Latest Developments in Fluid Mechanics and Energy

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Mechanics applmech	-	1.4	2020	22.5 Days	CHF 1200
Applied Sciences applsci	2.7	4.5	2011	16.9 Days	CHF 2400
Energies energies	3.2	5.5	2008	16.1 Days	CHF 2600
Fluids fluids	1.9	2.8	2016	20.7 Days	CHF 1800
Journal of Marine Science and Engineering jmse	2.9	3.7	2013	15.4 Days	CHF 2600
Processes processes	3.5	4.7	2013	13.7 Days	CHF 2400

15 pages, 3332 KiB

Open AccessArticle

Changes in the Available Potential and Kinetic Energy of Mesoscale Vortices When They Are Stretched into Filaments

by Vladimir V. Zhmur, Tatyana V. Belonenko, Vladimir S. Travkin, Elena V. Novoselova, David A. Harutyunyan and Roshin P. Raj

J. Mar. Sci. Eng. 2023, 11(6), 1131; https://doi.org/10.3390/jmse11061131 - 27 May 2023

Viewed by 1398

Abstract

The article discusses various aspects of the interaction of vortices with the barotropic flow. Vortex interaction with a flow results in rotation variants, nutational oscillations, and unlimited stretching of its core. The vortex remains in a localized formation, with the semi-axes of the [...] Read more.

The article discusses various aspects of the interaction of vortices with the barotropic flow. Vortex interaction with a flow results in rotation variants, nutational oscillations, and unlimited stretching of its core. The vortex remains in a localized formation, with the semi-axes of the ellipse experiencing fluctuations near an average value in the first two cases. In the third case, the vortex is significantly elongated, and its shape in the horizontal plane changes as follows: one axis of the ellipse increases, and the other decreases. In this case, the vortex, when viewed from above, stretches into a thread, while remaining ellipsoidal. These vortex formations are called filaments. The latter arise from initially almost circular vortices in the horizontal plane and represent structures with non-zero vorticity elongated in one direction. Here, we aim to study the energy transformation of a vortex during its evolution process, mainly due to changes in its shape by stretching. The energy evolution of a mesoscale vortex located in the Norwegian Sea is analyzed using GLORYS12V1 ocean reanalysis data to verify the theoretical conclusions. During the evolution, the vortex is found to transform from a round shape and becomes elongated, and after three weeks its longitudinal scale becomes 4 times larger than the transverse one. During the transformation of a vortex, the kinetic energy and available potential energy decrease respectively by 3 times and 1.7 times. Concurrently, the total energy of the vortex is found to decrease by 2.3 times. We argue that the stretching of vortices results in a loss of energy as well as its redistribution from mesoscale to submesoscale. The lost part of the energy returns to the flow and results in the occurrence of the reverse energy cascade phenomenon. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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23 pages, 11637 KiB

Open AccessArticle

Experimental and Numerical Investigation on Slamming Mechanism of a Mooring Column-Stabilised Semi-Submersible

by Zhi Yao, Fali Huo, Yuanyao Zhu, Chenxuan Tang, Kunqiao Jia, Dong Li and Yong Ma

Processes 2023, 11(3), 725; https://doi.org/10.3390/pr11030725 - 28 Feb 2023

Cited by 1 | Viewed by 1141

Abstract

Semi-submersible offshore platforms play a vital role in deep-sea energy exploitation. However, the vast waves threaten the platform’s operation, usually leading to severe consequences. It is essential to study the wave-slamming mechanism of offshore platforms under extreme wave conditions. Existing research usually simplifies [...] Read more.

Semi-submersible offshore platforms play a vital role in deep-sea energy exploitation. However, the vast waves threaten the platform’s operation, usually leading to severe consequences. It is essential to study the wave-slamming mechanism of offshore platforms under extreme wave conditions. Existing research usually simplifies the offshore platform slamming problem. This paper establishes a model of a semi-submersible platform and a flexible mooring system in a numerical pool by means of the computational fluid dynamics (CFD) method. The distribution and the sensitivity of the slamming load on columns and deck in waves were investigated, and the model was verified through the basin test. Firstly, based on the Reynolds-averaged Navier–Stokes model, this study considers the volume-of-fluid method to track the free liquid level. After the column and floating body grid are locally refined, the slamming load under extreme regular wave impact is measured by measuring points on the column and deck. Then, the slamming experiment of the semi-submersible was carried out in the basin. The experiment model with a scale ratio of 1:100 was established to investigate the platform’s motion and slamming loads under extreme regular and irregular waves. The findings indicate that the slamming load at the junction of the column and deck significantly increased, exhibiting a ‘double-peak’ phenomenon at the middle of the column. The maximum pressure of slamming at the top of the column demonstrated an inverted U-shaped distribution, with negative pressure occurring after the peak value, indicating a pronounced oscillation effect. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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22 pages, 17915 KiB

Open AccessArticle

The PIV Measurements of Time-Averaged Parameters of the Synthetic Jet for Different Orifice Shapes

by Emil Smyk, Paweł Gil, Petra Dančová and Miroslav Jopek

Appl. Sci. 2023, 13(1), 328; https://doi.org/10.3390/app13010328 - 27 Dec 2022

Cited by 1 | Viewed by 1870

Abstract

In the present study, the flow fields generated by a synthetic jet (SJ) were investigated with particle image velocimetry (PIV). The SJ time-averaged parameters, such as velocity, turbulent kinetic energy (TKE), and vorticity, were compared by using the Reynolds number ( [...] Read more.

In the present study, the flow fields generated by a synthetic jet (SJ) were investigated with particle image velocimetry (PIV). The SJ time-averaged parameters, such as velocity, turbulent kinetic energy (TKE), and vorticity, were compared by using the Reynolds number (

R e = 5000

) and dimensionless stroke length (

L_{0} = 2; 10

). Three different orifice shapes with the same equivalent diameter were used: circle, square, and slot. The flow fields of the investigated parameters were presented and discussed at a distance from the orifice

x / d \leq 10

, and the difference in radial and axial profiles were compared. The impact of the orifice shape and dimensionless stroke length on the investigated parameters was discussed. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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11 pages, 5290 KiB

Open AccessArticle

Pressure Losses Downstream of a Compact Valve in the Inlet Chamber of an Intermediate-Pressure Steam Turbine

by Vaclav Slama, David Simurda and Richard Lenhard

Energies 2022, 15(22), 8753; https://doi.org/10.3390/en15228753 - 21 Nov 2022

Viewed by 1554

Abstract

Deep knowledge about pressure and energy losses in each part of a steam turbine is crucial for assuring the required efficiency and operational reliability. This paper presents the experimental as well as the numerical study of pressure losses in the inlet chamber of [...] Read more.

Deep knowledge about pressure and energy losses in each part of a steam turbine is crucial for assuring the required efficiency and operational reliability. This paper presents the experimental as well as the numerical study of pressure losses in the inlet chamber of an intermediate-pressure steam turbine. Measurements were carried out on a complex model, where not only was there an inlet turbine chamber, but also a compact valve assembly situated upstream and nozzles situated downstream. The compact valve as well as the turbine inlet chamber were relatively small. Therefore, greater pressure losses were expected. The aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences was responsible for acquiring the measurements, which were carried out in a modular in-draft wind tunnel. In order to learn further details, numerical simulations were carried out. Doosan Skoda Power was responsible for this. A package of ANSYS software tools was used. Measured data were described and compared with numerical ones. Pressure losses were generalized in the form of the total pressure loss coefficient. As a result, pressure losses in similar turbine compact inlet chambers can be predicted with the required accuracy. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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17 pages, 2518 KiB

Open AccessTechnical Note

An Analytical Solution to Two-Region Flow Induced by Constant-Head Pumping in an Unconfined Aquifer

by Yijie Zong and Liang Xiao

Appl. Sci. 2022, 12(22), 11493; https://doi.org/10.3390/app122211493 - 12 Nov 2022

Cited by 1 | Viewed by 1231

Abstract

This paper proposes an analytical solution to the problem of two-region flow induced by constant-head pumping tests in an unconfined aquifer based on the Dupuit assumption. The two-region flow includes a finite non-Darcian pattern near the pumping well and a semi-finite Darcian pattern [...] Read more.

This paper proposes an analytical solution to the problem of two-region flow induced by constant-head pumping tests in an unconfined aquifer based on the Dupuit assumption. The two-region flow includes a finite non-Darcian pattern near the pumping well and a semi-finite Darcian pattern in the rest region. By Izbash’s equation, the solution to the two-region flow is derived using the Boltzmann method. The reliability of the proposed solution is investigated through comparisons with the numerical solution by COMSOL Multiphysics and the hydraulic head−time data from the pumping test in Wisconsin. The influences of the finite non-Darcian flow pattern on the hydraulic head and pumping rate are also discussed. The results demonstrate that a greater degree of non-Darcian turbulence can effectively increase the pumping flow rate, although such influence can be reduced over time. A method for determining the range of the non-Darcian region has been developed and validated by the specific discharge and Reynolds number. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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17 pages, 5113 KiB

Open AccessArticle

An Analysis of Energy and Internal Flow Characteristics of Open Inlet Channel Axial Flow Pumping Devices

by Chuanliu Xie, Cheng Zhang, Tenglong Fu, Andong Feng, Tao Zhang and Fan Yang

Processes 2022, 10(11), 2284; https://doi.org/10.3390/pr10112284 - 04 Nov 2022

Viewed by 1119

Abstract

For the purpose of studying the dynamic and inner flow features of an open inlet channel axial flow pump unit, in the present study, numerical calculations using the SST k-ω turbulence model are applied to an open inlet channel axial flow [...] Read more.

For the purpose of studying the dynamic and inner flow features of an open inlet channel axial flow pump unit, in the present study, numerical calculations using the SST k-ω turbulence model are applied to an open inlet channel axial flow pumping unit based on the NS equation, and experimental validation is then performed. The experimental output indicates that the designed working conditions are Q = 350 L/s, head H = 5.065 m, efficiency η = 79.56%, and the maximum operating head is H = 9.027 m, which is about 1.78 times that of the design head; further, the pump device can operate in a wide range of working conditions. In addition, the design working conditions are within the range of high-efficiency operating conditions. The calculated values and the experimental comparison are all within a 5.0% margin of error; further, the numerical calculations are reliable. The hydraulic loss of the inlet channel under the design condition Q = 350 L/s is 0.0676 m, which satisfies the relationship of the quadratic function. The uniformity of the impeller inlet velocity is 80.675%, and the weighted average angle of the velocity is 79.223°. The hydraulic loss of the outlet channel under the design condition Q = 350 L/s is 0.3183 m, and the hydraulic loss curve is a parabola with an upward opening. The flow state of the pump device is sensitive to changes in the working conditions; additionally, the flow state is optimal under the design working conditions. In this study, the energy and inner flow features of the open inlet axial flow pumping units are revealed, and the research outcomes can be used as a reference for the design and operation of similar pumping units. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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25 pages, 27715 KiB

Open AccessArticle

Turbulent Eddy Generation for the CFD Analysis of Hydrokinetic Turbines

by Matteo Gregori, Francesco Salvatore and Roberto Camussi

J. Mar. Sci. Eng. 2022, 10(10), 1332; https://doi.org/10.3390/jmse10101332 - 20 Sep 2022

Viewed by 1458

Abstract

This paper presents a novel theoretical and computational methodology for the generation of an onset turbulent field with prescribed properties in the numerical simulation of an arbitrary viscous flow. The methodology is based on the definition of a suitable distribution of volume force [...] Read more.

This paper presents a novel theoretical and computational methodology for the generation of an onset turbulent field with prescribed properties in the numerical simulation of an arbitrary viscous flow. The methodology is based on the definition of a suitable distribution of volume force terms in the right-hand side of the Navier–Stokes equations. The distribution is represented by harmonic functions that are randomly variable in time and space. The intensity of the distribution is controlled by a simple PID strategy in order to obtain that the generated turbulent flow matches a prescribed turbulence intensity. A further condition is that a homogeneous isotropic flow is established downstream of the region where volume force terms are imposed. Although it is general, the proposed methodology is primarily intended for the computational modelling of hydrokinetic turbines in turbulent flows representative of tidal or riverine installations. A first numerical application is presented by considering the injection of homogeneous and isotropic turbulence with 16% intensity into a uniform unbounded flow. The analysis of statistical properties as auto-correlation, power spectral density, probability density functions, demonstrates that the generated flow tends to achieve satisfactory levels of stationarity and isotropy, whereas the simple control strategy used determines underestimated turbulent intensity levels. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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17 pages, 6416 KiB

Open AccessArticle

Experimental Investigation on Ignition of Hyperburner Based on Gliding Arc Plasma Igniter Driven by Pressure Difference

by Xinyao Cheng, Huimin Song, Jiulun Sun, Wei Cui, Zhibo Zhang, Min Jia, Di Jin and Yifei Zhu

Processes 2022, 10(9), 1886; https://doi.org/10.3390/pr10091886 - 17 Sep 2022

Cited by 1 | Viewed by 1336

Abstract

The hyperburner is a key component of a TBCC engine, and its reliable ignition and stable operation are critical. The gliding arc plasma igniter driven by differential pressure has the technical advantages of low energy consumption and high jet temperature. In this paper, [...] Read more.

The hyperburner is a key component of a TBCC engine, and its reliable ignition and stable operation are critical. The gliding arc plasma igniter driven by differential pressure has the technical advantages of low energy consumption and high jet temperature. In this paper, the electrical and flow characteristics of the gliding arc plasma igniter are studied, and the basic ignition experiment in the hyperburner is carried out. Electrical characteristic experiments show that the discharge duration, the evolution of the gliding arc and the fracture frequency are affected by the pressure difference between the inlet and outlet of the igniter (Δp). With the increase in Δp, the frequency of the trapezoidal envelope in the voltage and current waveforms increases, and the frequency of the evolution and fracture of the gliding arc increases. The continuous discharge time of the gliding arc decreases when Δp = 550 Torr. The flow characteristic experiments show that the velocity of the swirl sheath is increased and the protective effect on the gliding arc is enhanced with the increase in Δp. In the range of 20–550 Torr, the jet length first increases and then decreases with the increase in Δp. The jet length reaches a maximum of 31 mm at Δp = 50 Torr. Basic ignition experiments show that proper Δp can widen the lean ignition limit and shorten the ignition delay time. In the working conditions of this paper, the ignition effect is the best when Δp = 350 Torr, which can widen the lean ignition limit by 37.5% and shorten the ignition delay time by 17%. After increasing the oil–gas ratios, the combustion is more complete and the ignition delay time can be shortened by 93.1% at most. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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14 pages, 7362 KiB

Open AccessArticle

Optimization Design and Internal Flow Analysis of Prefabricated Barrel in Centrifugal Prefabricated Pumping Station with Double Pumps

by Chuanliu Xie, Tao Zhang, Zhenyang Yuan, Andong Feng and Liming Wu

Processes 2022, 10(9), 1877; https://doi.org/10.3390/pr10091877 - 16 Sep 2022

Cited by 2 | Viewed by 1235

Abstract

In order to improve the hydraulic performance of the centrifugal prefabricated pumping station and improve its internal flow pattern, this paper optimizes the geometric model of the centrifugal prefabricated pumping station based on the orthogonal optimization method. Through the subjective analysis method and [...] Read more.

In order to improve the hydraulic performance of the centrifugal prefabricated pumping station and improve its internal flow pattern, this paper optimizes the geometric model of the centrifugal prefabricated pumping station based on the orthogonal optimization method. Through the subjective analysis method and range analysis method, it is concluded that the primary and secondary order affecting the hydraulic performance of the prefabricated pumping station is: center distance Y, pump spacing S, inlet radius R, suspension height Z, inlet height H, and the optimal parameter combination is pump spacing 550 mm (5.5 d), The suspension height is 300 mm (3.0 d), the center distance is 100 mm (1.0 d), the inlet height is 700 mm (7.0 d), and the inlet radius is 75 mm (0.75 d). The orthogonal optimization results show that under the design condition (Q_d = 33.93 m³/h), the efficiency of the centrifugal prefabricated pumping station is 64.69%, which is increased by 0.70%, compared with the initial scheme. The head is 8.76 m, which is increased by 0.10 m, compared with the initial scheme. After optimization, the recirculation vortex at the water inlet of the prefabricated pumping station is smaller than that before optimization, the flow velocity uniformity in the prefabricated barrel is improved, and the flow field is more stable. The research results of this paper can provide theoretical guidance and engineering reference value for the same type of prefabricated pumping stations. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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11 pages, 3435 KiB

Open AccessArticle

Experimental Study of Supercavitation Bubble Development over Bodies in a Free-Surface Flow

by Lotan Arad Ludar and Alon Gany

J. Mar. Sci. Eng. 2022, 10(9), 1244; https://doi.org/10.3390/jmse10091244 - 04 Sep 2022

Cited by 4 | Viewed by 1917

Abstract

This research conducts experimental studies on supercavitation bubble development and characteristics within free-surface water and the role of cavitator, comparing the results to those of similar experiments carried on in a duct flow. Tests have been conducted on cylindrical bodies (47 mm diameter) [...] Read more.

This research conducts experimental studies on supercavitation bubble development and characteristics within free-surface water and the role of cavitator, comparing the results to those of similar experiments carried on in a duct flow. Tests have been conducted on cylindrical bodies (47 mm diameter) moving underwater at different velocities in a 10-m-diameter circular pool of about 50 cm water level. A comparison has been made for supercavitation bubbles resulting from six different cavitator geometries (flat, sphere, cone, ogive, inverted sphere, and truncated cone). The comparison referred to the conditions of the bubble formation, as well as to the shape and development. It was found that the different cavitators produced different bubble geometries as opposed to the results of experiments conducted in a duct flow by the authors. Nevertheless, the order of onset of cavitation bubble creation (with relation to the cavitation number and flow velocity) was similar. One of the conclusions of this study was that the pressure difference used for defining the cavitation number has a significant impact on the correlation between the bubble characteristics and cavitation number. This fact should be considered when comparing data from different sources. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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15 pages, 5586 KiB

Open AccessArticle

Optimization and Internal Flow Analysis of Inlet and Outlet Horn of Integrated Pump Gate

by Chuanliu Xie, Tenglong Fu, Weipeng Xuan, Chuanzhen Bai and Liming Wu

Processes 2022, 10(9), 1753; https://doi.org/10.3390/pr10091753 - 02 Sep 2022

Cited by 3 | Viewed by 1198

Abstract

In order to improve the hydraulic performance of the integrated pump gate, the flow pattern of the inlet and outlet of the pump gate is improved. This paper adopts the SST k-ω turbulence model to numerically calculate the initial scheme of the integrated [...] Read more.

In order to improve the hydraulic performance of the integrated pump gate, the flow pattern of the inlet and outlet of the pump gate is improved. This paper adopts the SST k-ω turbulence model to numerically calculate the initial scheme of the integrated pump gate, verifies its internal flow pattern through experiments, then adds and optimizes the design of the inlet and outlet horn pipes of the integrated pump gate through orthogonal optimization. The research results conclude that the hydraulic performance of the integrated pump gate is significantly improved after adding the inlet and outlet horn. Under the design flow condition (Q_d = 11.5 L/s), the efficiency of the pump gate increased from 60.50% to 67.19%, the head increased from 2.7569 m to 3.1178 m, the hydraulic loss in the inlet channel decreased from 0.064 m to 0.027 m, and the hydraulic loss in the outlet channel decreased from 1.337 m to 1.027 m. The optimized trumpet pipe can improve the inlet conditions of the pump while weakening the vortices in the outlet channel, thus improving the efficiency and safety of the integrated pump gate. The research results of this paper are of reference value for similar projects. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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21 pages, 49497 KiB

Open AccessArticle

Numerical Study for Flow Loss Characteristic of an Axial-Flow Pump as Turbine via Entropy Production Analysis

by Fan Yang, Zhongbin Li, Yiping Cai, Dongjin Jiang, Fangping Tang and Shengjie Sun

Processes 2022, 10(9), 1695; https://doi.org/10.3390/pr10091695 - 26 Aug 2022

Cited by 12 | Viewed by 1634

Abstract

Low-head vertical axial-flow pump as turbine (PAT) devices play a vital part in the development of clean energy for hydropower in plain areas. The traditional method of evaluating the flow loss in hydraulic machinery is calculated by the pressure drop method, the limitation [...] Read more.

Low-head vertical axial-flow pump as turbine (PAT) devices play a vital part in the development of clean energy for hydropower in plain areas. The traditional method of evaluating the flow loss in hydraulic machinery is calculated by the pressure drop method, the limitation of which is that the location of the occurrence of large losses cannot be accurately determined. In this paper, entropy production theory is introduced to evaluate the irreversible losses in the axial-flow PAT from the perspective of the second law of thermodynamics. A three-dimensional model of the axial-flow PAT is established and solved numerically using the Reynolds time-averaged equation, and the turbulence model is adopted as Shear Stress Transport–Curvature Correction (SST-CC) model. The validity of the entropy production theory to evaluate the energy loss distribution of the axial-flow PAT is illustrated by comparing the flow loss calculated by the pressure drop and the entropy production theory, respectively. The entropy production by turbulent dissipative dominates the total entropy production in the whole flow conduit, and the turbulent dissipative entropy accounts for the smallest percentage of the whole conduit entropy production at the optimal working condition Q_bep, which is 51%. The impeller and the dustpan-shaped conduit are the essential sources of hydraulic loss in the entire flow conduit of the axial-flow PAT, and most of the energy loss of the impeller occurs at the blade leading edge, the trailing edge, and the flow separation zone near the suction surface. The energy loss of the dustpan-shaped conduit results from the high-speed flow from the impeller outlet to dustpan-shaped conduit to form a vortex, backflow and other chaotic flow patterns. Flow impact, flow separation, vortex and backflow are the main causes of high entropy production and energy loss. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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