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Article
Publication date: 17 October 2018

Sanjay Komala Sheshachala and Ramon Codina

This paper aims to present a finite element formulation to approximate systems of reaction–diffusion–advection equations, focusing on cases with nonlinear reaction. The…

234

Abstract

Purpose

This paper aims to present a finite element formulation to approximate systems of reaction–diffusion–advection equations, focusing on cases with nonlinear reaction. The formulation is based on the orthogonal sub-grid scale approach, with some simplifications that allow one to stabilize only the convective term, which is the source of potential instabilities. The space approximation is combined with finite difference time integration and a Newton–Raphson linearization of the reactive term. Some numerical examples show the accuracy of the resulting formulation. Applications using classical nonlinear reaction models in population dynamics are also provided, showing the robustness of the approach proposed.

Design/methodology/approach

A stabilized finite element method for advection–diffusion–reaction equations to the problem on nonlinear reaction is adapted. The formulation designed has been implemented in a computer code. Numerical examples are run to show the accuracy and robustness of the formulation.

Findings

The stabilized finite element method from which the authors depart can be adapted to problems with nonlinear reaction. The resulting method is very robust and accurate. The framework developed is applicable to several problems of interest by themselves, such as the predator–prey model.

Originality/value

A stabilized finite element method to problems with nonlinear reaction has been extended. Original contributions are the design of the stabilization parameters and the linearization of the problem. The application examples, apart from demonstrating the validity of the numerical model, help to get insight in the system of nonlinear equations being solved.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 11
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 19 September 2008

Javier Principe and Ramon Codina

The purpose of this paper is to describe a finite element formulation to approximate thermally coupled flows using both the Boussinesq and the low Mach number models with…

1729

Abstract

Purpose

The purpose of this paper is to describe a finite element formulation to approximate thermally coupled flows using both the Boussinesq and the low Mach number models with particular emphasis on the numerical implementation of the algorithm developed.

Design/methodology/approach

The formulation, that allows us to consider convection dominated problems using equal order interpolation for all the valuables of the problem, is based on the subgrid scale concept. The full Newton linearization strategy gives rise to monolithic treatment of the coupling of variables whereas some fixed point schemes permit the segregated treatment of velocity‐pressure and temperature. A relaxation scheme based on the Armijo rule has also been developed.

Findings

A full Newtown linearization turns out to be very efficient for steady‐state problems and very robust when it is combined with a line search strategy. A segregated treatment of velocity‐pressure and temperature happens to be more appropriate for transient problems.

Research limitations/implications

A fractional step scheme, splitting also momentum and continuity equations, could be further analysed.

Practical implications

The results presented in the paper are useful to decide the solution strategy for a given problem.

Originality/value

The numerical implementation of a stabilized finite element approximation of thermally coupled flows is described. The implementation algorithm is developed considering several possibilities for the solution of the discrete nonlinear problem.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 18 no. 7/8
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 15 June 2010

Ramon Codina, Javier Principe and Matías Ávila

The purpose of this paper is to describe a variational multiscale finite element approximation for the incompressible Navier‐Stokes equations using the Boussinesq approximation to…

345

Abstract

Purpose

The purpose of this paper is to describe a variational multiscale finite element approximation for the incompressible Navier‐Stokes equations using the Boussinesq approximation to model thermal coupling.

Design/methodology/approach

The main feature of the formulation, in contrast to other stabilized methods, is that the subscales are considered as transient and orthogonal to the finite element space. These subscales are solution of a differential equation in time that needs to be integrated. Likewise, the effect of the subscales is kept, both in the nonlinear convective terms of the momentum and temperature equations and, if required, in the thermal coupling term of the momentum equation.

Findings

This strategy allows the approaching of the problem of dealing with thermal turbulence from a strictly numerical point of view and discussion important issues, such as the relationship between the turbulent mechanical dissipation and the turbulent thermal dissipation.

Originality/value

The treatment of thermal turbulence from a strictly numerical point of view is the main originality of the work.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 20 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 July 2006

Guillaume Houzeaux and Ramon Codina

To develop a numerical methodology to simulate the lost foam casting (LFC), including the gas back‐pressure effects.

619

Abstract

Purpose

To develop a numerical methodology to simulate the lost foam casting (LFC), including the gas back‐pressure effects.

Design/methodology/approach

Back‐pressure effects are due to the interactions of many physical processes. The strategy proposed herein tries to model all these processes within a simple formula. The main characteristic of the model consists of assuming that the back‐pressure is a known function of the external parameters (coating, temperature, gravity, etc.) that affects directly the heat transfer coefficient from the metal to the foam. The general framework of the simulation is a finite element model based on an arbitrary Lagrangian Eulerian (ALE) approach and the use of level set function to capture the metal front advance.

Findings

After experimental tunings, the model provides a way to include the back‐pressure effects in a simple way.

Research limitations/implications

The method is not completely predictive in the sense that a priori tuning is necessary to calibrate the model.

Practical implications

Provides more realistic results than classical models.

Originality/value

The paper proposes a theoretical framework of a finite element method for the simulation of LFC process. The method uses an ALE method on a fixed mesh and a level‐set function to capture metal front advance. It proposes an original formula for the heat transfer coefficient that enables one to include back‐pressure effects.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 16 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 September 2000

Ramon Codina, Christopher Morton, Eugenio Oñate and Orlando Soto

Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite…

370

Abstract

Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite element formulation is presented first, and then the methodology followed to obtain significant data from the calculations is described. The quality of the ventilation of the building is defined by the average residence times, and the feasibility of this ventilation by the actions created on the instruments and the general flow pattern.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 10 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 3 May 2016

Camilo Andrés Bayona Roa, Joan Baiges and R Codina

The purpose of this paper is to apply the variational multi-scale framework to the finite element approximation of the compressible Navier-Stokes equations written in conservation…

1771

Abstract

Purpose

The purpose of this paper is to apply the variational multi-scale framework to the finite element approximation of the compressible Navier-Stokes equations written in conservation form. Even though this formulation is relatively well known, some particular features that have been applied with great success in other flow problems are incorporated.

Design/methodology/approach

The orthogonal subgrid scales, the non-linear tracking of these subscales, and their time evolution are applied. Moreover, a systematic way to design the matrix of algorithmic parameters from the perspective of a Fourier analysis is given, and the adjoint of the non-linear operator including the volumetric part of the convective term is defined. Because the subgrid stabilization method works in the streamline direction, an anisotropic shock capturing method that keeps the diffusion unaltered in the direction of the streamlines, but modifies the crosswind diffusion is implemented. The artificial shock capturing diffusivity is calculated by using the orthogonal projection onto the finite element space of the gradient of the solution, instead of the common residual definition. Temporal derivatives are integrated in an explicit fashion.

Findings

Subsonic and supersonic numerical experiments show that including the orthogonal, dynamic, and the non-linear subscales improve the accuracy of the compressible formulation. The non-linearity introduced by the anisotropic shock capturing method has less effect in the convergence behavior to the steady state.

Originality/value

A complete investigation of the stabilized formulation of the compressible problem is addressed.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

Available. Content available
Article
Publication date: 1 July 2006

Vaughan Voller

288

Abstract

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 16 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 3 August 2015

Matias Avila, R Codina and Javier Principe

The purpose of this paper is to present a finite element approximation of the low Mach number equations coupled with radiative equations to account for radiative heat transfer…

146

Abstract

Purpose

The purpose of this paper is to present a finite element approximation of the low Mach number equations coupled with radiative equations to account for radiative heat transfer. For high-temperature flows this coupling can have strong effects on the temperature and velocity fields.

Design/methodology/approach

The basic numerical formulation has been proposed in previous works. It is based on the variational multiscale (VMS) concept in which the unknowns of the problem are divided into resolved and subgrid parts which are modeled to consider their effect into the former. The aim of the present paper is to extend this modeling to the case in which the low Mach number equations are coupled with radiation, also introducing the concept of subgrid scales for the radiation equations.

Findings

As in the non-radiative case, an important improvement in the accuracy of the numerical scheme is observed when the nonlinear effects of the subgrid scales are taken into account. Besides it is possible to show global conservation of thermal energy.

Originality/value

The original contribution of the work is the proposal of keeping the VMS splitting into the nonlinear coupling between the low Mach number and the radiative transport equations, its numerical evaluation and the description of its properties.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 25 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 February 2016

Ramón Alberto Manso Rodríguez and Manuel Osvaldo Machado Rivero

This paper aims to examine the use of different mobile devices by libraries to develop programs for information skills training, focusing on the application of quick response (QR…

1818

Abstract

Purpose

This paper aims to examine the use of different mobile devices by libraries to develop programs for information skills training, focusing on the application of quick response (QR) codes for such a purpose.

Design/methodology/approach

The study was developed in two stages; primarily an analysis of the literature was conducted to determine the theoretical framework underlying the use of this tool for information literacy. The second part examined the practical application of this tool, with examples of several university libraries. In all, 13 academic libraries were included as the sample, which were chosen randomly from a global search on the Internet under the thematic basis for the theme of the study and thus evaluate the different employment opportunities of mobile telephony in developing skills information on users. The study is complemented with an assessment from the practice of the applicability of the principles described, arriving at conclusions and recommendations.

Findings

The purpose of the study is to recognize the use given to mobile technologies from libraries, particularly the use of QR codes, to help meet the demands of users in relation to skills training information, just as you may have the need.

Originality/value

The benefits of the use of mobile devices for the development of information literacy actions are identified and the set of actions that can be implemented for training information skills through the use of QR codes are set based on all outlined by the Association of College and Research Libraries goals.

Details

The Electronic Library, vol. 34 no. 1
Type: Research Article
ISSN: 0264-0473

Keywords

Available. Open Access. Open Access
Article
Publication date: 15 August 2019

Carina Rey Martin, Concepción Rodriguez Parada and Enric Camón Luis

The purpose of this paper is to analyse the level of transparency of the libraries of Catalan universities that are members of the Consortium of University Services of Catalonia…

1055

Abstract

Purpose

The purpose of this paper is to analyse the level of transparency of the libraries of Catalan universities that are members of the Consortium of University Services of Catalonia (CSUC).

Design/methodology/approach

The analysis involved reviewing the information available on the websites of the ten libraries belonging to CSUC. For each library’s website, the presence of 18 indicators was explored. These indicators had been defined by the Commitment and Transparency Foundation (Spain).

Findings

There is a notable difference between the level of transparency of Catalan universities and their libraries. Moreover, the universities’ culture of transparency is not reflected in that of the libraries. Four of the libraries can be considered transparent because they have accomplished from 12 to 18 indicators; three can be considered “translucent”, due to their indicators ranging from 11 to 7 points; and three are considered opaque as a result of obtaining from 1 to 5 indicators.

Practical implications

There is a need to review the volume and quality of information that can be consulted on library websites, considering that all services and entities funded with public money must inform citizens of the principles that govern their management and the results obtained.

Originality/value

The information regarding transparency is incomplete and should be organised with parameters that make it easier to find. Libraries that occupy the lowest positions in the ranking all belong to private universities. Their poor results are due to the lack of information justifying their management or providing information on how the service is organised. Some conclusions of this study are very similar to those of the study on Madrid’s Madroño Consortium (Pacios Lozano, 2016) which has been taken into account in this paper.

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