Sebastian Prinz, Jörg Schumacher and Thomas Boeck
This paper aims to address the performance of different subgrid-scale models (SGS) for hydro- (HD) and magnetohydrodynamic (MHD) channel flows within a collocated finite-volume…
Abstract
Purpose
This paper aims to address the performance of different subgrid-scale models (SGS) for hydro- (HD) and magnetohydrodynamic (MHD) channel flows within a collocated finite-volume scheme.
Design/methodology/approach
First, the SGS energy transfer is analyzed by a priori tests using fully resolved DNS data. Here, the focus lies on the influence of the magnetic field on the SGS energy transport. Second, the authors performed a series of 18 a posteriori model tests, using different grid resolutions and SGS models for HD and MHD channel flows.
Findings
From the a priori analysis, the authors observe a quantitative reduction of the SGS energy transport because of the action of the magnetic field depending on its orientation. The a posteriori model tests show a clear improvement because of the use of mixed-models within the numerical scheme.
Originality/value
This study demonstrates the necessity of improved SGS modeling strategies for magnetohydrodynamic channel flows within a collocated finite-volume scheme.
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Keywords
Aleksandra Drizo and Joseph Pegna
To provide a comprehensive state of the art review of environmental impact assessment (EIA) of existing rapid prototyping (RP) and rapid tooling (RT), and identify prospective…
Abstract
Purpose
To provide a comprehensive state of the art review of environmental impact assessment (EIA) of existing rapid prototyping (RP) and rapid tooling (RT), and identify prospective research needs.
Design/methodology/approach
The sparse literature on the EIA of RP and RT is balanced by that of the comparatively mature field of industrial ecology (IE). Hence, the review emphasizes portable IE measurement and evaluations methods. As RP and RT can also be viewed as design tools and mass customization manufacturing, other EIA may be needed.
Findings
The scarcity of research to date combined with rapid technological advances leaves a large number of unresolved issues. In addition, the special character of RP and RT, as design and manufacturing enablers implies that future research is needed.
Research limitations/implications
This review is drawn from a technology in rapid evolution. Hence, unresolved issues focus on technologies that already are on the market and the research needs are formulated in terms of state of the art process research.
Practical implications
As technological advances multiply, so does the number of unresolved environmental problems. The review of unresolved issues points to a pressing need to assess the consequences of RP and RT while identified research needs point the way to anticipated areas where further assessment methods will be needed.
Originality/value
This paper intends to raise awareness about the potential environmental impacts from RP and RT, by presenting the problems associated with current methods for measuring environmental effects and discussing some of the most urgent unresolved issues, specifically with respect to materials. Indirect effects of other uses of RP and RT are discussed only briefly for lack of available data.
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Raghavaiah N.V. and Naga Srinivasulu G.
The purpose of this paper is to investigate the performance of Passive Direct Methanol Fuel Cell (PDMFC) experimentally using various Membrane Electrode Assembly (MEA) shapes such…
Abstract
Purpose
The purpose of this paper is to investigate the performance of Passive Direct Methanol Fuel Cell (PDMFC) experimentally using various Membrane Electrode Assembly (MEA) shapes such as square, rectangle, rhombus, and circle with equal areas and equal perimeters. The variation in MEA shape/size is achieved by altering gasket openings in the dynamic regions.
Design/methodology/approach
In the equal areas of MEA shapes, gasket opening areas of 1963.5 (+/−0.2) mm2 are used. Whereas in the equal perimeters of shapes, gasket opening perimeters of 157.1 (+/−0.2) mm are used. In this experimentation, Nickel-201 current collectors with 45.3% of circular openings are used on both the anode and cathode sides. The experiment is carried out at a 5 molar methanol concentration to find out the highest power density of the cell.
Findings
In the equal areas, among the shapes that are chosen for investigation, the square shape opening consisting of a perimeter of 177.2 mm has developed a maximum power density of 6.344 mWcm−2 and a maximum current density of 65.2 mAcm−2. Similarly, in equal perimeters, the rhombus shape opening with an area of 1400 mm2 has developed a maximum power density of 7.714 mWcm−2 and a maximum current density of 85.3 mAcm−2.
Originality/value
The novelty of this research work is instead of fabricating various shapes and sizes of highly expensive MEAs, the desired shapes and sizes of the MEA are achieved by altering gasket openings over dynamic regions to find out the highest power density of the cell.
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Ilse Valenzuela Matus, Jorge Lino Alves, Joaquim Góis, Paulo Vaz-Pires and Augusto Barata da Rocha
The purpose of this paper is to review cases of artificial reefs built through additive manufacturing (AM) technologies and analyse their ecological goals, fabrication process…
Abstract
Purpose
The purpose of this paper is to review cases of artificial reefs built through additive manufacturing (AM) technologies and analyse their ecological goals, fabrication process, materials, structural design features and implementation location to determine predominant parameters, environmental impacts, advantages, and limitations.
Design/methodology/approach
The review analysed 16 cases of artificial reefs from both temperate and tropical regions. These were categorised based on the AM process used, the mortar material used (crucial for biological applications), the structural design features and the location of implementation. These parameters are assessed to determine how effectively the designs meet the stipulated ecological goals, how AM technologies demonstrate their potential in comparison to conventional methods and the preference locations of these implementations.
Findings
The overview revealed that the dominant artificial reef implementation occurs in the Mediterranean and Atlantic Seas, both accounting for 24%. The remaining cases were in the Australian Sea (20%), the South Asia Sea (12%), the Persian Gulf and the Pacific Ocean, both with 8%, and the Indian Sea with 4% of all the cases studied. It was concluded that fused filament fabrication, binder jetting and material extrusion represent the main AM processes used to build artificial reefs. Cementitious materials, ceramics, polymers and geopolymer formulations were used, incorporating aggregates from mineral residues, biological wastes and pozzolan materials, to reduce environmental impacts, promote the circular economy and be more beneficial for marine ecosystems. The evaluation ranking assessed how well their design and materials align with their ecological goals, demonstrating that five cases were ranked with high effectiveness, ten projects with moderate effectiveness and one case with low effectiveness.
Originality/value
AM represents an innovative method for marine restoration and management. It offers a rapid prototyping technique for design validation and enables the creation of highly complex shapes for habitat diversification while incorporating a diverse range of materials to benefit environmental and marine species’ habitats.