Kannan B.T. and Panchapakesan N.R.
This study aims to investigate the effects of nozzle momentum flux distribution on the flow field characteristics.
Abstract
Purpose
This study aims to investigate the effects of nozzle momentum flux distribution on the flow field characteristics.
Design/methodology/approach
The nozzle configuration consists of a central nozzle surrounded by four nozzles. All nozzles have the same diameter and constant separation between nozzles. OpenFOAM® is used for simulating the jet flow. Reynolds-averaged Navier-Stokes (RANS) equations are solved iteratively with a first-order closure for turbulence. Pitot-static tube with differential pressure transducer is used for mean velocity measurements. The comparison of computed results with experimental data shows similar trend and acceptable validation.
Findings
According to the results, the momentum flux distribution significantly alters the near field of multiple turbulent round jets. Highly non-linear decay region in the near field is found for the cases having higher momentum in the outer jets. As a result of merging, increased positive pressure is found in the mixing region. Higher secondary flows and wider mixing region are reported as a result of momentum transfer from axial to lateral directions by Reynolds stresses.
Research limitations/implications
The present study is limited to isothermal flow of air jet in air medium.
Social implications
Optimum momentum flux distribution in multijet injector of a combustor can reap better mixing leading to better efficiency and lesser environmental pollution.
Originality/value
As summary, the contributions of this paper in the field of turbulent jets are following: simulations for various momentum distribution cases have been performed. In all the cases, the flow at the nozzle exit is subsonic along with constant velocity profile. To simulate proper flow field, a large cylinder-type domain with structured grid is used with refinements toward the nozzle exit and jet axis. The results show that the non-linearity increases with increase in momentum of outer jets. Longer merging zones are reported for cases with higher momentum in outer nozzles using area-averaged turbulent kinetic energy. Similarly, wider mixing regions are reported using secondary flow parameter and visualizations.
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A. Saario and A. Oksanen
The purpose of this paper is to study the effect of a computational grid in computational fluid dynamics‐based mathematical modeling, focusing on but not limiting the attention to…
Abstract
Purpose
The purpose of this paper is to study the effect of a computational grid in computational fluid dynamics‐based mathematical modeling, focusing on but not limiting the attention to industrial‐scale boilers.
Design/methodology/approach
A full boiler model is used to show the difficulties related to judging iteration and discretization errors in boiler modeling. Then, a single jet is studied in detail to determine the proper degree of local grid refinement required in the vicinity of jets in the full boiler model. Both a nonreactive axisymmetric jet exhausting into a quiescent atmosphere and a reactive jet exhausting into a crossfiow are studied.
Findings
Over two million computational cells are required for the grid‐independent solution for a single jet. Local grid refinement is shown to be a good option for improving the results consistently without an excessive increase in the number of computational cells. Using relatively coarse grids of tetrahedral cells with a finite‐volume‐based solver may cause serious errors in results, typically by overpredicting the jet spreading rate and underpredicting the mean axial centerline velocity. Relatively coarse grids of hexahedral cells are less prone to error in a case where a jet exhausts into a quiescent atmosphere. However, their performance deteriorates when a crossfiow is introduced. As assumed, the differences in the predicted reaction rate and species concentrations are significant in the reactive case. It is confirmed that the standard k‐ε model tends to overpredict the axisymmetric jet spreading rate. The estimated inlet turbulence intensity is not among the most critical factors in modeling. Estimations of the axisymmetric jet centerline velocity from the analytical correlation may not coincide with the modeling results.
Practical implications
The error caused by the computational grid may easily dominate the errors caused by simplifying models used in industrial‐scale boiler modeling (turbulence, combustion, radiative heat transfer, etc.).
Originality/value
The present study deals with grid independency issues in industrial‐scale boiler modeling in a systematic and profound manner.
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Rajesh Kumar S., Nishchay Sadrani and Kannan B.T.
The purpose of this study reports the effects of aspect ratio (AR) on mean flow characteristics of the cruciform orifice jet.
Abstract
Purpose
The purpose of this study reports the effects of aspect ratio (AR) on mean flow characteristics of the cruciform orifice jet.
Design/methodology/approach
The aspect ratio is the height-to-width ratio of the lobe of the cruciform shape. The aspect ratios considered are 0.25, 0.5, 0.75, 1, 2, 3 and 4. The turbulent jet flow is issued through an orifice being fitted to the jet tunnel facility. The velocity measurements are recorded with the help of pitot-static tube connected to a digital manometer setup. The Reynolds number calculated using the equivalent diameter 50.46 × 10–3 m and exit velocity 51.23 m/s was 1.75 × 105. Based on the experimental data, the streamline velocity decay plots, the potential core length (PCL), mean velocity profiles and velocity half widths were plotted, and discussions were made based on the measured data. A smoke-based flow visualization was carried out at moderate Reynolds number 5396.
Findings
The PCL remains almost constant for the aspect ratio 0.25:1 and then starts decreasing for the aspect ratio 1:4. The decrease in PCL indicates improved mixing. The off-center peaks are found along the major axis in mean velocity profiles for almost all cruciform jets. More than one axis switching occurs and can be identified by the crossover points. The location of the first crossover point shifts forward, and the second crossover point shows an oscillating trend. The flow visualization exhibits the jet evolution, and the distance up to which the jet maintains the cruciform shape is increased with the aspect ratio.
Research limitations/implications
The experiments are limited to air in air jet under isothermal conditions.
Social implications
The cruciform orifices can be used as fuel injectors and in air-conditioning systems, thereby improving efficiency and energy usage.
Originality/value
The aspect ratio effects on PCL and axis switching are used to explain the mixing characteristics. Flow visualization was also used to support the discussion.
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Dawn Pradeeb S.A., Subramanian Thanigaiarasu and Nagarajakrishnan Premanand
Control over large-scale coherent structures and stream-wise vortices lead to enhanced entrainment/conservation of the jet which is desirable for most free jet applications such…
Abstract
Purpose
Control over large-scale coherent structures and stream-wise vortices lead to enhanced entrainment/conservation of the jet which is desirable for most free jet applications such as design of combustion chamber in jet engines and flame length elongation of welding torch used for metal cutting.
Design/methodology/approach
A co-flow nozzle with lip thickness of 2 mm, between the primary (inner) and secondary (outer) flow, is selected. Three nozzle combinations are used, i.e. C–C (circle–circle), C–E (circle–ellipse) and C–S (circle–square) for acquiring comparative data. For these nozzle combinations, inner nozzle exit plane is kept as a circle, whereas the outer nozzle exit planes are varied to circle, ellipse and square. The exit plane area of outer nozzle for the nozzle combinations has equivalent diameter, De. The nozzles are fabricated in a way that the outer nozzle can be rotated along the longitudinal axis, keeping the inner nozzle intact.
Findings
The C–C nozzle combination is effective in low Mach number regime in decaying the jet, when the rotational component is introduced. Around 30% reduction in the jet core length is observed for the C–C nozzle combinations without any lip. The C–E nozzle shows sedative result in decaying or preserving the jet. The C–S nozzle combination shows interesting phenomenon, whereby the low subsonic case tends to conserve the jet by 15% and the higher subsonic case tends to decay the jet by 10%.
Originality/value
The developed nozzle systems show both conservative and destructive effect on the jet, which is desirable for the mentioned applications.
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Sandra Maria Correia Loureiro, Inês Costa and Padma Panchapakesan
The purpose of this paper is to explore the effect of social influence and individual vanity on passion for fashion of clothes and accessories and the mediating role of…
Abstract
Purpose
The purpose of this paper is to explore the effect of social influence and individual vanity on passion for fashion of clothes and accessories and the mediating role of exhibitionist tendency.
Design/methodology/approach
The study was conducted in two phases. The first was exploratory (n=109), using online panel interviews, carried out among a sample of fashion enthusiasts. The quantitative phase (n=425). Shopping mall intercept field survey methodology has been utilised to collect data. Consumers who just completed their shopping and were about to leave the shopping malls were approached by trained interviewers.
Findings
The content analysis of phase 1 yielded four major aspects and more two aspects less cited that participants seek in posts and online information that motivate them for shopping, such as inspirational outfits, products and brands posted, self-identification with the style, value for money, friends and fashion magazines and runway shows. The findings of phase 2 reveal that the social influence is more important than individual vanity in enhancing the desire to buy and use fashion clothes and accessories. Further, the exhibitionist tendency acts as a mediator between passionate desire for fashion and self-expression word-of-mouth.
Originality/value
As far as authors know, this is the first attempt to explore the effect of two components of narcissism in fashion context and to analyse the social and individual influence on passionate desire to use fashion.
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Panchapakesan Padma and Urs Wagenseil
The purpose of this paper is to develop a model of antecedents and consequences of service excellence (SE) in the retail industry.
Abstract
Purpose
The purpose of this paper is to develop a model of antecedents and consequences of service excellence (SE) in the retail industry.
Design/methodology/approach
Based on an extensive literature review, this paper has come up with the definition of potential antecedents and their consequences for SE in the retail service.
Findings
While the seven factors, service leadership, service culture, quality management and business excellence, service innovation, customer engagement, service brand image and service encounters have been proposed as antecedents of SE in retail service, employee loyalty, employee pride, customer delight, customer commitment and brand love, have been identified as consequences.
Research limitations/implications
A major limitation of the study is that the developed model is not empirically validated.
Practical implications
The current research asserts that leadership in service firms has to build a professional service culture system in order to achieve business/competition advantages of SE.
Social implications
This paper has emphasised that businesses cannot only act with the perspective of gaining short-term profit on every customer transaction. Customers have to be valued and firms have to focus on building long-term relationships with their customers.
Originality/value
This study has extended the research on SE by developing a new model with possible antecedents and outcomes in the retail context.
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Dung Le, Tuyet-Mai Nguyen, Sara Quach, Park Thaichon and Vanessa Ratten
New information and communication technologies have transformed the ways businesses communicate and maintain relationships with their customers. In this chapter, we review the…
Abstract
New information and communication technologies have transformed the ways businesses communicate and maintain relationships with their customers. In this chapter, we review the main topics in academic research pertaining to digital marketing and relationship perspectives. The discussion involves email and website marketing, search engine marketing, user-generated content, co-creation marketing, social media marketing, prosumption marketing in the sharing economy, immersive marketing and AI-based marketing. On this basis, the chapter proposes some future research directions including influencer marketing, live streaming, social service enhancement and the dark side of social media marketing, consumer-to-consumer interactions on two-sided platforms, psychological mechanisms related to the use of mixed realities, and the experience of AI-enabled service automation and relevant ethical issues. Furthermore, emerging technologies such as the Internet of things (IoT) and blockchain are expected to be the next breakthrough in marketing, which warrant further research to examine their impact on the customer-firm relationship. It is suggested the researchers could focus on the adoption and application of blockchain technology, participative marketing via IoT, as well as the privacy and data protection issues related to these technologies. This chapter provides a comprehensive picture of the connection between digital marketing and relationship marketing in academic research.
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Padma Panchapakesan, Muslim Amin and Halimin Herjanto
The objective of this study is to investigate the effect of service excellence and guest delight on guest affective commitment to luxury restaurants, more specifically, the…
Abstract
Purpose
The objective of this study is to investigate the effect of service excellence and guest delight on guest affective commitment to luxury restaurants, more specifically, the mediating effect of guest delight in the relationship between service excellence and guest affective commitment.
Design/methodology/approach
Data were collected from 270 guests with a response rate of 67.5%. SmartPLS software was used for data analysis.
Findings
The findings indicate that service excellence and guest delight had increased guest affective commitment to the luxury restaurant. It has been determined that guest delight acts as a mediator between service excellence and guest affective commitment.
Practical implications
Providing a high level of service excellence and delighting, thereby encouraging luxury guests to have a high level of commitment to the restaurant. Therefore, luxury guests' expectations must be exceeded to obtain their commitment to the restaurant.
Originality/value
This research study provides a substantial contribution to the hospitality literature by providing a significant concept of guest delight that can offer the opportunity to establish a new understanding of guest affective commitment in the luxury restaurant context.