Maximum Pressure Head Research Articles

Design and construction of GaInSn experimental facility for studies of mixed-convection MHD flows

A multifunctional liquid metal loop named MaTHE-XJTU (Magneto-Thermo-Hydrodynamic Experiments-Xi'an Jiaotong University) that utilizes eutectic alloy GaInSn as a working fluid has been designed and constructed. The function of the MaTHE-XJTU facility is to study the magnetohydrodynamic (MHD) flow and mixed convection characteristics under the coupling effect. The main operating parameters of the loop are: the maximum magnetic field intensity is 3T, the effective magnetic field region is 300 mm × 800 mm × 1000 mm, the maximum flow rate of electromagnetic pump (EM pump) is 8 m3/h, the maximum pressure head of EM pump is 0.5 MPa. The paper describes the major components and basic operation procedures of the loop, the related flow diagnostics method, and near-future experiments. This loop could provide a high-parameter experimental platform (Ha∼104, Gr∼109, Re∼104) for investigations that improve the present understanding of magnetohydrodynamic and heat transfer performance in liquid metal blankets.

A cavalpulmonary assist device utilising impedance pumping enhanced by peristaltic effect.

Fontan procedure, the standard surgical palliation to treat children with single ventricular defects, causes systemic complications over years due to lack of pumping at cavopulmonary junction. A device developed specifically for cavopulmonary support is thus considered, while current commercial ventricular assist devices (VAD) induce high shear rates to blood, and have issues with paediatric suitability. To demonstrate the feasibility of a small, valveless, non-invasive to blood and pulsatile rotary pump, which integrates impedance and peristaltic effects. A prototype pump was designed and fabricated in-house without any effort to optimise its specification. It was then tested in vitro, in terms of effect of pumping frequency, background pressure differences and pump size on output performance. Net flow rate (NFR) and maximum pressure head delivery are both reasonably linearly dependent on pumping frequency within normal physiological range. Positive linearity is also observed between NFR and the extent of asymmetric pumping. The device regulates NFR in favourable pressure head difference and overcomes significant adverse pressure head difference. Additionally, performance is shown to be insensitive to device size. The feasibility of the novel rotary pump integrating impedance and peristaltic effects is demonstrated to perform in normal physiological conditions without any optimisation effort. It provides promising results for possible future paediatric cavopulmonary support and warrants further investigation of miniaturisation and possible haemolysis.

Visualized-experimental assessment on a two-phase thermosyphon loop downcomer state with wide range of filling ratios

The two-phase thermosyphon loop (TPTL), which has an excellent heat transfer performance with simple, compact structure and pump-free advantages, can effectively solve the heat transfer problem under high heat flux. It is necessary to optimize the TPTL to operate in good conditions, especially the state of the downcomer in which the liquid head is one of the critical parameters to determine the driving force of the circulation. However, in the existing studies, the flow features under high filling ratio and high heat flux were ignored in the downcomer. Since a high filling ratio has been proved to have good performance at high heat flux. Herein, the flow characteristics of the TPTL downcomer were seen and quantified using an experimental visual setup under different filling ratios in this study. Two flow features under high heat flux, for the first time, are reported: 1. two-phase flow in the downcomer at high filling ratios. 2. liquid column height oscillation under a partially liquid-filled state. According to the results, the filling ratio significantly impacts the flow characteristics of the downcomer. The TPTL downcomer state, contrary to the traditional understanding, can be partially filled with liquid but not totally filled with fluid all the time, implying that the driving force may be less than the typical assumption. TPTL with a high filling ratio can also provide a maximum gravity pressure head driving force due to the full downcomer. In addition, the bubble pump, which influences by the heat flux, also accelerates the mass flow in the TPTL. Consequently, TPTLs with a high filling ratio showed a significant thermal performance. A partially filled with the liquid phenomenon is demonstrated in moderate filling ratios, and the height of the liquid column will change as the heat flux increases, which indicates the self-regulation of TPTL. When the filling ratio is low, the liquid column height is greatly influenced by the filling ratio. The high liquid column will also give the TPTL excellent thermal performance. The ideal state of a TPTL downcomer is the downcomer filled with two-phase liquid under a high void fraction, which is realized by a high filling ratio TPTL. This paper sheds some light on the downcomer state of TPTLs to optimize the TPTL thermal performance.

The Safe Load-Bearing Capacity of Railway Tunnel Linings under High-Pressure and Water-Rich Conditions

High water pressure has been identified as the direct cause of water seepage problems in tunnels. Consequently, it is imperative to ascertain the safety load-bearing limits of tunnel linings in high-pressure, water-rich strata. In this study, FLAC3D (V5.0) numerical simulation software was employed to establish seepage models of tunnels under high-pressure, water-rich conditions, taking an actual engineering project as a reference. The hydrostatic pressure on tunnel linings under various conditions, including different permeability coefficients of the surrounding rock, grouting rings, levels of the water table, and coordinates of lining positions, was computed. By extracting the results of these simulations, correlations between lining water pressure and various parameters were analyzed, and preliminary hydrostatic pressure calculation formulas were deduced. Through regression analysis using SPSS (19.0) software, a general calculation formula for lining water pressure was derived. Given similar surrounding rock conditions, it was revealed that railway tunnel lining types adhere to a universal standard. The calculation formula for lining water pressure, when integrated with lithostatic pressure in the seepage model, facilitates the computation of the maximum pressure head that the tunnel lining can withstand under different conditions. A tabulation summarizing safe water head heights under various conditions is also presented, which enables rapid consultation of the safe load-bearing range of tunnel lining under corresponding conditions. This study provides a new calculation method for the lining water pressure of a water-rich railway tunnel, filling the literature gap. The safe tunnel head query table provides a new research approach for the design of water-rich tunnels. The research method in this article is rare in the literature, and the research approach has obvious innovations. The findings of this study have the potential to provide a theoretical foundation and data reference for the structural design of tunnel linings and the remediation of related issues.

A Transient-Based Analysis of a Leak in a Junction of a Series Pipe System: Mathematical Development and Numerical Modeling

In this paper, a numerical model is proposed to simulate the effect of a leak occurring at a pipe junction. The developed model, based on the method of characteristics, considers both hydraulic singularities, the leak and the junction, as superposed boundary conditions located in the same section. Obtained results representing the temporal evolution of pressure signals have allowed for locating the leak through the separation of its effect from that of the junction. For testing purposes, the transient was created by a sudden closure of a downstream valve in a reservoir-two series pipe-valve system. The novel proposed approach has proven its usefulness on locating and sizing the leak through detailed test cases. In sizing the leak, better accuracy is obtained when using the maximum pressure head reached by the incident wave before encountering the leaky junction instead of that of the transmitted wave through the leak. On the other hand, for the localization of the leak, rather than looking for an equivalent characteristic period of the two-pipe system, it was shown that the characteristic period of the pipe connected to the reservoir, once incorporated into the localization formula, leads to precise results with minimal uncertainty. For the piping system, two cases of configuration, viz. expansion and shrinkage (narrowing), were tested. In general, using the proposed approach, the maximum uncertainty values for the sizing and localization of a leak in the junction are 0.1513% and 1.09%, respectively. Additionally, the friction effect on the localization and sizing of the leak at the junction was investigated to conclude that the friction does not significantly affect the precision of the numerically obtained results for the sizing and localization of the leak at the junction.

Water Hammer Protection Measures and Calculation Analysis of Reservoir Water Pipelines

In fluid mechanics, the large pressure fluctuation caused by the rapid change of fluid flow in a closed pipeline is called water hammer. It has huge destructive power for pressurized water pipelines, which often lead to pipeline leakage or even burst. In this paper, through the analysis of the dynamic characteristics of the gas in the pressurized water pipeline, the necessity of setting the air valve is drawn. Then based on the Bentley HAMMER model, combined with the example of the reservoir water pipeline engineering, the water hammer analysis was carried out. Compared with the maximum pressure head before and after adding the air valve, it is reduced from 126.89 m to 62.11 m, a decrease of about 50%. At the same time, the negative pressure in the pipeline under transient conditions is also eliminated. The results show that the air valve used in the pressure water pipeline has a good effect on the prevention of water hammer.

Wetting hysteresis as the mechanism of heat pipe post-dryout thermal hysteresis and recovery

Heat pipes and vapor chambers are passive thermal management devices used for efficient heat transport by phase change. Their passive operation is enabled by capillary pumping of the working fluid in a porous wick, which is operationally limited by the maximum pressure head it can provide. This capillary limit marks the maximum heat input at which the capillary pressure generated can overcome the pressure drop in the wick; operating above the capillary limit at steady state leads to dryout. Heat pipes and vapor chambers are increasingly being used in electronics systems where end-user activity dictates the transient power input which can therefore be highly variable and time-dependent. It was recently shown that heat pipes can withstand a power pulse exceeding the capillary limit for brief time intervals. Under such operating conditions, the heat pipe will experience dryout only if the duration of the pulse load is longer than a certain characteristic time interval. The pulse-load-induced dryout may result in an increased thermal resistance when the power is reduced back down to pre-dryout levels, thus exhibiting a hysteresis in heat pipe thermal performance. In this work, we experimentally characterize the recovery from pulsed-load-induced dryout. We further propose that the observed change in steady-state thermal performance before and after dryout results from contact angle hysteresis at the three-phase contact line of the wick-liquid interface. A model is developed based on this proposed mechanism to predict the nature of recovery from dryout-induced thermal hysteresis, as well as to identify that a given heat pipe has a maximum possible hysteresis. The experiments illustrate the trends inferred from the model for the recovery process and confirm the existence of a “maximum hysteresis line,” which identifies the worst-case scenario for thermal hysteresis after heat pipe dryout. Based on these mechanistic learnings, a new testing protocol is proposed for experimentally characterizing this post-dryout maximum hysteresis signature for a heat pipe.

Modeling transient cavitating flow in large drop crude oil pipelines

Transient cavitating flow is a dangerous condition in the operation of large drop crude oil pipelines. Accurately predicting the high pressure generated by cavity collapse is the premise of analyzing and formulating pipeline safety management and control strategies. A new numerical simulation method for one dimension cavitating flow in crude oil pipelines considering the effect of unsteady friction was proposed. The unsteady friction (UF) term is coupled to the classical discrete gas cavity model (DGCM) for modeling the cavitating flow, and the proposed model is called UF-DGCM. The method of characteristics (MOC) is used to solve the UF-DGCM. The validity of the model has been verified with experimental data. The pipeline length of the two test cases is 37.23 m and 15.22 m, respectively, and the pipeline diameter is 22.1 mm and 20.0 mm, respectively. For the two test cases, the accuracy of the prediction results is improved by 6.7% and 4.4%, respectively. A case study of cavitating flow caused by pump shutdown in a pipeline with a length of 35 km and a diameter of 738 mm was performed using UF-DGCM, and the effects of water hammer wave speed, crude oil vapor pressure, and pump shutdown time on cavitating flow were analyzed. The results show that the maximum pressure peak is dependent on the water hammer wave speed. About the increase in the wave speed value of 200 m/s will lead to an increase in the maximum pressure head value of 10.1 m. The increase of pump shutdown time will inhibit the growth of cavities, and increasing the pump shutdown time by 4 s will shorten the existence time of cavities by about 3 s. The extension of the pump shutdown time will prevent cavitating flow. The proposed improved model is more suitable for transient cavitating flow analysis, and the results of flow parameters research will be helpful to prevent cavitating flow in crude oil pipelines.

A compact Double-spiral electromagnetic pump for liquid metal cooling

This paper reports a novel conception of the high-performance double spiral electromagnetic pump (DS-EMP) to efficiently drive liquid metal (LM) fluid with minimum volume. The mathematic model and experimental test methods have been adopted to investigate the driving characteristics of DS-EMP. The result shows that the performance of DS-EMP can be regulated by changing the number of the spiral flow channel. Increasing the number of spiral flow channels is conducive to achieving a high-pressure head. Reducing the number of spiral flow channels is beneficial for obtaining a large flow rate. The experimental result indicates that it can provide the maximum pressure head of 76.5 kPa @200A and the corresponding maximum flow rate of 2.19 L/min with a compact volume of 0.8 L. The LM cooling loop driven by DS-EMP was established to achieve efficient cooling of 156 W/cm2 (755 W) heat flux with a flow rate of 1.86 L/min.

Supercritical Flow over a Submerged Vertical Negative Step

The transition from supercritical to subcritical flow around a fully submerged abrupt negative step in a horizontal rectangular open channel has been investigated. In a laboratory experiment the one-dimensional energy and the momentum conservation equations were studied by means of depth and pressure measurements by piezometers installed along the bottom and the step face. Froude number varied in the range 1.9 to 5.8 while the step height to critical depth ratio was in the range 1.34 to 2.56. The results are presented in dimensionless form using mainly a characteristic length scale that is the sum of critical depth and step height and the Froude number of the supercritical flow upstream. Five different types of rapidly varying flow are observed when the subcritical downstream tailwater depth varied. The supercritical water jet at the top of the step either strikes the bottom downstream of the step when the maximum pressure head is greater, or moves to the surface of the flow when it is lower than tailwater depth, and the separation of the two flow regimes occurs when the tailwater depth to the characteristic length scale is around 1.05. The normalized energy loss and a closure parameter for the momentum equation are presented in dimensionless diagrams for practical use by the design engineer. Finally, the one-dimensional equations of motion including Boussinesq terms are solved numerically and the results found are congruent to the experimental findings.

Effect of Wave Load on Decompression of Underwater Workers: CFD-VPM Simulation

Lee, W.D.; Kang, C.; Hong, S.; Lee, T.K., and Lee, J., 2021. Effect of wave load on decompression of underwater workers: CFD-VPM simulation. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 614–618. Coconut Creek (Florida), ISSN 0749-0208. Hydrodynamic pressure from cyclic wave action causes water pressure increases and vibration, and these pressure changes can have a significant impact on underwater workers in high-pressure environments. This study investigated the impact of wave loading on decompression procedures for underwater workers using a coupled CFD-VPM. Computational Fluid Dynamics (CFD) were used to simulate wave propagation, and the Varying Permeability Model (VPM) was used to simulate the dive profile. Results of the wave propagation simulation showed that wave height and nonlinearity increased due to shoaling when approaching a beach, and the period was shortened. The maximum dynamic pressure head exceeded 1 m at depths less than 45 m and reached 10.3 m at a depth of 3 m. Simulations of the dive profile revealed that decompression time increased by 11 m and 9 s (28.36 %) under extraordinary wave conditions when underwater work was performed for 2 hours at a depth of 20 m. Furthermore, decompression time increased by 12 min and 40 s (10 %) at a working depth of 30 m. For safe underwater work operations under extraordinary wave conditions, decompression procedures should account for the pressure rise and vibration caused by wave action.

Electrostatic bellow muscle actuators and energy harvesters that stack up.

Future robotic systems will be pervasive technologies operating autonomously in unknown spaces that are shared with humans. Such complex interactions make it compulsory for them to be lightweight, soft, and efficient in a way to guarantee safety, robustness, and long-term operation. Such a set of qualities can be achieved using soft multipurpose systems that combine, integrate, and commute between conventional electromechanical and fluidic drives, as well as harvest energy during inactive actuation phases for increased energy efficiency. Here, we present an electrostatic actuator made of thin films and liquid dielectrics combined with rigid polymeric stiffening elements to form a circular electrostatic bellow muscle (EBM) unit capable of out-of-plane contraction. These units are easy to manufacture and can be arranged in arrays and stacks, which can be used as a contractile artificial muscle, as a pump for fluid-driven soft robots, or as an energy harvester. As an artificial muscle, EBMs of 20 to 40 millimeters in diameter can exert forces of up to 6 newtons, lift loads over a hundred times their own weight, and reach contractions of over 40% with strain rates over 1200% per second, with a bandwidth over 10 hertz. As a pump driver, these EBMs produce flow rates of up to 0.63 liters per minute and maximum pressure head of 6 kilopascals, whereas as generator, they reach a conversion efficiency close to 20%. The compact shape, low cost, simple assembling procedure, high reliability, and large contractions make the EBM a promising technology for high-performance robotic systems.

Flow Pressure Behavior Downstream of Ski Jumps

Ski jump spillways are frequently implemented to dissipate energy from high-speed flows. The general feature of this structure is to transform the spillway flow into a free jet up to a location where the impact of the jet creates a plunge pool, representing an area for potential erosion phenomena. In the present investigation, several tests with different ski jump bucket angles are executed numerically by means of the OpenFOAM® digital library, taking advantage of the Reynolds-averaged Navier–Stokes equations (RANS) approach. The results are compared to those obtained experimentally by other authors as related to the jet length and shape, obtaining physical insights into the jet characteristics. Particular attention is given to the maximum pressure head at the tailwater. Simple equations are proposed to predict the maximum dynamic pressure head acting on the tailwater, as dependent upon the Froude number, and the maximum pressure head on the bucket. Results of this study provide useful suggestions for the design of ski jump spillways in dam construction.

Small Scale Low Height Wave Energy Seawater Pump for Achieving Environmental and Economic Sustainability

This study is about the design and development of seawater pump powered by low height sea wave at near shore region. This study focuses on developing seawater pump that does not use any electricity for delivering high pressure saline water to on shore region which is in line with the global renewable energy quest. Malaysia is blessed with the geographic location of surrounded by sea which enable this technology to be utilized. The challenge in utilizing such technology is due to the nature of the sea wave surrounding Malaysia that is classified as low height sea wave which increase the difficulty in utilizing such technology in neither electricity generation nor sea water delivery. On top of that, there is limited study available in this area especially low wave height. The prototype is designed based on point absorber concept with piston type pump configuration for water delivery. Then the prototype is tested at the Mukah Beach with average recorded wave height of less than 1m. Findings demonstrated that a single prototype pump is capable of delivering maximum pressure head of 10m with maximum flow of 1.2Litre per minute (LPM). For three pumps connected in series, the maximum pressure head can reach up to 25m pressure head with maximum flow rate of 1.5LPM. Similarly, when connected in parallel, the system capable to deliver up to 14m of pressure head and 3LPM of flow rate. The findings indicate that the prototype is significant for seawater delivering. Although the output of the prototype is small, its potential is yet to be fully unleashed. Therefore, it is highly recommended for future study the prototype to be pair together with more similar pumps in series or parallel configurations to form a system of pumps to create higher flow and higher head for more application. This study concludes that the designed and developed prototype is useful for delivering saline water for various application such as seawater desalination or electricity generation in near shore area or islands.

Influence of hydraulic properties on physically modelling slope stability and the definition of rainfall thresholds for shallow landslides

Physically-based models are recognized as a good tool for slope stability analysis and have been implemented for the definition of rainfall thresholds for landslides. In this study, a methodology for estimating rainfall intensity and duration thresholds for shallow sliding failure, using the physical model TRIGRS, was implemented in a tropical mountainous basin of the Valle de Aburrá (Colombia). The variation of pressure head and factor of safety during different rainfall events and hydraulic conditions is studied for specific grid cells. Steady state and a maximum pressure head were reached for each grid cell regardless of the different rainfall intensities and hydraulic conductivities simulated, but the time in which this condition is reached depends on these variables and occurs faster for steeper slopes. The influence of hydraulic properties on the stability results and the position of the rainfall intensity and duration thresholds were studied with parametric analysis. Very low values of saturated hydraulic conductivity do not allow rainfall intensity and duration thresholds to be developed. The rainfall threshold position also has a greater variation with respect to the parameters of the soil water retention curve and the initial infiltration rate (or long-term background rainfall rate) for low values of saturated hydraulic conductivity.

Design and Development of Zero Electricity Water Pump for Rural Development

This study aims to develop a water pump that utilizes natural hydro energy as driving force to deliver water to a higher ground. The conceptual design of using water wheel to extract kinetic energy from water flow and transfer the energy to power multiple piston pump was created based on the extensive literature review findings. The actual prototype is then built and modified to suit the actual environment considerations. Findings show that single pump is able to produce maximum pressure head of 7.14 meters and the maximum volume flowrate achieved is 19.2 l/hr (320ml/min). However, when multiple piston is connected in series (in this research three pistons is used), the maximum water head increased to 13.77 meters and the maximum volume flowrate about 19.2 l/hr. This result shows that the water pump can be used in remote area or places at higher ground that does not have constant water access. Performance of the whole system can be improved by several factors such as adding more blades to the water wheel, steeper angle and better piston shaft design for water pump, and also proper water sealing of the whole system to prevent head loss and increase the overall performance.

Numerical modeling of continuous-flow left ventricular assist device performance.

Responses of five rotary blood pumps, namely HeartAssist 5, HeartMate II, HeartWare, Sputnik 1, and Sputnik 2, were extensively assessed in six test cases using a mathematical model of the cardiovascular system. Data for the rotary pumps were derived from pressure-flow curves reported in the literature. The test cases were chosen to attempt to cover most common clinical conditions, such as partial or full support or transitions between different levels of ventricular support. The investigated parameters are collected in a table and presented in figures, such as pressure-volume loops, H-Q curves, pump flow, and aortic pressure waveforms. HeartAssist, Sputnik 1, and Sputnik 2 pumps provide comparable level of aortic pressure, pump flow pulsatility PI(QP), and aortic pressure pulsatility PI(AoP) due to the similarity of pressure-flow characteristic curves of these pumps. HeartMate II provides a minimal backflow among other investigated rotary blood pumps due to the maximum pressure head at zero flow. HeartWare provides minimal pulsation of flow, which is confirmed by a flow range from -2 to 7 L/min in case 1. At the same time, the greatest degree of unloading was demonstrated by the HeartWare due to the flatness of the pressure-flow curve shape. The conclusions were made based on the obtained results, including the influence of pressure-flow curve shape on the pump performance and occurrences of adverse events, such as backflow or suction. For example, the increase of the pressure head at zero flow decreases the likelihood of backflow through the pump, and with it, increasing the flow under minimal pressure head increases the likelihood of suction.

Numerical Modeling and Hydraulic Optimization of a Surge Tank Using Particle Swarm Optimization

In a pressurized water conveyance system, such as a hydropower system, during hydraulic transients, maximum and minimum pressures at various controlling sections are of prime concern for designing a safe and efficient surge tank. Similarly, quick damping of surge waves is also very helpful for the sound functioning of the hydro-mechanical system. Several parameters like diameter of the surge tank, diameter of the orifice, operating discharge, working head, etc., influence the maximum/minimum surge, damping of surge waves in the surge tank, and the difference of maximum pressure head at the bottom tunnel and maximum water level in the surge tank. These transient behaviors are highly conflicting in nature, especially for different diameters of orifices (DO) and diameters of surge tanks (DS). Hence, a proper optimization method is necessary to investigate the best values of DO and DS to enhance the safety and efficiency of the surge tank. In this paper, these variables are accurately determined through numerical analysis of the system by the Method of Characteristics (MOC). Furthermore, the influence on the transient behavior with changing DO and DS is investigated and finally, optimum values of DO and DS are determined using Particle Swarm Optimization (PSO) to minimize the effects of hydraulic transients on the system without compromising the stability and efficiency of the surge tank. The obtained results show significant improvements over the contemporary methods of finding DO and DS for surge tank design.

Mitigating peak pressure of storm geysering by orifice plates installed at the top of vent pipes.

Large air pockets can be trapped in storm sewer systems during intense rain events. Uncontrolled release of these air pockets may cause geysering and pressure surges, resulting in flooding, pipe failures and safety issues. Thus, there is a great need to develop methods to retrofit existing sewer systems and to provide guidance on system design. A large-scale physical model was established to evaluate air-control orifice plates in reducing geysering intensity by utilizing air cushion effects over the process of air escape. Experimental results indicate that the magnitude of pressure fluctuations can be reduced significantly with partially open vent pipes. The maximum pressure head can be reduced by approximately two-thirds, and the magnitude of relative pressure oscillation decreased by about 95% when the diameter ratio of the air-control orifice to the vent pipe is below 25%. Air-water mixture jets can be avoided in such cases. The effect of using multiple vent pipes with orifice plates was also evaluated and found to be effective. Thus, air-control vent pipes can be applied to alleviate geysering and related pressure transients.

Uncertainty Analysis of Transient Flow in Water Distribution Networks

For transient analysis of a pipe network, the unsteady flow governing equations should be solved to obtain the extreme pressure heads in the system, which may be faced with several uncertainties. To evaluate that to what extent the input uncertainties can affect the system responses, a simulation model based on the fuzzy sets theory is introduced. For this purpose, triangular fuzzy numbers are used to represent the input uncertainties. Then, to obtain the extreme pressure heads in each location of the network and at each level of uncertainty, four independent optimization problems are solved. In these problems, the nodal maximum and minimum pressure heads are the objective functions and the simulation parameters are the decision variables. Accordingly, for fuzzy analysis of a pipe network, a complicated many-objective optimization problem arises. To solve the problem efficiently a many-objective genetic algorithm is coupled to the transient simulation model. To speed up the analysis, a transient simulation model in the frequency domain is used. The proposed model is applied to a pipe network and the results are discussed. The model is found computationally fast and promising for real applications.