A Computational Fluid Dynamics Investigation of using Large-Scale Geometric Roughness Elements in Open Channels

The hydraulic behavior of the flow can be changed by using large-scale geometric roughness elements in open channels. This change can help in controlling erosions and sedimentations along the mainstream of the channel. Roughness elements can be large stone or concrete blocks placed at the channel's bed to impose more resistance in the bed. The geometry of the roughness elements, numbers used, and configuration are parameters that can affect the flow's hydraulic characteristics. In this paper, velocity distribution along the flume was theoretically investigated using a series of tests of T-shape roughness elements, fixed height, arranged in three different configurations, differ in the number of lines of roughness element. These elements were used to find the best configuration of roughness elements that can be applied to change the flow's hydraulic characteristics. ANSYS Parametric Design Language, APDL, and Computational Fluid Dynamics, CFD, was used to simulate the flow in an open channel with roughness elements. CFD can be used to study the hydrodynamics of open channels under different conditions with inclusive details rather than relying on the costly field and time-consuming. Runs were implemented with different conditions, the discharge, and water depth in upstream and downstream of the flume. T-shape roughness elements with height equal to 3cm placed in three different configurations, two lines, four lines, and fully rough configurations were tested. The results show that the effect of roughness elements increasing with increasing the number of lines of roughness elements. Cases of four lines and fully rough configurations have almost the same hydraulic performance by having the same results of the velocity decrease percentage, which is decreased by approximately about 66% and 61% of the control case's velocity in the zone near the roughness elements consequently. But the difference is that four lines configuration is affected in a part of the test section. This behavior increases the velocity values by about 11% in the other side and by about 10% near the free surface in the case of four lines configuration and increased by about 32% above the roughness elements in a fully rough configuration.

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Investigations on Large-Scale Geometric Roughness Elements in Open Channels with Different Heights

Association of Arab Universities Journal of Engineering Sciences ◽

10.33261/jaaru.2021.28.1.002 ◽

2021 ◽

Vol 28 (1) ◽

pp. 07-14

Author(s):

Iman A. Alwan ◽

Riyadh Z. Azzubaidi

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Free Surface ◽

Large Scale ◽

Open Channel ◽

Control Case ◽

Hydraulic Characteristics ◽

Roughness Elements ◽

Computational Fluid Dynamics Cfd ◽

Effective Case

Large-scale geometric roughness elements is one of the solutions that is used to protect openchannels from erosion. It is use to change the hydraulic characteristics of the flow. It may be concrete blocksor large stone placed at the bed of the channel to impose more resistance in the bed. The height of theseroughness elements is an important parameter that can affect the hydraulic characteristics of the flow. Usinga series of tests of T-shape roughness elements at three different heights, 3, 4.5, and 6cm, arranged in thefully rough configuration in order to investigate the velocity distributions along the flume. ANSYSParametric Design Language, APDL, and Computational Fluid Dynamics, CFD, were used to simulate theflow in an open channel with roughness elements. This simulation helps to find the best height of roughnesselements that can be used to change the hydraulic characteristics of the flow. The results showed that thevelocity values are decreased near the bed by about 61%, 58%, and 64% in case of 3cm, 4.5cm, and 6cmroughness heights consequently compared with the velocity of the control case. The velocity values areincreased near the free surface by about 32% and 19% in case of roughness elements height 6cm comparedwith 3cm and 4.5cm roughness heights respectively. The case of 6cm roughness height is considered to bethe effective case for decreasing the velocity values near the bed of the flume.

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On the effects of membrane viscosity on transient red blood cell dynamics

Soft Matter ◽

10.1039/d0sm00587h ◽

2020 ◽

Vol 16 (26) ◽

pp. 6191-6205 ◽

Cited By ~ 1

Author(s):

Fabio Guglietta ◽

Marek Behr ◽

Luca Biferale ◽

Giacomo Falcucci ◽

Mauro Sbragaglia

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Cell ◽

Red Blood Cell ◽

Blood Circulation ◽

Hydraulic Properties ◽

Large Scale ◽

Mechanical Response ◽

Cell Dynamics ◽

Membrane Viscosity

Computational Fluid Dynamics is currently used to design and improve the hydraulic properties of biomedical devices, wherein the large scale blood circulation needs to be simulated by accounting for the mechanical response of RBCs at the mesoscale.

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Coordinate Free Programming of Computational Fluid Dynamics Problems

Scientific Programming ◽

10.1155/2000/419840 ◽

2000 ◽

Vol 8 (4) ◽

pp. 211-230 ◽

Cited By ~ 5

Author(s):

Philip W. Grant ◽

Magne Haveraaen ◽

Michael F. Webster

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Software Engineering ◽

Software Development ◽

Coordinate Systems ◽

Scientific Applications ◽

Software Modules ◽

The Difference ◽

Engineering Practices ◽

Dynamics Problems

It has long been acknowledged that the development of scientific applications is in need of better software engineering practices. Here we contrast the difference between conventional software development of CFD codes with a method based on coordinate free mathematics. The former approach leads to programs where different aspects, such as the discretisation technique and the coordinate systems, can get entangled with the solver algorithm. The latter approach yields programs that segregate these concerns into fully independent software modules. Such considerations are important for the construction of numerical codes for practical problems. The two approaches are illustrated on the coating problem: the simulation of coating a wire with a polymer.

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Flow Visualization of Spinning and Nonspinning Soccer Balls Using Computational Fluid Dynamics

Applied Sciences ◽

10.3390/app10134543 ◽

2020 ◽

Vol 10 (13) ◽

pp. 4543 ◽

Cited By ~ 1

Author(s):

Takeshi Asai ◽

Yasumi Nakanishi ◽

Nakaba Akiyama ◽

Sungchan Hong

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Lattice Boltzmann Method ◽

Vortex Structure ◽

Lattice Boltzmann ◽

Large Scale ◽

Vortex Pair ◽

Vortex Structures ◽

Soccer Ball ◽

Boltzmann Method

Various studies have been conducted on the aerodynamic characteristics of nonspinning and spinning soccer balls. However, the vortex structures in the wake of the balls are almost unknown. One of the main computational fluid dynamics methods used for the analysis of vortex structures is the lattice Boltzmann method as it facilitates high-precision analysis. Studies to elucidate the dominant vortex structure are important because curled shots and passes involving spinning balls are frequently used in actual soccer games. In this study, we identify the large-scale dominant vortex structure of a soccer ball and investigate the stability of the structure using the lattice Boltzmann method, wind tunnel tests, and free-flight experiments. One of the dominant vortex structures in the wake of both nonspinning and spinning balls is a large-scale counter-rotating vortex pair. The side force acting on a spinning ball stabilizes when the fluctuation of the separation points of the ball is suppressed by the rotation of the ball. Thus, although a spinning soccer ball is deflected by the Magnus effect, its trajectory is regular and stable, suggesting that a spinning ball can be aimed accurately at the outset of its course.

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Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and Computational Fluid Dynamics Simulations

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4037906 ◽

2017 ◽

Vol 140 (3) ◽

Cited By ~ 14

Author(s):

Alessandro Bianchini ◽

Francesco Balduzzi ◽

Giovanni Ferrara ◽

Lorenzo Ferrari ◽

Giacomo Persico ◽

...

Keyword(s):

Fluid Dynamics ◽

Experimental Data ◽

Computational Fluid Dynamics ◽

Wind Tunnel ◽

Wind Turbines ◽

Large Scale ◽

Vertical Axis ◽

Performance Estimation ◽

Small Scale ◽

Dynamics Simulations

Darrieus vertical axis wind turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, computational fluid dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools. In this study, a two-dimensional (2D) unsteady Reynolds-averaged Navier–Stokes (U-RANS) computational model was applied to analyze the wake characteristics on the midplane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out for analyzing the structure of the wake and correlating the main macrostructures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.

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Computational Modelling of Self-Excited Combustion Instabilities

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/2000-gt-0104 ◽

2000 ◽

Cited By ~ 4

Author(s):

Steve J. Brookes ◽

R. Stewart Cant ◽

Iain D. J. Dupere ◽

Ann P. Dowling

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Heat Release ◽

Large Scale ◽

Computational Modelling ◽

Combustion Efficiency ◽

Design Tool ◽

Premixed Combustion ◽

Combustion Instabilities ◽

Combustion Systems

It is well known that lean premixed combustion systems potentially offer better emissions performance than conventional non-premixed designs. However, premixed combustion systems are more susceptible to combustion instabilities than non-premixed systems. Combustion instabilities (large-scale oscillations in heat release and pressure) have a deleterious effect on equipment, and also tend to decrease combustion efficiency. Designing out combustion instabilities is a difficult process and, particularly if many large-scale experiments are required, also very costly. Computational fluid dynamics (CFD) is now an established design tool in many areas of gas turbine design. However, its accuracy in the prediction of combustion instabilities is not yet proven. Unsteady heat release will generally be coupled to unsteady flow conditions within the combustor. In principle, computational fluid dynamics should be capable of modelling this coupled process. The present work assesses the ability of CFD to model self-excited combustion instabilities occurring within a model combustor. The accuracy of CFD in predicting both the onset and the nature of the instability is reported.

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