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Challenges and Research Trends of Computational Hydraulics and Fluid Mechanics

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A3: Wind, Wave and Tidal Energy".

Deadline for manuscript submissions: closed (10 January 2022) | Viewed by 10229

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Dipartimento di Ingegneria, Università degli Studi Roma TRE, Via Vito Volterra 62, 00146 Rome, Italy
Interests: computational hydraulics and fluid mechanics; free surface flows; shallow water flows

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Guest Editor
Istituto per le Applicazioni del Calcolo CNR, via dei Taurini 19, 00185 Rome, Italy
Interests: non-equilibrium, rarefied flows, reactive flows in complex media, self-assembly and many-body dynamics in high internal phase emulsions and foams
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Special Issue Information

Dear Colleagues,

This Special Issue will illustrate new research trends in computational hydraulics and fluid mechanics, with a particular focus on renewable energy, sustainability, and environmental issues. Contributions regarding the development of new methods and/or the application of known methods to challenging problems are welcome.

Prof. Michele la Rocca
Dr. Andrea Montessori
Guest Editors

Manuscript Submission Information

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Keywords

  • Computational hydraulics 
  • Computational fluid mechanics 
  • Innovative computational methods 
  • Free surface flows 
  • Shallow water flows 
  • Multiphase flows 
  • Complex flows

Published Papers (5 papers)

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Research

22 pages, 3139 KiB  
Article
Analysis of Performance of Cavitation Models with Analytically Calculated Coefficients
by Andrea Savio, Marta Cianferra and Vincenzo Armenio
Energies 2021, 14(19), 6425; https://doi.org/10.3390/en14196425 - 08 Oct 2021
Cited by 3 | Viewed by 2085
Abstract
Cavitation is often simulated using a mixture model, which considers the transport of an active scalar, namely the vapor fraction αv. Source and sink terms of the transport equation of αv, namely vaporization and condensation terms, rule the dynamics [...] Read more.
Cavitation is often simulated using a mixture model, which considers the transport of an active scalar, namely the vapor fraction αv. Source and sink terms of the transport equation of αv, namely vaporization and condensation terms, rule the dynamics of the cavity and are described through different models. These models contain empirical coefficients generally calibrated through optimization processes. The purpose of this paper is to propose an analytical approach for the calculation of the coefficients, based on the time scales of vaporization and condensation processes. Four different models are compared considering as a test-case a two-dimensional flow around a cylinder. Some relevant quantities are analyzed both for standard value of coefficients, as found in the literature, and the coefficients calculated through the analytical approach. The study shows that the analytical computation of the coefficients of the model substantially improve the results, and the models considered give similar results, both in terms of cavitation regime and mean vapor fraction produced. Full article
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17 pages, 3300 KiB  
Article
Numerical Investigation on Two-Phase Flow Heat Transfer Performance and Instability with Discrete Heat Sources in Parallel Channels
by Changming Hu, Rui Wang, Ping Yang, Weihao Ling, Min Zeng, Jiyu Qian and Qiuwang Wang
Energies 2021, 14(15), 4408; https://doi.org/10.3390/en14154408 - 21 Jul 2021
Cited by 6 | Viewed by 1885
Abstract
With the rapid development of integrated circuit technology, the heat flux of electronic chips has been sharply improved. Therefore, heat dissipation becomes the key technology for the safety and reliability of the electronic equipment. In addition, the electronic chips are distributed discretely and [...] Read more.
With the rapid development of integrated circuit technology, the heat flux of electronic chips has been sharply improved. Therefore, heat dissipation becomes the key technology for the safety and reliability of the electronic equipment. In addition, the electronic chips are distributed discretely and used periodically in most applications. Based these problems, the characteristics of the heat transfer performance of flow boiling in parallel channels with discrete heat source distribution are investigated by a VOF model. Meanwhile, the two-phase flow instability in parallel channels with discrete heat source distribution is analyzed based on a one-dimensional homogeneous model. The results indicate that the two-phase flow pattern in discrete heat source distribution is more complicated than that in continuous heat source distribution. It is necessary to optimize the relative position of the discrete heat sources, which will affect the heat transfer performance. In addition, compared with the continuous heat source, the flow stability of discrete heat sources is better with higher and lower inlet subcooling. With a constant sum of heating power, the greater the heating power near the outlet, the better the flow stability. Full article
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17 pages, 9312 KiB  
Article
Hydraulic Evaluation of the Levee System Evolution on the Kurobe Alluvial Fan in the 18th and 19th Centuries
by Tadaharu Ishikawa and Hiroshi Senoo
Energies 2021, 14(15), 4406; https://doi.org/10.3390/en14154406 - 21 Jul 2021
Cited by 5 | Viewed by 1754
Abstract
The development process and flood control effects of the open-levee system, which was constructed from the mid-18th to the mid-19th centuries, on the Kurobe Alluvial Fan—a large alluvial fan located on the Japan Sea Coast of Japan’s main island—was evaluated using numerical flow [...] Read more.
The development process and flood control effects of the open-levee system, which was constructed from the mid-18th to the mid-19th centuries, on the Kurobe Alluvial Fan—a large alluvial fan located on the Japan Sea Coast of Japan’s main island—was evaluated using numerical flow simulation. The topography for the numerical simulation was determined from an old pictorial map in the 18th century and various maps after the 19th century, and the return period of the flood hydrograph was determined to be 10 years judging from the level of civil engineering of those days. The numerical results suggested the followings: The levees at the first stage were made to block the dominant divergent streams to gather the river flows together efficiently; by the completed open-levee system, excess river flow over the main channel capacity was discharged through upstream levee openings to old stream courses which were used as temporary floodways, and after the flood peak, a part of the flooded water returned to the main channel through the downstream levee openings. It is considered that the ideas of civil engineers of those days to control the floods exceeding river channel capacity, embodied in their levee arrangement, will give us hints on how to control the extraordinary floods that we should face in the near future when the scale of storms will increase due to the global climate change. Full article
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11 pages, 2203 KiB  
Article
Rigid-Flexible Modal Analysis of the Hydraulic 6-DOF Parallel Mechanism
by Chenyang Zhang and Hongzhou Jiang
Energies 2021, 14(6), 1604; https://doi.org/10.3390/en14061604 - 13 Mar 2021
Cited by 4 | Viewed by 1918
Abstract
In view of the problems encountered in previous hydraulic 6-DOF parallel mechanism projects, flexible modes appear that the actual natural frequencies of x and y degrees of freedom of the parallel mechanism are lower than those obtained through calculation. The phenomenon above not [...] Read more.
In view of the problems encountered in previous hydraulic 6-DOF parallel mechanism projects, flexible modes appear that the actual natural frequencies of x and y degrees of freedom of the parallel mechanism are lower than those obtained through calculation. The phenomenon above not only decreases the dynamic response characteristics of the mechanism, but also leads to doubts about the actual performance of the mechanism. The real reason for the phenomenon above is solved in this paper. First the flexible structure of the hydraulic cylinder is analyzed and simplified, and then the dynamic model of the rigid-flexible 6-DOF parallel mechanism is established with the extended Hamilton’s principle. Finally the rigid-flexible modes are calculated with the dynamic model obtained, further analysis and verification with a simulation model and an experimental platform are also conducted. Results show that the phenomenon of the flexible modes is mainly caused by the O-rings of the step-seals of the guide sleeve and those with less elasticity should be adopted to keep the dynamic characteristics of the parallel mechanism. Full article
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12 pages, 2861 KiB  
Article
Experimental Study of the Direct Drive Hydraulic System with the Torque Mode
by Chenyang Zhang and Hongzhou Jiang
Energies 2021, 14(4), 941; https://doi.org/10.3390/en14040941 - 10 Feb 2021
Cited by 1 | Viewed by 1689
Abstract
The torque mode is more suitable for the direct drive 6 degree of freedom (6-DOF) parallel mechanism than the speed mode that both dynamic coupling and current coupling among motors are easily solved, but its key parameters and dynamic characteristics have never been [...] Read more.
The torque mode is more suitable for the direct drive 6 degree of freedom (6-DOF) parallel mechanism than the speed mode that both dynamic coupling and current coupling among motors are easily solved, but its key parameters and dynamic characteristics have never been studied, which are important and are the goals of this paper. First the hydraulic system of the direct drive 6-DOF parallel mechanism is simplified. Then the transfer function of the direct drive hydraulic system with the torque mode is deduced together with that of the speed mode. Finally, comparative experiments are conducted. Results show that the dynamic characteristics of the system with the torque mode which are generally worse than those with the speed mode, are mainly determined by the parameters of the motor-pump second-order element of the transfer function composed of two under-damped second-order elements, proportion differentiation (PD) control strategy and dynamic pressure feedback (DPF) control strategy are useful for the system with the torque mode, but practical and effective methods are still needed. Full article
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