Sudden Valve Closure Research Articles

Backward flow and jet formation of liquid and granular medium in a gravity drainage system following a sudden valve closure

The sudden closure of a valve during the gravity-driven drainage of the liquid or granular medium causes the backward flow of material and generates a strong backward pressure wave. The phenomenon, which has a strong similarity with classical water hammer, is reported for the first time. Under specific conditions, the formation of the jet is observed at the free surface. The current article presents a detailed computational investigation of the unique phenomenon of backward propagation of materials and jet formation. A detailed comparison of the flow phenomenon for liquid and granular medium of constant bulk density is reported providing a particular emphasis on jet formation in these two cases. Distinct stages of flow dynamics are observed particularly for granular medium. For liquid, the runout time for the jet formation has been quantified analytically to appreciate the energy dissipation. The analytical model also produces good agreement (+10.75%, −8.9%) with the trained model based on numerical results. A detailed parametric study is incorporated for aspect ratio and valve height ratio to characterize and compare the phenomenon for both the flowing medium, − liquid, and granular matter.

Reliability sensitivity analysis for water hammer-induced stress failure of fluid-conveying pipe

The water hammer, resulting from sudden valve closures or similar operations, is a primary cause of leakage and damage in fluid-conveying pipe systems. This work aims to investigate the reliability sensitivity of fluid-conveying pipes under the water hammer. A reliability model for the fluid-conveying straight pipe, involving uncertainty and fluid-structure interaction, is developed based on the stress-strength interference theory. Then the method of characteristics is employed to analyze the nonlinear behaviors of the pipe. To avoid excessive model evaluations, the Kriging surrogate strategy is used to evaluate rapidly the statistics of nonlinear responses. Furthermore, the Kriging model coupled with the single-loop Monte Carlo simulation is presented for estimating reliability sensitivity indices. The accuracy of results is verified by the Monte Carlo simulation. The results reveal that the proposed method is feasible for the reliability sensitivity analysis of fluid-conveying pipe under the water hammer. Moreover, the wall thickness has the most obvious influence on stress failure, followed by the inner radius, while the pipe length, Young's modulus, density of the pipe material, and Poisson ratio show a low effect. This work can not only guide the safety design of pipe but also enrich the theory and application of statistical analysis and reliability sensitivity evaluation for liquid-conveying pipe systems.

Numerical modeling of transient non Newtonian thinning fluid flow

This study concerns a numerical simulation of transient non-Newtonian fluid flow in a hydraulic pipe resulting from sudden valve closure, commonly known as waterhammer or hydraulic shock. The fluid behaves as a law power model. The basic equations are solved numerically by the characteristic method to obtain average pressure and velocity across a right sections of pipe and, a flow velocity profile by a Runge–Kutta scheme of fourth-order. The results of the present model agree suitably with those found in the literature [1]. This study highlights the remarkable effects of the properties of this fluids on the pressure oscillations generated by hydraulic waterhammer compared to fluids of Newtonian behavior.

Efficient approach toward the application of the Godunov method to hydraulic transients

Abstract The proposed study investigated the applicability of the finite volume method (FVM) based on the Godunov scheme to transient water hammer with shock front simulation, in which intermediate fluxes were computed using either first-order or second-order Riemann solvers. Finite volume (FV) schemes are known to conserve mass and momentum and produce the efficient and accurate realization of shock waves. The second-order solution of the Godunov scheme requires an efficient slope or a flux limiter for error minimization and time optimization. The study examined a range of limiters and found that the MINMOD limiter is the best for modeling water hammer in terms of computational time and accuracy. The first- and second-order FVMs were compared with the method of characteristics (MOCs) and experimental water hammer measurements available in the literature. Both the FV methods accurately predicted the numerical and experimental results. Parallelization of the second-order FVM reduced the computational time similar to that of first-order. Thus, the study presented a faster and more accurate FVM which is comparable to that of MOC in terms of computational time and precision, therefore it is a good substitute for the MOC. The proposed study also investigated the implementation of a more complex convolution-based unsteady friction model in the FVM to capture real pressure dissipation. The comparison with experimental data proved that the first-order FV scheme with the convolution integral method is highly accurate for computing unsteady friction for sudden valve closures.

Hydraulic transients in pipelines due to various valve closure schemes

In this study, the hydraulic transient in a pipeline model was considered by utilizing the method of characteristics. The pipeline conveys water from the upstream reservoir to the downstream one, while a valve was set at the downstream end of it. The effect of sudden, linear and stepwise valve closure schemes were analysed by employing a stainless-steel pipe and a ductile pipe. Sudden valve closure was noted to generate higher-pressure transients than linear and stepwise schemes. As the closure time period increases, the value of the maximum pressure transient decreases, in both linear and stepwise arrangements. The transient pressure was perceived to be higher in stainless-steel pipe than in ductile one, in three closure schemes. The simulations were performed by a purpose-developed MATLAB code.

Uncertainty Quantification for Damping in Transient Pressure Oscillations

AbstractThe uncertainty of a model to determine the damping of pressure head oscillations following a sudden valve closure in a simple piping system in a pressurized closed conduit is quantified us...

INVESTIGATING USE OF PRESSURE PULSES TO ASSESS NEAR WELLBORE RESERVOIR PARAMETERS

Pressure surge in a pipe due to sudden flow rate change or full-stop of fluid flow is a pressure wave propagating in fluid along the pipe. This phenomenon has been used to determine the flow rate and to detect and monitor changes in effective flow diameter. It turns out that the pressure surge, also known as pressure pulse, can be used to estimate the formation transmissivity and storativity in the near wellbore region. In this study, propagation of pressure pulse generated by sudden valve closure is simulated with a transient pipe flow model, and it is coupled with a transient analytical reservoir model. The coupled model is used to estimate the reservoir parameters by history matching approach, which is to iterate the transmissivity and the storativity values until an acceptable match is obtained between the measured and simulated pressure history at the upstream of valve. The developed modeling and estimation scheme is applied with two data sets from a field well test to estimate reservoir parameters. The reservoir parameters transmissivity and storativity in the near wellbore region were obtained from the history matching analysis. Matching analysis with the coupled model on the recorded wellhead pressure during two tests showing obvious different flowing conditions points out very similar reservoir parameter values.

Water Hammer Phenomenon: Analysis and Solutions ظاھرة الطرق المائى : التحلیل والحلول

تعتبر المطرقة المائية ظاھرة معقدة يجب التعرف على تأثيرھا الضار حتى نجدالحلول المناسبة لمنع ھذه الاضرار وتنشأ المطرقة المائية نتيجة التغيرالمفاجى فى سرعة المياه داخل الأنابيب نتيجة انقطاع المغذى لمحرکاتالطلمبات فجاة أو القفل المفاجئ للمحابس أثناء التشغيل وينتج عنھا ارتفاعوانخفاض مفاجئ فى الضغط وظھور موجة ضغط موجبة وسالبة تتحرکبسرعة الصوت مما يسبب أضرار بالغة مثل ( انفجار المواسير – تدميرالطلمبات – تدمير المحابس .... ) وتھدف الدارسة إلى تحليل ووضع الحلوللظاھرة الطرق المائى أو منعھا عن طريق ترکيب أجھزة الحماية مثل( خزاناتالفائض – خزانات المياه والھواء – محابس الأمان – محابس الھواء ) تناولالبحث تطبيق عملى على أحدى منظومات محطات الرى فى مشروع الصالحيةالزراعى حوالى ۳۳٥٥۱ فدان ( محافظة الاسماعيلية ) واشتمل العمل علىالقياسات العملية للتصرفات والضغوط داخل المواسير فى حالة السريانالمنتظم وتم تسجيل أعلى ضغط وأقل ضغط على اللوحة الرئيسية للتشغيل عندانقطاع التيار وفى وجود خزان المياه والھواء تم التحليل باستخدام الطريقةللحصول على النتائج التسجيل وأسفرت ( AFT impulse ) النظرية الحسابيةالنتائج إلى أن استخدام أجھزة الحماية مثل خزانات المياه والھواء أو خزاناتالفائض تؤدى إلى حماية منظومة الرى من ظاھرة الطرق المائى کذلک کانتلحل مشاکل الطرق المائى CFD من النتائج أھمية وسھولة الطرق الحسابيةبالمقارنة إلى التحليل النظرى أو العملى AFT Impulse باستخدام برنامجتطابقت النتائج العملية والنظرية والحاسبية إلى حد کبير .Abstract: Water hammer (hydraulic transient) is a complex phenomenon. The cause of a hydraulic transient is the rapid change in the velocity of the flow in a closed pipe due to sudden power failure or sudden valve closure which generates high and low pressure waves transmit through the pipe line with a speed of sound. The generated waves can cause serious problems in the pipeline system such as pipe burst, pumps and valves failure. The aim of the study is to analyze experientially, theoretically and computationally to find out a solution for this phenomenon. This was done through applying some practical methods techniques of water hammer control devices used in irrigation pumping systems. In Salhia Agriculture Project site, Ismailia 33551 feddan were selected to carry out the water hammer investigation. The steady state calculation was first executed to measure the flow rate and the head, unsteady state flow calculation was carried out to identify the maximum and minimum pressure during the sudden pump trips. The results showed that the control devices such as the air vessels or surge tanks would mitigate the pressure rise and prevent the formation of negative pressure. Water hammer analysis using AFT impulse program is an effective and reliable tool to choose the required surge protection device. Installation of surge control device in the system such as one air vessel 50 m3 air volumes provides an acceptable level of protection to the irrigation pumping systems, as there are no cavitations at the pipeline and the maximum pressure reduces from 11 bars to 6 bars. A good a agreement among the experimental, theoretical and computational associated results was found.

Estimation and examination of linepack pressures in long liquid pipelines

In the past, many researchers have carried out water-hammer pressure analysis using Joukowsky equation. However, it has been observed that the computed pressure surge is no longer applicable based on the equation. The Joukowsky equation cannot be used even within the reflection time of the long pipeline. In such cases, the actual pressure rise due to the sudden closure of a quick acting valve will be several times more than that of the sudden increase in pressure as calculated by the Joukowsky equation. The phenomenon of rising pressure at the upstream of an instantaneously closed valve with the passage of time caused by the pipe friction is commonly called as linepacking. In this paper, various parameters affecting the linepack pressure have been thoroughly investigated. As the relative roughness increases, the resulting non-dimensional linepack pressure \( \left( {P_{LP} /P_{o} } \right) \) significantly increases and the proportionality constant was equal to 1.5. The linepack pressure was determined to be decreasing with increasing valve closure time. The dominant parameter that influences the linepack pressure is found to be the Reynolds number as compared to the Mach number, and the relative roughness. Furthermore, the linepack pressure is found to be proportional to frictional head loss \( \left( {h_{L} /D} \right) \), and inversely proportional to inlet pressure \( \left( {P_{o} /\left( {\gamma L_{o} } \right)} \right) \). Finally, a linear regression equation was developed in terms of non-dimensional variables to estimate the linepack pressure using hand calculations without undergoing numerical modeling procedures. The proposed equation was validated for sudden valve closure pressure histories available in the literature. The proposed method is applicable to long distance water supply pipelines where the linepack pressures are significant.

Implementation and Validation of a Free Open Source 1D Water Hammer Code

This paper presents a free code for calculating 1D hydraulic transients in liquid-filled piping. The transient of focus is the Water Hammer phenomenon which may arise due to e.g., sudden valve closure, pump start/stop etc. The method of solution of the system of partial differential equations given by the continuity and momentum balance is the Method of Characteristics (MOC). Various friction models ranging from steady-state and quasi steady-state to unsteady friction models including Convolution Based models (CB) as well as an Instantaneous Acceleration Based (IAB) model are implemented. Furthermore, two different models for modelling cavitation/column separation are implemented. Column separation may occur during low pressure pulses if the pressure decreases below the vapour pressure of the fluid. The code implementing the various models are compared to experiments from the literature. All experiments consist of an upstream reservoir, a straight pipe and a downstream valve.

Deriving the governing equation for a shock damper to model the unsteady flow caused by sudden valve closure and sudden demand change

The focus of this work is on deriving the governing equations for the ‘shock damper’ an instrument used in water flow systems. The shock damper is a mechanical tool with a single degree of freedom system that includes a tank, connecting pipe, mass, spring and damper. This tool serves as a boundary condition for characteristic line equations. Additional equations are included by considering the conservation of mass, momentum and energy. This system of equations is then explicitly solved at each time step. In order to illustrate how the shock damper performs, two gravity feed systems with and without a damper are considered. In the first system, the control valve suddenly shuts and in the second system, rapid demand change occurs in one of the nodes to impose a water hammer condition. Subsequently, unsteady flow parameters such as minimum/maximum flow velocity and pressure are evaluated and a sensitivity analysis is carried out. The results demonstrate that despite being simple and economically efficient, the shock damper is highly capable of moderating unsteady flow characteristics.

Non-conservative pressure-based compressible formulation for multiphase flows with heat and mass transfer

A pressure-based compressible multiphase flow solver has been developed based on non-conservative discretization of the mixture continuity equation. The formulation is an extension of the single phase incompressible pressure-correction approach, such that it can be applied to both two-phase flows using interface resolving methods and general n-phase ensemble-averaged mixture flows. The formulation is currently presented with the single pressure and single temperature assumption, but extension to multiple temperatures is straightforward. A robust treatment of phase change allows the method to model conditions with rapid phase change such as expansion through nozzles and valves. The method has been validated thoroughly using canonical single phase problems such as the shock tube, tank filling and sudden valve closure problems. Multiphase flow validation has been carried out for sound propagation in mixtures using the ensemble-averaged model and pressure wave transmission and reflection across an air-water interface, using the level set interface tracking method. The method has been used to study sound propagation in saturated steam-water systems under thermodynamic non-equilibrium, where the expected drastic reduction in the speed of sound is reproduced. Finally the method is applied to the problem of critical (choked) flow in a nozzle for a saturated steam-water system.

Experimental Verification of Steel Pipe Collapse under Vacuum Pressure Conditions

Steel pipes are used widely in hydroelectric systems and in pumping systems. Both systems are subject to hydraulic transient effects caused by changes in boundary conditions, such as sudden valve closures, pump failures, or accidents. Water column separation, and its associated vaporization pressure inside the pipe, can cause the collapse of thin walled steel pipes subject to atmospheric pressure, as happened during the well known Oigawa Power Plant accident in Japan, in 1950.The conditions under which thin walled pipes subject to external pressure can collapse have been studied mathematically since the second half of the XIX century, with classical authors Southwell and Von Mises obtaining definitive equations for long and short pipes in the second decade of the XX century, in which the fundamental variables are the diameter to thickness ratio D/t and the length to diameter ratio L/D.In this paper, the predicted critical D/t ratio for steel pipe collapse is verified experimentally, in a physical model able to reproduce hydraulic transients, generating vacuum pressures through rapid upstream valve closures.

Experimental observation on factors affecting intrusion volumes during low or negative pressure events

External water intrusion during low or negative pressure transient events in urban water supply systems may cause pollution and health problems. The volume of intrusion pollutants is one of the significant indicators that can reflect the degree of health risks when a pollution incident occurs. A pilot-scale platform was constructed in this study to simulate intrusion events, which were caused by the sudden valve closure in a laboratorial water distribution system. The simulation aimed to determine the critical factors affecting the intrusion volume during low or negative pressure events and to present an intrusion volume model. Intrusion volumes were measured under different conditions with different flow velocities, internal and external pressures, and orifice diameters. The intrusion volume was considerably affected by the size of leakage points, initial flow velocity, and external pressure at leakage points. It also had a positive correlation with each of the three factors. Theoretical intrusion volumes were calculated with the orifice equation and compared with the measured intrusion volumes. A correction coefficient was introduced to improve the traditional equation of the intrusion flow rate.

Simulation of thermal fluid dynamics in parabolic trough receiver tubes with direct steam generation using the computer code ATHLET

Abstract In the present feasibility study the system code ATHLET, which originates from nuclear engineering, is applied to a parabolic trough test facility. A model of the DISS (DIrect Solar Steam) test facility at Plataforma Solar de Almería in Spain is assembled and the results of the simulations are compared to measured data and the simulation results of the Modelica library “DissDyn”. A profound comparison between ATHLET Mod 3.0 Cycle A and the “DissDyn” library reveals the capabilities of these codes. The calculated mass and energy balance in the ATHLET simulations are in good agreement with the results of the measurements and confirm the applicability for thermodynamic simulations of DSG processes in principle. Supplementary, the capabilities of the 6-equation model with transient momentum balances in ATHLET are used to study the slip between liquid and gas phases and to investigate pressure wave oscillations after a sudden valve closure.

Analysis of Water Hammer Attenuation in Applications with Varying Valve Closure Times

AbstractA multiple scales asymptotic analysis is developed to describe the attenuation of a water hammer pressure wave initiated by a time-varying valve closure. The analytical results expose a simple rule-of-thumb relationship between water hammer pressure wave attenuation and the periodic average of the absolute flow velocity that is predicted by a quasi-steady friction model. The effect of flow reversals on the pressure wave attenuation is examined through comparison with a similar method applied to the water hammer generated during flow establishment, wherein flow reversals do not occur and there is a nonzero net flow. Although the analytical description is based on the assumption that the water hammer is generated by a sudden valve closure, its practical usefulness is extended by using the numerical solution as a guide to demonstrate its validity for a range of valve closure durations. A qualitative upper limit on closure times to which the analytic results may be applied is also found. All results a...

Case studies for solving the Saint-Venant equations using the method of characteristics: pipeline hydraulic transients and discharge propagation

Hydraulic transients occur during a change from one equilibrium state to another, for example, in flows. The pipeline project should provide the head and discharge in any operating states, e.g., sudden valve opening or closure. Among the various numerical approaches for the calculation of pipeline transients, the method of characteristics (MOC) is advantageous This study aims to present a hydraulic transitory study as MOC applications for solving the Saint- Venant equations in two case studies: 1) in a penstock of a small hydropower system as a simple pipeline in the case of valve-closure in the downstream boundary with a reservoir in the upstream boundary; and 2) for discharge propagation into a channel by velocity and depth of the flow channel along space evaluation. The main data for the first case study consisted of a design head that is 182 meters, a turbine discharge of 13.82 m3/s, a diameter of 4 meters and length pipe (penstock) of 2,152.50 meters. Regarding the second case study, the entry hydrogram was given to a rectangular channel with a width of 6.1 meters, length of 3,048 meters, slope of 0.0016 meters, and exhibited uniform flow with nominal depth of 2.44 meters. The characteristic curve of the discharge in the downstream extremity is Q = 158.(y – 3.25)32.The proposed methodology by Chaudry [5] concerning the development of hydrodynamic models was used. The obtained results for first case study showed that the simulated values for valve pressure while varying turning the valve between 4 and 12 seconds results in maximum values of pressures that oscillated between 219.97mca and 212.39 mca (4s) and 196.42mca and 190.86mca (12s). For the second case study, the values of discharge, velocity, and depth for x=0 and elapsed time of 850s were, respectively, 127.70m3/s, 3.87m/s, and 5.36m. For x=0 and an elapsed time of 1,230s, the values were 87.92m3/s, 4.49m/s, and 3.21m. Therefore, the MOC numerical approach has been confirmed to be useful for several engineering purposes, including cases of hydraulic transients and discharge propagation in hydraulic systems

Non-Newtonian fluid hammer in elastic circular pipes: Shear-thinning and shear-thickening effects

The present study aims to bridge the gap between water hammer theory and non-Newtonian fluid mechanics. To achieve this, a detailed numerical study is carried out to investigate the effect of sudden valve closure on the flow dynamics of power-law fluids in circular pipes. An unsteady two-dimensional pipe flow model is employed which takes into consideration both fluid compressibility and pipe elasticity. The present model is numerically integrated in time using the fourth-order accurate Runge–Kutta method while spatial terms are discretized using second-order accurate central difference expressions. Present results show that laminar pipe transients are significantly affected by the shear-thinning and shear-thickening behavior of the non-Newtonian fluid. Reported unsteady velocity profiles during the pipe transient show an excessive Richardson annular effect in the case of shear-thinning fluids, which is reduced significantly in the case of shear-thickening fluids. Present results also show that the shear-thickening behavior leads to more rapid attenuation of the fluid transient. Moreover, shear-thickening effects give rise to excessive pipeline packing which results in a pressure rise at the valve that could significantly exceed the theoretical maximum predicted by the inviscid Joukowsky pressure rise.

관수로 부정류 마찰항 보정을 위한 Levenberg Marquardt 방법의 적용연구

이 논문에서는 관망시스템의 마찰항을 보정하기 위해서, 부정류 마찰 모형과 Levenberg Marquardt 방법을 합성하였다. 부정류 마찰항을 고려하기 위한 방법으로 빈도 의존 마찰항을 사용하였으며, 특성선 방법을 모형 개발의 기반으로 하였다. 최적화에 필요한 Hessian과 Jacobian 행렬을 구하기위해서 수압을 직접 마찰항에 미분한 항을 계산하였으며, 특성선 방법상에서의 다양한 수압과 유량에 대한 마찰계수의 민감도를 수식으로 유도하였다. 간단한 관망을 가정한 뒤, 갑작스런 밸브의 거동으로 도입된수압의 시계열을 확보하였고, 이를 이용하여 정상류 마찰 모형과 부정류 마찰모형의 마찰항 보정을 수행하였다. 제안된 방법과 진화 연산 알고리즘의 마찰항 수렴거동을 비교하였으며, Leveberg Marquardt 방법의 안정적이고 신속한 수렴결과를 확인하였다. In this study, a conventional pipeline unsteady friction model has been integrated into Levenberg Marquardt method to calibrate friction coefficient in a pipeline system. The method of characteristics has been employed as the modeling platform for the frequency dependant model of unsteady friction. In order to obtain Hessian and Jacobian matrix for optimization, the direct differentiation of pressure to friction factor was calculated and sensitivities to friction for heads and discharges were formulated for implementation to the integration constant in the characteristic method. Using a hypothetical simple pipeline system, time series of pressure, introduced by a sudden valve closure, were obtained for various Reynolds numbers. Convergency in fiction factors were evaluated both in steady and unsteady friction models. The comparison of calibration performance between the proposed method and genetic algorithm indicates that faster and stabler behaviour of Levenberg Marquardt method than those of evolutionary calibration.

Developing an optimal valve closing rule curve for real-time pressure control in pipes

Sudden valve closure in pipeline systems can cause high pressures that may lead to serious damages. Using an optimal valve closing rule can play an important role in managing extreme pressures in sudden valve closure. In this paper, an optimal closing rule curve is developed using a multi-objective optimization model and Bayesian networks (BNs) for controlling water pressure in valve closure instead of traditional step functions or single linear functions. The method of characteristics is used to simulate transient flow caused by valve closure. Non-dominated sorting genetic algorithms-II is also used to develop a Pareto front among three objectives related to maximum and minimum water pressures, and the amount of water passes through the valve during the valve-closing process. Simulation and optimization processes are usually time-consuming, thus results of the optimization model are used for training the BN. The trained BN is capable of determining optimal real-time closing rules without running costly simulation and optimization models. To demonstrate its efficiency, the proposed methodology is applied to a reservoir-pipe-valve system and the optimal closing rule curve is calculated for the valve. The results of the linear and BN-based valve closure rules show that the latter can significantly reduce the range of variations in water hammer pressures.