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Fluids
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Unsteady Flows in Pipes
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Unsteady Flows in Pipes

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: closed (31 July 2022) | Viewed by 18840

Special Issue Editors

Dr. Kamil Urbanowicz

E-Mail Website
Guest Editor
Department of Mechanical Engineering and Mechatronics, West Pomeranian University of Technology Szczecin, Piastów 19, 70-310 Szczecin, Poland
Interests: water hammer; unsteady pipe flow; transient flow, cavitation; unsteady friction; retarded strain; numerical modelling; analytical solutions
Special Issues, Collections and Topics in MDPI journals
Dr. Ali Triki

E-Mail Website
Guest Editor
Advanced Materials, Applied Mechanics, Innovative Processes and Environment (2MPE), Higher Institute of Applied Sciences and Technology of Gabès, University of Gabès, Zrig, Gabès 6029, Tunisia
Interests: storm water management and modeling; hydraulic transients; open-channel hydraulics; physical modeling of hydraulic structures; computational hydraulics; pressurized-pipe flow; water hammer modeling; free-surface flows

Special Issue Information

Dear Colleagues,

Unsteady liquid pipe flow has accompanied humankind since ancient times, however, it was only recently that engineers understood the physical nature of this phenomenon and described it with the known basic equations of fluid mechanics: equations of continuity, motion and energy. 

At present, unsteady pipe flow is still not fully understood, especially in some complicated situations (transient flow with cavitation, air pockets, leaks, etc.). The key issues for this problem may include: single versus multiple phase flow; laminar versus turbulent flow; elastic versus viscoelastic strain behavior; gaseous versus vaporous cavitation; accelerated versus pulsatile flow; Newtonian versus non-Newtonian flow; rigid versus flexible pipe walls; and fast (impulsive) versus slow-transient flow. Consideration of the aforementioned issues should often include the selected accompanying phenomena: mechanical energy dissipation due to fluid friction (frequency-dependent friction); mechanical energy dissipation due to the occurrence of viscoelastic retarded deformations of the pipe walls; liquid column separation resulting from cavitation; fluid structure interaction, etc.

Hydraulic, water supply and cooling systems as well as their various components are exposed to extreme transient states caused by the dynamic excitation forces, which result from either abrupt changes in the hydraulic motor or actuator load, or from changes in the direction or velocity of the working liquid flow. For the design of automatic control systems, it is vital to accurately determine the characteristics of the dynamic processes in transient states. This is also essential for the analysis of the strength of pipes and other system components. 

The aim of this Special Issue is to collect a variety of theoretical, analytical, computational and experimental papers about fluid transients in pipes. Moreover, all studies involving non-Newtonian unsteady fluid pipe flow are also welcome.

Dr. Kamil Urbanowicz
Dr. Ali Triki
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • transient pipe flow
  • water hammer
  • column separation
  • viscoelastic pipe
  • unsteady friction
  • frequency-dependent model
  • analytical solution
  • cavitation
  • unsteady flow
  • numerical methods
  • method of characteristics
  • partial differential equations
  • retarded strain

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Published Papers (6 papers)

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Research

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15 pages, 468 KiB  
Article
New Dimensionless Number for the Transition from Viscous to Turbulent Flow
by Carmine Di Nucci, Daniele Celli, Davide Pasquali and Marcello Di Risio
Fluids 2022, 7(6), 202; https://doi.org/10.3390/fluids7060202 - 13 Jun 2022
Cited by 3 | Viewed by 2209
Abstract
Within the framework of Classical Continuum Thermomechanics, we consider an unsteady isothermal flow of a simple isotropic linear viscous fluid in the liquid state to investigate the transient flow conditions. Despite the attention paid to this problem by several research works, it seems [...] Read more.
Within the framework of Classical Continuum Thermomechanics, we consider an unsteady isothermal flow of a simple isotropic linear viscous fluid in the liquid state to investigate the transient flow conditions. Despite the attention paid to this problem by several research works, it seems that the understanding of turbulence in these flow conditions is controversial. We propose a dimensionless procedure that highlights some aspects related to the transition from viscous to turbulent flow which occurs when a finite amplitude pressure wave travels through the fluid. This kind of transition is demonstrated to be described by a (first) dimensionless number, which involves the bulk viscosity. Furthermore, in the turbulent flow regime, we show the role played by a (second) dimensionless number, which involves the turbulent bulk viscosity, in entropy production. Within the frame of the 1D model, we test the performance of the dimensionless procedure using experimental data on the pressure waves propagation in a long pipe (water hammer phenomenon). The obtained numerical results show good agreement with the experimental data. The results’ inspection confirms the predominant role of the turbulent bulk viscosity on energy dissipation processes. Full article
(This article belongs to the Special Issue Unsteady Flows in Pipes)
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13 pages, 52520 KiB  
Article
High-Speed Imaging of Water Hammer Cavitation in Oil–Hydraulic Pipe Flow
by Marcus Jansson, Magnus Andersson and Matts Karlsson
Fluids 2022, 7(3), 102; https://doi.org/10.3390/fluids7030102 - 9 Mar 2022
Cited by 5 | Viewed by 3190
Abstract
A pipe water hammer with column separation was studied in a range of flow rates (Re=465 to 2239) in a test rig with an acrylic glass observation section. Pressure transients were measured with piezoresistive pressure sensors, while the gas [...] Read more.
A pipe water hammer with column separation was studied in a range of flow rates (Re=465 to 2239) in a test rig with an acrylic glass observation section. Pressure transients were measured with piezoresistive pressure sensors, while the gas evaporation and condensation were captured by high-speed recording with a Photron SA-Z at a frame rate of 75,000 fps. Separation lengths were estimated by a threshold value in the images. The results did not show a sharp gas–oil interface but consisted of small, dispersed bubbles mixed with larger vapor structures, where the bubbles seemed to become smaller after each collapse. These findings differ from the transient cavitating characteristics commonly reported in nonhydraulic piping systems governed by different fluid properties and time scales. Good repeatability, both in terms of pressure transients and bubble distribution, was observed. The column separation was quantified as a metric of separation length, which was consistent between the tests. Combined with pressure measurements, these results may assist in obtaining a better understanding of the transient cavitation dynamics within oil–hydraulic systems as well as be used to improve modelling strategies towards more accurate cavitation erosion predictions. Full article
(This article belongs to the Special Issue Unsteady Flows in Pipes)
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29 pages, 158835 KiB  
Article
Pipeline Condition Assessment by Instantaneous Frequency Response over Hydroinformatics Based Technique—An Experimental and Field Analysis
by Muhammad Hanafi Yusop, Mohd Fairusham Ghazali, Mohd Fadhlan Mohd Yusof and Muhammad Aminuddin Pi Remli
Fluids 2021, 6(11), 373; https://doi.org/10.3390/fluids6110373 - 21 Oct 2021
Cited by 1 | Viewed by 1923
Abstract
A common issue in water infrastructure is that it suffers from leakage. The hydroinformatics technique for recognizing the presence of leaks in the pipeline system by means of pressure transient analysis was briefly explored in this study. Various studies have been done of [...] Read more.
A common issue in water infrastructure is that it suffers from leakage. The hydroinformatics technique for recognizing the presence of leaks in the pipeline system by means of pressure transient analysis was briefly explored in this study. Various studies have been done of improvised leak detection methods, and Hilbert Huang Transform has the potential to overcome the concern. The HHT processing algorithm has been successfully proven through simulation and experimentally tested to evaluate the ability of pressure transient analysis to predict and locate the leakage in the pipeline system. However, HHT relies on the selection of the suitable IMF in the pre-processing phase which will determine the precision of the estimated leak location. This paper introduces a NIKAZ filter technique for automatic selector of Intrinsic Mode Function (IMF). A laboratory-scale experimental test platform was constructed with a 68-metre long Medium Polyethylene (MDPE) pipe with 63 mm in diameter used for this study and equipped with a circular orifice as an artificial leak in varying sizes with a system of 2 bar to 4 bar water pressure. The results showed that, although with a low ratio of signal-to-noise, the proposed method could be used as an automatic selector for Intrinsic Mode Function (IMF). Experimental tests showed the efficiency, and the work method was successful as an automatic selector of IMF. The proposed mathematical algorithm was then finally evaluated on field measurement tested on-site of a real pipeline system. The results recommended NIKAZ as an automatic selector of IMF to increase the degree of automation of HHT technique, subsequently enhancing the detection and identification of water pipeline leakage. Full article
(This article belongs to the Special Issue Unsteady Flows in Pipes)
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11 pages, 26452 KiB  
Article
Numerical Analysis for Heat Transfer Augmentation in a Circular Tube Heat Exchanger Using a Triangular Perforated Y-Shaped Insert
by Lokesh Pandey and Satyendra Singh
Fluids 2021, 6(7), 247; https://doi.org/10.3390/fluids6070247 - 5 Jul 2021
Cited by 9 | Viewed by 2952
Abstract
The present investigation constitutes CFD analysis of the heat transmission phenomenon in a tube heat exchanger with a Y-shaped insert with triangular perforation. The analysis is accomplished by considering air as a working fluid with a Reynolds number ranging from 3000 to 21,000. [...] Read more.
The present investigation constitutes CFD analysis of the heat transmission phenomenon in a tube heat exchanger with a Y-shaped insert with triangular perforation. The analysis is accomplished by considering air as a working fluid with a Reynolds number ranging from 3000 to 21,000. The segment considered for analysis consists of a circular tube of 68 mm diameter and 1.5 m length. The geometrical parameter considered is the perforation index (0%, 10%, 20%, and 30%). The constant heat flux is provided at the tube wall and a pressure-based solver is used for the solution. The studies are performed for analyzing the effects of inserts on the heat transfer and friction factor in the circular tube heat exchanger which results in augmented heat transfer at a higher perforation index (PI) and lower friction factor. The investigation results show that the highest heat transfer is 5.84 times over a simple plain tube and the maximum thermal performance factor (TPF) is 3.25 at PI = 30%, Re = 3000. Full article
(This article belongs to the Special Issue Unsteady Flows in Pipes)
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14 pages, 3388 KiB  
Article
An Analytical Solution for Unsteady Laminar Flow in Tubes with a Tapered Wall Thickness
by Travis Wiens and Elnaz Etminan
Fluids 2021, 6(5), 170; https://doi.org/10.3390/fluids6050170 - 23 Apr 2021
Cited by 3 | Viewed by 2724
Abstract
Transient fluid flows through tubes are critical in such topics as water hammer, ram pumps and pipeline dynamics. While analytical solutions exist in the literature for simple geometries such as tapered and non-tapered tube diameters, one area that is lacking is the case [...] Read more.
Transient fluid flows through tubes are critical in such topics as water hammer, ram pumps and pipeline dynamics. While analytical solutions exist in the literature for simple geometries such as tapered and non-tapered tube diameters, one area that is lacking is the case where the wave speed changes along the length. An example of this is a flexible pipe with a tapered wall thickness. In order to calculate the transient pressure response of such a system, this previously required a computationally expensive gridded method of characteristics (MOC) solution. This paper describes an analytical solution to the dynamic laminar flow of liquid in a tube where the wave speed varies along its length. This frequency-domain solution includes frequency-dependent friction effects. A comparison to a method of characteristics (MOC) solution is used to verify the solution. The paper also discusses some numerical issues and provides an approximate method that can be used for high-frequency calculations where limited numerical precision can cause errors. Finally, a preliminary comparison of the computational performance is presented, in which the new method is an order of magnitude faster to calculate than an MOC solution. Full article
(This article belongs to the Special Issue Unsteady Flows in Pipes)
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Review

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15 pages, 1349 KiB  
Review
Detection of Partial Blockages in Pressurized Pipes by Transient Tests: A Review of the Physical Experiments
by Bruno Brunone, Filomena Maietta, Caterina Capponi, Huan-Feng Duan and Silvia Meniconi
Fluids 2023, 8(1), 19; https://doi.org/10.3390/fluids8010019 - 3 Jan 2023
Cited by 14 | Viewed by 3031
Abstract
Pressure waves, while traveling along pressurized pipes, collect precious information about possible faults (e.g., leaks and partial blockages). In fact, the characteristics of the pressure wave reflected by the fault are strongly related to it. To encourage the use of the transient test-based [...] Read more.
Pressure waves, while traveling along pressurized pipes, collect precious information about possible faults (e.g., leaks and partial blockages). In fact, the characteristics of the pressure wave reflected by the fault are strongly related to it. To encourage the use of the transient test-based technologies (TTBTs) for partial blockage (PB) detection in pressurized pipe systems, it can be of interest to critically analyze the available experimental results and to point out the aspects that need to be investigated in more detail, since no review has been executed so far. Such a deficiency has two negative consequences. The first one is that TTBTs are still relegated to limbo by technicians. The second one is that not enough material is available for refining tools to extract all the information contained in the acquired pressure signals and then to pursue an effective PB detection. As main results of the executed analysis, the following issues can be counted: (i) the lack of tests carried out in large diameter and concrete pipes; (ii) the absence of tests carried out in complex pipe systems (e.g., looped networks); and (iii) the extreme need for considering real pipe systems. The fulfillment of the last issue will greatly contribute to the solutions of the other ones. Full article
(This article belongs to the Special Issue Unsteady Flows in Pipes)
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