Effect of Wall Roughness and Flow Velocity on Water Hammer

2014 ◽  
Vol 1014 ◽  
pp. 185-191
Author(s):  
Qing Zheng Meng ◽  
Cheng Yang ◽  
Li Sheng Liu ◽  
Zhen Wang
Keyword(s):  
Flow Velocity ◽  
Pressure Wave ◽  
Pipe Wall ◽  
Influence Factors ◽  
Normal Pressure ◽  
Water Hammer ◽  
Simulation Software ◽  
Wall Roughness ◽  
Great Loss ◽  
Waveform Amplitude

Water hammer can occur in any fluid pipeline systems. The pressure caused by water hammer are far exceeding the pressure range of the pipe limit, and it can lead to the failure or fracture of the pipeline. Since a great loss has been caused by that, two influence factors (flow velocity and roughness of the pipe-wall) associated with water hammer have been performed by using the numerical simulation software CFX. Analysis of the results show that each factor effects differently in waveform, amplitude, period, attenuation of the water hammer wave. The different velocities only influences the peak of pressure wave but not the waveform and period. The pressure reduction as the increase of roughness can be neglected compared to the normal pressure.

Hydromechanics Research with Influence of Pipe Shape on Water Hammer Based on CFX

2014 ◽  
Vol 1014 ◽  
pp. 151-156
Author(s):  
Qing Zheng Meng ◽  
Cheng Yang ◽  
Li Sheng Liu ◽  
Zhen Wang
Keyword(s):  
Numerical Simulation ◽  
Flow Regime ◽  
Pressure Range ◽  
Influence Factor ◽  
Normal Pressure ◽  
Water Hammer ◽  
Simulation Software ◽  
Important Influence ◽  
Pipe Network ◽  
Great Loss

One common and prominent reason for the tube explosion issue of pipe network is the water hammer. Because the pressure levels caused by water hammer are far exceeding the pressure range of the pipe limit. Since a great loss has been caused by water hammer damage, an important influence factor (shape of pipe) on the phenomena associated with water hammer have been performed by using the platform of numerical simulation software CFX. Analysis of the results show that the vortex and reflux phenomena appear in elbow pipe, different shape of pipe will lead to various flow regime. The pressure caused by shape is slight and can be negligible compared to the normal pressure. But it does has influence on period, 90-degree elbow will reduce 0.01s in period.

Dynamic Pipe Stresses During Water Hammer: III — Complex Stress Relationships

2002 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Pressure Wave ◽  
Dynamic Stress ◽  
Pipe Wall ◽  
Three Dimensional ◽  
Complex Stress ◽  
Water Hammer ◽  
Dynamic Stresses ◽  
Vibration Theory ◽  
Pressure Spike ◽  
Fluid Transients

Complex three-dimensional dynamic stresses occur in a pipe following a water hammer event. Equations from vibration theory were adapted for use to describe the dynamic stresses at any point along the pipe wall. Hoop, radial, and axial dynamic stress equations are presented to approximate the stresses at a point on the pipe wall. Dynamic stress equations for beams and other simple shapes are also considered. The dynamic pipe stresses are affected principally by the types of water hammer waves or fluid transients, by the wave impacts at elbows or tees, and by the reflections of the waves from these elbows or tees. The three fluid transients considered are a moving step pressure wave, a ramp pressure, and a moving pressure spike. Approximate techniques are presented for evaluating the effects on piping due to the impingement of these transients on an elbow. For an equivalent pressure in a long pipe, application of the step pressure created the largest stress increases of the three transients considered. The vibration equations also prompt a solution to reduce water hammer effects. To this end, slow closing valves are frequently employed. Vibration theory may be applied to quantify the stress reductions afforded by these valves. Pipe stress equations may be manipulated to reduce pipe stresses for a linearly increasing, or ramp, pressure wave traveling along the pipe.

Effects of Weakly Compressibility on Propagating Properties of Water Hammer in a Long Pipe

2013 ◽  
Vol 444-445 ◽  
pp. 490-497
Author(s):  
Kun Xiong Zhou ◽  
Li Xiang Zhang
Keyword(s):  
Pressure Wave ◽  
Pipe Wall ◽  
High Water ◽  
Water Hammer ◽  
Wave Form ◽  
Pressure Waves ◽  
Water Head ◽  
The Waves ◽  
Theoretical Analyses

This paper is concerned with propagating features of pressure waves induced by water hammer in a long liquid-conveyed pipe subjected to hyper high water head. Effects of dynamically weak compressibility of the water in pipe and pipe wall elasticity on the propagating physics were investigated by comparing in-site measurements and theoretical analyses. The pressure wave form and propagating speed were significantly effected due to weak compressibility of the water and the interactions of the waves. The wave performs a strong unsteadiness while it propagates along the pipe. This study tries to explain an event with consideration of both the dynamically weak compressibility of the water in pipe and the closing features of the valves controlled actively.

Dynamic Pipe Stresses During Water Hammer: A Finite Element Approach

2007 ◽  
Vol 129 (2) ◽  
pp. 226-233 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Finite Element ◽  
Pressure Wave ◽  
Maximum Stress ◽  
Pipe Wall ◽  
Applied Pressure ◽  
Three Dimensional ◽  
Water Hammer ◽  
Sudden Increase ◽  
Element Analysis ◽  
Dynamic Stresses

Water hammer is defined as a sudden increase in pipe pressure, which results in pressure waves that travel along the pipe at sonic velocities. In the wake of the pressure wave, dynamic stresses are created in the pipe wall, which contribute to pipe failures. A finite element analysis computer program was used to determine the three-dimensional dynamic stresses that result from pipe wall vibration at a distance from the end of a pipe, during a water-hammer event. The analysis was used to model a moving shock wave in a pipe, using a step pressure wave. Both aluminum and steel were modeled for an 8 NPS pipe, using ABAQUS®. For either material, the maximum stress was seen to be equal when damping was neglected. At the time the maximum stress occurred, the hoop stress was equivalent to twice the stress that would be expected if an equivalent static stress was applied to the inner wall of the pipe. Also, the radial stress doubled the magnitude of the applied pressure.

Dynamic Pipe Stresses During Water Hammer: I — A Finite Element Approach

2002 ◽  
Author(s):  
Robert A. Leishear ◽  
Edward F. Young ◽  
Curtis A. Rhodes ◽  
Elisabeth M. Alford
Keyword(s):  
Finite Element ◽  
Pressure Wave ◽  
Maximum Stress ◽  
Pipe Wall ◽  
Axial Stress ◽  
Applied Pressure ◽  
Water Hammer ◽  
Sudden Increase ◽  
Element Analysis ◽  
Dynamic Stresses

Water hammer is defined as a sudden increase in pipe pressure, which results in pressure waves that travel along the pipe at sonic velocities. In the wake of the pressure wave, dynamic stresses are created in the pipe wall, which contribute to pipe failures. A finite element analysis, computer program was used to determine the three dimensional dynamic stresses which result from pipe wall vibration at a distance from the end of a pipe, during a water hammer event. The analysis was used to model a moving shock wave in a pipe, using a step pressure wave. Both aluminum and steel were modeled for an 8 NPS pipe, using Abaqus®. For either material, the maximum stress was seen to be equal when damping was neglected. At the time the maximum stress occurred, the hoop stress was equivalent to twice the stress that would be expected if an equivalent static stress was applied to the inner wall of the pipe. At the same time, the radial stress was limited to the magnitude of the applied pressure, and the axial stress was equal to zero.

scholarly journals A Story on the Wave Spectral Properties of Water Hammer

2021 ◽  
Author(s):  
Shiblu Sarker
Keyword(s):  
Spectral Density ◽  
Pressure Wave ◽  
Spectral Properties ◽  
Unsteady Flows ◽  
Water Hammer ◽  
Excessive Pressure ◽  
Pipe System ◽  
Power Spectral ◽  
Physical Information ◽  
Frequency Domain Approach

The prevention of excessive pressure build-up in pipelines requires a thorough understanding of water hammer. Seminal scholars have looked into this phenomena and come up with useful solutions using theoretical techniques. In this study, We propose a power spectral density approach on the pressure wave generated by water hammer in order to improve our understanding of the frequency-domain approach. This approach has the potential to explain some useful properties of the unsteady flow at a given section, attempting to make investigations of the dynamic characteristics of pipelines more effectively. We employ a basic pipe system to mimic the proposed approach based on the data acquired, which yields a lot of relevant physical information for pipeline construction. The proposed method is expected to be useful and efficient in gaining a better understanding of the intricate properties of unsteady flows as well as sound acoustics in a pipe system and their design.

scholarly journals Assessment of water hammer effects on boiling water nuclear reactor core dynamics

2007 ◽  
Vol 22 (1) ◽  
pp. 18-33 ◽  
Author(s):  
Anis Bousbia-Salah
Keyword(s):  
Pressure Wave ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Reactor ◽  
Reactor Core ◽  
Water Hammer ◽  
Pressure Wave Amplitude ◽  
Sensitivity Studies ◽  
Rapid Transients ◽  
Complex Phenomena

Complex phenomena, as water hammer transients, occurring in nuclear power plants are still not very well investigated by the current best estimate computational tools. Within this frame work, a rapid positive reactivity addition into the core generated by a water hammer transient is considered. The numerical simulation of such phenomena was carried out using the coupled RELAP5/PARCS code. An over all data comparison shows good agreement between the calculated and measured core pressure wave trends. However, the predicted power response during the excursion phase did not correctly match the experimental tendency. Because of this, sensitivity studies have been carried out in order to identify the most influential parameters that govern the dynamics of the power excursion. After investigating the pressure wave amplitude and the void feed back responses, it was found that the disagreement between the calculated and measured data occurs mainly due to the RELAP5 low void condensation rate which seems to be questionable during rapid transients. .

Effect of Pipe Wall Roughness On Porous Breakwater Structure On Wave Deformation

2021 ◽  
Vol 69 (5) ◽  
pp. 147-151
Author(s):  
Syamsuri A M ◽  
Suriamihardja D A ◽  
Thaha M A ◽  
Rachman T
Keyword(s):  
Pipe Wall ◽  
Wall Roughness ◽  
Wave Deformation

scholarly journals Waves of Accelerated Motion in a Glacier Approaching Surge: the Mini-Surges of Variegated Glacier, Alaska, U.S.A.

1987 ◽  
Vol 33 (113) ◽  
pp. 27-46 ◽  
Author(s):  
Barclay Kamb ◽  
Hermann Engelhardt
Keyword(s):  
Flow Velocity ◽  
Pressure Wave ◽  
Water Pressure ◽  
Water System ◽  
Pressure Rise ◽  
Strain Wave ◽  
Overburden Pressure ◽  
Flow Acceleration ◽  
Accelerated Motion ◽  
Velocity Peak

AbstractPeriods of dramatically accelerated motion, in which the flow velocity increases suddenly from about 55 cm/d to a peak of 100–300cm/d and then decreases gradually over the course of a day, occurred repeatedly during June and July 1978–81 in Variegated Glacier (Alaska), a surging-type glacier that surged in 1982–83. These “mini-surges” appear to be related mechanistically to the main surge. The flow-velocity peak propagates down-glacier as a wave at a speed of about 0.3 km/h, over a reach of about 6 km in length. It is accompanied by a propagating pressure wave in the basal water system of the glacier, in which, after a preliminary drop, the pressure rises rapidly to a level greater than the ice-overburden pressure at the glacier bed, and then drops gradually over a period of 1–2 d, usually reaching a new low for the summer. The peak velocity is accompanied by a peak of high seismic activity due to widespread fresh crevassing. It is also accompanied by a rapid uplift of the glacier surface, amounting to 6–11 cm, which then relaxes over a period of 1–2 d. Maximum uplift rate coincides with the peak in flow velocity; the peak in accumulated uplift lags behind the velocity peak by 2 h. The uplift is mainly due to basal cavitation driven by the high basal water pressure, although the strain wave associated with the mini-surge motion can also contribute. Basal cavitation is probably responsible for the pulse of high turbidity that appears in the terminal outflow stream in association with each mini-surge. In the down-glacier reach, where the mini-surge waves are attenuating, the observed strain wave corresponds to what is expected for the propagating pulse in flow velocity, but in the reach of maximum mini-surge motion the strain wave has a form quite different, possibly related to special features in the mini-surge initiation process from that point up-stream. The flow acceleration in the mini-surges is due to enhanced basal sliding caused by the high basal water pressure and the consequent reduction of bed friction. A preliminary velocity increase shortly before the pressure wave arrives is caused by the forward shove that the main accelerated mass exerts on the ice ahead of it, and the resulting preliminary basal cavitation causes the drop in water pressure shortly before the pressure wave arrives. The mini-surge wave propagation is controlled by the propagation of the water-pressure wave in the basal water-conduit system. The propagation characteristics result from a longitudinal gradient (up-glacier increase) in hydraulic conductivity of the basal water system in response to the up-glacier increase of the basal water pressure in the mini-surge wave. The mini-surge waves are initiated in a succession of areas situated generally progressively up-glacier during the course of the summer season. In these areas, presumably, melt water that has accumulated in subglacial (?) reservoirs is released suddenly into the basal water system immediately below, generating a pressure rise that propagates down-stream from there. Relationships of the mini-surges to the main surge are seen in the role of high basal water pressure in causing the rapid glacier motion in both phenomena, in the pulse-propagation features of both, and in the high outflow turbidity associated with both. The mini-surges of Variegated Glacier have a strong resemblance to movement and uplift events observed in Unteraargletscher and Findelengletscher, Switzerland. This bears on the question whether the mini-surges are a particular characteristic of surge-type glaciers prior to surge.

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