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Water
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Computational Fluid Mechanics and Hydraulics
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Computational Fluid Mechanics and Hydraulics

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydraulics and Hydrodynamics".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 47432

Special Issue Editors

Dr. Ahmad Shakibaeinia

E-Mail Website
Guest Editor
Department of Civil, Geological and Mining Engineering Chairholder, Canada Research Chair in Computational Hydrosystems Polytechnique Montreal, Montreal, QC, Canada
Interests: computational hydraulics & fluid mechanics; multiphase and multi-physics flows; fluvial mechanics
Prof. Dr. Amir Reza Zarrati

E-Mail
Co-Guest Editor
Amirkabir University of Technology, Tehran, Iran
Interests: Open channel; HydraulicsScouring; Hydraulic Structures

Special Issue Information

Dear Colleagues,

Rapid advances in computational power in recent years have provided us with the opportunity to solve the challenging problems in many science and engineering fields. Fluid mechanics and hydraulics are no exception. This special issue of Water focuses on computational aspects of hydraulics and fluid mechanics researches. It aims to present and discuss the latest advancements in the numerical techniques and their application for simulation of environmental fluid mechanics and hydraulics problems. It encourages the original scientific contributions to:

  • development, enhancement (of efficiency and accuracy) and validation of the conventional numerical methods, such as finite difference method (FDM), finite volume method (FVM), and finite element method (FEM), as well as the younger generations of numerical methods, such as smoothed particle hydrodynamics (SPH), moving particle semi-implicit (MPS), Lattice Boltzmann (LBM) methods, etc.
  • application of the numerical techniques and models for simulation and study of fluid flow and transport processes, especially in natural or man-made hydro-systems (e.g., rivers, lakes, estuaries, coasts, and hydraulic structures).

Prof. Dr. Ahmad Shakibaeinia
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. Water is an international peer-reviewed open access semimonthly 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

  • Computational fluid dynamics
  • Computational hydraulics
  • Numerical techniques
  • Hydro-systems (rivers, lakes, estuaries, coasts, and hydraulic structures)
  • Free surface flows
  • Multiphase flows
  • Transport processes

Published Papers (12 papers)

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Editorial

Jump to: Research, Review

3 pages, 176 KiB  
Editorial
Computational Fluid Mechanics and Hydraulics
by Ahmad Shakibaeinia and Amir Reza Zarrati
Water 2022, 14(24), 3985; https://doi.org/10.3390/w14243985 - 7 Dec 2022
Viewed by 1476
Abstract
Rapid advances in computational power and numerical techniques in recent years have provided us with the opportunity to solve challenging problems in many science and engineering fields [...] Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)

Research

Jump to: Editorial, Review

14 pages, 3687 KiB  
Article
Influence of Negatively Buoyant Jets on a Strongly Curved Open-Channel Flow Using RANS Models with Experimental Data
by Xueming Wang, Abdolmajid Mohammadian and Colin D. Rennie
Water 2022, 14(3), 347; https://doi.org/10.3390/w14030347 - 25 Jan 2022
Cited by 3 | Viewed by 1952
Abstract
Experimental and numerical studies of flow structures in a strongly curved 135-degree laboratory flume were carried out to investigate the influence of negatively buoyant jets using the finite volume method. The performance results of three different turbulence models were investigated by comparing the [...] Read more.
Experimental and numerical studies of flow structures in a strongly curved 135-degree laboratory flume were carried out to investigate the influence of negatively buoyant jets using the finite volume method. The performance results of three different turbulence models were investigated by comparing the numerical results with the experimental measurements. The present study demonstrates that fully 3D numerical models are capable of simulating the primary flow pattern in a strongly curved channel with the presence of a negatively buoyant jet. The comparison also shows that the k-omega SST model can satisfactorily predict some of the smaller flow features in bend flow, such as the inner bank circulation cell and the overall form of the vorticity distributions. It was found that the flow distribution and the strength of secondary flow vary due to the interaction between the jet mixing behavior and the secondary flow in the channel bend. The presence of negatively buoyant jets attenuated the development of the outer bank cell as salinity increased. In the inner bank region, flow separation was strengthened by the participation of the negatively buoyant jets. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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17 pages, 12831 KiB  
Article
Three-Dimensional Hydrostatic Curved Channel Flow Simulations Using Non-Staggered Triangular Grids
by Wei Zhang, Miguel Uh Zapata, Damien Pham Van Bang and Kim Dan Nguyen
Water 2022, 14(2), 174; https://doi.org/10.3390/w14020174 - 9 Jan 2022
Cited by 3 | Viewed by 2106
Abstract
Non-staggered triangular grids have many advantages in performing river or ocean modeling with the finite-volume method. However, horizontal divergence errors may occur, especially in large-scale hydrostatic calculations with centrifugal acceleration. This paper proposes an unstructured finite-volume method with a filtered scheme to mitigate [...] Read more.
Non-staggered triangular grids have many advantages in performing river or ocean modeling with the finite-volume method. However, horizontal divergence errors may occur, especially in large-scale hydrostatic calculations with centrifugal acceleration. This paper proposes an unstructured finite-volume method with a filtered scheme to mitigate the divergence noise and avoid further influencing the velocities and water elevation. In hydrostatic pressure calculations, we apply the proposed method to three-dimensional curved channel flows. Approximations reduce the numerical errors after filtering the horizontal divergence operator, and the approximation is second-order accurate. Numerical results for the channel flow accurately calculate the velocity profile and surface elevation at different Froude numbers. Moreover, secondary flow features such as the vortex pattern and its movement along the channel sections are also well captured. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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17 pages, 7330 KiB  
Article
CFD-DEM Modeling of Dense Sub-Aerial and Submerged Granular Collapses
by Maryam Shademani, Bruno Blais and Ahmad Shakibaeinia
Water 2021, 13(21), 2969; https://doi.org/10.3390/w13212969 - 21 Oct 2021
Cited by 7 | Viewed by 2582
Abstract
Sub-aerial (dry) and submerged dense granular collapses are studied by means of a three-phase unresolved computational fluid dynamics-discrete element method (CFD-DEM) numerical model. Physical experiments are also performed to provide data for validation and further analysis. Validations show good compatibility between the numerical [...] Read more.
Sub-aerial (dry) and submerged dense granular collapses are studied by means of a three-phase unresolved computational fluid dynamics-discrete element method (CFD-DEM) numerical model. Physical experiments are also performed to provide data for validation and further analysis. Validations show good compatibility between the numerical and experimental results. Collapse mechanism as well as post-collapse morphological parameters, such as granular surface profile and runout distance, are analyzed. The spatiotemporal variation of solid volume fraction is also investigated. The effect granular column aspect ratio is studied and found to be a key factor in granular morphology for both submerged and dry conditions. The volume fraction analysis evolution shows an expansion and re-compaction trend, correlated with the granular movement. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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22 pages, 75124 KiB  
Article
An Anti-Clustering Model for Stability Enhancement of a 3D Moving Particle Semi-Implicit Method and Two-Phase Coupling between MPS and Euler Grids
by Meiyan Feng, Shenghong Huang and Guofu Lian
Water 2021, 13(7), 887; https://doi.org/10.3390/w13070887 - 24 Mar 2021
Cited by 1 | Viewed by 1822
Abstract
As a Lagrangian gridless particle method, the MPS (Moving Particle Semi-implicit) method has a wide engineering application. However, for complex 3D flows, unphysical pressure oscillations often occur and result in the failure of simulations. This paper compares the stability enhancement methods proposed by [...] Read more.
As a Lagrangian gridless particle method, the MPS (Moving Particle Semi-implicit) method has a wide engineering application. However, for complex 3D flows, unphysical pressure oscillations often occur and result in the failure of simulations. This paper compares the stability enhancement methods proposed by different researchers to develop a 3D, stable MPS method. The results indicate that the proposed methods are incapable of eliminating the particle clustering that leads to instability as the main source in coarser particle spacing cases. An anti-clustering model, referring to the SPH (Smoothed Particle Hydrodynamics) artificial viscosity model, is proposed to further reduce instability. Combining various proposed methods and models, several typical examples are simulated comparatively. The results are compared with those of the VOF (Volume of Fluid) model using commercial software to validate the accuracy and stability of the combination of the proposed methods and models. It is concluded that (1) 3D cases that adopt a high-order Laplacian model and high-order source terms in PPE are more accurate than those adopting the low-order operators; (2) the proposed anti-clustering model can produce a tuned interparticle force to prevent particle clustering and introduce no additional viscosity effects in the flow of the normal state, which plays a very positive role for further stability enhancement of MPS; (3) particle resolution significantly maintains simulation accuracy given the stable algorithms by the combination of stability enhancement methods. The 3D MPS method is coupled with the Euler grid (FLUENT V17 software, ANSYS, Pittsburgh, PA, USA) in two phases. In particular, the 3D MPS algorithm is used to calculate the liquid-phase change from the continuous to the dispersed, and the finite volume method based on the Euler grid is adopted to measure the corresponding gas-phase motion. The atomization of the liquid jet under static air flow is calculated and compared with the results of the VOF method, which can capture the continuous interface. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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13 pages, 2054 KiB  
Article
Comparison between the Lagrangian and Eulerian Approach in Simulation of Free Surface Air-Core Vortices
by Maryam Azarpira, Amir Reza Zarrati and Pouya Farrokhzad
Water 2021, 13(5), 726; https://doi.org/10.3390/w13050726 - 7 Mar 2021
Cited by 6 | Viewed by 7171
Abstract
The problematic consequences regarding formation of air-core vortices at the intakes and the drastic necessity of a thorough investigation into the phenomenon has resulted in particular attention being placed on Computational Fluid Dynamics (CFD) as an economically viable method. Two main approaches could [...] Read more.
The problematic consequences regarding formation of air-core vortices at the intakes and the drastic necessity of a thorough investigation into the phenomenon has resulted in particular attention being placed on Computational Fluid Dynamics (CFD) as an economically viable method. Two main approaches could be taken using CFD, namely the Eulerian and Lagrangian methods each of which is characterized by specific advantages and disadvantages. Whereas many researchers have used the Eulerian approach for vortex simulation, the Lagrangian approach has not been found in the literature. The present study dealt with the comparison of the Lagrangian and Eulerian approaches in the simulation of vortex flow. Simulations based on both approaches were carried out by solving the Navier–Stokes equations accompanied by the LES turbulence model. The results of the numerical model were evaluated in accordance with a physical model for steady vortex flow using particle image velocimetry (PIV), revealing that both approaches are sufficiently capable of simulating the vortex flow but with the difference that the Lagrangian method has greater computational cost with less accuracy. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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17 pages, 6838 KiB  
Article
Deep Learning Method Based on Physics Informed Neural Network with Resnet Block for Solving Fluid Flow Problems
by Chen Cheng and Guang-Tao Zhang
Water 2021, 13(4), 423; https://doi.org/10.3390/w13040423 - 5 Feb 2021
Cited by 60 | Viewed by 13328
Abstract
Solving fluid dynamics problems mainly rely on experimental methods and numerical simulation. However, in experimental methods it is difficult to simulate the physical problems in reality, and there is also a high-cost to the economy while numerical simulation methods are sensitive about meshing [...] Read more.
Solving fluid dynamics problems mainly rely on experimental methods and numerical simulation. However, in experimental methods it is difficult to simulate the physical problems in reality, and there is also a high-cost to the economy while numerical simulation methods are sensitive about meshing a complicated structure. It is also time-consuming due to the billion degrees of freedom in relevant spatial-temporal flow fields. Therefore, constructing a cost-effective model to settle fluid dynamics problems is of significant meaning. Deep learning (DL) has great abilities to handle strong nonlinearity and high dimensionality that attracts much attention for solving fluid problems. Unfortunately, the proposed surrogate models in DL are almost black-box models and lack interpretation. In this paper, the Physical Informed Neural Network (PINN) combined with Resnet blocks is proposed to solve fluid flows depending on the partial differential equations (i.e., Navier-Stokes equation) which are embedded into the loss function of the deep neural network to drive the model. In addition, the initial conditions and boundary conditions are also considered in the loss function. To validate the performance of the PINN with Resnet blocks, Burger’s equation with a discontinuous solution and Navier-Stokes (N-S) equation with continuous solution are selected. The results show that the PINN with Resnet blocks (Res-PINN) has stronger predictive ability than traditional deep learning methods. In addition, the Res-PINN can predict the whole velocity fields and pressure fields in spatial-temporal fluid flows, the magnitude of the mean square error of the fluid flow reaches to 10−5. The inverse problems of the fluid flows are also well conducted. The errors of the inverse parameters are 0.98% and 3.1% in clean data and 0.99% and 3.1% in noisy data. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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23 pages, 13792 KiB  
Article
SPH-ALE Scheme for Weakly Compressible Viscous Flow with a Posteriori Stabilization
by Antonio Eirís, Luis Ramírez, Javier Fernández-Fidalgo, Iván Couceiro and Xesús Nogueira
Water 2021, 13(3), 245; https://doi.org/10.3390/w13030245 - 20 Jan 2021
Cited by 7 | Viewed by 2692
Abstract
A highly accurate SPH method with a new stabilization paradigm has been introduced by the authors in a recent paper aimed to solve Euler equations for ideal gases. We present here the extension of the method to viscous incompressible flow. Incompressibility is tackled [...] Read more.
A highly accurate SPH method with a new stabilization paradigm has been introduced by the authors in a recent paper aimed to solve Euler equations for ideal gases. We present here the extension of the method to viscous incompressible flow. Incompressibility is tackled assuming a weakly compressible approach. The method adopts the SPH-ALE framework and improves accuracy by taking high-order variable reconstruction of the Riemann states at the midpoints between interacting particles. The moving least squares technique is used to estimate the derivatives required for the Taylor approximations for convective fluxes, and also provides the derivatives needed to discretize the viscous flux terms. Stability is preserved by implementing the a posteriori Multi-dimensional Optimal Order Detection (MOOD) method procedure thus avoiding the utilization of any slope/flux limiter or artificial viscosity. The capabilities of the method are illustrated by solving one- and two-dimensional Riemann problems and benchmark cases. The proposed methodology shows improvements in accuracy in the Riemann problems and does not require any parameter calibration. In addition, the method is extended to the solution of viscous flow and results are validated with the analytical Taylor–Green, Couette and Poiseuille flows, and lid-driven cavity test cases. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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24 pages, 7103 KiB  
Article
Improved δ-SPH Scheme with Automatic and Adaptive Numerical Dissipation
by Abdelkader Krimi, Luis Ramírez, Sofiane Khelladi, Fermín Navarrina, Michael Deligant and Xesús Nogueira
Water 2020, 12(10), 2858; https://doi.org/10.3390/w12102858 - 14 Oct 2020
Cited by 11 | Viewed by 2525
Abstract
In this work we present a δ-Smoothed Particle Hydrodynamics (SPH) scheme for weakly compressible flows with automatic adaptive numerical dissipation. The resulting scheme is a meshless self-adaptive method, in which the introduced artificial dissipation is designed to increase the dissipation in zones [...] Read more.
In this work we present a δ-Smoothed Particle Hydrodynamics (SPH) scheme for weakly compressible flows with automatic adaptive numerical dissipation. The resulting scheme is a meshless self-adaptive method, in which the introduced artificial dissipation is designed to increase the dissipation in zones where the flow is under-resolved by the numerical scheme, and to decrease it where dissipation is not required. The accuracy and robustness of the proposed methodology is tested by solving several numerical examples. Using the proposed scheme, we are able to recover the theoretical decay of kinetic energy, even where the flow is under-resolved in very coarse particle discretizations. Moreover, compared with the original δ-SPH scheme, the proposed method reduces the number of problem-dependent parameters. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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24 pages, 4192 KiB  
Article
Large Eddy Simulation of Near-Bed Flow and Turbulence over Roughness Elements in the Shallow Open-Channel
by Zeng Zhang and S. Samuel Li
Water 2020, 12(10), 2701; https://doi.org/10.3390/w12102701 - 27 Sep 2020
Cited by 3 | Viewed by 2576
Abstract
Turbulent flows in rough open-channels have complex structures near the channel-bed. The near-bed flow can cause bed erosion, channel instability, and damages to fish habitats. This paper aims to improve our understanding of the structures. Transverse square bars placed at the channel-bed form [...] Read more.
Turbulent flows in rough open-channels have complex structures near the channel-bed. The near-bed flow can cause bed erosion, channel instability, and damages to fish habitats. This paper aims to improve our understanding of the structures. Transverse square bars placed at the channel-bed form two-dimensional roughness elements. Turbulent flows over the bars are predicted using large eddy simulation (LES). The predicted flow quantities compare well with experimental data. The LES model predicts mean-flow velocity profiles that resemble those in the classic turbulent boundary layer over a flat plate and profiles that change patterns in the vicinity of roughness elements, depending on the pitch-to-roughness height ratio λ/k. The relative turbulence intensity and normalized Reynolds shear stress reach maxima of 15% and 1.2%, respectively, at λ/k = 8, compared to 9% and 0.2% at λ/k = 2. The predicted bottom boundary layers constitute a large portion of the total depth, indicating roughness effect on the flow throughout the water column. Fluid exchange between the roughness cavity and outer region occurs due to turbulence fluctuations. The fluctuations increase in intensity with increasing λ/k ratio. This ratio dictates the number of eddies in the cavity as well as their locations and shapes. It also controls turbulence stress distributions. LES can be used to explore strategies for erosion control, channel restoration, and habitat protection. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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Review

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32 pages, 7107 KiB  
Review
Review and Comparison of Numerical Simulations of Secondary Flow in River Confluences
by Rawaa Shaheed, Xiaohui Yan and Abdolmajid Mohammadian
Water 2021, 13(14), 1917; https://doi.org/10.3390/w13141917 - 11 Jul 2021
Cited by 12 | Viewed by 3806
Abstract
River confluences are a common feature in natural water resources. The flow characteristics in confluences are complicated, especially at junction areas between tributaries and the main river. One of the typical characteristics of confluences is secondary flow, which plays an important role in [...] Read more.
River confluences are a common feature in natural water resources. The flow characteristics in confluences are complicated, especially at junction areas between tributaries and the main river. One of the typical characteristics of confluences is secondary flow, which plays an important role in mixing, velocity, sediment transport, and pollutant dispersion. In addition to the experimental and field studies that have been conducted in this area, the development of computational fluid dynamics has allowed researchers in this field to use different numerical models to simulate turbulence properties in rivers, especially secondary flows. Nowadays, the hydrodynamics of flows in confluences are widely simulated by using three-dimensional models in order to fully capture the flow structures, as the flow characteristics are considered to be turbulent and three-dimensional at river junctions. Several numerical models have been recommended for this purpose, and various turbulence models have been used to simulate the flows at confluences. To assess the accuracy of turbulence models, flows have been predicted by applying different turbulence models in the numerical model and the results have been compared with other data, such as field, laboratory, and experimental data. The purpose behind these investigations was to find the suitable model for each case of turbulent flow and for different types of confluences. In this study, the performances of turbulence models for confluences are reviewed for different numerical simulation strategies. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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32 pages, 4832 KiB  
Review
A Review of Numerical Simulations of Secondary Flows in River Bends
by Rawaa Shaheed, Abdolmajid Mohammadian and Xiaohui Yan
Water 2021, 13(7), 884; https://doi.org/10.3390/w13070884 - 24 Mar 2021
Cited by 16 | Viewed by 3739
Abstract
River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the [...] Read more.
River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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