7,538 research outputs found
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Harvesting condensed atmospheric vapour as dew water can be an alternative or
complementary potable water resource in specific arid or insular areas. Such
radiation-cooled condensing devices use already existing flat surfaces (roofs)
or innovative structures with more complex shapes to enhance the dew yield. The
Computational Fluid Dynamic - CFD - software PHOENICS has been programmed and
applied to such radiation cooled condensers. For this purpose, the sky
radiation is previously integrated and averaged for each structure. The
radiative balance is then included in the CFD simulation tool to compare the
efficiency of the different structures under various meteorological parameters,
for complex or simple shapes and at various scales. It has been used to precise
different structures before construction. (1) a 7.32 m^2 funnel shape was
studied; a 30 degree tilted angle (60 degree cone half-angle) was computed to
be the best compromise for funnel cooling. Compared to a 1 m^2 flat condenser,
the cooling efficiency was expected to be improved by 40%. Seventeen months
measurements in outdoor tests presented a 138 % increased dew yield as compared
to the 1 m^2 flat condenser. (2) The simulation results for 5 various condenser
shapes were also compared with experimental measurement on corresponding pilots
systems: 0.16 m^2 flat planar condenser, 1 m^2 and 30 degree tilted planar
condenser, 30 m^2 and 30 degree tilted planar condenser, 255 m^2 multi ridges,
a preliminary construction of a large scale dew plant being implemented in the
Kutch area (Gujarat, India)
CFD STUDIO: AN EDUCATIONAL SOFTWARE FOR CFD ANALYSIS
The main goal of this paper is to demonstrate the general characteristics of the educational
user-friendly CFD Studio package for CFD teaching. The package was designed for
teaching 2D fluid mechanics and heat transfer process, including conduction, coupled
conduction/convection, natural and forced convection, external and internal flows, among
other phenomena. The finite volume methodology and its related topics can also be taught
using the software. Therefore, general aspects of the three main modules, pre-processor,
solver and post-processor are discussed aiming to show the generality of the tool. These
modules are integrated in the application by a so-called numerical problem project
which guide the student through the steps to obtain the solution. To approximate the
partial differential equations the finite volume approach is employed using a fully-implicit
formulation with the interpolation schemes CDS, UDS and WUDS. Mesh editing and nonorthogonal
boundary-fitted mesh generation, using algebraic interpolation and elliptic
equations, are important features of the package. Coupled heat transfer problems are
handled using the solid-block formulation and the pressure-velocity coupling uses the
SIMPLE and SIMPLEC methods with non-staggered grids. To demonstrate the
capabilities two fluid flow and heat transfer problem projects are presented
Exploring the Interplay between CAD and FreeFem++ as an Energy Decision-Making Tool for Architectural Design
The energy modelling software tools commonly used for architectural purposes do not allow
a straightforward real-time implementation within the architectural design programs. In addition,
the surrounding exterior spaces of the building, including the inner courtyards, hardly present
a specific treatment distinguishing these spaces from the general external temperature in the thermal
simulations. This is a clear disadvantage when it comes to streamlining the design process in relation
to the whole-building energy optimization. In this context, the present study aims to demonstrate
the advantages of the FreeFem++ open source program for performing simulations in architectural
environments. These simulations include microclimate tests that describe the interactions between
a building architecture and its local exterior. The great potential of this mathematical tool can be
realized through its complete system integration within CAD (Computer-Aided Design) software
such as SketchUp or AutoCAD. In order to establish the suitability of FreeFem++ for the performance
of simulations, the most widely employed energy simulation tools able to consider a proposed
architectural geometry in a specific environment are compared. On the basis of this analysis,
it can be concluded that FreeFem++ is the only program displaying the best features for the
thermal performance simulation of these specific outdoor spaces, excluding the currently unavailable
easy interaction with architectural drawing programs. The main contribution of this research is,
in fact, the enhancement of FreeFem++ usability by proposing a simple intuitive method for the
creation of building geometries and their respective meshing (pre-processing). FreeFem++ is also
considered a tool for data analysis (post-processing) able to help engineers and architects with
building energy-efficiency-related tasks
The influence of convective exchanges on coandã effect
Modeling Coandã effect has been a fundamental issue in fluid dynamic research in the XX century. It has lost some interest because of the improvement in CFD, even if it could be still important in the area of the preliminary design of aerodynamic devices that benefits of fluid deflection by convex surfaces. An effective model of Coandã effect has not been defined, and fundamental questions are still open. The influence of convective heat exchange on Coandã adhesion of a fluid stream on a convex surface in the presence of a temperature gradient between the fluid and the convex surface is a problem, which affects many practical cases, but it is still marginally approached by scientific literature. This paper aims to start an effective research direction on the effects of convective heat exchange on Coandã effect. It approaches the problem with a set of CFD simulations. It analyses the previous hypotheses, which are based on Prandtl number and evidences the need of a more effective model that accounts also for the Reynolds number
Aerated blast furnace slag filters for enhanced nitrogen and phosphorus removal from small wastewater treatment plants
Rock filters (RF) are a promising alternative technology for natural
wastewater treatment for upgrading WSP effluent. However, the application
of RF in the removal of eutrophic nutrients, nitrogen and phosphorus, is very
limited. Accordingly, the overall objective of this study was to develop a lowcost
RF system for the purpose of enhanced nutrient removal from WSP
effluents, which would be able to produce effluents which comply with the
requirements of the EU Urban Waste Water Treatment Directive (UWWTD)
(911271lEEC) and suitable for small communities. Therefore, a combination
system comprising a primary facultative pond and an aerated rock filter
(ARF) system-either vertically or horizontally loaded-was investigated at
the University of Leeds' experimental station at Esholt Wastewater
Treatment Works, Bradford, UK.
Blast furnace slag (BFS) and limestone were selected for use in the ARF
system owing to their high potential for P removal and their low cost. This
study involved three major qperiments: (1) a comparison of aerated
vertical-flow and horizontal-flow limestone filters for nitrogen removal; (2) a
comparison of aerated limestone + blast furnace slag (BFS) filter and
aerated BFS filters for nitrogen and phosphorus removal; and (3) a
comparison of vertical-flow and horizontal-flow BFS filters for nitrogen and
phosphorus removal.
The vertical upward-flow ARF system was found to be superior to the
horizontal-flow ARF system in terms of nitrogen removal, mostly thiough
bacterial nitrification processes in both the aerated limestone and BFS filter
studies. The BFS filter medium (whieh is low-cost) showed a much higher
potential in removing phosphortls from pond effluent than the limestone
medium. As a result, the combination of a vertical upward-flow ARF system
and an economical and effective P-removal filter medium, such as BFS,
was found to be an ideal optionfor the total nutrient removal of both nitrogen
and phosphorus from wastewater.
In parallel with these experiments, studies on the aerated BFS filter effective
life and major in-filter phosphorus removal pathways were carried out. From
the standard batch experiments of Pmax adsorption capacity of BFS, as well
as six-month data collection of daily average P-removal, it was found that
the effective life of the aerated BFS filter was 6.5 years. Scanning electron
microscopy and X-ray diffraction spectrometric analyses on the surface of
BFS, particulates and sediment samples revealed that the apparent
mechanisms of P-removal in the filter are adsorption on the amorphous
oxide phase of the BFS surface and precipitation within the filter
Simulation of Vacuum Assisted Resin Infusion (VARI) process for the production of composite material parts
The Vacuum Assisted Resin Infusion (VARI) is manufacturing process used worldwide to produce composite parts having great diversity of dimensions (from small to very large ones) and geometrical complexity. This manufacturing process is particularly versatile, to produce small series of high performance structural parts. In these cases, the simulations of the VARI process is a very useful tool to define the infusion strategy and to plan and predict the resin flow progress in order to reduce the material waste and manufacturing cycle time and obtaining lighter structures, having lower void fraction and higher fibre content and mechanical performance. The numerical simulation of the VARI process implies the modelling of different complex phenomena, such as flow in porous media, mechanical deformation, heat exchange and chemical reaction. Therefore, a finite element software was used to solve a combination of governing equations based on a combination of pre-defined theoretical assumptions, by considering a moving mesh and appropriated boundary conditions. In this work, results obtained from simulations of VARI process were used to define the best strategy to be applied in the production of composite parts with different geometries, sizes and materials and predict the possibility of defects occur. In order to validate the accuracy of simulations, the numerical results were compared with those experimental ones obtained from the production of different composite parts where the best processing strategies were implemented. After analysing and discussing the theoretical and experimental obtained results, changes were applied to the numerical model to improve simulation accuracy.(undefined
Study of fluid-solid coupling for complex geometries in OpenFOAM
The focus of this research will be the modelling of heat transfer with fluid-solid coupling for complex geometries in OpenFOAM. In the initial stage, selected aspects of the OpenFOAM toolkit will be introduced, including its fundamentals and usage. Afterwards, the available tools to model heat transfer in a solid wall in contact with a channel of a complex cross-section, through which the fluid flows will be explored. The outcome of this work will be an algorithm that could guide users in simulating a similar cas
The LifeV library: engineering mathematics beyond the proof of concept
LifeV is a library for the finite element (FE) solution of partial
differential equations in one, two, and three dimensions. It is written in C++
and designed to run on diverse parallel architectures, including cloud and high
performance computing facilities. In spite of its academic research nature,
meaning a library for the development and testing of new methods, one
distinguishing feature of LifeV is its use on real world problems and it is
intended to provide a tool for many engineering applications. It has been
actually used in computational hemodynamics, including cardiac mechanics and
fluid-structure interaction problems, in porous media, ice sheets dynamics for
both forward and inverse problems. In this paper we give a short overview of
the features of LifeV and its coding paradigms on simple problems. The main
focus is on the parallel environment which is mainly driven by domain
decomposition methods and based on external libraries such as MPI, the Trilinos
project, HDF5 and ParMetis.
Dedicated to the memory of Fausto Saleri.Comment: Review of the LifeV Finite Element librar
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