Pipe Systems With Micro-Turbines: Water Hammer Considerations

2003 ◽  
Author(s):  
Qinfen Zhang ◽  
Bryan Karney
Keyword(s):  
Boundary Condition ◽  
Numerical Model ◽  
Comprehensive Analysis ◽  
Pipe System ◽  
Flow Balance ◽  
Pipe Networks ◽  
Nodal Flow ◽  
Speed Change ◽  
Pipe Systems ◽  
Basic Equations

Micro and small turbines, as a means of producing clean and renewable energy by transforming hydropower to electricity, can be used extensively in pipe systems. With respect to hydraulic transient modeling, governed turbines have two additional features compared to the more familiar pump boundary condition: namely, wicket gate adjustments and more complicated device characteristics. Based on head balance (or nodal flow balance) considerations, torque (or speed change) relations, and the governor equation, a numerical model of the turbine boundary condition in a pipe system is established. The combinations of the three basic equations under specific situations are then discussed. To verify in a general way this numerical model, a penstock failure at Lapino Power Plant (Poland) is simulated. The current work sets the stage for a more comprehensive analysis of turbines and related unsteady flow issues in topologically complex pipe networks.

Vortex Induced Vibrations and Fatigue Assessment of Pipe-in-Pipe Systems

2018 ◽  
Author(s):  
Zhengmao Yang ◽  
Fartein Thorkildsen ◽  
Kristian Norland
Keyword(s):  
Numerical Model ◽  
Structural Response ◽  
Mode Shapes ◽  
Pipe Surface ◽  
Fatigue Assessment ◽  
Pipe System ◽  
Vortex Induced Vibrations ◽  
Pipe Systems ◽  
Girth Welds ◽  
Outer Pipe

The high thermal insulation potential of a pipe-in-pipe system makes it the preferred solution for challenging flow assurance conditions. Due to the higher bending stiffness of a pipe-in-pipe system, longer free spans would be expected for pipelines resting on uneven seabed. However, there are no clearly defined standard formulae for the calculation of structural response of free spanning pipe-in-pipe system exposed to vortex induced vibration (VIV) and the resulting fatigue damage. If the same method as for a single wall pipe was applied, the combined equivalent pipe properties would be assumed and the VIV response and stresses of the equivalent pipe could be obtained. However, the longitudinal stresses in the inner and outer pipe to be used for the fatigue assessment of the girth welds would not be easily obtained, especially for sliding pipe-in-pipe systems. Based on previous experience and development work for pipe-in-pipe systems, a numerical model for VIV assessment of sliding pipe-in-pipe systems is proposed giving improved interpretation of individual pipe characteristics. Modal analyses of sliding pipe-in-pipe systems are performed by using this numerical model. The natural frequencies and mode shapes are extracted. According to the numerical analysis results, the longitudinal stress ranges due to VIV are obtained and fatigue assessment of the pipeline girth welds for the inner and outer pipes are performed. In order to understand the interaction between the outer and inner pipe, the effect of friction and initial gap between the centralizers and outer pipe surface are studied.

Applicability of Preissmann box scheme for calculation of transcritical flow in pipes

2019 ◽  
Vol 19 (5) ◽  
pp. 1429-1437
Author(s):  
Yanmei Wang ◽  
Chengcai Zhang ◽  
Zhansong Li ◽  
Bin Sun ◽  
Haolan Zhou
Keyword(s):  
Numerical Model ◽  
Momentum Equation ◽  
Internal Boundary ◽  
Urban Drainage ◽  
Box Scheme ◽  
Pipe Networks ◽  
Wide Range ◽  
Transcritical Flow ◽  
Transcritical Flows ◽  
Supercritical Flows

Abstract The accurate computer simulation of pipe flow is of great importance in the design of urban drainage. The Preissmann box scheme is usually used to model a wide range of subcritical and supercritical flows. However, care must be taken over the modelling of transcritical flows since, unless the correct internal boundary conditions are imposed, the scheme becomes unstable. In this paper, using the scheme in conjunction with the reduced momentum equation and applying boundary condition structure inherent to subcritical flow to all regimes, is an approach that enables efficient numerical simulation of transcritical flows in pipe networks. The approach includes three steps. First, a unified mathematical model which is based on the Preissmann slot model is derived. Second, the Preissmann box scheme is used to solve the set of equations, by analyzing and discussing the origin of the invalidity of applying the scheme, and a numerical model suitable for transcritical flow is proposed by the method of changing the convection acceleration term. Third, the numerical model is assessed by comparison with analytical, experimental and numerical results. The proposed models verified that this method can make the Preissmann box scheme applicable to the computation of transcritical flow in pipes.

scholarly journals Finite volume simulation of unsteady water pipe flow

2014 ◽  
Vol 7 (2) ◽  
pp. 83-92 ◽  
Author(s):  
J. Fernández-Pato ◽  
P. García-Navarro
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Finite Volume ◽  
Water Pressure ◽  
Laboratory Data ◽  
Network Models ◽  
Finite Volume Methods ◽  
Analytic Solutions ◽  
Surface Flow ◽  
Pipe Networks

Abstract. The most commonly used hydraulic network models used in the drinking water community exclusively consider fully filled pipes. However, water flow numerical simulation in urban pipe systems may require to model transitions between surface flow and pressurized flow in steady and transient situations. The governing equations for both flow types are different and this must be taken into account in order to get a complete numerical model for solving dynamically transients. In this work, a numerical simulation tool is developed, capable of simulating pipe networks mainly unpressurized, with isolated points of pressurization. For this purpose, the mathematical model is reformulated by means of the Preissmann slot method. This technique provides a reasonable estimation of the water pressure in cases of pressurization. The numerical model is based on the first order Roe's scheme, in the frame of finite volume methods. The novelty of the method is that it is adapted to abrupt transient situations, with subcritical and supercritical flows. The validation has been done by means of several cases with analytic solutions or empirical laboratory data. It has also been applied to some more complex and realistic cases, like junctions or pipe networks.

scholarly journals Relining of pipe systems: conditions, benefits and application through case-study

2017 ◽  
Vol 19 (1) ◽  
pp. 7-14
Author(s):  
Victor Vladimirov ◽  
Thomas Simoner ◽  
Ioan Bica
Keyword(s):  
Urban Agglomerations ◽  
Pipe System ◽  
Diameter Pipe ◽  
Pipe Systems ◽  
The City

Abstract Relining is one of the best alternatives available today for pipe system rehabilitation. This trenchless solution is particularly interesting for urban agglomerations, as a smaller diameter pipe is pushed or pulled through the old pipeline. Relining creates a leak-tight “pipe within a pipe” system, which is as good as new in both structural and hydraulic terms. Relining can be performed with both circular and special, non-circular (NC) profiles. The latter is especially advantageous for the rehabilitation of old sewers, many of which were constructed in a variety of ovoid-like shapes. This paper presents the typical steps that are performed for pipeline rehabilitation with non-circular profiles, as well as an applied case study (a project implemented in the city of Würzburg in Germany).

scholarly journals Hydraulic simulation of perforated pipe systems feeding vertical flow constructed wetlands

2018 ◽  
Vol 77 (5) ◽  
pp. 1431-1440 ◽  
Author(s):  
Urte Paul ◽  
Christian Karpf ◽  
Thomas Schalk
Keyword(s):  
Constructed Wetlands ◽  
Goodness Of Fit ◽  
Hydraulic Modeling ◽  
Vertical Flow ◽  
Nsga Ii ◽  
Hydraulic Simulation ◽  
Pipe System ◽  
Vertical Flow Constructed Wetlands ◽  
Pipe Systems ◽  
Perforated Pipe

Abstract For successfully operating a vertical flow constructed wetland, the uniform distribution of wastewater on the surface of the soil filter is essential. In research, however, this aspect is often overlooked. This study presents a methodology for assessing discharge uniformity from perforated pipe systems via hydraulic modeling. First, the requirements and conditions for the simulation of perforated pipe systems are investigated and the model basics are explained. Then the whole process of model build-up, calibration, application and analysis is presented and discussed. The modeling is done by the software EPANET and supported by pressure measurements in the pipe system of a small wetland treating domestic sewage. A crucial factor in the modeling process is the choice of loss coefficients in dividing junctions. Different approaches for calculating such coefficients are compared. Model calibration is undertaken via the multicriterion optimization algorithm NSGA-II. By calibrating two parameters, a reasonable goodness of fit with the measured pressure values was achieved. Model results show that distribution uniformity of the pipe system in question is poor. An outlook on potential applications of hydraulic modeling of perforated pipe systems in vertical flow constructed wetlands is given.

scholarly journals NUMERICAL SIMULATION OF 1964 TSUNAMI ACROSS THE PACIFIC OCEAN

1986 ◽  
Vol 1 (20) ◽  
pp. 5
Author(s):  
Michael H. Chen
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Numerical Model ◽  
Pacific Ocean ◽  
Arrival Time ◽  
Two Dimensional ◽  
Open Sea ◽  
The Pacific ◽  
The Pacific Ocean

A two dimensional numerical longwave model using an appropriate open sea boundary condition has been developed. The use of the open-sea boundary condition makes it possible to simulate longwave propagation using a smaller region without covering the entire ocean. The numerical model is used to predict the arrival time of tsunamis resulting from the 1964 Alaskan earthquake at various stations with reasonable success.

Solar Load Ratio Parameters for a Passive Solar Heat Pipe System

2015 ◽  
Author(s):  
Logan S. Poteat ◽  
M. Keith Sharp
Keyword(s):  
Heat Pipe ◽  
Load Ratio ◽  
Building Design ◽  
Weather Data ◽  
Prediction Algorithm ◽  
Solar Heat ◽  
Pipe System ◽  
Thermal Network ◽  
Pipe Systems ◽  
Passive Solar

The Solar Load Ratio (SLR) method is a performance prediction algorithm for passive solar space heating systems developed at Los Alamos National Laboratory. Based on curve fits of detailed thermal simulations of buildings, the algorithm provides fast estimation of monthly solar savings fraction for direct gain, indirect gain (water wall and concrete wall) and sunspace systems of a range of designs. Parameters are not available for passive solar heat pipe systems, which are of the isolated gain type. While modern computers have increased the speed with which detailed simulations can be performed, the quick estimates generated by the SLR method are still useful for early building design comparisons and for educational purposes. With this in mind, the objective of this project was to develop SLR predictions for heat pipe systems, which use heat pipes for one-way transport of heat into the building. A previous thermal network was used to simulate the heat pipe system with Typical Meteorological Year (TMY3) weather data for 13 locations across the US, representing ranges of winter temperature and available sunshine. A range of (nonsolar) load-to-collector ratio LCR = 1–15 W/m2K was tested for each location. The thermal network, along with TMY3 data, provided monthly-average-daily absorbed solar radiation and building load to calculate SLR. Losses from the solar aperture in a heat pipe system are very low compared to conventional passive solar systems, thus the load-to-collector ratio of the solar aperture was neglected in these preliminary calculations. Likewise, nighttime insulation is unnecessary for a heat pipe system, and was not considered. An optimization routine was used to determine an exponential fit (the heart of the SLR method) to simulated monthly solar savings fraction (SSF) across all locations and LCR values. Accuracy of SSF predicted by SLR compared to the thermal network results was evaluated. The largest errors (up to 50%) occurred for months with small heating loads (< 80 K days), which inflated SSF. Limiting the optimization to the heating season (October to March), reduced the error in SSF to an average of 4.24% and a standard deviation of 5.87%. These results expand the applications of the SLR method to heat pipe systems, and allow building designers to use this method to estimate the thermal benefits of heat pipe systems along with conventional direct gain, indirect gain and sunspace systems.

Innovative Configurations of Large Scale Heat Pipes

2005 ◽  
Author(s):  
Jessica Sheehan ◽  
Donald Jordan ◽  
Douglas T. Queheillalt ◽  
Pamela M. Norris
Keyword(s):  
Heat Pipe ◽  
Large Scale ◽  
Heat Pipes ◽  
Heat Spreader ◽  
Pipe System ◽  
Pipe Systems

A large-scale heat pipe is one of many possible solutions to the modern day problem of quickly dissipating high amounts of concentrated heat. While heat pipes are a proven technology, little research has been directed at large-scale heat pipe systems. Two configurations of large-scale heat pipes are investigated in this study. The two configurations examined were a 2’ × 2’ heat spreader plate (a type of heat pipe) and an innovative heat pipe system that combines traditional heat pipes and heat spreader plates. The heat spreader plate, when tested, quickly becomes isothermal and works as a traditional heat pipe. This demonstrates the ability of this large-scale heat pipe configuration to work effectively to spread out high amounts of deposited heat. The experimentation on the innovative heat pipe system gave similar results, showing that the configuration works as a traditional heat pipe.

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