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5 pages, 205 KiB

Open AccessEditorial

Hydraulic Dynamic Calculation and Simulation

by Costanza Aricò

Water 2021, 13(9), 1234; https://doi.org/10.3390/w13091234 - 29 Apr 2021

Cited by 1 | Viewed by 2567

Abstract

Hydraulic dynamics is emerging as a basic concept with applications and important implications for many industrial, civil, and environmental engineering problems [...] Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

Research

Jump to: Editorial

24 pages, 9316 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Numerical Simulations of the Flow Field of a Submerged Hydraulic Jump over Triangular Macroroughnesses

by Amir Ghaderi, Mehdi Dasineh, Francesco Aristodemo and Costanza Aricò

Water 2021, 13(5), 674; https://doi.org/10.3390/w13050674 - 2 Mar 2021

Cited by 26 | Viewed by 5015

Abstract

The submerged hydraulic jump is a sudden change from the supercritical to subcritical flow, specified by strong turbulence, air entrainment and energy loss. Despite recent studies, hydraulic jump characteristics in smooth and rough beds, the turbulence, the mean velocity and the flow patterns [...] Read more.

The submerged hydraulic jump is a sudden change from the supercritical to subcritical flow, specified by strong turbulence, air entrainment and energy loss. Despite recent studies, hydraulic jump characteristics in smooth and rough beds, the turbulence, the mean velocity and the flow patterns in the cavity region of a submerged hydraulic jump in the rough beds, especially in the case of triangular macroroughnesses, are not completely understood. The objective of this paper was to numerically investigate via the FLOW-3D model the effects of triangular macroroughnesses on the characteristics of submerged jump, including the longitudinal profile of streamlines, flow patterns in the cavity region, horizontal velocity profiles, streamwise velocity distribution, thickness of the inner layer, bed shear stress coefficient, Turbulent Kinetic Energy (TKE) and energy loss, in different macroroughness arrangements and various inlet Froude numbers (1.7 < Fr₁ < 9.3). To verify the accuracy and reliability of the present numerical simulations, literature experimental data were considered. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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14 pages, 5076 KiB

Open AccessArticle

Investigate Impact Force of Dam-Break Flow against Structures by Both 2D and 3D Numerical Simulations

by Le Thi Thu Hien and Nguyen Van Chien

Water 2021, 13(3), 344; https://doi.org/10.3390/w13030344 - 30 Jan 2021

Cited by 18 | Viewed by 3666

Abstract

The aim of this paper was to investigate the ability of some 2D and 3D numerical models to simulate flood waves in the presence of an isolated building or building array in an inundated area. Firstly, the proposed 2D numerical model was based [...] Read more.

The aim of this paper was to investigate the ability of some 2D and 3D numerical models to simulate flood waves in the presence of an isolated building or building array in an inundated area. Firstly, the proposed 2D numerical model was based on the finite-volume method (FVM) to solve 2D shallow-water equations (2D-SWEs) on structured mesh. The flux-difference splitting method (FDS) was utilized to obtain an exact mass balance while the Roe scheme was invoked to approximate Riemann problems. Secondly, the 3D commercially available CFD software package was selected, which contained a Flow 3D model with two turbulent models: Reynolds-averaged Navier-Stokes (RANs) with a renormalized group (RNG) and a large-eddy simulation (LES). The numerical results of an impact force on an obstruction due to a dam-break flow showed that a 3D solution was much better than a 2D one. By comparing the 3D numerical force results of an impact force acting on building arrays with the existence experimental data, the influence of velocity-induced force on a dynamic force was quantified by a function of the Froude number and the water depth of the incident wave. Furthermore, we investigated the effect of the initial water stage and dam-break width on the 3D-computed results of the peak value of force intensity. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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19 pages, 9232 KiB

Open AccessFeature PaperArticle

Impeller Optimization in Crossflow Hydraulic Turbines

by Marco Sinagra, Calogero Picone, Costanza Aricò, Antonio Pantano, Tullio Tucciarelli, Marwa Hannachi and Zied Driss

Water 2021, 13(3), 313; https://doi.org/10.3390/w13030313 - 27 Jan 2021

Cited by 14 | Viewed by 4026

Abstract

Crossflow turbines represent a valuable choice for energy recovery in aqueducts, due to their constructive simplicity and good efficiency under variable head jump conditions. Several experimental and numerical studies concerning the optimal design of crossflow hydraulic turbines have already been proposed, but all [...] Read more.

Crossflow turbines represent a valuable choice for energy recovery in aqueducts, due to their constructive simplicity and good efficiency under variable head jump conditions. Several experimental and numerical studies concerning the optimal design of crossflow hydraulic turbines have already been proposed, but all of them assume that structural safety is fully compatible with the sought after geometry. We show first, with reference to a specific study case, that the geometry of the most efficient impeller would lead shortly, using blades with a traditional circular profile made with standard material, to their mechanical failure. A methodology for fully coupled fluid dynamic and mechanical optimization of the blade cross-section is then proposed. The methodology assumes a linear variation of the curvature of the blade external surface, along with an iterative use of two-dimensional (2D) computational fluid dynamic (CFD) and 3D structural finite element method (FEM) simulations. The proposed methodology was applied to the design of a power recovery system (PRS) turbine already installed in an operating water transport network and was finally validated with a fully 3D CFD simulation coupled with a 3D FEM structural analysis of the entire impeller. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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23 pages, 14115 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Performance Improvement of a Drag Hydrokinetic Turbine

by Mabrouk Mosbahi, Mariem Lajnef, Mouna Derbel, Bouzid Mosbahi, Costanza Aricò, Marco Sinagra and Zied Driss

Water 2021, 13(3), 273; https://doi.org/10.3390/w13030273 - 23 Jan 2021

Cited by 15 | Viewed by 3682

Abstract

Hydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a [...] Read more.

Hydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a very low environmental impact due to their negligible effect on solid transport. Among them, kinetic turbines with vertical axis are very inexpensive and have almost zero impact on fish and local fauna. In application to tidal waves and sea waves, where vertically averaged velocities have alternate direction, a Savonius rotor also has the advantage of being productive during the whole time cycle. In this work, the effect of an upstream deflector system mounted upstream of a twisted Savonius rotor inside a channel has been investigated through numerical simulations and experimental tests. Numerical simulations were carried on using the ANSYS FLUENT 17.0 software. Based on this numerical study, it is shown that the proposed deflector system has improved the power coefficient of the Savonius rotor by 14%. The utilization of this new design system is predicted to contribute towards a more efficient use of flows in rivers and channels for electricity production in rural areas. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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17 pages, 8486 KiB

Open AccessArticle

DEM-CFD Simulation and Experiments on the Flow Characteristics of Particles in Vortex Pumps

by Xiongfa Gao, Weidong Shi, Ya Shi, Hao Chang and Ting Zhao

Water 2020, 12(9), 2444; https://doi.org/10.3390/w12092444 - 31 Aug 2020

Cited by 24 | Viewed by 3853

Abstract

Due to their outstanding anti-clogging ability, vortex pumps have been gradually promoted and applied in recent years. However, when transporting sewage containing solids, they will still encounter problems such as partial clogging, overwork wear, etc., therefore, it is particularly important to master the [...] Read more.

Due to their outstanding anti-clogging ability, vortex pumps have been gradually promoted and applied in recent years. However, when transporting sewage containing solids, they will still encounter problems such as partial clogging, overwork wear, etc., therefore, it is particularly important to master the flow characteristics of solid particles in the vortex pump. In this paper, the Discrete Element Model-Computational Fluid Dynamics (DEM-CFD) coupled calculation method is introduced into the numerical simulation of vortex pumps and particles with diameters of 1, 2 and 3 mm and concentrations of 1% and 5%, were subjected to numerical simulation and study of the flow characteristics of the particles, then rapeseed was used to represent solid particles in tests. It was obvious that the CFD results were in good agreement with the experimental results, whereby the high speed photography experimental results of the pump inlet section show that the experimental results are consistent with the numerical simulation results. The results show that there are three typical movement tracks of solid particles in the vortex pump: in Track A particles flow through the impeller and enter the volute by the through flow, in Track B particles go directly into the volute through the lateral cavity under the influence of circulation flow and in Track C the particles enter the impeller from the front cover end area of the impeller blade inlet and then into the volute through the back half area of blade. It can be found that the particles are mainly distributed at the back of the volute. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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26 pages, 8336 KiB

Open AccessArticle

Numerical Simulation of the Flow Field Characteristics of Stationary Two-Pipe Vehicles under Different Spacings

by Xiaomeng Jia, Xihuan Sun and Yongye Li

Water 2020, 12(8), 2158; https://doi.org/10.3390/w12082158 - 30 Jul 2020

Cited by 3 | Viewed by 2736

Abstract

The piped hydraulic transportation of tube-contained raw material is a new long- distance transportation technology. This technology has the advantages of high efficiency, energy savings and environmental protection. The research in the published literature has mostly been limited to the speed, flow field, [...] Read more.

The piped hydraulic transportation of tube-contained raw material is a new long- distance transportation technology. This technology has the advantages of high efficiency, energy savings and environmental protection. The research in the published literature has mostly been limited to the speed, flow field, pressure field and energy consumption of a single-pipe vehicle. With the continuous improvement and development of this technology, two-pipe vehicles will become the focus of future research. The change of the vehicle spacing will affect the starting speed, flow field distribution and pressure drop characteristics of the water flow within the pipeline; thus, a numerical simulation is used in this work to study the hydraulic characteristics of stationary two-pipe vehicles under different spacings and compare them with physical experiments. The results show that the simulation results are in good agreement with the experimental results, which indicates that it is feasible to study two-pipe vehicles using numerical simulation. The results also show that, as the vehicle spacing increases, the interaction between the two-pipe vehicles gradually weakens. When the vehicle spacing reaches 4 l (where l represents the length of a single-pipe vehicle), the interaction between the two-pipe vehicles becomes negligible. There is no vortex shedding in the pipeline under different vehicle spacings. This study provides a reference for choosing the proper spacing between two-pipe vehicles and provides a theoretical basis for further research on the hydraulic characteristics of two-pipe vehicles in motion. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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22 pages, 7621 KiB

Open AccessArticle

Numerical Study on Dynamical Structures and the Destratification of Vertical Turbulent Jets in Stratified Environment

by Xuan Huang, Ling-ling Wang and Jin Xu

Water 2020, 12(8), 2085; https://doi.org/10.3390/w12082085 - 23 Jul 2020

Cited by 3 | Viewed by 2197

Abstract

The law of pollutant emission and diffusion in stratified waters is a common issue. In this paper, numerical study on the interaction between vertical turbulent jets and the pycnocline is carried out to study the problems of jet’s emission through the large eddy [...] Read more.

The law of pollutant emission and diffusion in stratified waters is a common issue. In this paper, numerical study on the interaction between vertical turbulent jets and the pycnocline is carried out to study the problems of jet’s emission through the large eddy simulation (LES). A trigonometric function disturbance (TFD) method is developed to ensure the velocity distribution of the jet in the horizontal plane yield to Gaussian profile. Numerical simulations are carried out in the range of 1.11 < Fr_p < 4.77, corresponding to 1393 < Re_p < 5979, where the Froude number Fr_p and the Reynolds number Re_p are defined at the entrance of pycnocline. The coherent structure and internal waves are observed at the pycnocline during the process of jets impinging. After the impingement, the destratification effects can be found. It can be found that Fr_p = 3 is a threshold value for the interaction between jets and the pycnocline. When Fr_p > 3, the interaction becomes intensely. Furthermore, the fitting formula of the radial momentum flux dissipation rate that is used to describe the decay of energy contained by the jets during the impinging process, is established through the dimensionless analysis. As a result, the influence range of the jet on the horizontal plane can be evaluated by Re_p. It is also found that the destratification of jets is mainly affected by the velocity of the internal wave induced by jets. In addition, by employing the dimensionless time T related to that velocity, the law of destratification varies with dimensionless time is obtained, which can be summarized as follows: Due to the influence of the first internal wave, the thickness of the pycnocline increases rapidly and reaches a critical value at T = 1.4, after that, the increase of the thickness of the pycnocline becomes linear. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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22 pages, 8274 KiB

Open AccessEditor’s ChoiceArticle

Applied Strategy to Characterize the Energy Improvement Using PATs in a Water Supply System

by Luis E. Camilo Rosado, P. Amparo López-Jiménez, Francisco-Javier Sánchez-Romero, Pilar Conejos Fuertes and Modesto Pérez-Sánchez

Water 2020, 12(6), 1818; https://doi.org/10.3390/w12061818 - 24 Jun 2020

Cited by 15 | Viewed by 3165

Abstract

Sustainable development has been an idea raised in recent years. The results are related to the improvement and the use of new technologies to maximize efficiency in water management. However, energy consumption has been increasing as a consequence of new management and uses [...] Read more.

Sustainable development has been an idea raised in recent years. The results are related to the improvement and the use of new technologies to maximize efficiency in water management. However, energy consumption has been increasing as a consequence of new management and uses of water. Especially in pressurized water distribution systems, the use of pressure reduction valves (PRVs) increases the water usage efficiency but it decreases the energy consumption efficiency, since the valves dissipate energy that could be recovered. This research presents a proposal of a recovery system based on the installation of pumps used as turbines (PATs). These machines are located in different points of the high-pressure water distribution system in the Valencia Metropolitan System (Spain). An annual estimate of the theoretical recoverable energy as well as the “ideal” pump for each point were proposed. The theoretical recovered energy value was 847,301 kWh/year for a specific analyzed point. Besides, the characteristic curves of the PATs from a selected point were determined, estimating an improvement in the sustainable indexes. The calculus of these green parameters showed that the implementation of this solution caused a reduction in consumed energy of 1.50 kWh/m³. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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17 pages, 3722 KiB

Open AccessArticle

Improvement of Non-Hydrostatic Hydrodynamic Solution Using a Novel Free-Surface Boundary Condition

by Augusto Hugo Farias Cunha, Carlos Ruberto Fragoso, Jr., Cayo Lopes Bezerra Chalegre and David Motta-Marques

Water 2020, 12(5), 1271; https://doi.org/10.3390/w12051271 - 30 Apr 2020

Cited by 2 | Viewed by 2290

Abstract

Hydrodynamic models based on the RANS equation are well-established tools to simulate three-dimensional free surface flows in large aquatic ecosystems. However, when the ratio of vertical to horizontal motion scales is not small, a non-hydrostatic approximation is needed to represent these processes accurately. [...] Read more.

Hydrodynamic models based on the RANS equation are well-established tools to simulate three-dimensional free surface flows in large aquatic ecosystems. However, when the ratio of vertical to horizontal motion scales is not small, a non-hydrostatic approximation is needed to represent these processes accurately. Increasing efforts have been made to improve the efficiency of non-hydrostatic hydrodynamic models, but these improvements require higher implementation and computational costs. In this paper, we proposed a novel free-surface boundary condition based on a fictional sublayer at the free-surface (FSFS). We applied the FSFS approach at a finite difference numerical discretization with a fractional step framework, which uses a Neumann type of boundary condition to apply a hydrostatic relation in the top layer. To evaluate the model performance, we compared the Classic Boundary Condition Approach (CBA) and the FSFS approach using two numerical experiments. The experiments tested the model’s phase error, capability in solving wave celerity and simulate non-linear wave propagation under different vertical resolution scenarios. Our results showed that the FSFS approach had a lower phase error (2 to 5 times smaller) than CBA with a little additional computational cost (ca. 7% higher). Moreover, it can better represent wave celerity and frequency dispersion with 2 times fewer layers and low mean computational cost (CBA

δ

t = 2.62 s and FSFS

δ

t = 1.22 s). Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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16 pages, 4665 KiB

Open AccessEditor’s ChoiceArticle

Numerical Investigation of a High-Speed Electrical Submersible Pump with Different End Clearances

by Ling Zhou, Wanhong Wang, Jianwei Hang, Weidong Shi, Hao Yan and Yong Zhu

Water 2020, 12(4), 1116; https://doi.org/10.3390/w12041116 - 14 Apr 2020

Cited by 41 | Viewed by 3997

Abstract

The end clearance of the impeller is one of the most important structural parameters in the hydraulic design of a high-speed electrical submersible pump (ESP). In this paper, an ESP with a rotating speed of 6000 r/min was taken as the research object. [...] Read more.

The end clearance of the impeller is one of the most important structural parameters in the hydraulic design of a high-speed electrical submersible pump (ESP). In this paper, an ESP with a rotating speed of 6000 r/min was taken as the research object. Numerical calculations were carried out for five different end clearance conditions of 0.1 mm, 0.3 mm, 0.6 mm, 0.9 mm, and 1.2 mm, respectively, to obtain the performance and internal flow field under different situation. The simulation results were verified by the pump performance experiment. It showed that the increase of the end clearance led to a decrease of the head and efficiency of the electrical submersible pump. Through the analysis of the internal flow field, it was found that the existence of the end clearance reduced the flow rate and caused free pre-whirl. With the increase of the end clearance, the phenomenon of de-flow in the diffuser passage was aggravated, which further reduced the performance of the electrical submersible pump. Finally, the reasonable recommended value of the end clearance was given, which facilitated the optimization design and engineering application of the high-speed ESP. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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19 pages, 3897 KiB

Open AccessArticle

Numerical Simulation of Flow Velocity Characteristics during Capsule Hydraulic Transportation in a Horizontal Pipe

by Fei Li, Yongye Li, Xihuan Sun and Xiaoni Yang

Water 2020, 12(4), 1015; https://doi.org/10.3390/w12041015 - 2 Apr 2020

Cited by 5 | Viewed by 3202

Abstract

Capsule hydraulic transportation is a kind of low-carbon and environmentally friendly pipeline transportation technique. In this study, the flow velocity characteristics in the pipeline when the capsule is transported in a straight pipe section were simulated by adopting the RNG (Renormalization Group) k–ε [...] Read more.

Capsule hydraulic transportation is a kind of low-carbon and environmentally friendly pipeline transportation technique. In this study, the flow velocity characteristics in the pipeline when the capsule is transported in a straight pipe section were simulated by adopting the RNG (Renormalization Group) k–ε turbulence model based on Fluent software and experimentally verified. The results showed that the simulated value of flow velocity in the pipeline was basically consistent with the experimental value during transportation of the material by the capsule, and the maximum relative error was no more than 6.7%, proving that it is feasible to use Fluent software to simulate the flow velocity characteristics in the pipeline when the capsule is transported in a straight pipe section. In the process of material transportation, the flow velocity distribution of the cross-section near the upstream and downstream sections of the capsule was basically the same, which increased with the increased length–diameter ratio of the capsule. The axial flow velocity was smaller in the middle of the pipe and larger near the inner wall of the pipe. From the inner wall to the center of the pipe, the radial flow velocity first increased and then decreased. The circumferential flow velocity was distributed in the vicinity of the support body of the capsule. The axial flow velocity of the annular gap section around the capsule first increased and then decreased from the inner wall of the pipe to the outer wall of the capsule. In the process of transporting materials, the influence of the capsule on the flow of its downstream section was greater than that of its upstream section. These results could provide a theoretical basis for optimizing the technical parameters of capsule hydraulic transportation. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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23 pages, 11560 KiB

Open AccessArticle

Numerical Investigation of a Hydrosplitting Fracture and Weak Plane Interaction Using Discrete Element Modeling

by Shuaiqi Liu, Fengshan Ma, Haijun Zhao, Jie Guo, Xueliang Duan and Qihao Sun

Water 2020, 12(2), 535; https://doi.org/10.3390/w12020535 - 14 Feb 2020

Cited by 9 | Viewed by 3112 | Correction

Abstract

Water inrush caused by hydrosplitting is an extremely common disaster in the engineering of underground tunnels. In this study, the propagation of fluid-driven fractures based on an improved discrete element fluid-solid coupling method was modeled. First, the interactions between hydrosplitting fractures (HFs) and [...] Read more.

Water inrush caused by hydrosplitting is an extremely common disaster in the engineering of underground tunnels. In this study, the propagation of fluid-driven fractures based on an improved discrete element fluid-solid coupling method was modeled. First, the interactions between hydrosplitting fractures (HFs) and preexisting weak planes (WPs) with different angles were simulated considering water pressure in the initial fracture. Second, the influence of the in situ stress ratio and the property of WPs were analyzed, and corresponding critical pressure values of different interactions were calculated. Lastly, the maximum principal stress and maximum shear stress variation inside the pieces were reproduced. The following conclusions can be drawn: (1) Five different types of interaction modes between HFs and natural WPs were obtained, prone to crossing the WPs under inclination of 90°. (2) The initiation pressure value decreased with an increased in situ stress ratio, and the confining stress status had an effect on the internal principal stress. (3) During HFs stretching in WPs with a high elastic modulus, the value of the maximum principal stress was low and rose slowly, and the maximum shear stress value was smaller. Through comprehensive analysis, the diversity of the principal stress curves is fundamentally determined by the interaction mode between HFs and WPs, which are influenced by the variants mentioned in the paper. The analysis provides a better guideline for understanding the failure mechanism of water gushing out of deep buried tunnel construction and cracking seepage of high head tunnels. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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18 pages, 3949 KiB

Open AccessArticle

Improved Planning of Energy Recovery in Water Systems Using a New Analytic Approach to PAT Performance Curves

by Modesto Pérez-Sánchez, Francisco Javier Sánchez-Romero, Helena M. Ramos and P. Amparo López-Jiménez

Water 2020, 12(2), 468; https://doi.org/10.3390/w12020468 - 10 Feb 2020

Cited by 39 | Viewed by 3324

Abstract

The use of pumps working as turbines (PATs) to improve the energy efficiency of water networks has been studied in the last years. This recovery system is justified due to a low investment contrasting with the capacity to take advantage in certain points [...] Read more.

The use of pumps working as turbines (PATs) to improve the energy efficiency of water networks has been studied in the last years. This recovery system is justified due to a low investment contrasting with the capacity to take advantage in certain points with low and medium recoverable heads. Analyses of water systems using simulation software and/or optimization algorithms need the characteristic curves (head and efficiency) of the machines, which should be known with minor error by the water managers. The knowledge of the best efficiency point (BEP) as a turbine is one of the major limitations when the user wants to choose PATs. In this sense, the present research defines new approach equations to estimate the BEP of the PAT, as well as to predict the characteristic curves, comparing the results with the rest of the published methods. The comparison demonstrated that the new proposal reduced the error indexes, improved the R² and increased the accuracy of the error ellipse using an experimental database of 181 different PATs. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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28 pages, 31660 KiB

Open AccessArticle

The Action Mechanism of Rotor–Stator Interaction on Hydraulic and Hydroacoustic Characteristics of a Jet Centrifugal Pump Impeller and Performance Improvement

by Rong Guo, Rennian Li, Renhui Zhang and Wei Han

Water 2020, 12(2), 465; https://doi.org/10.3390/w12020465 - 10 Feb 2020

Cited by 3 | Viewed by 3128

Abstract

The aim of this study was to investigate the action mechanism of the rotor–stator interaction (RSI) on the transient flow field and hydrodynamic noise field inside the impeller of jet centrifugal pumps (JCPs) and optimize effects of the guide vane on the hydraulic [...] Read more.

The aim of this study was to investigate the action mechanism of the rotor–stator interaction (RSI) on the transient flow field and hydrodynamic noise field inside the impeller of jet centrifugal pumps (JCPs) and optimize effects of the guide vane on the hydraulic and hydroacoustic characteristics of the impeller. The numerical method of CFD (computational fluid dynamics) coupled with CFA (computational fluid acoustics) was used to analyze the correlation between the guide vane and the flow/sound performances of the impeller. The orthogonal test method, with the hydroacoustic performance of the impeller taken as the objective, was used to optimize the structural parameters of the guide vane for the stability of the hydraulic performance of the JCP. The results show that the RSI leads to a significant increase in the hydroacoustic level of the impeller, but it is indispensable for improving the hydraulic performance of the pump. The RSI effect on the fluctuation intensity of the transient flow field inside the impeller is much more sensitive than the time-average, and the fluctuation intensity of the flow field is positively correlated with the vortex intensity inside the impeller. When the impeller geometry is constant, the evolution processes of the flow field inside the impeller are mainly related to the blade number of the guide vane; when the number of guide vanes is given, the RSI effect on the hydroacoustic characteristic of the impeller is characterized by a positive correlation between the total sound pressure level (SPL) and the fluctuation intensity of the flow field. The frequency spectrum characteristics of the hydroacoustic SPL of the impeller are not consistent with the pressure fluctuation characteristics inside the impeller. The pressure fluctuation characteristics are related not only to the blade number and speed of the impeller but also to its wake characteristics determined by the guide vane. The optimization scheme for the stable hydraulic performance of the JCP significantly reduced the total SPL of the impeller compared with the original scheme, which verifies the feasibility of using the weight matrix optimization method to obtain the global optimization scheme. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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23 pages, 10463 KiB

Open AccessArticle

Physics-Based Simulation of Ocean Scenes in Marine Simulator Visual System

by Haijiang Li, Hongxiang Ren, Shaoyang Qiu and Chang Wang

Water 2020, 12(1), 215; https://doi.org/10.3390/w12010215 - 12 Jan 2020

Cited by 4 | Viewed by 7135

Abstract

The realistic simulation of ocean scenes is of great significance in many scientific fields. We propose an improved Smoothed Particle Hydrodynamics (SPH) framework to simulate the ocean scenes. The improved SPH combines nonlinear constant density constraints and divergence-free velocity field constraint. Density constraints [...] Read more.

The realistic simulation of ocean scenes is of great significance in many scientific fields. We propose an improved Smoothed Particle Hydrodynamics (SPH) framework to simulate the ocean scenes. The improved SPH combines nonlinear constant density constraints and divergence-free velocity field constraint. Density constraints adjust the particle distribution on position layer, so that the density is constrained to a constant state. The addition of the divergence-free velocity field constraint significantly accelerates the convergence of constant density constraint and further reduces the density change. The simulation results show that the improved SPH has high solution efficiency, large time steps, and strong stability. Then, we introduce a unified boundary handling model to simulate coupling scenes. The model samples the boundary geometry as particles by means of single layer nonuniform sampling. The contribution of the boundary particles is taken into account when the physical quantities of fluid particles are computed. The unified model can handle various types of complex geometry adaptively. When rendering the ocean, we propose an improved anisotropic screen space fluid method, which alleviates the discontinuity problem near the boundary and maintains the anisotropy of particles. The research provides a theoretical reference for the highly believable maritime scene simulation in marine simulators. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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30 pages, 8682 KiB

Open AccessArticle

2-D Characteristics of Wave Deformation Due to Wave-Current Interactions with Density Currents in an Estuary

by Woo-Dong Lee, Norimi Mizutani and Dong-Soo Hur

Water 2020, 12(1), 183; https://doi.org/10.3390/w12010183 - 9 Jan 2020

Cited by 6 | Viewed by 4165

Abstract

In this study, numerical simulations were conducted in order to understand the role of wave-current interactions in wave deformation. The wave-current interaction mechanisms, wave reflection and energy loss due to currents, the effect of incident conditions on wave-current interactions, the advection-diffusion characteristics of [...] Read more.

In this study, numerical simulations were conducted in order to understand the role of wave-current interactions in wave deformation. The wave-current interaction mechanisms, wave reflection and energy loss due to currents, the effect of incident conditions on wave-current interactions, the advection-diffusion characteristics of saltwater, and the effect of density currents on wave-current interactions were discussed. In addition, the effect of saltwater–freshwater density on wave-current interactions was investigated under a hypopycnal flow field via numerical model testing. Turbulence was stronger under the influence of wave-current interactions than under the influence of waves alone, as wave-current interactions reduced wave energy, which led to decreases in wave height. This phenomenon was more prominent under shorter wave periods and higher current velocities. These results increase our understanding of hydrodynamic phenomena in estuaries in which saltwater–freshwater and wave-current pairs coexist. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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15 pages, 5070 KiB

Open AccessArticle

Numerical Simulations of Hydraulic Characteristics of A Flow Discharge Measurement Process with A Plate Flowmeter in A U-Channel

by Yongye Li, Yuan Gao, Xiaomeng Jia, Xihuan Sun and Xuelan Zhang

Water 2019, 11(11), 2382; https://doi.org/10.3390/w11112382 - 14 Nov 2019

Cited by 3 | Viewed by 2520

Abstract

The use of a flow discharge measuring device in irrigated areas is the key to utilizing water in a planned and scientific manner and to developing water-saving irrigation techniques. In this study, a new type of flow discharge measuring device for a U-channel—a [...] Read more.

The use of a flow discharge measuring device in irrigated areas is the key to utilizing water in a planned and scientific manner and to developing water-saving irrigation techniques. In this study, a new type of flow discharge measuring device for a U-channel—a plate flowmeter—was designed, and then the hydraulic characteristics of the flow discharge measurement process using the plate flowmeter were simulated and experimentally verified by adopting an RNG (Renormalization Group) k-ε turbulence model based on Flow-3D software. The results showed that in the process of measuring flow discharge with the plate flowmeter, the transverse flow velocity, the vertical flow velocity, and the relationship between the measured flow discharge and the deflection angle of the angle-measuring plate were basically consistent with the experimental results. The maximum relative errors were 5.3%, 6.2%, and 6.8% respectively, proving that it was feasible to use Flow-3D software to simulate the hydraulic characteristics of the flow discharge measurement process using the plate flowmeter. The vertical flow velocities at the center of the upstream section of the channel increased gradually from the bottom of the channel to the free water surface. The vertical flow velocities at the center of the downstream section of the channel first increased and then decreased from the bottom of the channel to the free water surface, and the maximum vertical flow velocity was located at a position below the free water surface. The maximum range of influence of the plate flowmeter on the flow disturbance in the channel was from 0.75 m upstream to 1.24 m downstream of the plate flowmeter. These results can provide a theoretical basis for optimizing the structural parameters of a plate flowmeter. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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23 pages, 10756 KiB

Open AccessArticle

A Novel, Coupled CFD-DEM Model for the Flow Characteristics of Particles Inside a Pipe

by Haotong Zhou, Guihe Wang, Cangqin Jia and Cheng Li

Water 2019, 11(11), 2381; https://doi.org/10.3390/w11112381 - 14 Nov 2019

Cited by 18 | Viewed by 6150

Abstract

This study developed a novel, 3D coupled computational fluid dynamics (CFD)-discrete element method (DEM) model by coupling two software programs, OpenFOAM and PFC^3D, to solve problems related to fluid–particle interaction systems. The complete governing equations and the flow chart of the [...] Read more.

This study developed a novel, 3D coupled computational fluid dynamics (CFD)-discrete element method (DEM) model by coupling two software programs, OpenFOAM and PFC^3D, to solve problems related to fluid–particle interaction systems. The complete governing equations and the flow chart of the coupling calculations are clearly presented herein. The coupled CFD-DEM model was first benchmarked using two classic geo-mechanics problems, for which the analytical solutions are available. Then, the CFD-DEM model was employed to investigate the flow characteristics of a particle heap subjected to the effects of water inside a pipe under different conditions. The results showed that particle size and pipe inclination angle can significantly affect the particle flow morphology, total kinetic energy and erosion rate for mono-sized particles, whereas polydisperse particles had a slight effect. This model can accurately describe the flow characteristics of particles inside a pipe, and the results of this study were consistent with those of previous studies. The reliability of this model was further demonstrated, which showed that this model can provide valuable references for solving similar problems such as soil erosion and bridge scour problems. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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24 pages, 896 KiB

Open AccessArticle

Combined Use of High-Resolution Numerical Schemes to Reduce Numerical Diffusion in Coupled Nonhydrostatic Hydrodynamic and Solute Transport Model

by Augusto Hugo Farias Cunha, Carlos Ruberto Fragoso, Matheus Henrique Tavares, J. Rafael Cavalcanti, Marie-Paule Bonnet and David Motta-Marques

Water 2019, 11(11), 2288; https://doi.org/10.3390/w11112288 - 31 Oct 2019

Cited by 1 | Viewed by 2567

Abstract

In three-dimensional simulations of free-surface flow where the vertical velocities are relevant, such as in lakes, estuaries, reservoirs, and coastal zones, a nonhydrostatic hydrodynamic approach may be necessary. Although the nonhydrostatic hydrodynamic approach improves the physical representation of pressure, acceleration and velocity fields, [...] Read more.

In three-dimensional simulations of free-surface flow where the vertical velocities are relevant, such as in lakes, estuaries, reservoirs, and coastal zones, a nonhydrostatic hydrodynamic approach may be necessary. Although the nonhydrostatic hydrodynamic approach improves the physical representation of pressure, acceleration and velocity fields, it is not free of numerical diffusion. This numerical issue stems from the numerical solution employed in the advection and diffusion terms of the Reynolds-averaged Navier–Stokes (RANS) and solute transport equations. The combined use of high-resolution schemes in coupled nonhydrostatic hydrodynamic and solute transport models is a promising alternative to minimize these numerical issues and determine the relationship between numerical diffusion in the two solutions. We evaluated the numerical diffusion in three numerical experiments, for different purposes: The first two experiments evaluated the potential for reducing numerical diffusion in a nonhydrostatic hydrodynamic solution, by applying a quadratic interpolator over a Bilinear, applied in the Eulerian–Lagrangian method (ELM) step-ii interpolation, and the capability of representing the propagation of complex waves. The third experiment evaluated the effect on numerical diffusion of using flux-limiter schemes over a first-order Upwind in solute transport solution, combined with the interpolation methods applied in a coupled hydrodynamic and solute transport model. The high-resolution methods were able to substantially reduce the numerical diffusion in a solute transport problem. This exercise showed that the numerical diffusion of a nonhydrostatic hydrodynamic solution has a major influence on the ability of the model to simulate stratified internal waves, indicating that high-resolution methods must be implemented in the numerical solution to properly simulate real situations. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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20 pages, 8064 KiB

Open AccessArticle

Three-Dimensional Numerical Simulation of Dam Discharge and Flood Routing in Wudu Reservoir

by Youtong Rong, Ting Zhang, Ling Peng and Ping Feng

Water 2019, 11(10), 2157; https://doi.org/10.3390/w11102157 - 16 Oct 2019

Cited by 12 | Viewed by 4723

Abstract

The main objectives of the present work are to investigate the hydraulic characteristics of the dam discharge flow and its impact downstream. Building information modeling technology is adopted to generate the terrain entity and hydraulic structures. The calculation of the dam discharge and [...] Read more.

The main objectives of the present work are to investigate the hydraulic characteristics of the dam discharge flow and its impact downstream. Building information modeling technology is adopted to generate the terrain entity and hydraulic structures. The calculation of the dam discharge and flood routing simulation is achieved by employing Reynolds-Averaged Navier-Stokes equations with the RNG k-ε eddy viscosity model for its turbulence closure, as well as the Volume of Fluid method. An urban flood experiment and the field measurement records are utilized and validated the model accuracy. The flow field is obtained to assess the dam working conditions under different water levels. The results show that the maximum downstream flow depth, the maximum discharge capacity and the hydraulic jump length under normal water level is 18.6 m, 13,800 m³/s, and 108 m, respectively. The dam satisfies the safety demand under different water levels but close attention should be paid to the dam foundation, especially around the incident points of the discharge flow. Complex turbulent flow patterns, including collision, reflection, and vortices, are captured by three-dimensional simulation. The numerical simulation can assist the reservoir management vividly, so as to guarantee the stability of the dam operation. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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