Developments and Limits of Discrete Vapor Cavity Models of Transient Cavitating Pipe Flow: 1D and 2D Flow Numerical Analysis

Santoro, Vincenza Cinzia; Crimì, Alessio; Pezzinga, Giuseppe

doi:10.1061/(asce)hy.1943-7900.0001490

Cited by 16 publications

(11 citation statements)

References 15 publications

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“…For cases of V 0 ¼ 0.71 m/s and V 0 ¼ 1.40 m/s, the DVCM and DGCM perform poorly in predicting the formation and collapse of multiple cavities in the transient process. The classical DVCM is only slightly sensitive to grid number N x (Santoro et al 2018). As shown in Figure 4(d), the vapor fractions of the largest cavity calculated by both models are within the limitation of 10% of each pipe section.…”

Section: Comparison Of Numerical Results For Frictionless Casementioning

confidence: 77%

Parametric analysis of discrete multiple-cavity models with the quasi-two-dimensional friction model for transient cavitating pipe flows

Sun

Hao

Cheng

2022

Journal of Water Supply: Research and Technology-Aqua

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Discrete multiple-cavity models coupled with quasi-two-dimensional (quasi-2D) friction models are effective solutions to simulating transient cavitation pipe flows. The simulation accuracy of such models hinges upon the understanding of key parameters of the models, which remains elusive so far. To address such an open issue, this paper employs the discrete vapor cavity model (DVCM) and the discrete gas cavity model (DGCM), combined with the quasi-2D friction model, with a particular focus on revealing the sensitivity of these models to the key parameters such as grid number and weighting parameters. Based on the quantitative analysis and pressure fluctuation history, a method is developed to evaluate the accuracy of numerical results. Results show that the inclusion of the quasi-2D friction model improves the accuracy of predicting time of cavity formation and collapse; however, it does not affect the selection of grid number. Meanwhile, numerical results are sensitive to the weighting parameter of the viscous term in the quasi-2D friction model except for the case of low-intensity cavitation and its value of 1 is suggested for all cases. From the practical point of view, our finding is helpful to understand the feature of discrete multiple-cavity models and improve the simulating accuracy of transient cavitation pipe flows.

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Section: Comparison Of Numerical Results For Frictionless Casementioning

confidence: 77%

Parametric analysis of discrete multiple-cavity models with the quasi-two-dimensional friction model for transient cavitating pipe flows

Sun

Hao

Cheng

2022

Journal of Water Supply: Research and Technology-Aqua

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“…The first mathematical models of vapor cavity formation and collapse were based on the graphical method [60]. Subsequently, a variety of numerical models (e.g., the discrete vapor cavity model (DVCM) [61][62][63][64], the discrete gas cavity model (DGCM) [65][66][67], the generalized interface vapor cavity model (GIVCM)) [68] were developed leading to a better understanding of the water hammer phenomenon with column separation [69][70][71]. The numerical results were compared against experimental data to assess the limitation of the numerical models [72,73].…”

Section: Present Day: Current Researchmentioning

confidence: 99%

The Impact of Water Hammer on Hydraulic Power Units

et al. 2022

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Water hammer influences the life cycle of hydraulic passages and may even cause catastrophic structural failures. Several catastrophic failures of hydraulic power units have been reported in the literature due to the effects of transient regimes. The objective of the study is to highlight the global trend in water hammer assessment and to quantify the effect of factors influencing overpressure in hydraulic passages during load rejection in different hydropower plants. A brief and concise literature review is conducted to document the parameters associated with the water hammer phenomenon and to thereby identify the necessary prerequisites to validate theoretical and numerical results against experimental data. The purpose of the analysis is to identify extreme transient loads on hydraulic passages in order to properly adapt hydropower unit operation, to make recommendations for design and industry, and to guide the progress of adapted models and numerical simulations to capture complex phenomena. Empirical correlations are determined based on the experimental data that are transferable from one unit to another, even if a deep flow analysis is performed. The experimental results confirm that the rapid closure rate of the guide vanes has a significant impact on the phenomenon. A third order polynomial equation is applied to capture the general overpressure trends. Equation parameters change from case to case depending on the type of hydraulic power unit, closing rate and the type of hydraulic passage. The results confirm also that overpressure values depend significantly on other factors, some of which are not usually taken into account (e.g., runner speed). Experimental correlations make it possible to understand the water hammer phenomenon, which could help not just assessing and optimizing loads, but also verifying and validating more complex physical models, to ensure that hydraulic passages are reliable. A well-documented analysis also makes it possible to optimize equipment design, improve and adapt maintenance programs and to recommend appropriate operating parameters to increase equipment lifespan, while preventing incidents.

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“…Then the head pressure and tail pressure of the pig are brought into the pig model to calculate the speed of the pig. 4) Discrete Vapour Cavity Model (DVCM) Establishing a discrete vapor cavity model is to determine whether liquid column separation will occur in the pipeline [40]- [46]. As shown in Figure 6, we make the following assumptions: When the steam chamber is concentrated at section i, the incoming flow is Q i,in and the outgoing flow is Q i,out .…”

Section: A Mathematical Modelmentioning

confidence: 99%

Simulation Model and Case Study of Drainage Process After Pressure Test of Large Drop Natural Gas Pipeline

Liu

Peng

et al. 2020

IEEE Access

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The drainage process of a large drop natural gas pipeline after a pressure test is a complicated transient flow process. This process is a gas-phase and liquid-phase flow process connected by a pig, in which the pressure inside the tube, and the flow velocity of gas and liquid, and the movement state of the pig are constantly changing. At the same time, there are also a variety of complicated working conditions such as liquid evaporation and water hammer. Based on the pig transient model, a transient simulation model is established for the upstream gas section and downstream liquid sections of the pipeline in this paper, and the discrete vapor cavity model is used to simulate the drainage process. Taking a large drop pipe section of natural gas pipeline as an example, the paper studied the influences of key parameters such as flow velocity and pressure on the inlet and outlet of the pipeline on the drainage process and analyzed the complicated conditions such as discrete cavity and water hammer in the pipeline during the drainage process. In this paper, the law of pressure variation in the pipe is obtained, and the method of adjusting the inlet and outlet pressure and flow velocity of the pipe section by segmentation is proposed to avoid the occurrence of complex working conditions such as discrete cavity and water hammer. INDEX TERMS Pig, large drop, drainage, transient flow, numerical simulation, water hammer.

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Developments and Limits of Discrete Vapor Cavity Models of Transient Cavitating Pipe Flow: 1D and 2D Flow Numerical Analysis

Cited by 16 publications

References 15 publications

Parametric analysis of discrete multiple-cavity models with the quasi-two-dimensional friction model for transient cavitating pipe flows

Parametric analysis of discrete multiple-cavity models with the quasi-two-dimensional friction model for transient cavitating pipe flows

The Impact of Water Hammer on Hydraulic Power Units

Simulation Model and Case Study of Drainage Process After Pressure Test of Large Drop Natural Gas Pipeline

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