An artificial compressibility method for axisymmetric swirling flows

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Stavros N. Leloudas ◽  
Georgios N. Lygidakis ◽  
Argiris I. Delis ◽  
Ioannis K. Nikolos
Keyword(s):  
Time Integration ◽  
Momentum Equation ◽  
Research Literature ◽  
Swirling Flows ◽  
Computational Time ◽  
Finite Volume Scheme ◽  
Content Type ◽  
Artificial Compressibility ◽  
Rans Equations ◽  
Artificial Compressibility Method

Purpose This study aims to feature the application of the artificial compressibility method (ACM) for the numerical prediction of two-dimensional (2D) axisymmetric swirling flows. Design/methodology/approach The respective academic numerical solver, named IGal2D, is based on the axisymmetric Reynolds-averaged Navier–Stokes (RANS) equations, arranged in a pseudo-Cartesian form, enhanced by the addition of the circumferential momentum equation. Discretization of spatial derivative terms within the governing equations is performed via unstructured 2D grid layouts, with a node-centered finite-volume scheme. For the evaluation of inviscid fluxes, the upwind Roe’s approximate Riemann solver is applied, coupled with a higher-order accurate spatial reconstruction, whereas an element-based approach is used for the calculation of gradients required for the viscous ones. Time integration is succeeded through a second-order accurate four-stage Runge-Kutta method, adopting additionally a local time-stepping technique. Further acceleration, in terms of computational time, is achieved by using an agglomeration multigrid scheme, incorporating the full approximation scheme in a V-cycle process, within an efficient edge-based data structure. Findings A detailed validation of the proposed numerical methodology is performed by encountering both inviscid and viscous (laminar and turbulent) swirling flows with axial symmetry. IGal2D is compared against the commercial software ANSYS fluent – by using appropriate metrics and characteristic flow quantities – but also against experimental measurements, confirming the proposed methodology’s potential to predict such flows in terms of accuracy. Originality/value This study provides a robust methodology for the accurate prediction of swirling flows by combining the axisymmetric RANS equations with ACM. In addition, a detailed description of the convective flux Jacobian is provided, filling a respective gap in research literature.

scholarly journals Vulnerable adults in police custody

2019 ◽  
Vol 22 (1) ◽  
pp. 5-8
Author(s):  
Ian Cummins
Keyword(s):  
Design Methodology ◽  
Research Literature ◽  
Police Custody ◽  
England And Wales ◽  
Content Type ◽  
Increased Risk ◽  
Vulnerable Adults

Purpose The purpose of this paper is to discuss the recent National Appropriate Adult Network (NAAN) report on the role of the appropriate adult. Design/methodology/approach This paper is based on the NAAN report and a review of relevant policy and research literature. Findings There to Help 2 highlights that there are still significant gaps in the provision of appropriate adult schemes across England and Wales. These gaps potentially place vulnerable adults at increased risk. Originality/value This paper is a review of recent research.

scholarly journals A Fully Implicit Finite Volume Scheme for a Seawater Intrusion Problem in Coastal Aquifers

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1639
Author(s):  
Abdelkrim Aharmouch ◽  
Brahim Amaziane ◽  
Mustapha El Ossmani ◽  
Khadija Talali
Keyword(s):  
Finite Volume ◽  
Coastal Aquifers ◽  
Nonlinear Partial Differential Equations ◽  
Time Integration ◽  
Mass Conservation ◽  
Coupled System ◽  
Finite Volume Scheme ◽  
Time Step ◽  
Volume Scheme ◽  
Fully Implicit

We present a numerical framework for efficiently simulating seawater flow in coastal aquifers using a finite volume method. The mathematical model consists of coupled and nonlinear partial differential equations. Difficulties arise from the nonlinear structure of the system and the complexity of natural fields, which results in complex aquifer geometries and heterogeneity in the hydraulic parameters. When numerically solving such a model, due to the mentioned feature, attempts to explicitly perform the time integration result in an excessively restricted stability condition on time step. An implicit method, which calculates the flow dynamics at each time step, is needed to overcome the stability problem of the time integration and mass conservation. A fully implicit finite volume scheme is developed to discretize the coupled system that allows the use of much longer time steps than explicit schemes. We have developed and implemented this scheme in a new module in the context of the open source platform DuMu X . The accuracy and effectiveness of this new module are demonstrated through numerical investigation for simulating the displacement of the sharp interface between saltwater and freshwater in groundwater flow. Lastly, numerical results of a realistic test case are presented to prove the efficiency and the performance of the method.

A nonlinear magnetic circuit model for periodic eddy current problems using T,ϕ-ϕ formulation

2017 ◽  
Vol 36 (3) ◽  
pp. 649-664 ◽  
Author(s):  
Rene Plasser ◽  
Gergely Koczka ◽  
Oszkár Bíró
Keyword(s):  
Eddy Current ◽  
Magnetic Circuit ◽  
Iteration Process ◽  
Equation System ◽  
Circuit Model ◽  
Computational Time ◽  
Combined Method ◽  
3D Fem ◽  
Content Type ◽  
Transformer Model

Purpose A transformer model is used as a benchmark for testing various methods to solve 3D nonlinear periodic eddy current problems. This paper aims to set up a nonlinear magnetic circuit problem to assess the solving procedure of the nonlinear equation system for determining the influence of various special techniques on the convergence of nonlinear iterations and hence the computational time. Design/methodology/approach Using the T,ϕ-ϕ formulation and the harmonic balance fixed-point approach, two techniques are investigated: the so-called “separate method” and the “combined method” for solving the equation system. When using the finite element method (FEM), the elapsed time for solving a problem is dominated by the conjugate gradient (CG) iteration process. The motivation for treating the equations of the voltage excitations separately from the rest of the equation system is to achieve a better-conditioned matrix system to determine the field quantities and hence a faster convergence of the CG process. Findings In fact, both methods are suitable for nonlinear computation, and for comparing the final results, the methods are equally good. Applying the combined method, the number of iterations to be executed to achieve a meaningful result is considerably less than using the separated method. Originality/value To facilitate a quick analysis, a simplified magnetic circuit model of the 3D problem was generated to assess how the different ways of solutions will affect the full 3D solving process. This investigation of a simple magnetic circuit problem to evaluate the benefits of computational methods provides the basis for considering this formulation in a 3D-FEM code for further investigation.

Efficient evaluation of the earth return mutual impedance of overhead conductors over a horizontally multilayered soil

2014 ◽  
Vol 33 (4) ◽  
pp. 1379-1395 ◽  
Author(s):  
Jae-bok Lee ◽  
Jun Zou ◽  
Benliang Li ◽  
Munno Ju
Keyword(s):  
Unit Length ◽  
Oscillatory Integral ◽  
Electromagnetic Transients ◽  
Closed Form Expression ◽  
Computational Time ◽  
Horizontal Distance ◽  
Content Type ◽  
Mutual Impedance ◽  
The Earth ◽  
Highly Oscillatory

Purpose – The per-unit-length earth return mutual impedance of the overhead conductors plays an important role for analyzing electromagnetic transients or couplings of multi-conductor systems. It is impossible to have a closed-form expression to evaluate this kind of impedance. The purpose of this paper is to propose an efficient numerical approach to evaluate the earth return mutual impedance of the overhead conductors above horizontally multi-layered soils. Design/methodology/approach – The expression of the earth return mutual impedance, which contains a complex highly oscillatory semi-infinite integral, is divided into two parts intentionally, i.e. the definite and the tail integral, respectively. The definite integral is calculated using the proposed moment functions after fitting the integrand into the piecewise cubic spline functions, and the tail integral is replaced by exponential integrals with newly developed asymptotic integrands. Findings – The numerical examples show the proposed approach has a satisfactory accuracy for different parameter combinations. Compared to the direct quadrature approach, the computational time of the proposed approach is very competitive, especially, for the large horizontal distance and the low height of the conductors. Originality/value – The advantage of the proposed approach is that the calculation of the highly oscillatory integral is completely avoided due to the fact that the moment function can be evaluated analytically. The contribution of the tail integral is well included by means of the exponential integral, though in an asymptotic way. The proposed approach is completely general, and can be applied to calculate the earth return mutual impedance of overhead conductors above a soil structure with an arbitrary number of horizontal layers.

scholarly journals Research and practice

2014 ◽  
Vol 70 (6) ◽  
pp. 1039-1053 ◽  
Author(s):  
Mark Hepworth ◽  
Philipp Grunewald ◽  
Geoff Walton
Keyword(s):  
Phenomenological Approach ◽  
Critical Discussion ◽  
Research Literature ◽  
Research Experience ◽  
Content Type ◽  
Information Behaviour ◽  
Relative Value ◽  
Participative Approach ◽  
Key Issues ◽  
Participative Design

Purpose – The purpose of this paper is to provide a critical discussion on the nature of research into people's information behaviour, and in particular the contribution of the phenomenological approach for the development of information solutions. Design/methodology/approach – The approach takes the form of a conceptual analysis drawing on the research literature and personal research experience. Findings – The paper brings to the foreground the relative value of different conceptual approaches and how these underpin and relate to the development of information solutions. Research limitations/implications – The paper, due to the breadth and complexity of the subject, serves to highlight key issues and bringing together ideas. Some topics deserve further explanation. However, this was beyond the scope of this paper. Practical implications – A conceptual framework is provided that indicates the value of the epistemic spectrum for information behaviour studies and provides support for action research and participative design. Social implications – Taking a phenomenological approach, and consequently either a first person approach and/or a highly participative approach to research, challenges the relationship between researcher and respondent. It also raises questions about why the authors conduct research and for whom it is intended. Originality/value – The paper makes explicit the underlying philosophical assumptions and how these ideas influence the way the authors conduct research; it highlights the significance of Cartesian dualism and indicates the significance of these assumptions for the development of information solutions. It supports the view that researchers and developers should be open to respondents leading the exploration of their needs.

scholarly journals On the construction of suitable weak solutions to the 3D Navier–Stokes equations in a bounded domain by an artificial compressibility method

2017 ◽  
Vol 20 (01) ◽  
pp. 1650064 ◽  
Author(s):  
Luigi C. Berselli ◽  
Stefano Spirito
Keyword(s):  
Bounded Domain ◽  
Weak Solutions ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Bounded Domains ◽  
Suitable Weak Solutions ◽  
Navier Stokes Equations ◽  
Artificial Compressibility ◽  
Artificial Compressibility Method

We prove that suitable weak solutions of 3D Navier–Stokes equations in bounded domains can be constructed by a particular type of artificial compressibility approximation.

Corporate governance, product market competition and firm performance: evidence from Iran

Humanomics ◽  
2017 ◽  
Vol 33 (1) ◽  
pp. 38-55 ◽  
Author(s):  
Mahdi Moradi ◽  
Mohammad Ali Bagherpour Velashani ◽  
Mahdi Omidfar
Keyword(s):  
Corporate Governance ◽  
Board Of Directors ◽  
Market Competition ◽  
Product Market ◽  
Research Literature ◽  
Product Market Competition ◽  
Governance Mechanisms ◽  
Management Performance ◽  
Content Type ◽  
The Board Of Directors

Purpose The purpose of this study is to investigate the effect of product market competition and corporate governance on firm’s management performance in the Tehran Stock Exchange market. According to the research literature, the governance mechanisms used in this study consist of ownership structure, structure of the board of directors and capital structure. In addition, Herfindahl–Hirschman Index and market size were used to measure the product market competition. Design/methodology/approach This study used one selected sample among the firms in the capital market of Iran from 2004 to 2012. Findings The results of this study indicated that there is a significant relation among the major governance mechanisms (including ownership concentration, independence of the board of directors and debt ratio) and product market competition and management performance. The findings of this study also showed that product market competition is effective on the relation between corporate governance and the performance, and this is what has been ignored in most of the conducted studies. Originality/value In general, the results of this study supported the idea that product market competition is effective on implementation and efficiency of governance mechanisms.

Qualitative generalising in accounting research: concepts and strategies

2016 ◽  
Vol 29 (6) ◽  
pp. 1100-1131 ◽  
Author(s):  
Lee D. Parker ◽  
Deryl Northcott
Keyword(s):  
Design Methodology ◽  
Research Literature ◽  
Key Factors ◽  
General Applicability ◽  
Information Systems Management ◽  
Content Type ◽  
Accounting Research ◽  
Research Findings ◽  
Quality Of Research

Purpose – The purpose of this paper is to identify and articulate concepts and approaches to qualitative generalisation that will offer qualitative accounting researchers avenues for enhancing and justifying the general applicability of their research findings and conclusions. Design/methodology/approach – The study and arguments draw from multidisciplinary approaches to this issue. The analysis and theorising is based on published qualitative research literatures from the fields of education, health sciences, sociology, information systems, management and marketing, as well as accounting. Findings – The paper develops two overarching generalisation concepts for application by qualitative accounting researchers. These are built upon a number of qualitative generalisation concepts that have emerged in the multidisciplinary literatures. It also articulates strategies for enhancing the generalisability of qualitative accounting research findings. Research limitations/implications – The paper provides qualitative accounting researchers with understandings, arguments and justifications for the generalisability of their research and the related potential for wider accounting and societal contributions. It also articulates the key factors that impact on the quality of research generalisation that qualitative researchers can offer. Originality/value – This paper presents the most comprehensively sourced and developed approach to the concepts, strategies and unique deliverables of qualitative generalising hitherto available in the accounting research literature.

Accessible tourism: a bibliometric review (2008–2020)

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Guanghui Qiao ◽  
Liu Ding ◽  
Linlin Zhang ◽  
Huili Yan
Keyword(s):  
English Language ◽  
Research Literature ◽  
Future Research ◽  
Sampling Frame ◽  
Multiple Sources ◽  
Knowledge Maps ◽  
Tourism Research ◽  
Content Type ◽  
The Usa ◽  
Bibliometric Review

Purpose The purpose of this paper is to reveal the knowledge evolution process, research hotspots and future trends in the accessible tourism research literature from 2008 to 2020. Design/methodology/approach A total of 213 articles on accessible tourism were selected from the core collection database of Web of Science (WoS) and analyzed using CiteSpace. Findings Over the 13-year period between 2008 and 2020, an increasing number of studies have been published concerning accessible tourism, but the overall base is still small. The research content mainly includes six modules. Among institutions, the University of Technology Sydney has published the largest number of papers. Cooperation among countries involves the USA, the United Kingdom, Australia, Portugal and China. Tourism Management is the leading journal for disseminating research on accessible tourism. Definition of “Accessible tourism” and the different scope of this phenomenon are re-discussed. In recent years, “experience” and “participation” have become the “new favorites” in accessible tourism research, which could reveal insights into future research directions. Research limitations/implications The sampling frame was defined in terms of the WoS database and even though this is an important database for global academic information, in the big data era, the authors may have to integrate information from multiple sources to comprehensively reveal and understand knowledge maps. Second, because of the operational constraints of the CiteSpace software, the authors only selected outputs published in peer-reviewed journals, excluding other published works, such as books and conference papers. Finally, because of the language restrictions of the authors, this research is limited to journals published in the English language. Practical implications Practically, the results of this study made a conclusion of accessible tourism research so that the researchers can easily know what has currently been done and what future research can do. Tourism managers can also understand the demands and the constraints of tourism for the people who have barriers to travel. They can supply more specific products for the accessible tourism and further promote the construction of barrier-free travel environments. Originality/value This paper unifies the literature on senior tourism and people with disabilities tourism, and uses CiteSpace to construct data and network visualizations, including a burst and dynamic analysis for the period covered by the sample. Furthermore, this paper proposed a more diversified accessible tourism.

Getting acquainted with social networks and apps: talking about TikTok

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Katie Elson Anderson
Keyword(s):  
Social Networks ◽  
Social Media ◽  
Literature Review ◽  
Design Methodology ◽  
Research Literature ◽  
Content Type ◽  
Social Media Platform ◽  
The Social ◽  
Media Platform ◽  
Information Professionals

Purpose This paper aims to provide information and promote discussion around the social media platform TikTok. Design/methodology/approach Research, literature review. Findings Libraries and library and information professionals should be aware of the potential of TikTok for engagement and information sharing. Originality/value Adds to the research on the social media platform TikTok.

Sign in / Sign up

Export Citation Format

Share Document