in good agreement with the experimental data. Through an order of magnitude analysis, two dimensionless parameters have been identified which can be used for the evaluation of viscous and turbulent shear stress terms. The influence of these non-dimensional parameters on pressure oscillations, wall-shear-stress, dissipation rate as well as profiles of velocity, turbulent production and dissipation are investigated. The non-dimensional parameter P, which represents time scale ratio of turbulence diffusion in the radial direction to the pressure wave speed, is used to study the structure and strength of turbulence. It is found that for the case of P ≈ 1, for which the values of the non-dimensional groups are larger, the peaks of turbulence energy production and dissipation move rapidly away from the wall and turbulence structure is significantly changed. For the case of P ≫ 1, for which the values of non-dimensional parameters are smaller, these variations are found to be small.
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unsteady velocity profiles in laminar and turbulent Water Hammer flows
Journal of Fluids Engineering-transactions of The Asme, 2009Co-Authors: Alireza Riasi, Ahmad Nourbakhsh, Mehrdad RaiseeAbstract:The behavior of unsteady velocity profiles in laminar and turbulent Water Hammer flows is numerically investigated. In this way, the governing equations for the quasitwo-dimensional equations of transient flow in pipe are solved by using the modified implicit characteristics method. A k-w turbulence model which is accurate for two-dimensional boundary layers under adverse and favorable pressure gradients is applied. The numerical results for both steady and unsteady turbulent pipe flows are in good agreement with the experimental data. The results indicate that both decelerating and accelerating flows are produced in a wave cycle of Water Hammer. During deceleration of the flow, a region of reverse flows and also strong gradients is formed near to the pipe wall. In case of the turbulent Water Hammer, this region is very close to the pipe wall compared with the laminar Water Hammer. Moreover, point of inflection and also point of zero velocity are formed in the unsteady velocity profile due to the Water Hammer problem. The results show that the point of zero velocity does not move very far from its initial location, while the point of inflection moves rapidly from the wall.
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unsteady turbulent pipe flow due to Water Hammer using k θ turbulence model
Journal of Hydraulic Research, 2009Co-Authors: Alireza Riasi Phd Candidate, Ahmad Nourbakhsh, Mehrdad RaiseeAbstract:The behaviour of unsteady turbulent pipe flow resulting from Water Hammer is herein numerically studied. An accurate k–θ turbulence model for two-dimensional boundary layers under adverse and favorable pressure gradients (Wilcox 1994) was applied. The results of the numerical method are in good agreement with test data obtained from both steady and unsteady turbulent pipe flows. Also, the behaviour and the structure of turbulence in unsteady turbulent pipe flows caused by Water Hammer were investigated. A non-dimensional parameter P as the time scale ratio of turbulence diffusion in the radial direction to the pressure wave speed introduced by Ghidaoui et al. (2002) was used. The results show that for P ≈ 1, the turbulence structure is significantly changed in the first cycle of Water Hammer, which is important for Water quality modeling, whereas these variations are small for P ≫ 1.
Alireza Kerama - One of the best experts on this subject based on the ideXlab platform.
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fluid structure interaction with pipe wall viscoelasticity during Water Hammer
Journal of Fluids and Structures, 2012Co-Authors: A Arris S Tijsseling, Alireza Kerama, Qingzhi Hou, Ahmad AhmadiAbstract:Fluid–structure interaction (FSI) due to Water Hammer in a pipeline which has viscoelastic wall behaviour is studied. Appropriate governing equations are derived and numerically solved. In the numerical implementation of the hydraulic and structural equations, viscoelasticity is incorporated using the Kelvin–Voigt mechanical model. The equations are solved by two different approaches, namely the Method of Characteristics–Finite Element Method (MOC-FEM) and full MOC. In both approaches two important effects of FSI in fluid-filled pipes, namely Poisson and junction coupling, are taken into account. The study proposes a more comprehensive model for studying fluid transients in pipelines as compared to previous works, which take into account either FSI or viscoelasticity. To verify the proposed mathematical model and its numerical solutions, the following problems are investigated: axial vibration of a viscoelastic bar subjected to a step uniaxial loading, FSI in an elastic pipe, and hydraulic transients in a pressurised polyethylene pipe without FSI. The results of each case are checked with available exact and experimental results. Then, to study the simultaneous effects of FSI and viscoelasticity, which is the new element of the present research, one problem is solved by the two different numerical approaches. Both numerical methods give the same results, thus confirming the correctness of the solutions.
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fluid structure interaction with pipe wall viscoelasticity during Water Hammer
CASA-report, 2011Co-Authors: A Arris S Tijsseling, Alireza Kerama, Qingzhi Hou, Ahmad AhmadiAbstract:Fluid-structure interaction (FSI) due to Water Hammer in a pipeline which has viscoelastic wall behaviour is studied. Appropriate governing equations are derived and numerically solved. In the numerical implementation of the hydraulic and structural equations, viscoelasticity is incorporated using the Kelvin-Voigt mechanical model. The equations are solved by two different approaches, namely the Method of Characteristics - Finite Element Method (MOCFEM) and full MOC. In both approaches two important effects of FSI in fluid-filled pipes, namely Poisson and junction coupling, are taken into account. The study proposes a more comprehensive model for studying fluid transients in pipelines as compared to previous works, which take into account either FSI or viscoelasticity. To verify the proposed mathematical model and its numerical solutions, the following problems are investigated: axial vibration of a viscoelastic bar subjected to a step uniaxial loading, FSI in an elastic pipe, and hydraulic transients in a pressurized polyethylene pipe without FSI. The results of each case are checked with available exact and experimental results. Then, to study the simultaneous effects of FSI and viscoelasticity, which is the new element of the present research, one problem is solved by the two different numerical approaches. Both numerical methods give the same results, thus confirming the correctness of the solutions. Keywords: Water Hammer; fluid transient; pressure surge; fluid-structure interaction; pipe vibration; plastic pipe; viscoelasticity
