scholarly journals Numerical modelling of pipelines with air pockets and air valves

2016 ◽  
Vol 43 (12) ◽  
pp. 1052-1061 ◽  
Author(s):  
Vicente S. Fuertes-Miquel ◽  
P. Amparo López-Jiménez ◽  
F. Javier Martínez-Solano ◽  
Gonzalo López-Patiño
Keyword(s):  
Numerical Modelling ◽  
Water Column ◽  
Water Hammer ◽  
Extreme Conditions ◽  
Residual Velocity ◽  
Air Pocket ◽  
Air Valve ◽  
Air Pockets

This work considers the behaviour of air inside pipes when the air is expelled through air valves. Generally, the air shows isothermal behaviour. Nevertheless, when the transient is very fast, it shows adiabatic behaviour. In a real installation, an intermediate evolution between these two extreme conditions occurs. Thus, it is verified that the results vary significantly depending on the hypothesis adopted. To determine the pressure of the air pocket, the most unfavourable hypothesis (isothermal behaviour) is typically adopted. Nevertheless, from the perspective of the water hammer that takes place when the water column arrives at the air valve and abruptly closes, the most unfavourable hypothesis is the opposite (adiabatic behaviour). In this case, the residual velocity with which the water arrives at the air valve is higher, and, consequently, the water hammer generated is greater.

scholarly journals Impact pressure on an orifice plate by a rising water column driven by an air pocket in a vertical riser

2020 ◽  
Vol 81 (5) ◽  
pp. 1029-1038 ◽  
Author(s):  
Yu Qian ◽  
David Z. Zhu
Keyword(s):  
Water Column ◽  
Peak Pressure ◽  
Current Model ◽  
Strong Relationship ◽  
Water Hammer ◽  
Orifice Plate ◽  
Minor Effect ◽  
Initial Water ◽  
Air Pocket ◽  
Riser Height

Abstract Occurrences of storm geyser events have attracted significant attention in recent years. Previous studies suggest that using an orifice plate can reduce the intensity of a geyser event but may induce a water-hammer type of pressure on the orifice plate. This study was conducted to explore the factors that influence the pressure transients when an orifice plate was installed in a vertical riser. A novel model was developed to simulated the movement of a rising water column driven by an air pocket in a vertical riser with an orifice plate on the top. Water-hammer type of pressure occurs when the water column reaches the orifice plate. The current model accurately simulates the dynamics of the water column considering its mass loss due to the flow along the wall of the riser (film flow) and the existence of the orifice plate. It was found that the initial water column length and the driving pressure, as well as the riser material, have a strong relationship with the peak pressure. The riser diameter and riser height have minor effect on the peak pressure. The water-hammer induced peak pressure reaches the maximum when the orifice opening is around 0.2 times the diameter of the vertical riser.

scholarly journals Analysis of Sub-Atmospheric Pressures during Emptying of an Irregular Pipeline without an Air Valve Using a 2D CFD Model

Water ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 2526
Author(s):  
Aris D. Hurtado-Misal ◽  
Daniela Hernández-Sanjuan ◽  
Oscar E. Coronado-Hernández ◽  
Héctor Espinoza-Román ◽  
Vicente S. Fuertes-Miquel
Keyword(s):  
Water Column ◽  
Model Simulation ◽  
Water Velocity ◽  
Column Length ◽  
Cfd Model ◽  
Air Pocket ◽  
Pressure Water ◽  
Air Valve ◽  
Experimental Values ◽  
The Mathematical Model

Studying sub-atmospheric pressure patterns in emptying pipeline systems is crucial because these processes could cause collapses depending on the installation conditions (the underground pipe covering height, type, fill, and pipeline stiffness class). Pipeline studies have focused more on filling than on emptying processes. This study presents an analysis of the following variables: air pocket pressure, water velocity, and water column length during the emptying of an irregular pipeline without an air valve by two-dimensional computational fluid dynamics (2D CFD) model simulation using the software OpenFOAM. The mathematical model predicts the experimental values of the study variables. Water velocity vectors are also analysed within the experimental facility, assessing the sensitivity of the drain valve to different openings and changes in water column length during the hydraulic phenomenon.

scholarly journals Modulation of transient pressure by an air pocket in a horizontal pipe with an end orifice

2018 ◽  
Vol 77 (10) ◽  
pp. 2528-2536 ◽  
Author(s):  
Lin Li ◽  
David Z. Zhu
Keyword(s):  
Open Channel ◽  
Peak Pressure ◽  
Water Hammer ◽  
Sudden Increase ◽  
Transient Pressure ◽  
Horizontal Pipe ◽  
Air Pocket ◽  
Large Orifice ◽  
Air Pockets ◽  
End Wall

Abstract In urban drainage systems, a sudden increase in the flow rate can cause the transition of the flow from open channel to pipe flow, and the entrapment of large air pockets in sewers, which might result in serious geysers and water-hammer like pressure events. This paper presents a numerical analysis of flow processes associated with the pressurization and release of an air pocket in order to study its influence on transient pressure in a horizontal pipe with an end orifice. The influence of the air pocket inside the pipe on the peak pressure can be described in two distinct regimes. In regime I for the pipe with a small orifice, the peak pressure is modulated by the pressurization and expansion of the air pocket and its subsequent damping. In regime II for the pipe with a large orifice, air can be quickly expelled, and the water column directly impinges on the pipe end wall and causes water-hammer like pressure. With the increase of the orifice size, the peak pressure decreases due to the change in the water velocity. In the study cases, the peak pressure in regime I is about two times the inlet pressure, while it can be more than forty times in regime II.

Discussion on the Harm and Protection of Water Hammer of Cavities Collapsing during Long Distance Water Transfer Project

2013 ◽  
Vol 777 ◽  
pp. 407-411
Author(s):  
Li Zhao ◽  
Yu Dong Lu
Keyword(s):  
Water Hammer ◽  
Water Transfer ◽  
Constant Speed ◽  
Long Distance ◽  
Hydraulic Impact ◽  
Tube Explosion ◽  
Valve Effect ◽  
Air Valve ◽  
Pipeline Pressure

In long distance water transfer project, the pipeline pressure caused by the change of hydraulic impact on pipeline is the most dangerous, which cavities hammer boost up to the general water several times, the tube explosion phenomenon is most caused by water hammer of cavities collapsing. After long-term practice, two-way surge tower and constant speed buffer air valve effect remarkable on water hammer of cavities collapsing.

Experimental Validation of Existing Numerical Models for the Interaction of Fluid Transients With In-Line Air Pockets

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Jane Alexander ◽  
Pedro J. Lee ◽  
Mark Davidson ◽  
Huan-Feng Duan ◽  
Zhao Li ◽  
...  
Keyword(s):  
Time Delay ◽  
Wave Speed ◽  
Numerical Models ◽  
Diagnostic Process ◽  
Air Pocket ◽  
Fluid Transients ◽  
Entrapped Air ◽  
Air Pockets ◽  
The Given ◽  
Potential Tool

Entrapped air in pipeline systems can compromise the operation of the system by blocking flow and raising pumping costs. Fluid transients are a potential tool for characterizing entrapped air pockets, and a numerical model which is able to accurately predict transient pressures for a given air volume represents an asset to the diagnostic process. This paper presents a detailed study on our current capability for modeling and predicting the dynamics of an inline air pocket, and is one of a series of articles within a broader context on air pocket dynamics. This paper presents an assessment of the accuracy of the variable wave speed and accumulator models for modeling air pockets. The variable wave speed model was found to be unstable for the given conditions, while the accumulator model is affected by amplitude and time-delay errors. The time-delay error could be partially overcome by combining the two models.

scholarly journals Development of Pant-Type Harness with Fabric Air-Pocket for Pain Relief

2019 ◽  
Vol 9 (9) ◽  
pp. 1921
Author(s):  
Dongwoo Nam ◽  
Miyeon Kwon ◽  
Juhea Kim ◽  
Bummo Ahn
Keyword(s):  
Contact Area ◽  
Peak Pressure ◽  
Applied Pressure ◽  
The Body ◽  
Area Measurement ◽  
Medical Applications ◽  
Air Pocket ◽  
Long Time ◽  
Developed Pressure ◽  
Air Pockets

Harnesses can be used in various applications, such as entertainment, rescue operations, and medical applications. Because users are supported on the harness for a long time, they should feel comfortable wearing the harnesses. However, existing commercial harnesses are uncomfortable to wear and cause continuous serious pain. Therefore, in this study, a new pant-type harness with a fabric air pocket to reduce the applied pressure on the body, especially in the groin, is proposed. Keeping this in mind, we have designed and developed the pant-type harness. In addition, we performed pressure and contact area measurement experiments using the harness developed, pressure sensor, and a human mannequin. Peak and mean pressures and contact areas near the groin and waist were measured in the experiments. From the results, when air is injected in the air pockets, the peak pressure and contact area near the waist increased, and the peak pressure near the groin decreased. This means that the pressure applied on the human mannequin near the groin reduces because of the increased contact area near the waist, which is achieved by multi-layered air pockets. In this study, we proposed the optimal design of a novel pant-type harness that can address the limitations of existing harnesses. The proposed harness can be used for a prolonged time in applications, such as virtual reality entertainment, rescue operations, and rehabilitation.

Microfluidic Control Using Vapor Based Valves

2007 ◽  
Author(s):  
Wei Xu ◽  
Hong Xue ◽  
Mark Bachman ◽  
G. P. Li
Keyword(s):  
Temperature Gradient ◽  
Low Cost ◽  
Constant Flow ◽  
Lab On Chip ◽  
Air Pocket ◽  
Valve Function ◽  
Air Valve ◽  
On Chip ◽  
Silicon Based ◽  
At Will

Microflow valving and regulating are two important functions for microfluidic systems for applications such as Lab-on-Chip. Although silicon based counterparts have been studied extensively, few good technologies exist for polymer based microvalves and regulators. In this paper, we present designs and methods for microvalve and microflow regulators that are readily integrated into polymer microfluidic devices. The technologies utilize “air-pocket” structures built into the sidewalls of the microchannels. When liquid is filled in such a channel, air is trapped in “air pocket” structures due to the hydrophobicity of the polymer. By creating a small thermal gradient between the fluid in the channel and the air in the pockets, one can controllably evaporate fluid into the air pocket where it condenses. This displaces air out of the pocket into the flow channel, increasing the resistance to flow. The air valve retreats to its original pocket when the temperature gradient is removed, thus allowing one to increase or decrease fluid flow at will. If the temperature gradient is maintained long enough, the air will completely block the channel, forming an irreversible valving of the flow. Therefore, the same device can be used as either a valve or flow-regulating device. Microfluidic prototypes were built and tested using this technology. The results show successful constant flow delivery as well as valve function. This novel vapor based microflow valve and regulator has advantages of low cost, simple design, and both ease of fabrication and integration.

scholarly journals Effect of a Commercial Air Valve on the Rapid Filling of a Single Pipeline: a Numerical and Experimental Analysis

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1814 ◽  
Author(s):  
Óscar E. Coronado-Hernández ◽  
Mohsen Besharat ◽  
Vicente S. Fuertes-Miquel ◽  
Helena M. Ramos
Keyword(s):  
Mathematical Model ◽  
Air Water Interface ◽  
Water Pipelines ◽  
Polytropic Equation ◽  
Pipeline Failure ◽  
Air Valve ◽  
Thermodynamic Variables ◽  
Air Pockets ◽  
The Mathematical Model ◽  
Oscillation Equation

The filling process in water pipelines produces pressure surges caused by the compression of air pockets. In this sense, air valves should be appropriately designed to expel sufficient air to avoid pipeline failure. Recent studies concerning filling maneuvers have been addressed without considering the behavior of air valves. This work shows a mathematical model developed by the authors which is capable of simulating the main hydraulic and thermodynamic variables during filling operations under the effect of the air valve in a single pipeline, which is based on the mass oscillation equation, the air–water interface, the polytropic equation of the air phase, the air mass equation, and the air valve characterization. The mathematical model is validated in a 7.3-m-long pipeline with a 63-mm nominal diameter. A commercial air valve is positioned in the highest point of the hydraulic installation. Measurements indicate that the mathematical model can be used to simulate this phenomenon by providing good accuracy.

scholarly journals Parameters affecting water hammer in metal pipelines

2018 ◽  
Vol 44 ◽  
pp. 00183
Author(s):  
Kamil Urbanowicz ◽  
Mateusz Firkowski
Keyword(s):  
Numerical Modelling ◽  
Method Of Characteristics ◽  
Water Hammer ◽  
Supply System ◽  
Hydraulic Systems ◽  
Wave Pressure ◽  
Hydraulic Machinery ◽  
Metal Pipes ◽  
The Individual ◽  
Pressure Changes

The water hammer related to rapid wave pressure changes in hydraulic systems have been subjected to intensive research for more than a hundred years. Nevertheless, a large number of new papers appear each year. Current literature indicates model differences resulting from the used material of the pipe. In the hydraulic machinery, elastic (metal) pipes are usually used, while water transport in water supply system is currently realized with pipes whose deformation of the walls is viscoelastic. In this paper, the individual and group impact of all parameters influencing the results of numerical modelling of the water hammer occurring in the pipes will be analysed. The method of characteristics will be used to solve partial differential equations describing the flow.

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