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Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows

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

Deadline for manuscript submissions: closed (31 October 2020) | Viewed by 52357

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Dr. Silvia Di Francesco

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Faculty of Engineering Hydraulics and Hydraulic Works, Niccolo Cusano University, 00166 Rome, Italy
Interests: CFD; free surface flows; hydraulic risk analysis and mitigation; fluid–structure interaction; Lattice Boltzmann method
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Chiara Biscarini

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Guest Editor

Unesco Chair in Water Resources Management and Culture, Sustainable Heritage Conservation Centre (SheC), University for Foreigners of Perugia, Perugia, Italy
Interests: flood risk; water resources management; fluid–structure interaction; hydraulic modelling

Special Issue Information

Dear Colleagues,

This Special Issue aims to report the ongoing research into experimental and computational models in hydraulics as well as their novel applications in civil and environmental engineering ,with a particular emphasys on fluid–structure interaction problems.

Topics of primary interest include, but are not limited to: new numerical schemes for free surface and multiphase flows, high-performance computing, environmental hydraulics, dam break flows, urban floods, hydraulic risk analysis, sediment transport dynamics, fluid–structure interactions, multiphysics and multiscale methods.

All original contributions with experimental and/or numerical approaches in the mentioned areas will be considered for publication. We therefore invite you to submit your latest research findings showing your progress in the field of hydraulic engineering to this Special Issue of Water (ISSN 2073-4441)—an open access journal (https://www.mdpi.com/journal/water).

Dr. Silvia Di Francesco
Prof. Chiara Biscarini
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. 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
Flood risk management
Fluid–structure interaction
Open channel hydraulics

Published Papers (13 papers)

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Research

25 pages, 11772 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Geometric Parameters of the Antivortex on a Triangular Labyrinth Side Weir

by Saeed Abbasi, Sajjad Fatemi, Amir Ghaderi and Silvia Di Francesco

Water 2021, 13(1), 14; https://doi.org/10.3390/w13010014 - 24 Dec 2020

Cited by 25 | Viewed by 2549

Abstract

Side weirs are important structural measures extensively used, for instance, for regulating water levels in rivers and canals. If the length of the opening is limited, the amount of water diverted out of the channel and the effective length can be increased by applying a labyrinth side weir. The present study deals with numerical simulations regarding the hydraulic performance of a labyrinth side weir with a triangular plan in single-cycle mode. Specifically, six different types of antivortexes embedded inside it and in various hydraulic conditions at different Froude numbers are analyzed. The antivortexes are studied using two groups, permeable and impermeable, with three different heights: 0.5 P, 0.75 P, and 1 P (P: Weir height). The comparison of the simulated water surface profiles with laboratory results shows that the numerical model is able to capture the flow characteristics on the labyrinth side weir. The use of an antivortex in a triangular labyrinth side weir reduces the secondary flows due to the interaction with the transverse vortexes of the vertical axis and increases the discharge capacity by 11%. Antivortexes in a permeable state outperform those in an impermeable state; the discharge coefficient in the permeable state increases up to 3% with respect to the impermeable state. Finally, based on an examination of the best type of antivortex, taking into account shape, permeability, and height, the discharge coefficient increases to 13.4% compared to a conventional labyrinth side weir. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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16 pages, 10562 KiB

Open AccessArticle

Numerical Simulation of Free Surface Flow on Spillways and Channel Chutes with Wall and Step Abutments by Coupling Turbulence and Air Entrainment Models

by Le Thi Thu Hien and Duong Hoai Duc

Water 2020, 12(11), 3036; https://doi.org/10.3390/w12113036 - 29 Oct 2020

Cited by 3 | Viewed by 2361

Abstract

Spillways and channel chutes are widely used in hydraulic works. Two kinds of abutment—walls and steps—are usually constructed to dissipate energy; however, they may also cause cavitation at the abutment position. In this study, we used Flow 3D with the Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) turbulent models which included air entrainment to simulate the free surface flow through the spillway, channel chute and stilling basin of the Ngan Truoi construction to optimize the configuration of walls and dams. We measured the water level, velocity and pressure to estimate the influence of grid size and the turbulent model type used. Our results highlight the need to include air entrainment in the model simulating rapid flow over a hydraulic construction. With adjustments for energy loss, this study shows that walls provide the best results and the optimal distance between two walls is 2.8 m. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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13 pages, 3458 KiB

Open AccessEditor’s ChoiceArticle

Features and Control of Submerged Horizontal Vortex in Stepped Dissipation Wells

by Boran Zhang, Mengshan Shi, Lvtan Yao and Wuyi Wan

Water 2020, 12(8), 2117; https://doi.org/10.3390/w12082117 - 25 Jul 2020

Viewed by 2410

Abstract

Unlike a horizontal intake vortex, a submerged horizontal vortex is not bounded by a free surface. It has an axial air core submerged in a vessel such as a dissipation well. Due to the motion of its bound point (where the vortex ends), the front wall of the dissipation well could be damaged by cavitation. The goals of this study are to (1) summarize general features underlying the formation and collapsing of horizontal vortices in dissipation wells; (2) identify the features of submerged horizontal vortices; and (3) propose potential measures to mitigate cavitation damage. Through scaling down experiments performed in a transparent dissipation well with two optical sensors, various boundary conditions have been carried out to accomplish this investigation. It was found that a wider inlet flow falling with mixed air can facilitate the generation of submerged horizontal vortices. The optimal mappings between the inlet discharge and the water head differential for maintaining the vortices have been summarized. Depending on different applications, two configurations are proposed to mitigate the adverse effects of submerged horizontal vortices. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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18 pages, 7205 KiB

Open AccessArticle

Structural Safety Assessment of Connection between Sloshing Tank and 6-DOF Platform Using Co-Simulation of Fluid and Multi-Flexible-Body Dynamics

by Sang-Moon Yun, Sung-Pill Kim, Soh-Myung Chung, Woo-Jin Shin, Dae-Seung Cho and Jong-Chun Park

Water 2020, 12(8), 2108; https://doi.org/10.3390/w12082108 - 24 Jul 2020

Cited by 4 | Viewed by 3069

Abstract

Prediction of sloshing loads, which is one of the most important issues in the design of LNG carriers, has usually been carried out by experiments. When designing a 6-DOF platform equipment used for sloshing experiments, it should target a system containing a fluid, not a solid, thereby making it difficult to predict precisely the dynamic load due to the changes of a center of mass according to the tank’s movement. In the present study, two-way co-simulation technology between DualSPHysics and RecurDyn has been developed to analyze the mechanical behavior in multi-body system coupled with fluid motion; in which DualSPHysics is an open-source code based on particle method for fluid analysis and RecurDyn a commercial software for multi-flexible-body dynamics (MFBD). The developed technology was applied to the sloshing problem inside a tank connected to an upper plate on a 6-DOF platform. The simulation results were verified through comparison with the experiments conducted for this study independently, such as snapshots of flow motion, pressure on the cargo hold, and force applied to the tank-platform connection. Finally, to investigate the effects of fluid dynamic load on structural safety assessment, a two-way co-simulation between fluid-MFBD analysis was performed for two cases filling partially with fluid and solid. As a result, it was concluded that the sloshing experiment system used in this study was quite safe, and the feasibility of using the present co-simulation technology for structural safety assessment was confirmed. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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18 pages, 7730 KiB

Open AccessEditor’s ChoiceArticle

Energy Dissipation and Hydraulics of Flow over Trapezoidal–Triangular Labyrinth Weirs

by Amir Ghaderi, Rasoul Daneshfaraz, Mehdi Dasineh and Silvia Di Francesco

Water 2020, 12(7), 1992; https://doi.org/10.3390/w12071992 - 14 Jul 2020

Cited by 48 | Viewed by 4494

Abstract

In this work experimental and numerical investigations were carried out to study the influence of the geometric parameters of trapezoidal–triangular labyrinth weirs (TTLW) on the discharge coefficient, energy dissipation, and downstream flow regime, considering two different orientations in labyrinth weir position respective to the reservoir discharge channel. To simulate the free flow surface, the volume of fluid (VOF) method, and the Renormalization Group (RNG) k-ε model turbulence were adopted in the FLOW-3D software. The flow over the labyrinth weir (in both orientations) is simulated as a steady-state flow, and the discharge coefficient is validated with experimental data. The results highlighted that the numerical model shows proper coordination with experimental results and also the discharge coefficient decreases by decreasing the sidewall angle due to the collision of the falling jets for the high value of H/P (H: the hydraulic head, P: the weir height). Hydraulics of flow over TTLW has free flow conditions in low discharge and submerged flow conditions in high discharge. TTLW approximately dissipates the maximum amount of energy due to the collision of nappes in the upstream apexes and to the circulating flow in the pool generated behind the nappes; moreover, an increase in sidewall angle and weir height leads to reduced energy. The energy dissipation of TTLW is largest compared to vertical drop and has the least possible value of residual energy as flow increases. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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23 pages, 3486 KiB

Open AccessArticle

Fluid Structure Interaction of 2D Objects through a Coupled KBC-Free Surface Model

by Daniele Chiappini

Water 2020, 12(4), 1212; https://doi.org/10.3390/w12041212 - 24 Apr 2020

Viewed by 2569

Abstract

In this study, the capabilities of a coupled KBC-free surface model to deal with fluid solid interactions with the slamming of rigid obstacles in a calm water tank were analyzed. The results were firstly validated with experimental and numerical data available in literature and, thereafter, some additional analyses was carried out to understand the main parameters’ influence on slamming coefficient. The effect of grid resolution and Reynolds number were firstly considered to choose the proper grid and to present the weak impact of such a non-dimensional number on process evolution. Hence, the influence of Froude number on fluid-dynamics quantities was pointed out considering vertical impacts of both cylindrical, as in the references, and ellipsoidal obstacles. Different formulations of slamming coefficient were used and compared. Results are pretty encouraging and they confirm the effectiveness of lattice Boltzmann model to deal with such a problem. This leaves the door open to additional improvements addressed to the study of free buoyant bodies immersed in a fluid domain. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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31 pages, 10713 KiB

Open AccessArticle

Three-Dimensional Flow Characteristics in Slit-Type Permeable Spur Dike Fields: Efficacy in Riverbank Protection

by Shampa, Yuji Hasegawa, Hajime Nakagawa, Hiroshi Takebayashi and Kenji Kawaike

Water 2020, 12(4), 964; https://doi.org/10.3390/w12040964 - 28 Mar 2020

Cited by 12 | Viewed by 4227

Abstract

This paper focuses on finding efficient solutions for the design of a highly permeable pile spur (or slit type) dike field used in morphologically dynamic alluvial rivers. To test the suitability of different arrangements of this type of permeable pile spur dike field, laboratory experiments were conducted, and a three-dimensional multiphase numerical model was developed and applied, based on the experimental conditions. Three different angles to the approach flow and two types of individual pile position arrangements were tested. The results show that by using a series of slit-type spurs, the approach velocity of the flow can be considerably reduced within the spur dike zone. Using different sets of angles and installation positions, this type of permeable spur dike can be used more efficiently than traditional dikes. Notably, this type of spur dike can reduce the longitudinal velocity, turbulence intensity, and bed shear stress in the near-bank area. Additionally, the deflection of the permeable spur produces more transverse flow to the opposite bank. Arranging the piles in staggered grid positions among different spurs in a spur dike field improves functionality in terms of creating a quasi-uniform turbulence zone while simultaneously reducing the bed shear stress. Finally, the efficacy of the slit-type permeable spur dike field as a solution to the riverbank erosion problem is numerically tested in a reach of a braided river, the Brahmaputra–Jamuna River, and a comparison is made with a conventional spur dike field. The results indicate that the proposed structure ensures the smooth passing of flow compared with that for the conventional impermeable spur structure by producing a lower level of scouring (low bed shear stress) and flow intensification. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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Graphical abstract

16 pages, 3303 KiB

Open AccessEditor’s ChoiceArticle

Forcing for a Cascaded Lattice Boltzmann Shallow Water Model

by Sara Venturi, Silvia Di Francesco, Martin Geier and Piergiorgio Manciola

Water 2020, 12(2), 439; https://doi.org/10.3390/w12020439 - 06 Feb 2020

Cited by 6 | Viewed by 2653

Abstract

This work compares three forcing schemes for a recently introduced cascaded lattice Boltzmann shallow water model: a basic scheme, a second-order scheme, and a centred scheme. Although the force is applied in the streaming step of the lattice Boltzmann model, the acceleration is [...] Read more.

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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16 pages, 3643 KiB

Open AccessArticle

Discharge Coefficients for Sluice Gates Set in Weirs at Different Upstream Wall Inclinations

by Agostino Lauria, Francesco Calomino, Giancarlo Alfonsi and Antonino D’Ippolito

Water 2020, 12(1), 245; https://doi.org/10.3390/w12010245 - 15 Jan 2020

Cited by 15 | Viewed by 5582

Abstract

Laboratory experiments and numerical simulations are performed to measure discharge coefficients in the case of a gate located on the upstream wall of a weir for flood storage. The effect of the gate slope and the side contraction have been taken into account. The study was first performed experimentally, when three series of tests were carried out with (and without) a broad crested weir located under the gate, at different values of the inclination angle of the weir upstream wall, and at different values of the shape ratio and the relative opening. In order to provide useful suggestions for those involved in sluice gate construction and management, three equations were obtained based on multiple regression, relating the discharge coefficient to different parameters that characterize the phenomenon at hand, separating the case when the broad-crested weir was present. Then numerical simulations were executed by means of the Reynolds-averaged Navier–Stokes (RANS) equations with the k-ε turbulence closure model and in conjunction with the volume of fluid (VOF) method, to validate the numerical results against the experimental and to possibly investigate phenomena not caught by the experimental measurements. Simulated discharges were very close to the observed ones showing that the proposed three-dimensional numerical procedure is a favorable option to correctly reproduce the phenomenon. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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20 pages, 2561 KiB

Open AccessArticle

Analysis of the Flow in a Typified USBR II Stilling Basin through a Numerical and Physical Modeling Approach

by Juan Francisco Macián-Pérez, Rafael García-Bartual, Boris Huber, Arnau Bayon and Francisco José Vallés-Morán

Water 2020, 12(1), 227; https://doi.org/10.3390/w12010227 - 14 Jan 2020

Cited by 19 | Viewed by 8392

Abstract

Adaptation of stilling basins to higher discharges than those considered for their design implies deep knowledge of the flow developed in these structures. To this end, the hydraulic jump occurring in a typified United States Bureau of Reclamation Type II (USBR II) stilling basin was analyzed using a numerical and experimental modeling approach. A reduced-scale physical model to conduct an experimental campaign was built and a numerical computational fluid dynamics (CFD) model was prepared to carry out the corresponding simulations. Both models were able to successfully reproduce the case study in terms of hydraulic jump shape, velocity profiles, and pressure distributions. The analysis revealed not only similarities to the flow in classical hydraulic jumps but also the influence of the energy dissipation devices existing in the stilling basin, all in good agreement with bibliographical information, despite some slight differences. Furthermore, the void fraction distribution was analyzed, showing satisfactory performance of the physical model, although the numerical approach presented some limitations to adequately represent the flow aeration mechanisms, which are discussed herein. Overall, the presented modeling approach can be considered as a useful tool to address the analysis of free surface flows occurring in stilling basins. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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14 pages, 4367 KiB

Open AccessArticle

Study on Propellers Distribution and Flow Field in the Oxidation Ditch Based on Two-Phase CFD Model

by Yuquan Zhang, Chengyi Li, Yanhe Xu, Qinghong Tang, Yuan Zheng, Huiwen Liu and E. Fernandez-Rodriguez

Water 2019, 11(12), 2506; https://doi.org/10.3390/w11122506 - 27 Nov 2019

Cited by 14 | Viewed by 3504

Abstract

The oxidation ditch (OD) plays an important role in wastewater treatment plants. With increasing demand and production costs, the energy consumption and sludge deposition occurring in the OD must be diminished to enhance its development. In this paper, a two-phase computational fluid dynamics (CFD) model of water and activated sludge examined the flow field characteristics of an OD, consisting of two side-by-side propellers. The system was studied under five configurations, where the spacing between the propellers was set equal to −0.2, −0.1, 0, 0.1, 0.2 times the length of the OD. The viscosity and settling rate of activated sludge was imported in the numerical simulation through a user defined function (UDF). The optimal scheme of the propeller’s power consumption, velocity distribution, and sludge concentration distribution was obtained. The result shows that sludge concentrations are linked with dead zone velocity but not necessarily with low velocities. Experiments confirmed the validity of the velocity flow field simulated by the two-phase CFD model. Overall, these findings form the basis for the propellers distribution optimization and allow a deeper insight into the flow field of OD systems. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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21 pages, 6936 KiB

Open AccessArticle

Numerical Simulation of Air–Water Two-Phase Flow on Stepped Spillways behind X-Shaped Flaring Gate Piers under Very High Unit Discharge

by Zongshi Dong, Junxing Wang, David Florian Vetsch, Robert Michael Boes and Guangming Tan

Water 2019, 11(10), 1956; https://doi.org/10.3390/w11101956 - 20 Sep 2019

Cited by 22 | Viewed by 5282

Abstract

Stepped spillways are commonly used under relatively low unit discharge, where cavitation pitting can be avoided by self-aerated flow. However, there are several dams in China with stepped spillways in combination with X-shaped flaring gate piers with unit design discharge considerably larger than specified in the available guidelines. Consequently, air–water two-phase flow on stepped spillway behind X-shaped flaring gate piers under very high unit discharge was investigated using Computational Fluid Dynamics (CFD) simulations. The 3-D Reynolds-averaged Navier–Stokes equations were solved, including sub-grid models for air entrainment, density evaluation, and drift-flux, to capture self-aerated free-surface flow over the spillway. The pressure on the vertical step faces was compared with laboratory data. In addition, the air–water two-phase flow characteristics and prototype step failure of the simulated prototype spillway were analyzed based on the numerical results of velocity, pressure, and air concentration. Moreover, an optimized bottom-aeration was further studied. The results reveal that the involved models can predict the air concentration near the steps. The cavitation index at the stepped surface is below the threshold value, and the air concentration is insufficient under high unit discharges. Moreover, with the proposed optimization of the aerator air entrainment can be improved and thereby cavitation erosion risk can be reduced. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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19 pages, 1311 KiB

Open AccessArticle

Fluid Structure Interaction of Buoyant Bodies with Free Surface Flows: Computational Modelling and Experimental Validation

by Andrea Luigi Facci, Giacomo Falcucci, Antonio Agresta, Chiara Biscarini, Elio Jannelli and Stefano Ubertini

Water 2019, 11(5), 1048; https://doi.org/10.3390/w11051048 - 20 May 2019

Cited by 14 | Viewed by 4334

Abstract

In this paper we present a computational model for the fluid structure interaction of a buoyant rigid body immersed in a free surface flow. The presence of a free surface and its interaction with buoyant bodies make the problem very challenging. In fact, with light (compared to the fluid) or very flexible structures, fluid forces generate large displacements or accelerations of the solid and this enhances the artificial added mass effect. Such a problem is relevant in particular in naval and ocean engineering and for wave energy harvesting, where a correct prediction of the hydrodynamic loading exerted by the fluid on buoyant structures is crucial. To this aim, we develop and validate a tightly coupled algorithm that is able to deal with large structural displacement and impulsive acceleration typical, for instance, of water entry problems. The free surface flow is modeled through the volume of fluid model, the finite volume method is utilized is to discretize the flow and solid motion is described by the Newton-Euler equations. Fluid structure interaction is modeled through a Dirichlet-Newmann partitioned approach and tight coupling is achieved by utilizing a fixed-point iterative procedure. As most experimental data available in literature are limited to the first instants after the water impact, for larger hydrodynamic forces, we specifically designed a set of dedicated experiments on the water impact of a buoyant cylinder, to validate the proposed methodology in a more general framework. Finally, to demonstrate that the proposed numerical model could be used for a wide range of engineering problems related to FSI in multiphase flows, we tested the proposed numerical model for the simulation of a floating body. Full article

(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)

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