Simulation of transient flow caused by pump failure: Point-Implicit Method of Characteristics

2010 ◽  
Vol 37 (12) ◽  
pp. 1742-1750 ◽  
Author(s):  
M. Rohani ◽  
M.H. Afshar
Keyword(s):  
Method Of Characteristics ◽  
Transient Flow ◽  
Implicit Method ◽  
Pump Failure ◽  
Failure Point

Influence of velocity head on filling transients in a branched pipeline

2018 ◽  
Vol 35 (7) ◽  
pp. 2502-2513 ◽  
Author(s):  
Ling Wang ◽  
Fujun Wang ◽  
Bryan William Karney ◽  
Ahmad Malekpour ◽  
Zhengwei Wang
Keyword(s):  
Method Of Characteristics ◽  
Energy Equation ◽  
Transient Flow ◽  
Numerical Results ◽  
Velocity Head ◽  
Piezometric Head ◽  
Content Type ◽  
High Point ◽  
Hydraulic Transient ◽  
Column Separation

Purpose The velocity head is usually neglected in the energy equation for a pipeline junction when one-dimensional (1D) hydraulic transient flow is solved by method of characteristics. The purpose of this paper is to investigate the effect of velocity head on filling transients in a branched pipeline by an energy equation considering velocity head. Design/methodology/approach An interface tracking method is used to locate the air–water interface during pipeline filling. The pressured pipe flow is solved by a method of characteristics. A discrete gas cavity model is included to permit the occurrence of column separation. A universal energy equation is built by considering the velocity head. The numerical method is provisionally verified in a series pipeline and the numerical results and experimental data accord well with each other. Findings The numerical results show that some differences in filling velocity and piezometric head occur in the branched pipeline. These differences arise because the velocity head in the energy equation can become an important contributor to the hydraulic response of the system. It is also confirmed that a local high point in the profile is apt to experience column separation during rapid filling. Significantly, the magnitude of overpressure and cavity volume induced by filling transients at the local high point is predicted to increase with the velocity in the pipes. Originality/value The velocity head in the energy equation for a pipeline junction could play an important role in the prediction of filling velocity, piezometric head and column separation phenomenon, which should be given more attention in 1D hydraulic transient analysis.

APPLICATION OF THE IMPLICIT METHOD OF CHARACTERISTICS ON A REGULAR GRID FOR SOLVING THE GAS-DYNAMIC PROBLEMS

2021 ◽  
pp. 80-92
Author(s):  
A.M. Lipanov ◽  
Keyword(s):  
Solid Propellant ◽  
Method Of Characteristics ◽  
Rocket Engine ◽  
Second Order ◽  
Implicit Method ◽  
Dynamic Parameters ◽  
Time Layer ◽  
Engine Operation ◽  
Order Of Accuracy ◽  
Gas Dynamic

In this work, an implicit method is proposed to numerically solve a system of the onedimensional nonstationary equations of gas dynamics transformed by the method of characteristics. Internal points of the channel for a solid-propellant charge are considered at a preignition period of the solid-propellant rocket engine operation. The use of the implicit method makes it possible to calculate the values of gas-dynamic parameters at nodal points of the regular coordinate grid. Calculations of the gas-dynamic parameters both when integrating over time and along the spatial coordinate are performed with the second order of accuracy. Both subsonic and supersonic flows are studied. It is shown that, when predicting the expected pressure value during the transition from one time layer to another with the second order of accuracy, the twenty-fold efficiency of the implicit method is achieved in comparison with the explicit difference method. The trial calculation is performed.

Modeling of Fluid Interaction Produced by Water Hammer

2011 ◽  
Vol 1 (1) ◽  
pp. 29-41 ◽  
Author(s):  
Kaveh Hariri Asli ◽  
Faig Bakhman Ogli Naghiyev ◽  
Soltan Ali Ogli Aliyev ◽  
Hoosein Hariri Asli
Keyword(s):  
Method Of Characteristics ◽  
Transient Flow ◽  
Practical Investigations ◽  
Computationally Efficient ◽  
Hydraulic Simulation ◽  
Computational Performance ◽  
Difference Form ◽  
Large Water ◽  
Water Transmission ◽  
Fluid Interaction

This paper compares the computational performance of two numerical methods for two models of Transient Flow. One model was defined by method of the Eulerian based expressed in a method of characteristics “MOC”, finite difference form. The other model was defined by method of Regression. Each method was encoded into an existing hydraulic simulation model. Results indicated that the accuracy of the methods was comparable but that the “MOC” was more computationally efficient for analysis of large water transmission line. Practical investigations in this article have shown mainly this tendency.

Paper 1: Computer Solution of Surge Problems

1965 ◽  
Vol 180 (5) ◽  
pp. 62-82
Author(s):  
Victor L. Streeter
Keyword(s):  
Steady State ◽  
Differential Equations ◽  
High Speed ◽  
Transient Flow ◽  
Nonlinear Differential Equations ◽  
Pressure Fluctuations ◽  
Transient Pressure ◽  
Pump Failure ◽  
Flow Equations ◽  
Flow Impedance

Methods for handling the transient flow equations are developed for application of the high-speed digital computer. For incompressible flow cases ordinary nonlinear differential equations occur which are solved simultaneously by established sub-routines on the computer, such as the Runge-Kutta method. For the partial differential equations of compressible water hammer with nonlinear terms such as friction, the method of characteristics and of specified time intervals are employed for those problems in which the flow changes from one steady-state to another steady-state. For steady-oscillatory flow, impedance methods have been adapted to the computer with harmonic analysis of the exciting disturbance. Experimental evidence is presented to confirm the accuracy of the procedures for single and series pipes, for pump failures, and for reciprocating pumps. Additionally the design problem of optimum operation of a valve to minimize transient pressure fluctuations has been introduced and applied to single and series pipes, including a pump failure situation.

scholarly journals Numerical modeling transient flow in plastic pipes

2019 ◽  
Vol 286 ◽  
pp. 07001
Author(s):  
N. Achak ◽  
B. Bahrar ◽  
K. Gueraoui
Keyword(s):  
Numerical Modeling ◽  
Constitutive Equations ◽  
Method Of Characteristics ◽  
Transient Flow ◽  
Pipe Wall ◽  
Digital Processing ◽  
Numerical Code ◽  
Plastic Pipes ◽  
And Behavior ◽  
Good Agreement

We present a numerical code for calculating transient flow in plastic pipes, especially in the polyethylene pipe, to analysis effect of material viscoelasticity on water hammer phenomena. The set partial differential equations to be solved is obtained using conservation laws and behavior for the fluid and the pipe wall, associated with constitutive equations of the two media, and relationships compatibility of interfaces on velocities and stresses. A global digital processing is achieved using the method of characteristics. The results obtained are in good agreement with those found in the literature.

Application of Variational Methods to Transient Flow in Complex Liquid Transmission Systems

1977 ◽  
Vol 17 (02) ◽  
pp. 151-166 ◽  
Author(s):  
H.H. Rachford ◽  
E.L. Ramsey
Keyword(s):  
Equation Of State ◽  
Transient Response ◽  
Propagation Velocity ◽  
Wave Speed ◽  
Transient Flow ◽  
Water Injection ◽  
Injection System ◽  
Transmission Systems ◽  
Pump Failure ◽  
Piping Systems

Abstract Surge pressures in liquid pipelines are often sufficiently severe either to stress the pipe past its yield point or to produce cavitation. These phenomena are most likely to be serious in complex, phenomena are most likely to be serious in complex, interconnected piping like a water-injection system, an oil-gathering system, or a dense-phase LNG system. In any of these, pressure waves generated by changes in rates at pump stations or terminal points may add in magnitude as they propagate points may add in magnitude as they propagate through the system and result in locally excessive pressures. pressures. The magnitude and time of arrival of surges depends critically on the wave speed in the liquid/pipe system. Examples are given of typical liquids in which this speed is a strong function of pressure because the compressibility changes with pressure because the compressibility changes with pressure. One example illustrates that the transient pressure. One example illustrates that the transient response of models of pipeline networks carrying such fluids must properly reflect the dynamic, point-by-point influence of pressure on wave speed. point-by-point influence of pressure on wave speed. Otherwise, the model will improperly predict surge events and will be unsuitable as a basis for design or control. The transient flow of liquid through pipe is described by a nonlinear hyperbolic system of equations. The formulation described in this paper treats isothermal flow, taking proper account of the pipe expansibility and dependence of fluid pipe expansibility and dependence of fluid compressibility on pressure, factors that play a major role in determining the magnitude and propagation velocity of disturbances in liquid propagation velocity of disturbances in liquid systems. The solution of the single-pipe hyperbolic equations is approximated numerically using a convergent, discrete-time Galerkin procedure, and is structured to treat the boundary conditions necessary to model an interconnected system with nonlinear, time-dependent elements like pumps, valves, regulators, co other pressure-dependent flow control devices. The model was used to study the water-hammer pressure surges caused by pump failure in a complex, pressure surges caused by pump failure in a complex, multipump water-injection system. The effectiveness of control systems proposed to deal with surges caused by such changes in operation can be evaluated only by modeling the system response. One such control system was found to induce rather than alleviate pipe-damaging pressures during emergency shutdown. Introduction Liquid pipeline systems seldom achieve steady state. Random disturbances or intentional changes in operating conditions almost always cause some degree of pressure surge within a system. Moreover, under upset conditions, surges can become so extreme that equipment may be damaged or pipelines ruptured. Such pulses or surges in pressure have been the subject of much study and are well documented by many unexpected failures in liquid piping systems caused by severe changes in flow piping systems caused by severe changes in flow rate. Quantitative predictions of pressure surges have long been an integral part of piping-system design. Methods used generally have been based on the assumption of constant liquid compressibility, resulting in a linear or affine relationship for the equation of state. We shall illustrate that many important fluids have nonlinear pressure/density relationships, that the wave speed in such fluids is not constant but is subject to significant variation with pressure, and that such variations can strongly influence the transient response of the pipe/liquid system. For this reason, protective systems designed without correctly considering the effect of dynamic changes of pressure on wave speed may lead to serious operating problems. The purpose of this work is to develop a general mathematical model of isothermal fluid transmission systems that correctly treats any physically meaningful equation of state and, therefore, properly predicts surges in fluids with properly predicts surges in fluids with pressure-dependent wave speed. pressure-dependent wave speed. SPEJ P. 151

Application of the Method of Characteristics to the Transient Flow of Gases

1949 ◽  
Vol 161 (1) ◽  
pp. 250-258 ◽  
Author(s):  
J. Kestin ◽  
J. S. Glass
Keyword(s):  
High Speed ◽  
Method Of Characteristics ◽  
Transient Flow ◽  
Combustion Engine ◽  
State Diagram ◽  
The State ◽  
Intermittent Flow ◽  
Simple Method ◽  
Adiabatic Flow ◽  
The Method Of Characteristics

Although problems relating to non-uniform flow of a compressible fluid have been tackled by a number of workers, investigations have generally been limited to the study of one-dimensional non-viscous adiabatic flow. This type of flow, however, is associated with so many problems encountered by mechanical engineers that an easy and reliable method of solution is extremely important. The method of characteristics described in this paper provides a comparatively simple method of solving such problems by a graphical process. It consists essentially in the simultaneous construction of two corresponding diagrams:— (a) The state diagram showing the changes in the state of the fluid produced by spreading disturbances. (b) The position diagram depicting the spreading of the disturbances. The graphical construction of these diagrams is based upon certain special mathematical properties of the equations which describe the motion and enable boundary conditions corresponding to any particular problem to be readily taken into account. Applications include the phenomena occurring in internal combustion engine exhaust and intake pipes, in particular, those relating to the Kadenacy system of scavenging. It is also applicable to the type of flow encountered during the emptying of cylinders, in pulsating ram jet engines and, in general, in any engine making use of the intermittent flow of gases. The phenomena occurring in long indicator passages during tests on high-speed engines also come within its scope.

Modelling of transient flow in hydraulic pipelines

1997 ◽  
Vol 211 (6) ◽  
pp. 447-455 ◽  
Author(s):  
S E M Taylor ◽  
D N Johnston ◽  
D K Longmore
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Method Of Characteristics ◽  
Transient Flow ◽  
Finite Difference Methods ◽  
Time Varying ◽  
Hydraulic Systems ◽  
Laminar And Turbulent Flow ◽  
Simulation Results ◽  
Element Method

This paper describes a method of modelling time-varying flow in hydraulic pipelines which may be incorporated into time domain simulations of hydraulic systems operating with variable time steps. A previously reported finite element method is extended. New approximations to frequency-dependent friction for laminar and turbulent flow are presented. These are applicable to this finite element method as well as the method of characteristics and finite difference methods. Simulation results are compared against theory and excellent agreement is found.

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