Hydraulic transients in closed conduits have been a subject of both theoretical stud intense practical interest for more than one hundred years. While straightforward in te of the one-dimensional nature of pipe networks, the full description of transient fluid fl pose interesting problems in fluid dynamics. For example, the response of the turbu structure and strength to transient waves in pipes and the loss of flow axisymme pipes due to hydrodynamic instabilities are currently not understood. Yet, such u standing is important for modeling energy dissipation and water quality in transient flows. This paper presents an overview of both historic developments and presen research and practice in the field of hydraulic transients. In particular, the paper cusses mass and momentum equations for one-dimensional Flows, wavespeed, nu solutions for one-dimensional problems, wall shear stress models; two-dimensional and momentum equations, turbulence models, numerical solutions for two-dimen problems, boundary conditions, transient analysis software, and future practical an search needs in water hammer. The presentation emphasizes the assumptions and tions involved in various governing equations so as to illuminate the range of applic ity as well as the limitations of these equations. Understanding the limitations of cu models is essential for (i) interpreting their results, (ii) judging the reliability of the da obtained from them, (iii) minimizing misuse of water-hammer models in both research practice, and (iv) delineating the contribution of physical processes from the contribu of numerical artifacts to the results of waterhammer models. There are 134 refrences in this review article.@DOI: 10.1115/1.1828050 #

A Review of Water Hammer Theory and Practice

A selective literature review of transient-based leak detection methods

Power-to-gas (P2G) is the process whereby electricity is used to produce hydrogen or synthetic natural gas The electricity for the P2G process could, for instance, come from renewable energy which would otherwise be curtailed due to system or line constraints The existing natural gas network could then potentially be used as a means to store, transport, and reutilize this energy, thus preventing its waste While there are several ongoing discussions on P2G in different countries, these are generally not backed by quantitative studies on its potential network implications and benefits To bridge this gap, this paper introduces an original methodology to analyze different P2G processes and assess their operational impacts on both electricity and gas transmission networks This is carried out by using a novel integrated model specifically developed for the simulation of operational interdependences between the two networks considering P2G To demonstrate the several innovative features of the proposed model, technical, environmental, and economic operational aspects of P2G and its potential benefits are analyzed on the case of the Great Britains system, also providing insights into relief of gas and electrical transmission network constraints

/pdf/integrated-modeling-and-assessment-of-the-operational-impact-1evx5bz3sc.pdf

Integrated Modeling and Assessment of the Operational Impact of Power-to-Gas (P2G) on Electrical and Gas Transmission Networks

A method is presented for calculating the seismic response of a system of horizontal soil layers. The essential element of the method is a rheological model suggested by Iwan which takes account of the nonlinear hysteretic behavior of soils and has considerable flexibility for incorporating laboratory results on the dynamic behavior of soils. Finite rigidity is allowed in the underlying elastic medium, permitting energy to be radiated back into the underlying medium. Three alternate ways of integrating the equations of motion are compared, an implicit technique, an explicit technique, and integration along characteristics. An example is set up for comparing the different methods of integration and for comparing the nonlinear solution with a solution based on the widely used equivalent linear assumption. The example consists of a 200-m section of firm alluvium excited at its base by the N21E component of the Taft accelerogram multiplied by four to produce a peak acceleration of 0.7 g and a peak velocity of 67 cm/sec. The three techniques of integration give very similar results, but integration along characteristics has the advantage of avoiding spurious high-frequency oscillations in the acceleration time history at the surface. For the chosen example, which has a thick soil column and a strong input motion, the equivalent linear solution underestimates the intensity of surface motion for periods between 0.1 and 0.6 sec by factors exceeding two. The discrepancies, however, would probably be less for input motion of lower intensity. At longer periods the equivalent linear solution is in essential agreement with the nonlinear solution. For the same example both solutions show that, compared to a site with rock at the surface, motion at the surface of the soil is amplified for periods longer than 1.5 sec by as much as a factor of two. At shorter periods the amplitude is reduced.

Calculation of nonlinear ground response in earthquakes

https://www.win.tue.nl/~atijssel/pdf_files/Bergant-Simpson-Tijsseling_2006.pdf

Water hammer with column separation: A historical review

Fluid transient flow concepts basic differential flow concepts solution by characteristics method the complete equations other methods of solution complex systems with multi-pipe and non-pipe elements transients caused by turbomachines two-component and single-component two-phase transient flows valve stoking methods for controlling transients multi-element systems and transmission lines concepts of oscillatory flow and resonance analysis of oscillatory flow in systems natural gas pipeline transients open-channel transient flow special topics.

Fluid Transients in Systems

In this study the characteristics method is applied to wave propagation corresponding to earthquake intensities in models of unsaturated and saturated soils. Shear waves developed in linear, or in "strain-softening" materials, and pressure waves in viscoelastic materials are considered. One-dimensional transmissions in unsaturated layered systems are treated first, then the method is applied to two-dimensional simulations by the "lattice work" approach. The latter method may also be extended to treat three-dimensional problems. Pore pressure transients are investigated in a one-dimensional approach based on Darcy's law. By prescribing reductions of void ratios as a function of time, zones of potential liquefaction may be identified and their movement traced. By use of a lattice work representation, transient pore pressure within the upstream portion of an earth dam are investigated. /ASCE/

Soil Motion Computations by Characteristics Method

The use of interpolations in time, rather than the more widely used spatial interpolations, demonstrates several benefits in the application of the method of characteristics to wave problems in hydraulics. Two such time-line schemes are presented and analyzed in the solution of a linearized water hammer problem. Reachback time-line interpolations, where the characteristic lines are projected back before the current time step, demonstrate less damping than the corresponding spatial interpolation scheme at the same discretization. Implicit time-line interpolations, where the characteristic line is projected into the current time step, permit relaxation of the restrictive time step required by the Courant condition. An error analysis and numerical experiments demonstrate the degree of damping and dispersion introduced by both reachback and implicit time-line interpolation methods. The error analyses and their verification may encourage further application of these methods in appropriate problem domains.

E. Benjamin Wylie

Papers

Fluid Transients in Systems

Soil Motion Computations by Characteristics Method

Characteristics Method Using Time‐Line Interpolations

Simulation of Vaporous and Gaseous Cavitation

Network: System Transient Calculations by Implicit Method