scholarly journals Use of equivalent celerity to estimate maximum pressure increase in serial pipes during water hammer - numerical simulations in MATLAB

2018 ◽  
Vol 7 (1) ◽  
pp. 22-32
Author(s):  
Agnieszka Malesińska ◽  
Mariusz Rogulski ◽  
Pierfabrizio Puntorieri ◽  
Giuseppe Barbaro ◽  
Beata Kowalska
Keyword(s):  
Numerical Simulations ◽  
Water Hammer ◽  
Pressure Increase ◽  
Maximum Pressure

scholarly journals Water Hammer Control Using Additional Branched HDPE Pipe

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8008
Author(s):  
Michał Kubrak ◽  
Agnieszka Malesińska ◽  
Apoloniusz Kodura ◽  
Kamil Urbanowicz ◽  
Paweł Bury ◽  
...  
Keyword(s):  
Transient Flow ◽  
Oscillation Period ◽  
Water Hammer ◽  
Pressure Increase ◽  
Maximum Pressure ◽  
Main Pipeline ◽  
Closing Time ◽  
Hydraulic Transients ◽  
Flow Equations ◽  
Hdpe Pipe

In pressurised pipeline systems, various water hammer events commonly occur. This phenomenon can cause extensive damage or even lead to a failure of the pumping system. The aim of this work is to experimentally re-examine the possibility of using an additional polymeric pipe, installed at the downstream end of the main pipeline, to control water hammer. A previous study on this topic investigated additional polymeric pipes connected to the hydraulic system with a short joint section of the same diameter as the main pipeline. In the current research, a different method of including an additional pipe was considered which involved connecting it with a pipe of a smaller diameter than the main pipeline. Three additional HDPE pipes, with different volumes, were investigated. The performance of the devices was studied for hydraulic transients induced by both rapid and slow, manual valve closures. Experimental results show that the additional polymeric pipe can provide significant pressure surge damping during rapid water hammer events. As the valve closing time lengthens, the influence of the additional pipe on the maximum pressure increase is reduced. The additional HDPE pipe does not provide notable protection against hydraulic transients induced by slow valve closure in terms of reducing the first pressure peak. No relationship between the volume of the additional pipe and the damping properties was noticed. The observed pressure oscillations were used to evaluate a one-dimensional numerical model, in which an additional pipe is described as a lumped parameter of the system. The viscoelastic properties of the device were included using the one element Kelvin–Voigt model. Transient flow equations were solved with the implicit method of characteristics. Calculation results demonstrate that this approach allows one to reasonably reproduce unsteady flow oscillations registered during experiments in terms of the maximum pressure increase and pressure wave oscillation period.

scholarly journals Pressure generated at the instant of impact between a liquid droplet and solid surface

2018 ◽  
Vol 5 (12) ◽  
pp. 181101 ◽  
Author(s):  
Y. Tatekura ◽  
M. Watanabe ◽  
K. Kobayashi ◽  
T. Sanada
Keyword(s):  
Solid Surface ◽  
Shape Factor ◽  
Liquid Droplet ◽  
Pressure Rise ◽  
Propagation Speed ◽  
Spherical Shape ◽  
Water Hammer ◽  
Droplet Impact ◽  
Maximum Pressure ◽  
The Impact

The prime objective of this study is to answer the question: How large is the pressure developed at the instant of a spherical liquid droplet impact on a solid surface? Engel first proposed that the maximum pressure rise generated by a spherical liquid droplet impact on a solid surface is different from the one-dimensional water-hammer pressure by a spherical shape factor (Engel 1955 J. Res. Natl Bur. Stand. 55 (5), 281–298). Many researchers have since proposed various factors to accurately predict the maximum pressure rise. We numerically found that the maximum pressure rise can be predicted by the combination of water-hammer theory and the shock relation; then, we analytically extended Engel’s elastic impact model, by realizing that the progression speed of the contact between the gas–liquid interface and the solid surface is much faster than the compression wavefront propagation speed at the instant of the impact. We successfully correct Engel’s theory so that it can accurately provide the maximum pressure rise at the instant of impact between a spherical liquid droplet and solid surface, that is, no shape factor appears in the theory.

Maximum Pressure Head Due to Linear Valve Closure

1991 ◽  
Vol 113 (4) ◽  
pp. 643-647 ◽  
Author(s):  
Chyr Pyng Liou
Keyword(s):  
Flow Characteristic ◽  
Pressure Head ◽  
Head Loss ◽  
Water Hammer ◽  
Point Of View ◽  
Global Perspective ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Subtle Effect ◽  
Dimensionless Variables

The maximum pressure head resulting from one-speed closure of wide open valves is investigated. The dimensionless variables formulated in this study make the subtle effect of the initial valve head loss explicit and separate from that of the pipe frictional head loss. The maximum head is related to initial pipe frictional head loss, the initial valve head loss, the inherent flow characteristic of the valve, and the closure period by plots of dimensionless variables. The trends of the variation of the maximum pressure head are discussed. An example is used to illustrate the usage of the plots, and to show the advantage of having a global perspective of the phenomenon in the selection and sizing of valves from the water hammer point of view.

Numerical Analysis of Pipeline Equipment Effect on Water Hammer Using Characteristic Method

2003 ◽  
Author(s):  
Mohammad R. Ansari ◽  
Abdolreza Davari
Keyword(s):  
Momentum Conservation ◽  
Water Hammer ◽  
Loss Coefficient ◽  
Maximum Pressure ◽  
Characteristic Method ◽  
Pump Impeller ◽  
Air Chamber ◽  
Large Pressure Gradient ◽  
Pipeline Equipment ◽  
The Moment

In this attempt effect of pipeline equipment behavior was considered on water hammer numerically. The effect includes opening / closing of the shut off valves, loss of coefficient of the outlet bypass pipe for the air chamber, elasticity of the pipeline and loss coefficient due to friction. In order to study the behavior, mass and momentum conservation equations were solved numerically using characteristic method during transient conditions. As a water hammer phenomena accompanies with large pressure gradient, so the pipeline equipment behavior and their effect were analyzed with respect to the maximum pressure occurrence. For a pipeline of 5000 m length, 1 m diameter, 1 m3/s discharge and 100 m height between upstream and downstream, the following result were concluded: 1-If the moment of inertia of the pump impeller increases by 400 percent, the maximum pressure occurred by the water hammer will decrease by 9 percent. 2-During on and off of the shut off valve, 80 percent of pressure increase due to water hammer was created during the last 15 percent of valve closure. 3-If pressure wave velocity increases by 75 percent, then the maximum pressure generated due to the water hammer will increase by 27 percent. 4-If the loss coefficient of the by pass line of the air chamber decreases by 90 percent, then the maximum pressure due to the water hammer will decrease by 20 percent. 5-If the pipeline Moody friction coefficient increases by 92 percent, the maximum pressure due to the water hammer will increase by 66 percent.

scholarly journals Analysis of Water Hammer with Different Closing Valve Laws on Transient Flow of Hydrogen-Natural Gas Mixture

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Norazlina Subani ◽  
Norsarahaida Amin
Keyword(s):  
Natural Gas ◽  
Pressure Wave ◽  
Transient Flow ◽  
Water Hammer ◽  
Wave Profile ◽  
Maximum Pressure ◽  
Gas Mixture ◽  
Pressure Waves ◽  
Closing Time ◽  
Closure Laws

Water hammer on transient flow of hydrogen-natural gas mixture in a horizontal pipeline is analysed to determine the relationship between pressure waves and different modes of closing and opening of valves. Four types of laws applicable to closing valve, namely, instantaneous, linear, concave, and convex laws, are considered. These closure laws describe the speed variation of the hydrogen-natural gas mixture as the valve is closing. The numerical solution is obtained using the reduced order modelling technique. The results show that changes in the pressure wave profile and amplitude depend on the type of closing laws, valve closure times, and the number of polygonal segments in the closing function. The pressure wave profile varies from square to triangular and trapezoidal shape depending on the type of closing laws, while the amplitude of pressure waves reduces as the closing time is reduced and the numbers of polygonal segments are increased. The instantaneous and convex closing laws give rise to minimum and maximum pressure, respectively.

Understanding Line Packing in Frictional Water Hammer

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Jim C. P. Liou
Keyword(s):  
Numerical Methods ◽  
Wave Front ◽  
Water Hammer ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Governing Equations ◽  
Front Line ◽  
Wave Fronts ◽  
Friction Term

For valve closure transients in pipelines, friction attenuates the amplitude of water hammer wave fronts and causes line packing. The latter is a sustained head increase behind the wave front. Line packing can lead to overpressure. Because of the nonlinearity of the friction term in the governing equations of water hammer, a satisfactory analytical explanation of line packing is not available. Although numerical methods can be used to compute line packing, an analytical explanation is desirable to better understand the phenomenon. This paper explains line packing analytically and presents a formula to compute the line packing that leads to the maximum pressure at the closed valve.

Filtering Effects of Periodic Structure in Water Hammer

2014 ◽  
Vol 566 ◽  
pp. 50-55
Author(s):  
Minoru Nagai ◽  
Kazuaki Inaba ◽  
Kosuke Takahashi ◽  
Kikuo Kishimoto
Keyword(s):  
Numerical Simulations ◽  
Wave Front ◽  
Periodic Structure ◽  
Water Hammer ◽  
Numerical Results ◽  
Circumferential Direction ◽  
Experimental Setup ◽  
Projectile Impact ◽  
Frequency Components ◽  
Filtering Effect

In this study, we conducted water hammer experiments in the tube which was periodically supported by various numbers of clamps, named periodic structure, initiated by a projectile impact. The parts of the polycarbonate (PC) tube supported by 1-7 steel clamps make the tube stiffer and heavier than the original PC tube and are expected to cause a filtering effect of the frontal frequency components in the water hammer. According to our experimental observations, we confirmed that higher frequency components more than 1 kHz in the wave front were attenuated and the peak strains in circumferential direction of the tube were decreased 20% from the original PC tube. Moreover, we conducted numerical simulations of the water hammer wave similar to the experimental setup. Numerical results also revealed that frontal peak is attenuated 22% through periodic structure.

Charts for water hammer in pipelines resulting from valve closure

1980 ◽  
Vol 7 (2) ◽  
pp. 243-255 ◽  
Author(s):  
Eugen Ruus ◽  
Farouk A. El-Fitiany
Keyword(s):  
Pipe Wall ◽  
Pressure Head ◽  
Water Hammer ◽  
Wall Friction ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Closure Time ◽  
Basic Parameters

Maximum pressure head rises, which result from valve closure according to (a) uniform, (b) equal-percentage, and (c) optimum valve closure arrangements, are calculated and plotted for the valve end and for the midpoint of a simple pipeline. Basic parameters such as the pipeline constant, relative closure time, and pipe wall friction are considered for closures both from partial as well as from full valve openings. The results of this paper can be used to draw the maximum hydraulic grade line along the pipe for these closure arrangements. It is found that the equal-percentage closure arrangement yields consistently less pressure head rise than does the uniform closure arrangement. Further, the optimum closure arrangement yields consistently less head rise than the equal-percentage one. Closures from partial valve openings increase the pressure head rise considerably and must always be considered.

scholarly journals Numerical simulation of dust explosion in the spherical 20l vessel

2015 ◽  
Vol 63 (1) ◽  
pp. 289-293 ◽  
Author(s):  
Z. Salamonowicz ◽  
M. Kotowski ◽  
M. Półka ◽  
W. Barnat
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Combustion Process ◽  
Test Stand ◽  
Maximum Pressure ◽  
Dust Explosion ◽  
Computational Domain ◽  
Dispersion Process ◽  
Dust Dispersion ◽  
Positive Agreement

Abstract The paper presents experimental and numerical validation of the combustion process of coal and flour dust dispersed in a spherical chamber of 20 cubic decimetres volume. The aim of the study is to validate the numerical simulation results in relation to the experimental data obtained on the test stand. To perform the numerical simulations, a Computational Fluid Dynamics code FLUENT was used. Geometry of the computational domain was built in compliance with EN 14460. Numerical simulations were divided into two main steps. The first one consists in a dust dispersion process, where influence of standardized geometry was verified. The second part of numerical simulations investigated dust explosion characteristics in compliance with EN 14034. After several model modifications, outcomes of the numerical analysis shows positive agreement with both, the explosion characteristics for different dust concentration levels and the maximum pressure increase obtained on the test stand.

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