Numerical Simulation of Turbulent Pipe Flow for Water Hammer

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Hamid Shamloo ◽  
Maryam Mousavifard
Keyword(s):  
Shear Wave ◽  
Pressure Wave ◽  
Transient Flow ◽  
Water Hammer ◽  
Turbulent Pipe Flow ◽  
Turbulence Structure ◽  
Governing Equations ◽  
Structure Changes ◽  
Dominant Feature ◽  
Voigt Model

A numerical model of turbulent transient flow is used to study the dynamics of turbulence during different periods of water hammer in a polymeric pipe. The governing equations of the transient flow are solved by using the finite difference (FD) method, and the effects of viscoelasticity are modeled by means of a two-dimensional (2D) Kelvin–Voigt model. The experimental data with the Ghidaoui parameter P in the order of one are chosen in which the generated shear wave propagates toward the center of the pipe, while the pressure wave passes the length of the pipe. By studying the turbulence shear force during different times, it is shown that the turbulence structure changes considerably in the first cycle of water hammer. In the accelerated phases, the dominant feature is the creation of a shear wave near the wall, and in the decelerated phases the dominant feature is the propagation of the shear wave created in the accelerated phase.

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.

scholarly journals Surge Tank Analysis for Water Hammer Remedy for Long Distance Pipeline

2018 ◽  
Vol 11 (3) ◽  
pp. 47-53
Author(s):  
Nisreen J. Rasheed
Keyword(s):  
Friction Factor ◽  
Method Of Characteristics ◽  
Transient Flow ◽  
Water Hammer ◽  
Pipeline System ◽  
Surge Tank ◽  
Governing Equations ◽  
Long Distance ◽  
Several Variables ◽  
The Impact

Various protection methods can be used for protecting the pipeline system from the impact of water hammer. Which includes the use of special materials for supporting the pipeline and the installation of special devices such as surge tanks, relief valves, and air chambers. In this study, to protect the pipeline system and reduce the effect of water hammer, surge tank has been used. Governing equations of transient flow with and without surge tank is numerically simulated using MATLAB software. Sensitivity analysis was investigated using several variables such as pipe diameter, wave’s velocity and friction factor. Method of characteristics (MOC) was implemented in this study. It was found that the diameter and friction factor of pipe have a significant impact on the results of transient flow and surge tank compared to the effect of wave’s velocity. It has been reached that the capacities of surge tanks at diameter (1m), are (1475m3) at first, second and fourth stages, (1360m3) at third and fifth stages and (570m3) at sixth stage. And at diameter (1.2m), the capacities are (1700m3), (1530m3) and (1475m3) at first, second and third stages respectively. But at diameter (1.4m), the capacities are (1590m3) at first and second stages. For all values of wave’s velocity, the capacities of surge tanks are (1760m3), (1530m3) and (1420m3) at first, second and third stages respectively. But the capacities of surge tanks at friction factor (0.007) are (1810m3), (1585m3) and (1245m3) at first, second and third stages respectively. However, for the capacity of surge tanks at the friction factor (0.008), it was mentioned when the surge tanks capacity of the diameter (1.2m) was mentioned. And when the friction factor is (0.009), the capacities are (1460m3) at first stage, (1415m3) at second and third stages and (570m3) at fourth stage

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. .

Fluid Transmission Line Modeling Using a Variational Method

1998 ◽  
Vol 122 (1) ◽  
pp. 153-162 ◽  
Author(s):  
Jari Ma¨kinen ◽  
Robert Piche´ ◽  
Asko Ellman
Keyword(s):  
Differential Equations ◽  
Variational Method ◽  
Ordinary Differential Equations ◽  
Transmission Lines ◽  
Pipe Flow ◽  
Transient Flow ◽  
Numerical Models ◽  
Flow Simulation ◽  
Gibbs Phenomenon ◽  
Turbulent Pipe Flow

A variational method is used to derive numerical models for transient flow simulation in fluid transmission lines. These are generalizations of models derived using the more traditional modal method. Three different transient compressible laminar pipe flow models are considered (inviscous, one-dimensional linear viscous, and two-dimensional dissipative viscous flow), and a model for transient turbulent pipe flow is given. The (model) equations in the laminar case are given in the form of a set of constant coefficient ordinary differential equations, and for the turbulent case (model) in the form of a set of nonlinear ordinary differential equations. Explicit equations are given for various end conditions. Attenuation factors, similar to the window functions used in spectral analysis, are used to attenuate Gibbs phenomenon oscillations. [S0022-0434(00)03201-9]

Viscous Dispersion in Water Hammer

1960 ◽  
Vol 82 (4) ◽  
pp. 759-763 ◽  
Author(s):  
M. L. Walker ◽  
E. T. Kirkpatrick ◽  
W. T. Rouleau
Keyword(s):  
Exact Solution ◽  
Upper Bound ◽  
Pressure Wave ◽  
Practical Interest ◽  
Water Hammer ◽  
Inviscid Fluid ◽  
Uniform Velocity ◽  
Step Discontinuity

When a column of fluid moving with uniform velocity is instantaneously stopped at the downstream end a pressure wave is propagated upstream. In an inviscid fluid the wave is a step discontinuity, and the pressure so calculated serves as an easily obtained upper bound for all practical “water-hammer” problems, the exact solution of which may be either difficult or impossible to obtain. This paper describes an analysis of viscous dispersion in relation to the upper bound. The conclusion is reached that in problems of practical interest the bound is not significantly changed by the dispersive effects of viscosity.

scholarly journals Effects of a water hammer and cavitation on jet formation in a test tube

2015 ◽  
Vol 787 ◽  
pp. 224-236 ◽  
Author(s):  
Akihito Kiyama ◽  
Yoshiyuki Tagawa ◽  
Keita Ando ◽  
Masaharu Kameda
Keyword(s):  
Pressure Wave ◽  
Flow Analysis ◽  
Water Hammer ◽  
Test Tube ◽  
Liquid Interface ◽  
Phase Changes ◽  
Liquid Jet ◽  
Jet Formation ◽  
Wave Interactions ◽  
The One

We investigate the motion of a gas–liquid interface in a test tube induced by a large acceleration via impulsive force. We conduct simple experiments in which the tube partially filled with a liquid falls under gravity and hits a rigid floor. A curved gas–liquid interface inside the tube reverses and eventually forms a so-called focused jet. In our experiments, there arises either vibration of the interface or an increment in the velocity of the liquid jet, accompanied by the onset of cavitation in the liquid column. These phenomena cannot be explained by a considering pressure impulse in a classical potential flow analysis, which does not account for finite speeds of sound or phase changes. Here we model such water-hammer events as a result of the one-dimensional propagation of a pressure wave and its interaction with boundaries through acoustic impedance mismatching. The method of characteristics is applied to describe pressure-wave interactions and the subsequent cavitation. The model proposed is found to be able to capture the time-dependent characteristics of the liquid jet.

scholarly journals Development of A Process for Predicting the Overall Heat Transfer Coefficient for Transient Heat Transfer in An Exhaust System using CFD

2019 ◽  
Vol 8 (2) ◽  
pp. 2529-2533
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Analytical Solution ◽  
Transfer Coefficient ◽  
Gas Flow ◽  
Transient Flow ◽  
Exhaust System ◽  
Outlet Temperature ◽  
Governing Equations ◽  
Overall Heat Transfer Coefficient

The analysis of heat transfer of automotive exhaust system is most important since their prominence in the design and also in the optimization phase of exhaust after treatment system.This paperdeals with the process which can be useful to predict the overall heat transfer coefficient for the transient flow of pipe in the after treatment system. This considers the convection of heat along gas flow, the convection between gas and wall, conduction through wall, radiation and of course convection to the ambient. Governing equations are obtained for the transient flow in a pipe for calculating gas temperature and wall temperature at distance x and time t. Analytical solution will be computed using CFD techniques for these governing equations. From the obtained analytical solution to the transient flow in pipe an excel tool will be developed which can be able to give the outlet temperature of the pipe in transient flow at length x and time t, total heat loss from pipe to the ambient, overall heat transfer coefficient for the pipe

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