Numerical and Experimental Analyses of Breakwater Designs for Turbulent Flow Characteristics and Sediment Transport Under Coastal Wave Actions

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Hairui Wang ◽  
William Foltz ◽  
Ning Zhang ◽  
Dimitrios Dermisis
Keyword(s):  
Coastal Erosion ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Sediment Retention ◽  
Cfd Simulations ◽  
Cfd Models ◽  
Turbulent Characteristics ◽  
Scale Down ◽  
Pass Through ◽  
Coastal Louisiana

Abstract The goal of the study is to identify optimal breakwater designs to be placed on the banks of various water bodies in coastal Louisiana, to prevent the coastal erosion. Coastal erosion is a significant concern for Louisiana's wavy coastline. The loss of coastal wetlands is threatening the environment and the economic development. One of the ways to prevent coastal erosion and wetland losses is by using breakwaters designed to reduce the wave energy and change the transport of sediments brought by the waves. The objective of this research is to analyze the turbulent characteristics around specially designed three-dimensional (3D) breakwaters, and its impact on sediment deposition under coastal wave actions. Both computational fluid dynamics (CFD) simulations and experimental measurements were conducted. In order to validate the CFD models used for this study, the simulation results were compared to data measured from a scale-down experiment. Once the validity of the CFD models has been confirmed on three miniature panels, namely, a solid panel, a panel with three holes, and a panel with eight holes, the simulations were scaled up to the actual size of the designed breakwater panels for tests. The breakwater designs aim to allow sediment pass through the holes, to deposit sediment at target areas, and to reduce wave actions. There were three different panel-design cases simulated in this study. The results of 3D CFD simulations of these panels were compared and analyzed to determine the performance of each design in terms of wave reduction and sediment retention.

Numerical Analysis of the Turbulent Flow Characteristics Around Submerged Permeable Breakwaters

2018 ◽  
Author(s):  
William Foltz ◽  
Ning Zhang
Keyword(s):  
Coastal Erosion ◽  
Flow Characteristics ◽  
Wave Action ◽  
Water Bodies ◽  
Numerical Comparison ◽  
Ansys Fluent ◽  
Wave Patterns ◽  
Pass Through ◽  
Coastal Louisiana ◽  
Good Agreement

A breakwater is a structure used to reduce the energy of waves. When used properly, they can protect coasts from being affected by waves. One such application is to lessen erosion along Louisiana’s coastlines, where wave action is strong and is the main source of the erosion. Additionally, the breakwater can change how sediments are transported, and allow for the deposition and accumulation of sediment at target areas. This research aims to give a numerical comparison of the effectiveness of three different breakwater designs, and reveal the turbulence characteristics downstream of the breakwaters. Three breakwaters are examined: a solid panel without any holes, another panel with one hole, and a third panel with three holes. These breakwaters are expected to be placed on the banks of various water bodies in coastal Louisiana, to protect the surrounding wetlands from coastal erosion and land losses. The designs aim to reduce the wave action from the water bodies, while the holes on them allow the sediments to pass through and deposit on the wetlands downstream. To run the simulations, the CFD software ANSYS FLUENT was used. The numerical results were compared to experimental data, and the good agreement proves the accuracy of the results. The effects of different wave patterns on the downstream turbulence were also analyzed and discussed in this study.

scholarly journals Flow characteristics of individual lot stormwater detention

2016 ◽  
Vol 11 (4) ◽  
pp. 721-727
Author(s):  
Johnny Ong King Ngu ◽  
Darrien Yau Seng Mah ◽  
Charles Hin Joo Bong
Keyword(s):  
Turbulent Flow ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Scale Model ◽  
Storage Tanks ◽  
Cfd Simulations ◽  
Detention Tank ◽  
Cfd Models ◽  
Underground Storage Tanks ◽  
Run Off

In this paper the flow characteristics of stormwater are analyzed as it travels from a roof gutter down-pipe and the turbulent flow generated on entering an individual lot on-site stormwater detention (OSD) unit beneath a residential carport. Comparison was made between a full-scale model and computational fluid dynamic (CFD) simulations to determine the flow characteristics. These modular tanks with multi-unit chambers can capture the roof run-off from a 15-minute, 10-year return period storm. The results from the physical and CFD models matched well, suggesting that turbulent flow occurs when stormwater is directed to an individual lot stormwater detention tank. However, turbulence in the OSD was concentrated around the inlet, after which the pattern changed from turbulent to laminar flow. This work implies that the use of modular underground storage tanks is practical for managing stormwater from a roof.

scholarly journals Numerical Investigation of Vertical Crossflow Jets with Various Orifice Shapes Discharged in Rectangular Open Channel

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1505
Author(s):  
Hao Yuan ◽  
Ruichang Hu ◽  
Xiaoming Xu ◽  
Liang Chen ◽  
Yongqin Peng ◽  
...  
Keyword(s):  
Open Channel ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulent Model ◽  
3D Flow ◽  
Turbulent Characteristics ◽  
Square Jets ◽  
Flow Turbulence ◽  
Vertical Jet

Vertical jet in flowing water is a common phenomenon in daily life. To study the flow and turbulent characteristics of different jet orifice shapes and under different velocity ratios, the realizable k-ε turbulent model was adopted to analyze the three-dimensional (3D) flow, turbulence, and vortex characteristics using circular, square, and rectangular jet orifices and velocity ratios of 2, 5, 10, and 15. The following conclusions were drawn: The flow trajectory of the vertical jet in the channel exhibits remarkable 3D characteristics, and the jet orifice and velocity ratio have a significant influence on the flow characteristics of the channel. The heights at which the spiral deflection and maximum turbulent kinetic energy (TKE) occur for the circular jet are the smallest, while those for square jets are the largest. As the shape of the jet orifice changes from a circle to a square and then to a rectangle, the shape formed by the plane of the kidney vortices and the region above it gradually changes from a circle to a pentagon. With the increase in the velocity ratio, the 3D characteristics, maximum TKE, and kidney vortex coverage of the flow all gradually increase.

SPH-Based Numerical Modeling of Fluid Flow Interaction with Various Shapes of Breakwater

2019 ◽  
Author(s):  
Rezaldy Naufal Saleh ◽  
Dede Tarwidi ◽  
Jondri
Keyword(s):  
Numerical Modeling ◽  
Fluid Flow ◽  
Coastal Erosion ◽  
Fluid Velocity ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Sph Method ◽  
Flow Interaction ◽  
Scale Down

Various efforts have been made to prevent coastal erosion. One of the efforts to prevent coastal erosion is to build breakwaters. This paper presents numerical modeling of fluid flow interaction with various shapes of breakwater. Fluid flow impact on different shapes of breakwater, i.e. trapezoidal prism, cylinder, and sphere has been investigated. The three-dimensional numerical modeling is purposed to decisive which breakwaters shape that can reduce the fluid velocity rapidly, compared to other tested breakwaters shapes. In this study, fluid motion is generated by dam break scheme. The fluid motion is governed by momentum and continuity equation. The equations of fluid motion are resolved by smoothed particle hydrodynamics (SPH) method. DualSPHysics, an open-source code based on SPH method, is applied to simulate fluid motion and the interaction with the blocks of breakwater. According to numerical results, the trapezoidal prism shape of breakwater can scale down the fluid velocity faster than the cylinder and sphere shape of breakwater with maximum velocity is about 2.20 m/s. Further, the cylinder shape yields the highest fluid velocity around the breakwater. The trapezoidal prism shape can be used as an effective breakwater.

CFD Analysis of Turbulent Flow in a Nuclear Fuel Bundle With Mixing Vane

2002 ◽  
Author(s):  
Wang Kee In ◽  
Dong Seok Oh ◽  
Tae Hyun Chun
Keyword(s):  
Turbulent Flow ◽  
Nuclear Fuel ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Cfd Analysis ◽  
Mean Flow ◽  
Cfd Models ◽  
Fuel Bundle ◽  
Rod Array

A computational fluid dynamics (CFD) analysis was performed to investigate the coolant mixing in a nuclear fuel bundle that is promoted by the mixing vane on the grid spacer. Single and multiple subchannels of one grid span of the fuel bundle were modeled to simulate a 5×5 rod array experiment with the mixing vane. The three-dimensional CFD models were generated by a structured multi-block method. The standard k-ε turbulence model was used in the current CFD simulation since it is practically useful and converges well for the complex turbulent flow in a nuclear fuel bundle. The CFD predictions of axial and lateral mean flow velocities showed a somewhat large difference from the experimental results near the spacer but represented the overall characteristics of coolant mixing well in a nuclear fuel bundle with the mixing vane. Comparison of single and multiple subchannel predictions shows good agreement of the flow characteristics in the central subchannel of the rod array. The simulation of multiple subchannels shows a slightly off-centered swirl in the peripheral subchannels due to the external wall of the rod array. It also shows no significant swirl and crossflow in the wall subchannels and the corner subchannels.

scholarly journals Hydrodynamic Flow Characteristics in an Internally Circulating Fluidized Bed Gasifier

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
J. P. Simanjuntak ◽  
K. A. Al-attab ◽  
Z. A. Zainal
Keyword(s):  
Fluidized Bed ◽  
Flow Rate ◽  
Circulating Fluidized Bed ◽  
Draft Tube ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydrodynamic Flow ◽  
Orifice Diameter ◽  
Circulation Rate ◽  
Cfd Models

In this paper, the hydrodynamic flow inside an internally circulating fluidized bed (ICFBG) was characterized using experimental and three-dimensional computational fluid dynamics (CFD) models. Eulerian-Eulerian model (EEM) incorporating the kinetic theory of granular flow was implemented in order to simulate the gas–solid flow. A full-scale plexiglass cold flow experimental model was built to verify simulation results prior to the fabrication of the gasifier. Six parameters were manipulated to achieve the optimum design geometry: fluidization flow rate of the draft tube (Qdt), aeration flow rate of the annulus (Qan), initial bed static height (Hbs), draft tube height (Hdt), draft tube diameter (Ddt), and orifice diameter (Dor). The investigated parameters showed strong effect on the particle flow characteristics in terms of the pressure difference (ΔP) and solid circulation rate (Gs). The predicted results by simulation for the optimum case were in close agreement with experimental measurements with about 5% deviation. The results show that the ICFBG operated stably with the maximum Gs value of 86.6 kg/h at Qdt of 350 LPM, Qan of 150 LPM, Hbs of 280 mm, Hdt of 320 mm, Ddt of 100 mm, and Dor of 20 mm.

scholarly journals Particulate Deposition in a Patient With Tracheal Stenosis

2017 ◽  
Vol 1 (1) ◽  
Author(s):  
S. Taherian ◽  
H. R. Rahai ◽  
J. Bonifacio ◽  
B. Z. Gomez ◽  
Thomas Waddington
Keyword(s):  
Tracheal Stenosis ◽  
Air Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Ct Images ◽  
Patient Specific ◽  
Post Intervention ◽  
Cfd Simulations ◽  
Layer Manufacturing ◽  
Computational Fluid Dynamics Cfd

The presence of obstructions such as tracheal stenosis has important effects on respiratory functions. Tracheal stenosis impacts the therapeutic efficacy of inhaled medications as a result of alterations in particle transport and deposition pattern. This study explores the effects of the presence and absence of stenosis/obstruction in the trachea on air flow characteristics and particle depositions. Computational fluid dynamics (CFD) simulations were performed on three-dimensional (3D) patient-specific models created from computed tomography (CT) images. The analyzed model was generated from a subject with tracheal stenosis and includes the airway tree up to eight generations. CT scans of expiratory and inspiratory phases were used for patient-specific boundary conditions. Pre- and post-intervention CFD simulations' comparison reveals the effect of the stenosis on the characteristics of air flow, transport, and depositions of particles with diameters of 1, 2.5, 4, 6, 8, and 10 μm. Results indicate that the existence of the stenosis inflicts a major pressure force on the flow of inhaled air, leading to an increased deposition of particles both above and below the stenosis. Comparisons of the decrease in pressure in each generation between pre- and post-tracheal stenosis intervention demonstrated a significant reduction in pressure following the stenosis, which was maintained in all downstream generations. Good agreements were found using experimental validation of CFD findings with a model of the control subject up to the third generation, constructed via additive layer manufacturing from CT images.

Performance enhancement of Savonius wind turbine by blade shape and twisted angle modifications

2021 ◽  
pp. 095765092098794
Author(s):  
Ahmed M Nagib Elmekawy ◽  
Hassan A Hassan Saeed ◽  
Sadek Z Kassab
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Cfd Simulations ◽  
Sliding Mesh ◽  
Blade Shape ◽  
Rotor Shape ◽  
Twisting Angle

Three-dimensional CFD simulations are carried out to study the increase of power generated from Savonius vertical axis wind turbines by modifying the blade shape and blade angel of twist. Twisting angle of the classical blade are varied and several proposed novel blade shapes are introduced to enhance the performance of the wind turbine. CFD simulations have been performed using sliding mesh technique of ANSYS software. Four turbulence models; realizable k -[Formula: see text], standard k - [Formula: see text], SST transition and SST k -[Formula: see text] are utilized in the simulations. The blade twisting angle has been modified for the proposed dimensions and wind speed. The introduced novel blade increased the power generated compared to the classical shapes. The two proposed novel blades achieved better power coefficients. One of the proposed models achieved an increase of 31% and the other one achieved 32.2% when compared to the classical rotor shape. The optimum twist angel for the two proposed models achieved 5.66% and 5.69% when compared with zero angle of twist.

scholarly journals Radial Turbine Design for Solar Chimney Power Plants

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 674
Author(s):  
Paul Caicedo ◽  
David Wood ◽  
Craig Johansen
Keyword(s):  
Power Plants ◽  
Reference Frames ◽  
Three Dimensional ◽  
Discrete Ordinates ◽  
Large Area ◽  
Solar Chimney ◽  
Cfd Simulations ◽  
Radial Turbine ◽  
Design Changes ◽  
Turbine Design

Solar chimney power plants (SCPPs) collect air heated over a large area on the ground and exhaust it through a turbine or turbines located near the base of a tall chimney to produce renewable electricity. SCPP design in practice is likely to be specific to the site and of variable size, both of which require a purpose-built turbine. If SCPP turbines cannot be mass produced, unlike wind turbines, for example, they should be as cheap as possible to manufacture as their design changes. It is argued that a radial inflow turbine with blades made from metal sheets, or similar material, is likely to achieve this objective. This turbine type has not previously been considered for SCPPs. This article presents the design of a radial turbine to be placed hypothetically at the bottom of the Manzanares SCPP, the only large prototype to be built. Three-dimensional computational fluid dynamics (CFD) simulations were used to assess the turbine’s performance when installed in the SCPP. Multiple reference frames with the renormalization group k-ε turbulence model, and a discrete ordinates non-gray radiation model were used in the CFD simulations. Three radial turbines were designed and simulated. The largest power output was 77.7 kW at a shaft speed of 15 rpm for a solar radiation of 850 W/m2 which exceeds by more than 40 kW the original axial turbine used in Manzanares. Further, the efficiency of this turbine matches the highest efficiency of competing turbine designs in the literature.

scholarly journals Interactions between Tandem Cylinders in an Open Channel: Impact on Mean and Turbulent Flow Characteristics

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1718
Author(s):  
Hasan Zobeyer ◽  
Abul B. M. Baki ◽  
Saika Nowshin Nowrin
Keyword(s):  
Turbulent Flow ◽  
Open Channel ◽  
Recirculation Zone ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Recirculation ◽  
Tandem Cylinders ◽  
Flow Development ◽  
The Mean ◽  
Recirculation Length

The flow hydrodynamics around a single cylinder differ significantly from the flow fields around two cylinders in a tandem or side-by-side arrangement. In this study, the experimental results on the mean and turbulence characteristics of flow generated by a pair of cylinders placed in tandem in an open-channel flume are presented. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components. This study investigated the effect of cylinder spacing at 3D, 6D, and 9D (center to center) distances on the mean and turbulent flow profiles and the distribution of near-bed shear stress behind the tandem cylinders in the plane of symmetry, where D is the cylinder diameter. The results revealed that the downstream cylinder influenced the flow development between cylinders (i.e., midstream) with 3D, 6D, and 9D spacing. However, the downstream cylinder controlled the flow recirculation length midstream for the 3D distance and showed zero interruption in the 6D and 9D distances. The peak of the turbulent metrics generally occurred near the end of the recirculation zone in all scenarios.

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