Piping Fluid Transients Made Simple: Part I — Theory of the SSFFC Methodology

2005 ◽  
Author(s):  
Zakaria N. Ibrahim
Keyword(s):  
Fluid Flow ◽  
Steady State ◽  
Fluid Pressure ◽  
Piping System ◽  
Consecutive Series ◽  
Quasi Steady State ◽  
Sound Waves ◽  
Steady State Flow ◽  
State Flow ◽  
Pipe Segment

Piping systems transporting fluid between plant components are subjected to a variety of anticipated and/or postulated flow changes that disturb their steady state operations. These changes cause the fluid flow to accelerate and/or decelerate. However, consideration of fluid elasticity transforms these disturbances into weak and/or strong propagating sound waves, depending upon the abruptness level of the fluid state change. This generates dynamic forces on the pipe segments of the piping system. A simple concept for understanding the piping fluid transient phenomenon from its physical perspective is presented. The piping system consists of several pipe segments, each segment having a constant cross-sectional flow area. The pipe segment is further divided into a consecutive series of zones. Each zone comprises two or three sub-zones of quasi steady state flow. The sub-zones are separated by interface fronts at which the jump in fluid pressure and velocity occurs across them. These fronts propagate and clash with each other to create the next temporal set of sub-zones quasi steady state flow. This method is denoted in this paper as steady state flow fronts clashing ‘SSFFC’. Clashing between the incident, transmitted and/or reflected wave fronts within the zone is introduced. As a precursor to the second part of a two-part publication, the SSFFC is physically illustrated and mathematically formulated to establish the temporal fluid steady state contained within each sub-zone constituting the pipe segment. The developed formulations are comparable to those instituted by the conventional method of characteristics. The pipe segment generalized fluid flow transient forces based on SSFFC methodology are also formulated. In the concurrent publication that forms part two of this presentation [8], sample applications of SSFFC methodology are illustrated.

Piping Fluid Transients Made Simple: Part II — Application of the SSFFC Methods

2005 ◽  
Author(s):  
Zakaria N. Ibrahim
Keyword(s):  
Steady State ◽  
Fluid Pressure ◽  
Piping System ◽  
Consecutive Series ◽  
Quasi Steady State ◽  
Sound Waves ◽  
Steady State Flow ◽  
Flow Area ◽  
Cross Sectional ◽  
State Flow

Piping systems transporting fluid between plant components are subjected to a variety of anticipated and/or postulated flow changes that disturb their steady state operations. These changes cause the fluid flow to accelerate and/or decelerate. However, consideration of fluid elasticity transforms these disturbances into weak and/or strong propagating sound waves, depending upon the abruptness level of the fluid state change. This generates dynamic forces on the pipe segments of the piping system. A simple concept for understanding the piping fluid transient phenomenon from its physical perspective is presented. The piping system consists of several pipe segments, each segment having a constant cross-sectional flow area. The pipe segment is further divided into a consecutive series of zones. Each zone comprises two or three sub-zones of quasi steady state flow. The sub-zones are separated by interface fronts into which the jump in fluid pressure and velocity occurs across them. These fronts propagate and clash with each other to create the next temporal set of sub-zones quasi steady state flow. This method is denoted in this paper as steady state flow fronts clashing ‘SSFFC’. Clashing between the incident, transmitted and/or reflected wave fronts within the zone are introduced. As a follow-up to the first part of this two-part publication, this paper demonstrates two sample applications of SSFFC method utilizing the proposed wave front bookkeeping technique.

A Graphical Method for Storage Coefficient Determination from Quasi-Steady State Flow Data

1996 ◽  
Vol 27 (4) ◽  
pp. 247-254 ◽  
Author(s):  
Zekâi Şen
Keyword(s):  
Steady State ◽  
Graphical Method ◽  
Pumping Test ◽  
Quasi Steady State ◽  
Flow Data ◽  
Steady State Flow ◽  
Storage Coefficient ◽  
State Flow ◽  
Aquifer Test

A simple, approximate but practical graphical method is proposed for estimating the storage coefficient independently from the transmissivity value, provided that quasi-steady state flow data are available from a pumping test. In the past, quasi-steady state flow distance-drawdown data have been used for the determination of transmissivity only. The method is applicable to confined and leaky aquifers. The application of the method has been performed for various aquifer test data available in the groundwater literature. The results are within the practical limits of approximation compared with the unsteady state flow solutions.

scholarly journals Energy separation in transient and steady-state flow across the cylinder

2018 ◽  
Vol 45 (1) ◽  
pp. 83-94
Author(s):  
Jela Burazer
Keyword(s):  
Fluid Flow ◽  
Steady State ◽  
Energy Equation ◽  
Wake Flow ◽  
Energy Separation ◽  
Cylinder Wake ◽  
Flow Conditions ◽  
Steady State Flow ◽  
State Flow ◽  
Transient And Steady State

Energy separation is a spontaneous energy redistribution within a fluid flow. As a consequence, there are places with higher and lower values of total temperature in the fluid flow. It is characteristic for many flow geometries. This paper deals with the energy separation in a cylinder wake. Two flow conditions are being considered-transient and steady-state flow in the wake. Two different solvers from the open source package OpenFOAM are used in order to capture the phenomenon of energy separation. One of these solvers is modified for the purpose of calculation in a particular case of the vortex street flow. The energy equation based on the internal energy present in this solver is replaced by the energy equation written in the form of a total enthalpy. The other solver has been previously tested in the vortex tube flow, and can also capture the energy separation in the steady-state wake flow of the cylinder. In both cylinder wake flow conditions, a two-dimensional computational domain is used. Standard ?? ? ?? model is used for computations. It is proved that OpenFOAM is capable of capturing the energy separation phenomenon in a proper way in both of the wake flow cases. Good agreement between the experimental results and the ones from computations is obtained in the case of steady-state flow in the wake. Previous research findings are also confirmed in the case of vortex street flow.

scholarly journals Storage Coefficient Determination from Quasi-Steady State Flow

1987 ◽  
Vol 18 (2) ◽  
pp. 101-110 ◽  
Author(s):  
Zekâi Şen
Keyword(s):  
Steady State ◽  
Large Diameter ◽  
Field Measurements ◽  
Classical Type ◽  
Quasi Steady State ◽  
Steady State Flow ◽  
Storage Coefficient ◽  
State Flow ◽  
Unconfined Aquifers ◽  
Confined And Unconfined Aquifers

A method has been proposed for determining a unique storage coefficient value for confined and unconfined aquifers tapped by a large diameter well. The prerequisites for the application of this method are estimation of the transmissivity value and the field measurements of well radius, pumping discharge and time-drawdown measurements at large times, or preferably at the steady or quasi-steady state flow conditions. The application of the method does not require any complicated mathematical procedure of the classical type curve matching procedures. It is recommended especially as a supplementary method to the existing techniques in determining the storage coefficient.

Investigation of Steady-State Flow Forces in Spool Valves of Different Geometries and at Different Oil Temperatures With the Help of Measurements and CFD Simulations

2016 ◽  
Author(s):  
Patrik Bordovsky ◽  
Hubertus Murrenhoff
Keyword(s):  
Fluid Flow ◽  
Steady State ◽  
Measurement Data ◽  
Control Valve ◽  
Steady State Flow ◽  
Cfd Simulations ◽  
State Flow ◽  
Axial Forces ◽  
Spool Valves ◽  
Force Characteristics

When designing an actuator for a spool type directional control valve, axial forces acting on the spool have to be estimated. The steady-state flow force is the dominant axial force, which usually acts in the closing direction of the valve. However, many factors such as the valve geometry and the oil properties influence the flow force characteristics. Investigations regarding their effects on steady-state flow forces are described within this paper. Different spool geometries of a test 2/2-way spool valve are used for steady-state flow force measurements at different oil temperatures. The measurement data are used for validation of CFD simulations, which are carried out to scrutinise the flow inside the valve. Besides the steady-state flow forces, the fluid flow angles at the inlet and the outlet of the spool chamber are analysed. The results show that the spool geometry has a significant influence both on the flow rate and the steady-state flow force characteristics. Especially, the shape of the control edge has an impact on the flow patterns and on the magnitudes of steady-state flow forces. Moreover, the inlet and outlet fluid flow angles do not correlate with the expected values, which are commonly used for an analytical estimation of the flow forces. Furthermore, the oil temperature leads to quantitative deviations of the steady-state flow forces.

Calibration 7" – Cutthroat Flume as New Size for Discharge Measurement at Free Flow Condition

2020 ◽  
Vol 38 (12A) ◽  
pp. 1783-1789
Author(s):  
Jaafar S. Matooq ◽  
Muna J. Ibraheem
Keyword(s):  
Steady State ◽  
Flow Condition ◽  
Laboratory Experiments ◽  
Free Flow ◽  
Experimental Program ◽  
Steady State Flow ◽  
Empirical Formulas ◽  
State Flow ◽  
Operation Conditions ◽  
Throat Width

 This paper aims to conduct a series of laboratory experiments in case of steady-state flow for the new size 7 ̋ throat width (not presented before) of the cutthroat flume. For this size, five different lengths were adopted 0.535, 0.46, 0.40, 0.325 and 0.27m these lengths were adopted based on the limitations of the available flume. The experimental program has been followed to investigate the hydraulic characteristic and introducing the calibrated formula for free flow application within the discharge ranged between 0.006 and 0.025 m3/s. The calibration result showed that, under suitable operation conditions, the suggested empirical formulas can accurately predict the values of discharge within an error ± 3%.

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