N. Massarotti, P. Nithiarasu and A. Carotenuto
In this paper, microscopic and macroscopic approaches to the solution of natural convection in enclosures filled with fluid saturated porous media are investigated. At the…
Abstract
In this paper, microscopic and macroscopic approaches to the solution of natural convection in enclosures filled with fluid saturated porous media are investigated. At the microscopic level, the porous medium is represented by different assemblies of cylinders and the Navier‐Stokes equations are assumed to govern the flow. To represent the flow in a macroscopic porous medium approach, the generalised flow model is employed. The characteristic based split scheme is used to solve the conservation equations of both approaches. In addition to the comparison between microscopic and macroscopic approaches of fluid saturated porous enclosures, cavities with interface between fluid saturated porous medium and single phase fluid are also investigated.
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F. Arpino, A. Carotenuto, N. Massarotti and P. Nithiarasu
The purpose of this paper is to introduce a robust mathematical model and finite element‐based numerical approach to solve solid oxide fuel cell (SOFC) problems.
Abstract
Purpose
The purpose of this paper is to introduce a robust mathematical model and finite element‐based numerical approach to solve solid oxide fuel cell (SOFC) problems.
Design/methodology/approach
A robust mathematical model is constructed by studying pros and cons of different SOFC and other fuel cell models. The finite element‐based numerical approach presented is a unified approach to solve multi‐disciplinary aspects arising from SOFC problems. The characteristic‐based split approach employed here is an efficient way of solving various flow, heat and mass transfer regimes in SOFCs.
Findings
The results presented show that both the model and numerical algorithm proposed are robust. Furthermore, the approaches proposed are general and can be easily extended to other similar problems of practical interest.
Originality/value
The model proposed is the first of this kind and the unified approach for solving flow, heat and mass transfer within a fuel cell is also novel.
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A. Mauro, F. Arpino, N. Massarotti and P. Nithiarasu
The purpose of this paper is to describe two‐ and three‐dimensional numerical modelling of solid oxide fuel cells (SOFCs) by employing an accurate and stable fully matrix…
Abstract
Purpose
The purpose of this paper is to describe two‐ and three‐dimensional numerical modelling of solid oxide fuel cells (SOFCs) by employing an accurate and stable fully matrix inversion free finite element algorithm.
Design/methodology/approach
A general and detailed mathematical model has been developed for the description of the coupled complex phenomena occurring in fuel cells. A fully matrix inversion free algorithm, based on the artificial compressibility (AC) version of the characteristic‐based split (CBS) scheme and single domain approach have been successfully employed for the accurate and efficient simulation of high temperature SOFCs.
Findings
For the first time, a stable fully explicit algorithm has been applied to detailed multi‐dimensional simulation transport phenomena, coupled to chemical and electrochemical reactions, in fluid, porous and solid parts of a SOFC. The accuracy of the present results has been verified via comparison with experimental and numerical data available in the literature.
Originality/value
For the first time, thanks to a stabilization analysis conducted, the AC‐CBS algorithm has been successfully used to numerically solve the generalized model, applied in this paper to describe transport phenomena through free fluid channels and porous electrodes of SOFCs, without the need of further conditions at the fluid‐electrode interface.
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Fausto Arpino, Nicola Massarotti, Alessandro Mauro and Perumal Nithiarasu
The purpose of the paper is to numerically simulate steady‐state thermo‐solutal convection in rectangular cavities with different aspect ratios, subject to horizontal temperature…
Abstract
Purpose
The purpose of the paper is to numerically simulate steady‐state thermo‐solutal convection in rectangular cavities with different aspect ratios, subject to horizontal temperature and concentration gradients, and validate the results against numerical and experimental data available from literature.
Design/methodology/approach
The fully explicit Artificial Compressibility (AC) version of the Characteristic Based Split (CBS) scheme is adopted to solve double diffusion (DD) problems. A stabilization analysis is carried out to efficiently solve the problems considered in the present work. The thermal and solutal buoyancy forces acting on the fluid have been taken into account in case of aiding and opposing flow conditions.
Findings
The stability limits derived by the authors for the thermo‐solutal convection assume a fundamental role to efficiently solve the DD problems considered. In the cases characterized by higher Rayleigh number the convergent solution is obtained only by employing the new stability conditions. The efficient matrix free procedure employed is a powerful tool to study complex DD problems.
Originality/value
In this paper, the authors extend the stabilization analysis for the AC‐CBS scheme to the solution of DD, fundamental to efficiently solve the present problems, and apply the present fully explicit matrix free scheme, based on finite elements, to the solution of DD natural convection in cavities.
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N. Massarotti, P. Nithiarasu and O.C. Zienkiewicz
Natural convection in porous medium‐fluid interface problems are numerically studied by using the characteristic based split (CBS) algorithm. The finite element method is used to…
Abstract
Natural convection in porous medium‐fluid interface problems are numerically studied by using the characteristic based split (CBS) algorithm. The finite element method is used to solve the governing generalized porous medium equations. The accuracy of the scheme is estimated by comparing the present predictions for a porous cavity with those results available for the same problem. Two different types of interface problems have been considered. In the first case, the domain is vertically divided into two equal parts, while in the second problem the division is along the horizontal direction. Results obtained from the present investigation are compared extensively with existing experimental and numerical data and they are in good agreement with the available literature. Also present results are smooth along the interface and are without any jumps in the solution.
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P. Nithiarasu, N. Massarotti and J.S. Mathur
To numerically model forced convection heat transfer over arrays of solder balls.
Abstract
Purpose
To numerically model forced convection heat transfer over arrays of solder balls.
Design/methodology/approach
The characteristic based split (CBS) scheme has been used to solve the incompressible Navier‐Stokes equations on unstructured meshes.
Findings
The results show an increase in heat transport with increase in Reynolds numbers. A significant change in heat transfer is also noticed with change in angle of attack.
Originality/value
The presented results will be useful in designing cooling systems for electronic components.
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Gregor Kosec and Božidar Šarler
The purpose of this paper is to present the solution of a highly nonlinear fluid dynamics in a low Prandtl number regime, typical for metal‐like materials, as defined in the call…
Abstract
Purpose
The purpose of this paper is to present the solution of a highly nonlinear fluid dynamics in a low Prandtl number regime, typical for metal‐like materials, as defined in the call for contributions to a numerical benchmark problem for 2D columnar solidification of binary alloys. The solution of such a numerical situation represents the first step towards understanding the instabilities in a more complex case of macrosegregation.
Design/methodology/approach
The involved temperature, velocity and pressure fields are represented through the local approximation functions which are used to evaluate the partial differential operators. The temporal discretization is performed through explicit time stepping.
Findings
The performance of the method is assessed on the natural convection in a closed rectangular cavity filled with a low Prandtl fluid. Two cases are considered, one with steady state and another with oscillatory solution. It is shown that the proposed solution procedure, despite its simplicity, provides stable and convergent results with excellent computational performance. The results show good agreement with the results of the classical finite volume method and spectral finite element method.
Originality/value
The solution procedure is formulated completely through local computational operations. Besides local numerical method, the pressure velocity is performed locally also, retaining the correct temporal transient.
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Alexandre Lamoureux and Bantwal R. (Rabi) Baliga
The purpose of this paper is to first present the key features of hybrid numerical methods that enable cost-effective simulations of complex thermofluid systems, and then…
Abstract
Purpose
The purpose of this paper is to first present the key features of hybrid numerical methods that enable cost-effective simulations of complex thermofluid systems, and then demonstrate the formulation and application of such a method.
Design/methodology/approach
A hybrid numerical method is formulated for simulations of a closed-loop thermosyphon operating with slurries of a micro-encapsulated phase-change material suspended in distilled water. The slurries are modeled as homogeneous mixtures, with inputs of effective properties and overall heat-loss coefficients. Combinations of an axisymmetric two-dimensional (2D) control-volume finite-element method and a segmented-quasi-one-dimensional (1D) model are used to achieve cost-effective simulations. Proper matching of the solutions at the interfaces between adjacent axisymmetric 2D and quasi-1D zones is ensured by incorporating and heuristically determining suitable lengths of pre- and post-heating (and also pre- and post-cooling) sections.
Findings
In the demonstration problem, which would strictly require full three-dimensional simulations of the fluid flow and heat transfer phenomena, the proposed hybrid 1D/2D numerical method produces results that are in very good agreement with those obtained in a complementary experimental investigation.
Originality/value
The hybrid numerical methods discussed in this paper allow cost-effective computer simulations of complex thermofluid systems. These methods can therefore serve as very useful tools for the design, parametric studies, and optimization of such systems.
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Simona Di Fraia, Nicola Massarotti and P. Nithiarasu
This paper aims to provide a comprehensive literature review on modelling electro-osmotic flow in porous media.
Abstract
Purpose
This paper aims to provide a comprehensive literature review on modelling electro-osmotic flow in porous media.
Design/methodology/approach
Modelling electro-osmosis in fluid systems without solid particles has been first introduced. Then, after a brief description of the existing approaches for porous media modelling, electro-osmotic flow in porous media has been considered by analysing the main contributions to the development of this topic.
Findings
The analysis of literature has highlighted the absence of a universal model to analyse electro-osmosis in porous media, whereas many different methods and assumptions are used.
Originality/value
For the first time, the existing approaches for modelling electro-osmotic flow in porous have been collected and analysed to provide detailed indications for future works concerning this topic.