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Experiments and Numerical Analysis of Flow
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Experiments and Numerical Analysis of Flow

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Coastal Engineering".

Deadline for manuscript submissions: closed (15 January 2022) | Viewed by 20804

Special Issue Editor

Dr. Evangelos Keramaris

E-Mail Website
Guest Editor
Department of Civil Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece
Interests: experimental techniques; flows in porous media; eco/environmental hydraulics; computational hydraulics

Special Issue Information

Dear Colleagues,

Flow phenomena and the associated momentum transfer near the permeable bed are encountered in various fields (environmental hydraulics, geophysical fluid dynamics, and mechanical engineering, among others). Turbulence is found to be the primary mechanism of transport processes in most natural shear flows. The turbulent characteristics of flows are important in particle transport phenomena.

A thorough study of open channel flows is very significant for a wide range of applications, including restoration and enhancement of river aquatic systems. Additionally, the study of the impact of vegetation on turbulent flow in an open channel has particular importance. The presence of vegetation in rivers and open channel beds significantly influences velocity and depth flow.

This Special Issue aims to cover, without being limited to, the following areas: fluid mechanics; eco/environmental hydraulics; experimental techniques; advanced models in turbulence, heat transfer and mass transfer; sediment transport and morphodynamics in streams and rivers; vegetated flows; erosion processes; morphology and water quality; innovative management systems.

Dr. Evangelos Keramaris
Guest Editor

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. Journal of Marine Science and Engineering 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 2600 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

  • experimental hydraulics
  • computational fluid mechanics
  • advanced models in turbulence
  • heat transfer and mass transfer
  • riverine systems
  • sediment transport

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Published Papers (7 papers)

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Research

17 pages, 5848 KiB  
Article
Propagation and Separation of Downslope Gravity Currents over Rigid and Emergent Vegetation Patches in Linearly Stratified Environments
by Ying-Tien Lin, Yi-Qi Ye, Dong-Rui Han and Yu-Jia Chiu
J. Mar. Sci. Eng. 2022, 10(3), 308; https://doi.org/10.3390/jmse10030308 - 22 Feb 2022
Cited by 8 | Viewed by 2007
Abstract
Large eddy simulation (combined with the mixture model) and laboratory experiment were used to investigate the impact of emergent and rigid vegetation on the dynamics of downslope gravity currents in stratified environments. The reliability of the numerical model was assessed with the corresponding [...] Read more.
Large eddy simulation (combined with the mixture model) and laboratory experiment were used to investigate the impact of emergent and rigid vegetation on the dynamics of downslope gravity currents in stratified environments. The reliability of the numerical model was assessed with the corresponding laboratory measurements. The results show that the vegetation cylinders lead to severe lateral non-uniformity of the current front, causing more evident lobe and cleft structures. In stratified environments, the smaller driving force leads to less propagating velocity until the current separates from the slope. The transition point (from acceleration to deceleration phases) of current velocity appears earlier as the vegetation becomes denser. The peak value of the bulk entrainment coefficient Ebuik is inversely proportional to the vegetation density, while the final converged value of Ebuik is proportional to the vegetation density. Vegetation patches make the degree of fluctuation of the instantaneous entrainment coefficient Einst more intense, and even negative values appear locally, indicating that the gravity current is detrained into the ambient fluid. The velocity profiles of gravity current develop multi-peak patterns in stratified environments due to fingering intrusive patterns. Our analysis reveals that as the vegetation density increases, the generated wakes behind vegetation cylinders increase local entrainment and mixing, causing the density of current flow from vegetation to decrease and reach the neutral buoyancy layer of ambient fluids earlier, finally leading to a smaller separation depth. Full article
(This article belongs to the Special Issue Experiments and Numerical Analysis of Flow)
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23 pages, 9323 KiB  
Article
Prediction of the Influence of Runner Tip Clearance on the Performance of Tubular Turbine
by Yanzhao Wu, Xiaohang Wang, Xiaolong Yang, Junfeng Ding, Di Zhu, Ran Tao, Huanmao Wang and Ruofu Xiao
J. Mar. Sci. Eng. 2022, 10(2), 136; https://doi.org/10.3390/jmse10020136 - 20 Jan 2022
Cited by 9 | Viewed by 2399
Abstract
Tubular turbine is a type of turbine with low-head. Due to the fact that the runner of a tubular turbine is of axial-flow type, there will be a certain width of blade tip between the blade and the chamber. In order to explore [...] Read more.
Tubular turbine is a type of turbine with low-head. Due to the fact that the runner of a tubular turbine is of axial-flow type, there will be a certain width of blade tip between the blade and the chamber. In order to explore the influence of tip clearance width on the flow inside the turbine, taking the model tubular turbine as the research object, six different tip clearance widths were compared and analyzed. The research shows that the increase in blade tip clearance width affects the performance of the turbine, reduces the minimum pressure at blade tip and causes cavitation in advance. Larger tip clearance width significantly increases pressure pulsation intensity inside the turbine, especially in the vaneless region between the runner and guide vane and the area of the runner tip. However, the increase in tip clearance width can greatly reduce the axial force for about 100 N and radial excitation force for about 50% of rotating parts. Therefore, during the design and processing of tubular turbines, the blade tip clearance width should be carefully selected to ensure safe and stable operation of the unit. Full article
(This article belongs to the Special Issue Experiments and Numerical Analysis of Flow)
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21 pages, 8807 KiB  
Article
Two-Way Coupling Simulation of Solid-Liquid Two-Phase Flow and Wear Experiments in a Slurry Pump
by Lei Jiang, Ling Bai, Peng Xue, Guangjie Peng and Ling Zhou
J. Mar. Sci. Eng. 2022, 10(1), 57; https://doi.org/10.3390/jmse10010057 - 4 Jan 2022
Cited by 12 | Viewed by 2758
Abstract
The slurry pump is one of the most important pieces of equipment in mineral transportation and separation systems, and it has complex two-phase flow characteristics and wear mechanisms. By employing numerical and experimental methods, the solid–liquid two-phase flow characteristics and wear patterns were [...] Read more.
The slurry pump is one of the most important pieces of equipment in mineral transportation and separation systems, and it has complex two-phase flow characteristics and wear mechanisms. By employing numerical and experimental methods, the solid–liquid two-phase flow characteristics and wear patterns were investigated in this study. A two-way coupling discrete phase model (DPM) method was used to predict the flow pattern and the wear location and shows good agreement with the experimental observations. The pump performance characteristics of numerical results under pure water conditions were consistent with the experimental results. The effects of particle parameters and operating conditions on the internal flow field and wear were compared and discussed. The results show that the wear degree increased with the increase in volume flow rate and solid volume fraction. With the increase in particle size, the wear range at the impeller inlet became significantly smaller, but the wear degree became obviously larger. This study provides a basis for reducing the wear and improving the hydraulic performance of slurry pumps. Full article
(This article belongs to the Special Issue Experiments and Numerical Analysis of Flow)
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21 pages, 13202 KiB  
Article
Unstructured Finite-Volume Model of Sediment Scouring Due to Wave Impact on Vertical Seawalls
by Miguel Uh Zapata, Damien Pham Van Bang and Kim Dan Nguyen
J. Mar. Sci. Eng. 2021, 9(12), 1440; https://doi.org/10.3390/jmse9121440 - 16 Dec 2021
Cited by 2 | Viewed by 3129
Abstract
The numerical modeling of sediment transport under wave impact is challenging because of the complex nature of the triple wave–structure–sediment interaction. This study presents three-dimensional numerical modeling of sediment scouring due to non-breaking wave impact on a vertical seawall. The Navier–Stokes–Exner equations are [...] Read more.
The numerical modeling of sediment transport under wave impact is challenging because of the complex nature of the triple wave–structure–sediment interaction. This study presents three-dimensional numerical modeling of sediment scouring due to non-breaking wave impact on a vertical seawall. The Navier–Stokes–Exner equations are approximated to calculate the full evolution of flow fields and morphodynamic responses. The bed erosion model is based on the van Rijn formulation with a mass-conservative sand-slide algorithm. The numerical solution is obtained by using a projection method and a fully implicit second-order unstructured finite-volume method in a σ-coordinate computational domain. This coordinate system is employed to accurately represent the free-surface elevation and sediment/water interface evolution. Experimental results of the velocity field, surface wave motion, and scour hole formation hole are used to compare and demonstrate the proposed numerical method’s capabilities to model the seawall scour. Full article
(This article belongs to the Special Issue Experiments and Numerical Analysis of Flow)
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12 pages, 3678 KiB  
Article
1D–3D Coupling Algorithm of Gas Flow for the Valve System in a Compression Ignition Engine
by Kyeong-Ju Kong
J. Mar. Sci. Eng. 2021, 9(10), 1061; https://doi.org/10.3390/jmse9101061 - 27 Sep 2021
Viewed by 2304
Abstract
Emission control devices such as selective catalytic reduction (SCR), exhaust gas recirculation (EGR), and scrubbers were installed in the compression ignition (CI) engine, and flow analysis of intake air and exhaust gas was required to predict the performance of the CI engine and [...] Read more.
Emission control devices such as selective catalytic reduction (SCR), exhaust gas recirculation (EGR), and scrubbers were installed in the compression ignition (CI) engine, and flow analysis of intake air and exhaust gas was required to predict the performance of the CI engine and emission control devices. In order to analyze such gas flow, it was inefficient to comprehensively analyze the engine’s cylinder and intake/exhaust systems because it takes a lot of computation time. Therefore, there is a need for a method that can quickly calculate the gas flow of the CI engine in order to shorten the development process of emission control devices. It can be efficient and quickly calculated if only the parts that require detailed observation among the intake/exhaust gas flow of the CI engine are analyzed in a 3D approach and the rest are analyzed in a 1D approach. In this study, an algorithm for gas flow analysis was developed by coupling 1D and 3D in the valve systems and comparing with experimental results for validation. Analyzing the intake/exhaust gas flow of the CI engine in a 3D approach took about 7 days for computation, but using the developed 1D–3D coupling algorithm, it could be computed within 30 min. Compared with the experimental results, the exhaust pipe pressure occurred an error within 1.80%, confirming the accuracy and it was possible to observe the detailed flow by showing the contour results for the part analyzed in the 3D zone. As a result, it was possible to accurately and quickly calculate the gas flow of the CI engine using the 1D–3D coupling algorithm applied to the valve system, and it was expected that it can be used to shorten the process for analyzing emission control devices, including predicting the performance of the CI engine. Full article
(This article belongs to the Special Issue Experiments and Numerical Analysis of Flow)
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17 pages, 31876 KiB  
Article
Optimal Design of Slit Impeller for Low Specific Speed Centrifugal Pump Based on Orthogonal Test
by Yang Yang, Ling Zhou, Hongtao Zhou, Wanning Lv, Jian Wang, Weidong Shi and Zhaoming He
J. Mar. Sci. Eng. 2021, 9(2), 121; https://doi.org/10.3390/jmse9020121 - 26 Jan 2021
Cited by 28 | Viewed by 3747
Abstract
Marine centrifugal pumps are mostly used on board ship, for transferring liquid from one point to another. Based on the combination of orthogonal testing and numerical simulation, this paper optimizes the structure of a drainage trough for a typical low-specific speed centrifugal pump, [...] Read more.
Marine centrifugal pumps are mostly used on board ship, for transferring liquid from one point to another. Based on the combination of orthogonal testing and numerical simulation, this paper optimizes the structure of a drainage trough for a typical low-specific speed centrifugal pump, determines the priority of the various geometric factors of the drainage trough on the pump performance, and obtains the optimal impeller drainage trough scheme. The influence of drainage tank structure on the internal flow of a low-specific speed centrifugal pump is also analyzed. First, based on the experimental validation of the initial model, it is determined that the numerical simulation method used in this paper is highly accurate in predicting the performance of low-specific speed centrifugal pumps. Secondly, based on the three factors and four levels of the impeller drainage trough in the orthogonal test, the orthogonal test plan is determined and the orthogonal test results are analyzed. This work found that slit diameter and slit width have a large impact on the performance of low-specific speed centrifugal pumps, while long and short vane lap lengths have less impact. Finally, we compared the internal flow distribution between the initial model and the optimized model, and found that the slit structure could effectively reduce the pressure difference between the suction side and the pressure side of the blade. By weakening the large-scale vortex in the flow path and reducing the hydraulic losses, the drainage trough impellers obtained based on orthogonal tests can significantly improve the hydraulic efficiency of low-specific speed centrifugal pumps. Full article
(This article belongs to the Special Issue Experiments and Numerical Analysis of Flow)
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17 pages, 4487 KiB  
Article
A New Experimental Study and SPH Comparison for the Sequential Dam-Break Problem
by Selahattin Kocaman and Kaan Dal
J. Mar. Sci. Eng. 2020, 8(11), 905; https://doi.org/10.3390/jmse8110905 - 11 Nov 2020
Cited by 12 | Viewed by 3131
Abstract
The floods following the event of a dam collapse can have a significant impact on the downstream environment and ecology. Due to the limited number of real-case data for dam-break floods, laboratory experiments and numerical models are used to understand the complex flow [...] Read more.
The floods following the event of a dam collapse can have a significant impact on the downstream environment and ecology. Due to the limited number of real-case data for dam-break floods, laboratory experiments and numerical models are used to understand the complex flow behavior and to analyze the impact of the dam-break wave for different scenarios. In this study, a newly designed experimental campaign was conducted for the sequential dam-break problem in a rectangular channel with a steep slope, and the obtained results were compared against those of a particle-based numerical model. The laboratory tests permitted a better understanding of the physical process, highlighting five successive stages observed in the downstream reservoirs: dam-break wave propagation, overtopping, reflection wave, run-up, and oscillations. Experimental data were acquired using a virtual wave probe based on an image processing technique. A professional camera and a smartphone camera were used to obtain the footage of the experiment to examine the effect of the resolution and frame rate on image processing. The numerical results were obtained through the Smoothed Particle Hydrodynamics (SPH) method using free DualSPHysics software. The experimental and numerical results were in good agreement generally. Hence, the presented data can be used as a benchmark in future studies to validate the SPH and other Computational Fluid Dynamics (CFD) methods. Full article
(This article belongs to the Special Issue Experiments and Numerical Analysis of Flow)
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