William W. Liou, Yichuan Fang and Roy S. Baty
The frequencies of the bursting events associated with the streamwise coherent structures of spatially developing incompressible turbulent boundary layers were predicted. The…
Abstract
The frequencies of the bursting events associated with the streamwise coherent structures of spatially developing incompressible turbulent boundary layers were predicted. The structures were modeled as wavelike disturbances associated with the turbulent mean flow using a direct‐resonance theory. Global numerical solutions for the resonant eigenmodes of the Orr‐Sommerfeld and the vertical vorticity equations were developed. The global method involves the use of second and fourth order accurate finite difference formulae for the differential equations as well as the boundary conditions. The predicted resonance frequencies were found to agree very well with previous results using a local shooting technique and measured data.
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Oluyinka O. Bamiro and William W. Liou
The purpose of the current paper is to develop a numerical methodology, based on the immersed boundary-lattice Boltzmann computational framework, for the Neumann and Dirichlet…
Abstract
Purpose
The purpose of the current paper is to develop a numerical methodology, based on the immersed boundary-lattice Boltzmann computational framework, for the Neumann and Dirichlet boundary conditions in problems involving natural and forced convection heat transfer.
Design/methodology/approach
The direct forcing immersed boundary method is extended to study the heat transfer by incompressible flow within the thermal lattice Boltzmann method (LBM) computational framework. The direct forcing and heating immersed boundary-LBM introduces a heat source term to the thermal LBM to account for the heat transfer occurring at the immersed boundary. New numerical treatments for the Neumann type of boundary condition and for the calculation of the local Nusselt number are developed. The developed methodologies have been applied to flows around immersed bodies with natural and forced convection, including steady as well as unsteady flows.
Findings
Numerical experiments involving immersed bodies in natural and forced convection have been performed in order to assess the validity of the direct heating IB-LBM. The flow cases studied also include steady and transient flow phenomena. Flow velocity field and isotherms have been used for qualitative comparisons with existing, published results. The surface averaged Nusselt number, Strouhal number, and lift coefficient (for the unsteady flow cases) have been used for quantitative comparison with published results. The results show that there are satisfactory agreements, qualitatively and quantitatively, between the results obtained by using the present method and those previously published.
Originality/value
Limited application of immersed boundary to thermal flows within the LBM has been studied by researchers; the few past studies were limited to Dirichlet boundary conditions and/or using of feedback forcing and heating approaches. In the current paper, the direct forcing and heating approach was used which helps to eliminate the arbitrary constants used in the feedback approaches. The developed new numerical treatments for the Neumann type of boundary condition and for the calculation of the local Nusselt number eliminate the need to determine surface normal and temperature gradient in the normal direction for heat transfer calculation, which is particularly beneficial in cases with deforming or changing boundaries.
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Naren Shankar R. and Ganesan V.G.
The purpose of this study is to analyse numerically and experimentally the effects of lip thickness (LT) and bypass ratio on co-flowing nozzle under subsonic and correctly…
Abstract
Purpose
The purpose of this study is to analyse numerically and experimentally the effects of lip thickness (LT) and bypass ratio on co-flowing nozzle under subsonic and correctly expanded sonic jet decay at different Mach numbers.
Design/methodology/approach
Co-flowing jets from co-flowing nozzles of different LTs, 0.2, 1 and 1.5 Dp (where Dp is the primary nozzle exit diameter = 10 mm), with an annular gap of 10 mm at main jet exit Mach numbers 0.6 have been studied experimentally and the other cases have been performed numerically. The co-flowing jet with 2 mm LT was used for comparison.
Findings
Co-flowing jet axial pitot pressure decay, axial static pressure decay, axial velocity decay, radial velocity decay and streamline velocity contours were analyzed. The results illustrate that the mixing of the co-flowing jet with profound LT is prevalent to the co-flowing jet with 2 mm LT, at all Mach numbers of the current study. Also, the LT of the co-flowing jet has a strong impact on jet mixing. Co-flowing jets with 10 mm and 15 mm LT with a constant co-flow width of 10 mm experience a considerably advanced mixing than co-flowing jets with 2 mm LT and a co-flow width of 10 mm.
Practical implications
The application of bypassed co-flow jet is in turbofan engine operates efficiently in modern civil aircraft.
Originality/value
All subsonic jets are considered correctly expanded with negligible variation in axial static pressure. However, in the present study, static pressure along the centerline varies sinusoidally up to 9% and 12% above and below atmospheric pressure, respectively, for primary jet exit Mach number 1.0. The sinusoidal variation is less for primary jet exit Mach numbers 0.6 and 0.8 in static pressure decay.
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Jau Yang Liu, William Shiue, Fu Hsiang Chen and Ai Ting Huang
Corporate social responsibility has gradually become an essential enterprise responsibility under stakeholders’ expectations. Employee care strategies involve both qualitative and…
Abstract
Purpose
Corporate social responsibility has gradually become an essential enterprise responsibility under stakeholders’ expectations. Employee care strategies involve both qualitative and quantitative factors and are receiving special attention with the advent of the information age. In previous studies, a company’s policy of employee care may not fit with the needs of the employees. Consequently, the purpose of this paper is to investigate enterprises’ employee care from the employee’s perspective by adopting a hybrid multiple attribute decision making (MADM) model.
Design/methodology/approach
This study is based on 159 interviews with senior employees and/or department managers using a survey questionnaire. This study uses the MADM model to conduct the analysis. First, this research study used Decision-Making Trial and Evaluation Laboratory (DEMATEL) to construct an influential network relations map of the 4 dimensions and 13 criteria of employee care. Second, this study uses DEMATEL-based Analytic Network Process to conduct a weight analysis for each dimension and criterion. Third, this study uses VIKOR to calculate employees’ level of satisfaction as well as the gap from the “aspired level.”
Findings
The results of the study revealed the critical factors influencing employee care and proposed a systematic plan to be used as a reference for improvement. The improvement sequence revealed the following order: Equal employment opportunities→Good industrial relations and benefits→Responsibility to train and educate employees→Occupational health and safety. The empirical results showed there was still 35 percent room for improvement in the enterprises’ implementation policy of employee care.
Originality/value
The implementation of employee care has become an important issue for corporations since it helps to sustain and to increase an enterprise’s competitiveness in the business environment. However, the extant literature on employee care comes from enterprises’ perspectives instead of from employees’ perspectives. This research investigates the key factors of employee care and successfully shows MADM to be an effective model for the planning and implementation of corporate social responsibilities’ employee care from the perspective of employees.
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Ziqiang Han and William L. Waugh
This chapter provides the foundation for the book. The objective of this chapter is to outline the theme of the book and to provide the context for the chapters that follow…
Abstract
This chapter provides the foundation for the book. The objective of this chapter is to outline the theme of the book and to provide the context for the chapters that follow. Disaster recovery is a challenge for governments and for affected communities, families, and individuals. It is a challenge, because recovery from catastrophic disasters can be much more complicated and elusive than what can be addressed by national and international aid organizations given the time and other resources. The short literature review provides the research context, and the overview of the book describes each of the chapters briefly.
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Ling Wang, Fujun Wang, Bryan William Karney, Ahmad Malekpour and Zhengwei Wang
The velocity head is usually neglected in the energy equation for a pipeline junction when one-dimensional (1D) hydraulic transient flow is solved by method of characteristics…
Abstract
Purpose
The velocity head is usually neglected in the energy equation for a pipeline junction when one-dimensional (1D) hydraulic transient flow is solved by method of characteristics. The purpose of this paper is to investigate the effect of velocity head on filling transients in a branched pipeline by an energy equation considering velocity head.
Design/methodology/approach
An interface tracking method is used to locate the air–water interface during pipeline filling. The pressured pipe flow is solved by a method of characteristics. A discrete gas cavity model is included to permit the occurrence of column separation. A universal energy equation is built by considering the velocity head. The numerical method is provisionally verified in a series pipeline and the numerical results and experimental data accord well with each other.
Findings
The numerical results show that some differences in filling velocity and piezometric head occur in the branched pipeline. These differences arise because the velocity head in the energy equation can become an important contributor to the hydraulic response of the system. It is also confirmed that a local high point in the profile is apt to experience column separation during rapid filling. Significantly, the magnitude of overpressure and cavity volume induced by filling transients at the local high point is predicted to increase with the velocity in the pipes.
Originality/value
The velocity head in the energy equation for a pipeline junction could play an important role in the prediction of filling velocity, piezometric head and column separation phenomenon, which should be given more attention in 1D hydraulic transient analysis.
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Dedy Wiredja, Vesna Popovic and Alethea Blackler
Assessing airport service performance requires understanding of all passenger processing and discretionary activities at airport passenger terminals – a need that has not yet been…
Abstract
Purpose
Assessing airport service performance requires understanding of all passenger processing and discretionary activities at airport passenger terminals – a need that has not yet been addressed in the research to date. This paper aims to address this shortcoming in evaluating overall airport service based on passenger experience from departure to arrival.
Design/methodology/approach
Comparative analysis over 40 airport models, including their indicators and configuration of service measures, was undertaken in a previous work to identify key-design requirements in assessing airport service performance based on passenger experience (Wiredja et al., 2015). Based on these requirements, this paper constitutes the development of a passenger-centred model covering all service areas from departure to arrival terminals. The newly developed model is then examined using factor and regression analyses by involving 215 airline passengers from 22 world’s international airports.
Findings
Overall service performance is understood as a function of combined sub-performances of two groups of airport domains: processing domains and non-processing domains. The overall result demonstrated that the two sets of service factors and their relevant attributes had significant impact on overall service performance at processing and non-processing domains.
Research limitations/implications
The proposed model applies a set of dynamic performance measures that provide flexibility. These measures are adjustable depending on the needs. Adding or replacing measures defines the specificity of the domains and performances assessed. The model components can be modified in respective service attributes when passenger needs or priorities change. The only constant component is user-centred indicators (in this research, Passenger-centred indicators).
Originality/value
This research has generated new insights and knowledge that directly contribute to the assessment of airport service performance. The novelty of this research is the development of a passenger-centred approach in evaluating overall airport service based on passenger experience. This passenger-driven model provides a more integrated and robust approach in this field than previously available.
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Ngoc Dung Tran, Phuong Hoa Dinh, Dinh Hoang Uyen Nguyen and Van Vinh Nguyen
This paper aims to investigate “corporate governance” of the English East India Company (EIC) in the late 17th century through a case study of the Tonkin factory (1672–1697).
Abstract
Purpose
This paper aims to investigate “corporate governance” of the English East India Company (EIC) in the late 17th century through a case study of the Tonkin factory (1672–1697).
Design/methodology/approach
The paper draws upon British primary materials relating to the Tonkin factory to examine and analyze the EIC’s style of management in Tonkin (Vietnam) and Bantam (Java). Qualitative and comparative methods are applied to the analysis of reports, records and letters written by EIC staff.
Findings
The paper finds that the EIC faced principal-agent problems as it had difficulties administering its distant agents and subsidiaries in the 17th century. London was strategically weakened, both by the limiting power of regional headquarters and by its use of experienced factors. Before 1682, London failed to temper the Bantam Council’s influence, and there were serious internal conflicts and power struggles between English Tonkin employees seeking to improve their positions. After 1686, London successfully forced Madras to adopt a noninterventionist stance in Tonkin’s business, but it faced the problem of “adverse selection.”
Originality/value
This paper provides evidence from the Tonkin factory (1672–1697) to show the EIC’s governance in the perspective of the agency theory.