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

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 64 ◽  
Author(s):  
Rune Jensen ◽  
Jesper Larsen ◽  
Kasper Lassen ◽  
Matthias Mandø ◽  
Anders Andreasen
Keyword(s):  
Steady State ◽  
Water Hammer ◽  
Momentum Balance ◽  
Column Separation ◽  
Method Of Solution ◽  
Upstream Reservoir ◽  
Friction Models ◽  
Free Open Source ◽  
Free Code ◽  
Instantaneous Acceleration

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.

scholarly journals Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

Optimum Selection of Hydraulic Devices for Water Hammer Control in the Pipeline Systems Using Genetic Algorithm

2003 ◽  
Author(s):  
Bong Seong Jung ◽  
Bryan W. Karney
Keyword(s):  
Genetic Algorithm ◽  
Steady State ◽  
Optimization Problems ◽  
System Optimization ◽  
Water Hammer ◽  
Pipeline System ◽  
Optimal Size ◽  
Protection Strategy ◽  
Hydraulic Devices ◽  
Selection Of

Genetic algorithms have been used to solve many water distribution system optimization problems, but have generally been limited to steady state or quasi-steady state optimization. However, transient events within pipe system are inevitable and the effect of water hammer should not be overlooked. The purpose of this paper is to optimize the selection, sizing and placement of hydraulic devices in a pipeline system considering its transient response. A global optimal solution using genetic algorithm suggests optimal size, location and number of hydraulic devices to cope with water hammer. This study shows that the integration of a genetic algorithm code with a transient simulator can improve both the design and the response of a pipe network. This study also shows that the selection of optimum protection strategy is an integrated problem, involving consideration of loading condition, device and system characteristics, and protection strategy. Simpler transient control systems are often found to outperform more complex ones.

Application of Differential Transform Method to Heat Conduction in Tapered Fins

2001 ◽  
Vol 124 (1) ◽  
pp. 208-209 ◽  
Author(s):  
Charles W. Bert
Keyword(s):  
Heat Conduction ◽  
Steady State ◽  
Special Functions ◽  
Differential Transform Method ◽  
Series Method ◽  
Transform Method ◽  
Differential Transform ◽  
Method Of Solution ◽  
Triangular Profile ◽  
Steady State Heat

This paper analyzes steady-state heat conduction in a triangular-profile fin using a relatively new, exact series method of solution known as the differential transform method. This method converges with only six terms or less for the cases considered. Its advantage is that, unlike many popular methods, it is an exact method and yet it does not require the use of Bessel or other special functions.

Thermal Stresses in Transversely Isotropic Semi-Infinite Elastic Solids

1958 ◽  
Vol 25 (1) ◽  
pp. 86-88
Author(s):  
Brahmadev Sharma
Keyword(s):  
Thermal Stress ◽  
Steady State ◽  
Thermal Stresses ◽  
Elastic Solid ◽  
Transversely Isotropic ◽  
Elastic Solids ◽  
Stress Problem ◽  
Method Of Solution ◽  
General Method

Abstract A general method of solution of the steady-state thermal-stress problem of a transversely isotropic semi-infinite elastic solid is given in this paper.

Energy-Based Evaluation of 1D Unsteady Friction Models for Classic Laminar Water Hammer with Comparison to CFD

2020 ◽  
Vol 146 (3) ◽  
pp. 04019072
Author(s):  
Sharon Mandair ◽  
Robert Magnan ◽  
Jean-François Morissette ◽  
Bryan Karney
Keyword(s):  
Water Hammer ◽  
Friction Models

scholarly journals Dissipated work, stability and the internal flow structure of granular snow avalanches

2005 ◽  
Vol 51 (172) ◽  
pp. 125-138 ◽  
Author(s):  
Perry Bartelt ◽  
Othmar Buser ◽  
Martin Kern
Keyword(s):  
Steady State ◽  
Entropy Production ◽  
Dissipative Systems ◽  
Momentum Balance ◽  
Granular System ◽  
Snow Avalanches ◽  
Equilibrium Thermodynamics ◽  
Layer System ◽  
Constitutive Parameters ◽  
Non Equilibrium

AbstractWe derive work dissipation functionals for granular snow avalanches flowing in simple shear. Our intent is to apply constructive theorems of non-equilibrium thermodynamics to the snow avalanche problem. Snow chute experiments show that a bi-layer system consisting of a non-yielded flow plug overriding a sheared fluidized layer can be used to model avalanche flow. We show that for this type of constitutive behaviour the dissipation functionals are minimum at steady state with respect to variations in internal velocity; however, the functionals must be constrained by subsidiary mass- continuity integrals before the equivalence of momentum balance and minimal work dissipation can be established. Constitutive models that do not satisfy this equivalence are henceforth excluded from our consideration. Fluctuations in plug and slip velocity depend on the roughness of the flow surface and viscosity of the granular system. We speculate that this property explains the transition from flowing avalanches to powder avalanches. Because the temperature can safely be assumed constant, we demonstrate within the context of non-equilibrium thermodynamics that granular snow avalanches are irreversible, dissipative systems, minimizing – in space – entropy production. Furthermore, entropy production is linear both near and far from steady-state non-equilibrium because of the mass-continuity constraint. Finally, we derive thermodynamic forces and conjugate fluxes as well as expressing the corresponding phenomenological Onsager coefficients in terms of the constitutive parameters.

scholarly journals Influence of Combined Empirical Functions on Slug Flow Predictions of Pipelines With Variable Inclinations

2020 ◽  
Author(s):  
Hossein Zanganeh ◽  
Victoria Kurushina ◽  
Narakorn Srinil ◽  
Omar K. Matar
Keyword(s):  
Steady State ◽  
Slug Flow ◽  
Gas Flow ◽  
Mechanistic Model ◽  
Gas Production ◽  
High Mass ◽  
Momentum Balance ◽  
Liquid Holdup ◽  
Wide Range ◽  
Slug Flows

Abstract Prediction of internal multiphase flows in subsea pipelines is an integral part of the oil and gas production system design. High mass and pressure fluctuations are often encountered during the operation with a liquid-gas slug flow regime exhibiting a sequence of long gas bubbles and aerated liquid slugs. It is important for industry to realistically identify the slug flow occurrence and predict slug flow characteristics, depending on several multiphase flow-pipe parameters. These may be achieved using a one-dimensional, steady-state, mechanistic model accounting for a mass and momentum balance of the two liquid-gas fluids within a controlled volume often referred to as a slug unit. By reducing a 3-D flow problem to a 1-D one, several empirical or closure correlations and associated empirical coefficients have been introduced in the literature and used in commercial software predicting slug flows in subsea jumpers, pipelines and risers with variable inclinations. This study aims to investigate the influence of combined 25 closure functions on the predictions of slug flows in horizontal and inclined pipes based on a steady-state mechanistic model for a wide range of superficial liquid and gas velocities. The model with studied closures is implemented by the authors of this study as the numerical tool iSLUG. The model performance is verified with respect to the estimated film liquid holdup, film length and pressure drop per length of a slug unit for an empirically specified translational velocity, slug liquid holdup, slug liquid length and pipe wall wettability. Closure combinations are analyzed using the relative performance factors and compared against available experimental data in order to identify a set of functions suitable for upward, downward and horizontal flows, and the effect of diameter and inclination on the model prediction is considered. The present method and analysis outcomes may further contribute to the improvement of transient liquid-gas flow models to predict more practical cases.

Large Water‐Hammer Pressures for Column Separation in Pipelines

1991 ◽  
Vol 117 (10) ◽  
pp. 1310-1316 ◽  
Author(s):  
Angus R. Simpson ◽  
E. Benjamin Wylie
Keyword(s):  
Water Hammer ◽  
Column Separation ◽  
Large Water

Water Hammer and Column Separation Due to Accidental Simultaneous Closure of Control Valves in a Large Scale Two-Phase Flow Experimental Test Rig

2010 ◽  
Author(s):  
Anton Bergant ◽  
Jos M. C. van ’t Westende ◽  
Tiit Koppel ◽  
Janez Gale ◽  
Qingzhi Hou ◽  
...  
Keyword(s):  
Large Scale ◽  
Water Hammer ◽  
Water Levels ◽  
Test Rig ◽  
Two Phase ◽  
Transient Event ◽  
Control Valves ◽  
Column Separation ◽  
Pipe Joints ◽  
Large Water

A large-scale pipeline test rig at Deltares, Delft, The Netherlands has been used for filling and emptying experiments. Tests have been conducted in a horizontal 250 mm diameter PVC pipe of 258 m length with control valves at the downstream and upstream ends. This paper investigates the accidental simultaneous closure of two automatic control valves during initial testing of the test rig. The simultaneous closure of both valves has induced upsurge and downsurge at the same time. Large water hammer and column separation have caused failure of pipe supports and leakage at pipe joints. The incident was caused by a fault in an electronic conversion box due to power failure. Afterwards the downstream end automatic valve has been modified to a manually operated valve to avoid the accidental simultaneous closure of the valves. The accidental transient event has been fully recorded with pressures, flow rates and water levels. The measurements of the accident are presented, analyzed and discussed in detail. Photographs show the damages to the system.

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