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The purpose of this paper is to investigate the impact of near-wall treatment approaches, which are crucial parameters in predicting the flow characteristics of open channels, and the influence of different vegetation covers in different layers.

Ansys Fluent, a computational fluid dynamics software, was used to calculate the flow and turbulence characteristics using a three-dimensional, turbulent (k-e realizable), incompressible and steady-flow assumption, along with various near-wall treatment approaches (standard, scalable, non-equilibrium and enhanced) in the vegetated channel. The numerical study was validated concerning an experimental study conducted in the existing literature.

The numerical model successfully predicted experimental results with relative error rates below 10%. It was determined that nonequilibrium wall functions exhibited the highest predictive success in experiment Run 1, standard wall functions in experiment Run 2 and enhanced wall treatments in experiment Run 3. This study has found that plant growth significantly alters open channel flow. In the contact zones, the velocities and the eddy viscosity are low, while in the free zones they are high. On the other hand, the turbulence kinetic energy and turbulence eddy dissipation are maximum at the solid–liquid interface, while they are minimum at free zones.

This is the first study, to the best of the author’s knowledge, concerning the performance of different near-wall treatment approaches on the prediction of vegetation-covered open channel flow characteristics. And this study provides valuable insights to improve the hydraulic performance of open-channel systems.

Describes further development of a 3D finite difference code written to model turbulent flows in an open channel with a moving free surface. The code has been developed so that the computational domain can have side‐walls and/or periodic directions and that the flow may also be buoyancy driven. Either a full simulation or large eddy simulation (LES) of the turbulence can be performed. Results are presented of a simulation of periodic streamwise flow in an open channel with parallel side‐walls and also of a thermal jet into an open tank. Both simulations were carried out on a UNIX workstation using resolutions that enable the results to be viewed within an “engineering context”. The LES application demands numerical approximations which conserve mass, momentum and total energy with high precision, and which permit wave motion with very little numerical dispersion or dissipation. The free surface is tracked using a split‐merge technique which combines the volume of fluid (VOF) and height function methods in a way that is conservative.

An algorithm based on flux difference splitting is presented for the solution of two‐dimensional, steady, supercritical open channel flows. A transformation maps a non‐rectangular, physical domain into a rectangular one. The governing equations are then the shallow water equations, including terms of slope and friction, in a generalised coordinate system. A regular mesh on a rectangular computational domain can then be employed. The resulting scheme has good jump capturing properties and the advantage of using boundary/body‐fitted meshes. The scheme is applied to a problem of flow in a river whose geometry induces a region of supercritical flow.

The purpose of this paper is to numerically study heated channel flow using direct numerical simulation (DNS) and large eddy simulation (LES) method. Using different domain size and different grid resolution it is show that filtering procedure is influenced and may results in very different solutions.

Turbulent non-isothermal fully developed channel flow has been investigated using LES. The filtered Navier-stokes and energy equations were numerically solved with dynamic subgrid scale (SGS) model, standard Smagorinsky model or without additional model for the turbulent SGS stress and heat flux required to close the governing equations.

The numerical LES results in comparison with the DNS data demonstrate that the LES computations may not always offers a reliable prediction of non-isothermal turbulent flow in open channel. It has been found that, even though the models reproduces accurately results for the flow field the thermal field computed using LES do not necessary match the DNS results. Introducing SGS model for scalar do not always show large improvement. One of the reason is thickness of hydrodynamic and thermal boundary layer. In the cases when boundary layers are very different it is not easy optimally set up control volumes in the domain.

This is one of the first instance in which a results of numerical computations for different grid resolution, different stretching, SGS model is employed for non-isothermal turbulent channel flow. It shows that in the cases when boundary layers hydrodynamic and thermal are very different it is hardly find optimal grid resolution or stretching

The purpose of this study is to address the issue that the traditional V-shaped ball valve profile shape is limiting the flow control characteristics in a series structure and to optimize the design profile by proposing an open-hole profile.

This paper proposes a Gaussian process regression surrogate model based on the genetic algorithm optimization of swarm intelligence, combined with the Expected Improvement point addition criterion, to optimize and correct the design profile. The flow regulation performance of the optimized V-shaped regulating ball valve is verified through a combination of numerical simulation and experiment.

The results demonstrate that the optimized V-shaped regulating ball valve has higher flow regulation accuracy and a more stable flow regulation process. After optimization, the flow characteristic curve of the spool is closer to the ideal equal percentage characteristic. The simulation results of the flow field are consistent with the experimental results.

The proposed method significantly reduces the optimization time, has higher efficiency and solves the problem that traditional optimization methods struggle with, which is ensuring optimal flow regulation performance. Compared to the traditional trial-and-error optimization method, the proposed method is more effective. The feasibility of the method is supported by experimental results.

The purpose of this paper is to construct a numerical model for the numerical analysis of the hydraulic transient profile in Trabalhador channel for filling and emptying maneuvers and to determine the water level in time. Model results support operational managers in the decision-making process.

Physical data were provided for the construction and calibration of the numerical model. The equations of Saint-Venant were approximated by a finite difference scheme and the numerical model was written in Fortran. The results of filling and emptying of the channel simulations were compared with the measured water levels.

Measured water levels and those simulated by the numerical model have shown good correlation. The time recorded for the filling and emptying of the canal was also close between the measured and simulated data. The simulation design flow pointed to inundation in the channel banks. Simulation water levels were slightly higher than those measured.

In this model, the combination of canals and pressure conduits was not considered.

The findings confirm the measured time for filling and emptying of the canal, as well as inundation of canal banks for the maximum design flow. These results help in the management process.

This paper presents a numerical model for hydraulic transient analysis in channels with good agreement with the field data.

Describes the solution of the shallow water flow equations in strongly conservative form using a finite volume method. A SIMPLE‐like scheme is developed to treat the velocity depth coupling. The method is applied to flow in a sharply curved channel and the results compared with published data. An error analysis is included which indicates that the method proposed is suitable for solving two‐dimensional steady state problems in open channel flow.

Extreme weather events introduced by climate change have been frequent across the world for the past decade. For example, Takeda City, a mountainous area in the south-western Japan, experienced a severe river flood event caused by the factors of high flow, presence of bridges and driftwood accumulation in July 2012. This study aims to focus on this event (hereafter, Takeda flood) because the unique factors of driftwood and bridges were involved. In the Takeda flood, high flow, driftwood and bridge were the potential key factors that caused the flood. The authors studied to reveal the physical processes of the Takeda flood.

The authors conducted a fundamental laboratory experiment with a miniature bridge, open channel flow and idealized driftwood accumulation. They also performed a numerical simulation by using a smoothed particle hydrodynamics (SPH) method, which can treat fluid as particle elements. This model was chosen because the SPH method is capable of treating a complex flow such as a spray of water around a bridge.

The numerical simulation successfully reproduced the bridge- and driftwood-induced floods of the laboratory experiment. Then, the contribution of the studied key factors to the flood mechanism based on the fluid forces generated by high flow, bridge and driftwood (i.e. pressure distributions) was quantitatively assessed. The results showed that the driftwood accumulation and high flow conditions are potentially important factors that can cause a severe flood like the Takeda flood.

Simulated results with high flow conditions may be helpful to consider the countermeasure for future floods under climate change even though the test was simple and fundamental.

A mathematical model and numerical method for water flow and solute transport in a tidal river network is presented. The tidal river network is defined as a system of open channels or rivers with junctions and cross sections. As an example, the Pearl River in China is represented by a network of 104 channels, 62 nodes, and a total of 330 cross sections with 11 boundary sections for one of the applications. The simulations are performed with a supercomputer for seven scenarios of water flow and/or solute transport in the Pearl River, China, with different hydrological and weather conditions. Comparisons with available data are shown. The intention of this study is to summarize previous works and to provide a useful tool for water environmental management in a tidal river network, particularly for the Pearl River, China.

In Northern Regions, ice covers that form on rivers, streams, and lakes with the onset of winter, cause various problems related to winter navigation and pollution dispersion among others. Warm water, from industrial plants, discharged into these rivers cause partial or total melting of the ice cover over considerable distances. The present work investigates the melting of a thin non‐uniform ice cover subject to varying water and air temperatures under turbulent flow conditions. A two‐dimensional depth averaged turbulence model coupled with a heat transfer model is used to simulate laboratory conditions of ice cover melting. Computational results were compared with experimental investigations. The average melting of the ice cover was found to be in close agreement with the experimental measurements with the exception of the leading edge region.