scholarly journals Approximating a Three-Dimensional Fluidized Bed With Two-Dimensional Simulations

2008 ◽  
Author(s):  
Mirka Deza ◽  
Francine Battaglia ◽  
Theodore J. Heindel
Keyword(s):  
Fluidized Bed ◽  
Scale Up ◽  
Three Dimensional ◽  
Limited Range ◽  
Gas Holdup ◽  
Point Of View ◽  
Air Injection ◽  
Two Dimensional ◽  
Parametric Studies ◽  
Three Dimensional Simulations

Fluidized beds can be used to gasify biomass in the production of producer gas, a flammable gas that can replace natural gas in process heating. Modeling these reactors with computational fluid dynamics (CFD) simulations is advantageous when performing parametric studies for design and scale-up. From a computational resource point of view, two-dimensional simulations are easier to perform than three-dimensional simulations, but they may not capture the proper physics. This paper will compare two- and three-dimensional simulations in a 10.2 cm diameter fluidized bed with side air injection to determine when two-dimensional simulations are adequate to capture the bed hydrodynamics. Simulations will be completed in a glass bead fluidized bed operating at 1.5Umf and 3Umf, where Umf is the minimum fluidization velocity. Side air injection is also simulated to model biomass injection for gasification applications. The simulations are compared to experimentally obtained time-averaged local gas holdup values using X-ray computed tomography. Results indicate that for the conditions of this study, two-dimensional simulations qualitatively predict the correct hydrodynamics and gas holdup trends that are observed experimentally for a limited range of fluidization conditions.

scholarly journals Modeling a Biomass Fluidizing Bed With Side Port Air Injection

2009 ◽  
Author(s):  
Mirka Deza ◽  
Francine Battaglia ◽  
Theodore J. Heindel
Keyword(s):  
Fluidized Beds ◽  
Scale Up ◽  
Three Dimensional ◽  
Gas Holdup ◽  
Operating Conditions ◽  
Air Injection ◽  
Walnut Shell ◽  
Two Dimensional ◽  
Side Port ◽  
Three Dimensional Simulations

Fluidized beds are used to gasify materials such as coal or biomass in the production of producer gas. Modeling these reactors using computational fluid dynamics is advantageous when performing parametric studies for design and scale-up. While two-dimensional simulations are easier to perform than three-dimensional simulations, they may not capture the proper physics. This paper compares two- and three-dimensional simulations with experiments for a reactor geometry with side port air injection. The side port is located within the bed region so that the injected air can help promote mixing. Of interest in this study is validating the hydrodynamics of fluidizing biomass. Two operating conditions of the fluidized bed are studied for superficial gas velocities of 1.5Umf and 3.0Umf, where Umf is the minimum fluidization velocity. The material used to represent biomass is ground walnut shell because it tends to fluidize uniformly and falls within the Geldart type B classification. The simulations are compared to experimental data of time-averaged local gas holdup values using X-ray computed tomography. Results indicate that for the conditions of this study, two-dimensional simulations overpredict the gas holdup trends when compared to the experiments. However, the three-dimensional simulations compare exceptionally well with the experiments, thus predicting the fluidization hydrodynamics, irrespective of flowrate or complexity due to the side air port. Furthermore, the study demonstrates the importance of using a three-dimensional model for bubbling fluidized beds with complex physics.

Effects of Increasing Inlet Velocities and Side Port Air Injection on a Biomass Fluidizing Bed

2010 ◽  
Author(s):  
Mirka Deza ◽  
Francine Battaglia
Keyword(s):  
Complex Geometry ◽  
Air Flow ◽  
Three Dimensional ◽  
Air Injection ◽  
Single Side ◽  
X Ray Computed ◽  
Bed Material ◽  
Solid Distribution ◽  
Side Port ◽  
Three Dimensional Simulations

Fluidized beds are being used in practice to gasify biomass to create producer gas, a flammable gas that can be used for process heating. However, recent literature has identified the need to better understand and characterize biomass fluidization hydrodynamics, and computational fluid dynamics (CFD) is one approach in this effort. Previous work by the authors considered the validity of using two-dimensional versus three-dimensional simulations to model a cold-flow fluidizing biomass bed configured with a single side port air injection. The side port is introduced to inject air and promote mixing within the bed. Comparisons with experiments indicated that three-dimensional simulations were necessary to capture the fluidization behavior for the more complex geometry. This paper considers the effects of increasing fluidization air flow and side port air flow on the homogeneity of the bed material in a 10.2 cm diameter fluidized bed. Two air injection ports diametrically opposed to each other are also considered to determine their effects on fluidization hydrodynamics. Whenever possible, the simulations are compared to experimental data of time-averaged local gas holdup obtained using X-ray computed tomography. This study will show that increasing the fluidization and side port air flows contribute to a more homogeneous bed. Furthermore, the introduction of two side ports results in a more symmetric gas-solid distribution.

Bifurcation Characteristics of Flows in Rectangular Sudden Expansion Channels

2005 ◽  
Author(s):  
Francine Battaglia ◽  
George Papadopoulos
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Critical Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Expansion Ratio ◽  
Sudden Expansion ◽  
Two Dimensional ◽  
Effective Expansion ◽  
Three Dimensional Simulations

The effect of three-dimensionality on low Reynolds number flows past a symmetric sudden expansion in a channel was investigated. The geometric expansion ratio of in the current study was 2:1 and the aspect ratio was 6:1. Both experimental velocity measurements and two- and three-dimensional simulations for the flow along the centerplane of the rectangular duct are presented for Reynolds numbers in the range of 150 to 600. Comparison of the two-dimensional simulations with the experiments revealed that the simulations fail to capture completely the total expansion effect on the flow, which couples both geometric and hydrodynamic effects. To properly do so requires the definition of an effective expansion ratio, which is the ratio of the downstream and upstream hydraulic diameters and is therefore a function of both the expansion and aspect ratios. When the two-dimensional geometry was consistent with the effective expansion ratio, the new results agreed well with the three-dimensional simulations and the experiments. Furthermore, in the range of Reynolds numbers investigated, the laminar flow through the expansion underwent a symmetry-breaking bifurcation. The critical Reynolds number evaluated from the experiments and the simulations was compared to other values reported in the literature. Overall, side-wall proximity was found to enhance flow stability, helping to sustain laminar flow symmetry to higher Reynolds numbers in comparison to nominally two-dimensional double-expansion geometries. Lastly, and most importantly, when the logarithm of the critical Reynolds number from all these studies was plotted against the reciprocal of the effective expansion ratio, a linear trend emerged that uniquely captured the bifurcation dynamics of all symmetric double-sided planar expansions.

scholarly journals CAD Tools and Computing in Architectural and Urban Acoustics

Buildings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 235
Author(s):  
Joanna Jablonska ◽  
Roman Czajka
Keyword(s):  
Computer Aided Design ◽  
Three Dimensional ◽  
Computing Methods ◽  
Building Industry ◽  
Two Dimensional ◽  
Cad Tools ◽  
Architectural Acoustics ◽  
Urban Level ◽  
Aided Design ◽  
Three Dimensional Simulations

Contemporary architectural and urban planning aims at optimal development of the environment, including in terms of acoustics. As such, support with computer-aided design (CAD) tools is, nowadays, obligatory. The authors present investigation outcomes of three different CAD and computing methods extracted for the study. The scope covers different scales of considerations from architectural acoustics to the urban level, which relates to the standard architect’s commissions field. The described approaches are applicable for both academics and professionals in the broadly understood building industry There were analysed and synthesized experiences from the use of two-dimensional and three-dimensional simulations, computing based on standardized formulas, and an acoustic meter (here: the SVAN 979 for RT60, LAeq measurement). The article concludes with an assessment, which shows possible uses of methods and confirmations of their usability.

Two- and Three-Dimensional Simulations of the Flow Around a Cylinder Fitted With Strakes

2012 ◽  
Author(s):  
Bruno S. Carmo ◽  
Rafael S. Gioria ◽  
Ivan Korkischko ◽  
Cesar M. Freire ◽  
Julio R. Meneghini
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Free Stream ◽  
Three Dimensional ◽  
The Body ◽  
Vortex Wake ◽  
Two Dimensional ◽  
Flow Around A Cylinder ◽  
Three Dimensional Simulations ◽  
Angle Of Rotation

Two- and three-dimensional simulations of the flow around straked cylinders are presented. For the two-dimensional simulations we used the Spectral/hp Element Method, and carried out simulations for five different angles of rotation of the cylinder with respect to the free stream. Fixed and elastically-mounted cylinders were tested, and the Reynolds number was kept constant and equal to 150. The results were compared to those obtained from the simulation of the flow around a bare cylinder under the same conditions. We observed that the two-dimensional strakes are not effective in suppressing the vibration of the cylinders, but also noticed that the responses were completely different even with a slight change in the angle of rotation of the body. The three-dimensional results showed that there are two mechanisms of suppression: the main one is the decrease in the vortex shedding correlation along the span, whilst a secondary one is the vortex wake formation farther downstream.

scholarly journals Coherent structures and chaotic advection in three dimensions

2010 ◽  
Vol 654 ◽  
pp. 1-4 ◽  
Author(s):  
STEPHEN WIGGINS
Keyword(s):  
Dynamical Systems ◽  
Fluid Mechanics ◽  
Coherent Structures ◽  
Three Dimensional ◽  
Point Of View ◽  
Three Dimensions ◽  
Chaotic Advection ◽  
Periodic Flow ◽  
Two Dimensional ◽  
Time Periodic

In the 1980s the incorporation of ideas from dynamical systems theory into theoretical fluid mechanics, reinforced by elegant experiments, fundamentally changed the way in which we view and analyse Lagrangian transport. The majority of work along these lines was restricted to two-dimensional flows and the generalization of the dynamical systems point of view to fully three-dimensional flows has seen less progress. This situation may now change with the work of Pouransari et al. (J. Fluid Mech., this issue, vol. 654, 2010, pp. 5–34) who study transport in a three-dimensional time-periodic flow and show that completely new types of dynamical systems structures and consequently, coherent structures, form a geometrical template governing transport.

scholarly journals Modeling in AUTOCAD for bachelors

2021 ◽  
pp. 25-28
Author(s):  
Л.В. Карпюк ◽  
Н.О. Давіденко
Keyword(s):  
3D Model ◽  
Three Dimensional ◽  
Model Space ◽  
Educational Process ◽  
Point Of View ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Three Dimensional Objects ◽  
Graphic Editor

The article discusses the methods of using the AutoCad graphic editor for creating three-dimensional objects. The possibilities of three-dimensional modeling in the AutoCad graphic editor for optimizing the educational process of bachelors of technical specialties are also considered. The article analyzes the best ways to create mechanical engineering drawings.The most developed software tool for the production of design documentation is AutoCAD - a universal graphic design system. Creating models of any complexity in space by using this graphic editor, the user will be able to see their relative position, estimate the distance between them. The model can be freely moved in space, viewing many options. The ability to control the point of view allows to conveniently select the view of the 3D model that is being developed. Zooming, panning in real time with the ability to freely rotate the camera around the model provide the ability to quickly view objects from any point of view. The article provides examples of choosing the most optimal option for creating a three-dimensional model. The traditional way to create a 3D model drawing is to make 2D views of the model. When creating a flat drawing, there is a possibility of error when making projections, since they are created independently from each other and consist of several images. It is rather difficult to represent an object in space from a flat drawing. At present, modern software graphic editors are aimed at creating three-dimensional models that allow to create realistic models and, on their basis, get two-dimensional projections. Graphic editor AutoCad allows to create three-dimensional objects based on standard commands, in the form of a cylinder, cone, box, torus, etc., when editing which you can get the desired shapes. After creating a three-dimensional model, the user can get its two-dimensional projections not only on the main planes, but also on any plane at will. The 3D modeling method allows you to create a complex drawing with any number of images based on a 3D model. There are ways to create 2D plane drawings from a 3D model and the ability to edit ready-made designs that can be inserted from model space into paper space. Editing takes place by changing the parameters of a 3D object in model space, and these changes are automatically reflected in paper space. This method allows us to use the tools to quickly create a system of 3-4 linked views for a 3D AutoCad model.

scholarly journals Hadean/Eoarchean Tectonics and Mantle Mixing Induced by Impacts: a Three-dimensional Study

2021 ◽  
Author(s):  
Xavier Borgeat ◽  
Paul Tackley
Keyword(s):  
Plate Tectonics ◽  
Three Dimensional ◽  
Great Influence ◽  
Terrestrial Planet ◽  
Terrestrial Planets ◽  
Two Dimensional ◽  
Order Difference ◽  
Surface Mobility ◽  
Modelling Studies ◽  
Three Dimensional Simulations

Abstract The timing of the onset of plate tectonics on Earth remains a topic of strong debate, as does the tectonic mode that preceded modern plate tectonics. Understanding possible tectonic modes and transitions between them is also important for other terrestrial planets such as Venus and rocky exoplanets. Recent two-dimensional modelling studies have demonstrated that impacts can initiate subduction during the early stages of terrestrial planet evolution - the Hadean and Eoarchean in Earth's case. Here, we perform three-dimensional simulations of the influence of ongoing multiple impacts on early Earth tectonics and its effect on the distribution of compositional heterogeneity in the mantle, including the distribution of impactor material. We compare two-dimensional and three-dimensional simulations to determine when geometry is important. Results show that impacts can induce subduction in both 2-D and 3-D and thus have a great influence on the tectonic regime. The effect is particularly strong in cases that otherwise display stagnant-lid tectonics: impacts can shift them to having a plate-like regime. In such cases, however, plate-like behaviour is temporary: as the impactor flux decreases the system returns to what it was without impacts. Impacts result in both greater production of oceanic crust and greater recycling of it, increasing the build-up of subducted crust above the core-mantle boundary and in the transition zone. Impactor material is mainly located in the upper mantle, at least at the end of the modelled 500 million year period. In 2-D simulations, in contrast to 3-D simulations, impacts are less frequent but each has a larger effect on surface mobility, making the simulations more stochastic. These stronger 2-D subduction events can mix both recycled basalt and impactor material into the lower mantle. These results thus demonstrate that impacts can make a first-order difference to the early tectonics and mantle mixing of Earth and other large terrestrial planets, and that three-dimensional simulations are important so that effects are not over- or under-predicted.

HYBRID REFLECTIONS IN POST-MODERN GRAPHIC DESIGN POSTERS

ATLAS JOURNAL ◽  
2021 ◽  
Vol 7 (44) ◽  
pp. 2207-2213
Author(s):  
Fatıma TOKGÖZ GÜN ◽  
Mehmet ÖZKARTAL
Keyword(s):  
Graphic Design ◽  
Hybrid Methods ◽  
Three Dimensional ◽  
Point Of View ◽  
Two Dimensional ◽  
Use Of Technology ◽  
Work Area ◽  
Poster Art ◽  
Motion Images ◽  
Over Time

Hybrid works in art have many examples from past to present. Hybridization in poster art has been in question since the first years when posters started to appear. Hybridization in designs can occur in terms of both method and technique. In present study, it is mentioned how graphic design has removed the boundaries between itself and many disciplines since the use of technology in the field of art and how it allows hybrid studies. As it is known, the main purpose of graphic design is to convey an existing idea to the other party in the simplest way. For this reason, graphic design, which updates itself over time, has added motion and sound to its work area and shows itself with effective designs. While technically designs consist of two-dimensional studies for years, they can also be designed in three-dimensional or even four-dimensional forms with hybrid methods. While poster designs are prepared as flat and static, they update themselves with kinetic typography and motion images. Moreover, with hybrid presentations such as augmented reality and virtual reality in current works, designs interact more with people. It is seen that the artists who can think from a hybrid point of view attract more attention and interaction with the hybridity reflected in their designs, and they also reach the intended result in a catchy manner.

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