M. Mulas, S. Chibbaro, G. Delussu, I. Di Piazza and M. Talice
This paper presents a unified numerical method able to address a wide class of fluid flow problems of engineering interest. Arbitrary fluids are treated specifying totally…
Abstract
This paper presents a unified numerical method able to address a wide class of fluid flow problems of engineering interest. Arbitrary fluids are treated specifying totally arbitrary equations of state, either in analytical form or through look‐up tables. The most general system of the unsteady Navier–Stokes equations is integrated with a coupled implicit preconditioned method. The method can stand infinite CFL number and shows the efficiency of a quasi‐Newton method independent of the multi‐block partitioning on parallel machines. Computed test cases ranging from inviscid hydrodynamics, to natural convection loops of liquid metals, and to supersonic gasdynamics, show a solution efficiency independent of the class of fluid flow problem.
Details
Keywords
Michele Ciofalo and Fabrizio Cricchio
The buoyancy‐driven magnetohydrodynamic flow in a cubic enclosure was investigated by three‐dimensional numerical simulation. The enclosure was volumetrically heated by a uniform…
Abstract
The buoyancy‐driven magnetohydrodynamic flow in a cubic enclosure was investigated by three‐dimensional numerical simulation. The enclosure was volumetrically heated by a uniform power density and cooled along two opposite vertical walls, all remaining walls being adiabatic. A uniform magnetic field was applied orthogonally to the gravity vector and to the temperature gradient. The Prandtl number was 0.0321 (characteristic of Pb–17Li at 300°C), the Rayleigh number was 104, and the Hartmann number was made to vary between 0 and 2×103. The steady‐state Navier–Stokes equations, in conjunction with a scalar transport equation for the fluid's enthalpy and with the Poisson equation for the electrical potential, were solved by a finite volume method using a purposely modified CFD code and a computational grid with 643 nodes in the fluid. Emphasis was laid on the effects of increasing the Hartmann number on the complex three‐dimensional flow and current pattern.
Details
Keywords
This chapter presents the first sociological study of outrigger canoe racing, or va'a, in Fiji, a sport deeply embedded in Pacific seafaring heritage. It begins with a brief…
Abstract
This chapter presents the first sociological study of outrigger canoe racing, or va'a, in Fiji, a sport deeply embedded in Pacific seafaring heritage. It begins with a brief history of va'a in Fiji, which emerged in the 1980s as part of a postcolonial ‘revival’ of indigenous cultural practices. The chapter subsequently examines the paddling community's notable inclusivity (in terms of gender, ethnicity, age and body shape), persisting exclusivity (in terms of class and geographical location) and dynamic engagement with the sport's cultural anchoring. A key contention of this chapter is that va'a, in its ongoing social construction, has become simultaneously a competitive sport with modern equipment and structures, a hip and cool recreational activity and a cohesive community with shared commitment to the relational value of the ocean, notwithstanding long-standing power differentials. The sport is hence positioned as integral to living, evolving culture rather than timeless indigeneity.
Details
Keywords
Sara Rainieri, Fabio Bozzoli, Linda Schiavi and Giorgio Pagliarini
The aim of this paper is to investigate the convective heat transfer in swirl tubes, which are obtained by roto‐translating a circular section eccentric with respect to the…
Abstract
Purpose
The aim of this paper is to investigate the convective heat transfer in swirl tubes, which are obtained by roto‐translating a circular section eccentric with respect to the rotation axis. The geometry is numerically investigated with the aim of evaluating the convective heat transfer enhancement effect due to the secondary flow induced by the centrifugal force.
Design/methodology/approach
The governing equations, i.e. continuity, momentum and energy equations, are integrated numerically within Comsol Multiphysics® environment, under the assumption of incompressible Newtonian and constant properties fluid and of periodically fully developed laminar flow for what concerns both the hydrodynamic and the thermal problem under the uniform wall heat flux thermal boundary condition.
Findings
The heat transfer performance of the geometry is discussed in relation to the flow pattern. In particular, the numerical results show that two different stable flow regimes may exist, according to the ratio of the Reynolds number to the dimensionless helix pitch. The Nusselt number augmentation becomes significant for high Prandtl number fluids when a critical Re/P* value, corresponding to the onset of the centrifugal forces induced secondary flow, is reached.
Originality/value
The geometry here investigated represents an interesting solution to enhance the convective heat transfer in situations in which the flow, although disturbed, persists in the laminar regime. This type of enhanced tubes shows then interesting heat transfer performances (which becomes particularly significant for high Prandtl number values) by thus suggesting convenient applications also for highly viscous fluids which are often treated under the laminar flow regime.
Details
Keywords
Ganesh Narayanan, Milan Joshi, Prasun Dutta and Kanak Kalita
Computational fluid dynamics (CFD) technique is the most commonly used numerical approach to simulate fluid flow behaviour. Owing to its computationally, cost-intensive nature CFD…
Abstract
Purpose
Computational fluid dynamics (CFD) technique is the most commonly used numerical approach to simulate fluid flow behaviour. Owing to its computationally, cost-intensive nature CFD models may not be easily and quickly deployable. In this regard, this study aims to present a support vector machine (SVM)-based metamodelling approach that can be easily trained and quickly deployed for carrying out large-scale studies.
Design/methodology/approach
Radial basis function and ε^*-insensitive loss function are used as kernel function and loss function, respectively. To prevent overfitting of the model, five-fold cross-validation root mean squared error is used while training the SVM metamodel. Rather than blindly using any SVM tuning parameters, a particle swarm optimisation (PSO) is used to fine-tune them. The developed SVM metamodel is tested using various error metrics on disjoint test data.
Findings
Using the SVM metamodel, a parametric study is conducted to understand the effect of various factors influencing the behaviour of the turbulent fluid flow in the pipe bend with CFD simulation data set. Based on the parametric study carried out, it is seen that the diametric position has the most effect on dimensionless axial velocity, whereas Reynolds number has the least effect.
Originality/value
This paper provides an effective PSO-tuned SVM metamodelling approach, which may be used as a significant cost-saving approach to quickly and accurately estimate fluid flow characteristics that, in general, require the use of expensive CFD models.
Details
Keywords
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.
Details
Keywords
Maria Cleofe Giorgino and Federico Barnabè
Drawing motivation from the greater exposure to uncertainty and condition changes that affect large projects due to their long lifecycle, this paper aims to investigate how the…
Abstract
Purpose
Drawing motivation from the greater exposure to uncertainty and condition changes that affect large projects due to their long lifecycle, this paper aims to investigate how the time factor affects the use of governance mechanisms to pursue the success of these projects.
Design/methodology/approach
To pursue its aim, the article applies the dichotomization between the hard and soft mechanisms of project governance to the analysis of a historical case study, whose findings are organized over the short, medium and long periods. The case selected is referred to the peculiar water system, made up of tunnels named “bottini,” that was in use in Siena (Italy) as the old aqueduct. Specifically, the study focuses on the project of expansion of this water system that was realized during the 14th century for the construction of the “Bottino maestro di Fontegaia.”
Findings
This article highlights the different relevance that, during the lifecycle of large projects, is assumed by hard and soft governance mechanisms, with the former having main relevance in a short and medium period, and the latter usually emerging in the medium period and, subsequently, playing a growing role for the project success in the long period.
Originality/value
The article contributes to the literature on large projects by providing novel insights about how the time factor impacts the governance of these projects. Furthermore, the case study, with its unique history, highlights the relevance of combining effectively the hard and the soft dimensions of project governance to pursue success.
Details
Keywords
Se Heine non giunse fino a Roma, in compenso vi arrivarono altri non meno illustri tedeschi, il cui genio si immortalò nel campo musicale. Per non parlare di Händel, che visit�…
Abstract
Se Heine non giunse fino a Roma, in compenso vi arrivarono altri non meno illustri tedeschi, il cui genio si immortalò nel campo musicale. Per non parlare di Händel, che visitò Roma nel 1707, nè di Gluck, che vi venne nel 1756, ricorderemoper il'700 — Wolfango Amedeo Mozart e — per 1'800 — Riccardo Wagner.
Luca Daconto and Gabriele Manella
The chapter addresses the issue of contemporary public space. In the urban setting, social groups form different publics that become mutually inter-visible in public spaces…
Abstract
The chapter addresses the issue of contemporary public space. In the urban setting, social groups form different publics that become mutually inter-visible in public spaces: relational arenas, in which it is possible to learn living with strangers, recognizing the right to the city for all people. In contemporary city, some theories argue that we would assist to the crisis of public space. Indeed, the forming of a public realm is more difficult, because social groups build separate and self-segregating routes, and urban public spaces are increasingly privatized, controlled, and reorganized to be more compatible with the global city, the city-users, and the hypermobile upper classes.
Shifting the attention to Sala Borsa (a public library in the centre of Bologna), the authors argue that the changes in the socio-spatial morphology of contemporary cities do not prevent the forming of a public arena, accessible also to the marginal groups, as the homeless. Because of its centrality, its free access, its innovative and multimedia environment, Sala Borsa is a crowded, lively, and symbolic public space. In this public library, social groups appropriate different spaces and times through the production of porous boundaries. Nevertheless, the identity of public-library-user taken once in Sala Borsa produces an inclusive regime of inter-visibility, where also homeless people are present.
Details
Keywords
Lisa Ariemma and Judith Burnside-Lawry
The tendency to utilize transnational organizations (TNO), with the tacit support of transnational institutions such as the European Union, to realize mega projects affecting…
Abstract
The tendency to utilize transnational organizations (TNO), with the tacit support of transnational institutions such as the European Union, to realize mega projects affecting local populations and territories distant from decision-making boardrooms, may result in increasing democratic alienation between those who are charged with implementing these projects and local citizens.
This chapter presents Stage 2 of a study to examine democratic participation and communicative action between a transnational organization, governing bodies, and the citizens affected by a high-speed rail project in Susa Valley, Italy. Findings related to potential democratic alienation between citizens and decision-makers are presented. Societal factors which contribute to this alienation, such as a communication deficit, are considered, as well as the strategies adopted to counter this participatory gap – including a reliance on electronic media for disseminating information and the creation of transnational resistance networks.
Results suggest that the emergence of transnational resistance networks such as the Forum Against Unnecessary and Imposed Mega Projects – spearheaded by members of the No TAV social movement, may provide new avenues for democratic participation and citizen engagement.