Computational fluid dynamics modelling of hydraulics and sedimentation in process reactors during aeration tank settling

2006 ◽  
Vol 53 (12) ◽  
pp. 257-264 ◽  
Author(s):  
M.D. Jensen ◽  
P. Ingildsen ◽  
M.R. Rasmussen ◽  
J. Laursen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Control Method ◽  
Waste Water Treatment ◽  
Aeration Tank ◽  
Cfd Modelling ◽  
Design Changes ◽  
Dynamics Modelling ◽  
Tank Design ◽  
Tank Settling

Aeration tank settling is a control method allowing settling in the process tank during high hydraulic load. The control method is patented. Aeration tank settling has been applied in several waste water treatment plants using the present design of the process tanks. Some process tank designs have shown to be more effective than others. To improve the design of less effective plants, computational fluid dynamics (CFD) modelling of hydraulics and sedimentation has been applied. This paper discusses the results at one particular plant experiencing problems with partly short-circuiting of the inlet and outlet causing a disruption of the sludge blanket at the outlet and thereby reducing the retention of sludge in the process tank. The model has allowed us to establish a clear picture of the problems arising at the plant during aeration tank settling. Secondly, several process tank design changes have been suggested and tested by means of computational fluid dynamics modelling. The most promising design changes have been found and reported.

Computational Fluid Dynamics modelling of sedimentation on Mars

2020 ◽  
Author(s):  
Nikolaus J. Kuhn ◽  
Federica Trudu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gravitational Force ◽  
Settling Velocity ◽  
Cfd Modelling ◽  
Running Water ◽  
Sediment Sorting ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamics Modelling ◽  
Laminar State

<p>Gravity affects sedimentation of particles suspended in water and gases in two ways: directly by the gravitational force that pulls a particle towards the surface and indirectly by the flow conditions of water or gas around the particles. The latter create a drag which is affected by the settling velocity. Consequently, drag coefficients observed on Earth sand-sized particles cannot be used on Mars because they are likely to overestimate the drag generated by the turbulent flow around the particle on Earth may shift into a more laminar state that generates lower drag. The effect of gravity on settling velocity is not linearly related to particle size, which may affect the sorting of the sand grains deposited from running water.  Experiments carried out during parabolic flights at reduced gravity indicate that the potential error in particle settling and sorting is significant, i.e. leading to wrong interpretations of the flow velocities at the time of deposition. This in turn has implications for reconstruction of Martian environmental conditions from rock textures determined from close-up imagery. This study uses computational fluid dynamics (CFD) modelling to independently assess the effect of gravity on sediment settling velocities and sediment sorting. The CFD modelling also offers a wide capability for reconstruction sedimentation on Mars and thus supports the reconstruction of it’s environmental past, as well as the search for traces of life. </p>

Computational Fluid Dynamics Modelling for the Prediction of NOx in a Waste Gas Boiler

2016 ◽  
Author(s):  
Adam Blackmore ◽  
Jennifer Woloshyn ◽  
Duane Baker
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Nitrogen Oxides ◽  
Field Measurements ◽  
Industrial Scale ◽  
Nox Emissions ◽  
Cfd Modelling ◽  
Waste Gas ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamics Modelling

Recent results from CFD modelling of a waste gas boiler (WGB) to predict Nitrogen Oxides (NOx) emissions are presented. A verification / validation discussion is highlighted comparing the computational fluid dynamics (CFD) modelling with field measurements of NOx and flame characteristics. Challenges associated with the accurate prediction of NOx emissions are discussed along with the ability of CFD to accurately model emissions from an industrial scale WGB.

Sliding mesh computational fluid dynamics—a predictive tool in stirred tank design

1997 ◽  
Vol 211 (3) ◽  
pp. 149-156 ◽  
Author(s):  
Z Jaworski ◽  
M L Wyszynski ◽  
I P T Moore ◽  
A W Nienow
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Initial Conditions ◽  
Integrated Design ◽  
Flow Characteristics ◽  
Cfd Modelling ◽  
Predictive Tool ◽  
Sliding Mesh ◽  
Tank Design ◽  
Experimental Values

The use of a fully predictive numerical model of flow in a stirred, baffled tank is presented and validated for the laminar flow regime. This approach employs a commercial computational fluid dynamics (CFD) package with sliding mesh facility. The comparison of computed and experimental values for various flow characteristics shows a very good agreement without the need to input any experimental values for the boundary or initial conditions. It is proposed that the model/experiment error ratio (involving relative errors) may be generally adopted as a criterion for the quality of CFD modelling. This ratio should not be much larger, and does not need to be smaller, than unity. The ratio obtained in this work was just over unity. The state of the art CFD packages are now believed to be able to form a suitable basis for the process engineering aspects of an integrated design of stirred tanks, including mechanical engineering and other related issues.

scholarly journals Wind-Induced Phenomena in Long-Span Cable-Supported Bridges: A Comparative Review of Wind Tunnel Tests and Computational Fluid Dynamics Modelling

2021 ◽  
Vol 11 (4) ◽  
pp. 1642
Author(s):  
Yuxiang Zhang ◽  
Philip Cardiff ◽  
Jennifer Keenahan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Careful Analysis ◽  
Wind Effects ◽  
Wind Tunnel Tests ◽  
Long Span Bridges ◽  
Long Span ◽  
Comparative Review ◽  
Dynamics Modelling

Engineers, architects, planners and designers must carefully consider the effects of wind in their work. Due to their slender and flexible nature, long-span bridges can often experience vibrations due to the wind, and so the careful analysis of wind effects is paramount. Traditionally, wind tunnel tests have been the preferred method of conducting bridge wind analysis. In recent times, owing to improved computational power, computational fluid dynamics simulations are coming to the fore as viable means of analysing wind effects on bridges. The focus of this paper is on long-span cable-supported bridges. Wind issues in long-span cable-supported bridges can include flutter, vortex-induced vibrations and rain–wind-induced vibrations. This paper presents a state-of-the-art review of research on the use of wind tunnel tests and computational fluid dynamics modelling of these wind issues on long-span bridges.

Characterisation of Cell Adhesion to Substrate Materials and the Resistance to Enzymatic and Mechanical Cell-Removal

2008 ◽  
Vol 1097 ◽  
Author(s):  
Helen Jane Griffiths ◽  
John G Harvey ◽  
James Dean ◽  
James A Curran ◽  
Athina E Markaki ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cell Adhesion ◽  
Liquid Flow ◽  
Adhesive Strength ◽  
Cell Detachment ◽  
Shear Forces ◽  
Cfd Modelling ◽  
Computational Fluid Dynamics Cfd

AbstractCell-implant adhesive strength is important for prostheses. In this paper, an investigation is described into the adhesion of bovine chondrocytes to Ti6Al4V-based substrates with different surface roughnesses and compositions. Cells were cultured for 2 or 5 days, to promote adhesion. The ease of cell removal was characterised, using both biochemical (trypsin) and mechanical (accelerated buoyancy and liquid flow) methods. Computational fluid dynamics (CFD) modelling has been used to estimate the shear forces applied to the cells by the liquid flow. A comparison is presented between the ease of cell detachment indicated using these methods, for the three surfaces investigated.

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