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Article
Publication date: 19 June 2019

Jéromine Dumon, Yannick Bury, Nicolas Gourdain and Laurent Michel

The development of reusable space launchers requires a comprehensive knowledge of transonic flow effects on the launcher structure, such as buffet. Indeed, the mechanical…

Abstract

Purpose

The development of reusable space launchers requires a comprehensive knowledge of transonic flow effects on the launcher structure, such as buffet. Indeed, the mechanical integrity of the launcher can be compromised by shock wave/boundary layer interactions, that induce lateral forces responsible for plunging and pitching moments.

Design/methodology/approach

This paper aims to report numerical and experimental investigations on the aerodynamic and aeroelastic behavior of a diamond airfoil, designed for microsatellite-dedicated launchers, with a particular interest for the fluid/structure interaction during buffeting. Experimental investigations based on Schlieren visualizations are conducted in a transonic wind tunnel and are then compared with numerical predictions based on unsteady Reynolds averaged Navier–Stokes and large eddy simulation (LES) approaches. The effect of buffeting on the structure is finally studied by solving the equation of the dynamics.

Findings

Buffeting is both experimentally and numerically revealed. Experiments highlight 3D oscillations of the shock wave in the manner of a wind-flapping flag. LES computations identify a lambda-shaped shock wave foot width oscillations, which noticeably impact aerodynamic loads. At last, the experiments highlight the chaotic behavior of the shock wave as it shifts from an oscillatory periodic to an erratic 3D flapping state. Fluid structure computations show that the aerodynamic response of the airfoil tends to damp the structural vibrations and to mitigate the effect of buffeting.

Originality/value

While buffeting has been extensively studied for classical supercritical profiles, this study focuses on diamond airfoils. Moreover, a fluid structure computation has been conducted to point out the effect of buffeting.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 9
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 4 February 2019

Jernej Drofelnik, Andrea Da Ronch, Matteo Franciolini and Andrea Crivellini

This paper aims to present a numerical method based on computational fluid dynamics that allows investigating the buffet envelope of reference equivalent wings at the…

Abstract

Purpose

This paper aims to present a numerical method based on computational fluid dynamics that allows investigating the buffet envelope of reference equivalent wings at the equivalent cost of several two-dimensional, unsteady, turbulent flow analyses. The method bridges the gap between semi-empirical relations, generally dominant in the early phases of aircraft design, and three-dimensional turbulent flow analyses, characterised by high costs in analysis setups and prohibitive computing times.

Design/methodology/approach

Accuracy in the predictions and efficiency in the solution are two key aspects. Accuracy is maintained by solving a specialised form of the Reynolds-averaged Navier–Stokes equations valid for infinite-swept wing flows. Efficiency of the solution is reached by a novel implementation of the flow solver, as well as by combining solutions of different fidelity spatially.

Findings

Discovering the buffet envelope of a set of reference equivalent wings is accompanied with an estimate of the uncertainties in the numerical predictions. Just over 2,000 processor hours are needed if it is admissible to deal with an uncertainty of ±1.0° in the angle of attack at which buffet onset/offset occurs. Halving the uncertainty requires significantly more computing resources, close to a factor 200 compared with the larger uncertainty case.

Practical implications

To permit the use of the proposed method as a practical design tool in the conceptual/preliminary aircraft design phases, the method offers the designer with the ability to gauge the sensitivity of buffet on primary design variables, such as wing sweep angle and chord to thickness ratio.

Originality/value

The infinite-swept wing, unsteady Reynolds-averaged Navier–Stokes equations have been successfully applied, for the first time, to identify buffeting conditions. This demonstrates the adequateness of the proposed method in the conceptual/preliminary aircraft design phases.

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Article
Publication date: 8 May 2018

Antonio Memmolo, Matteo Bernardini and Sergio Pirozzoli

This paper aims to show results of numerical simulations of transonic flow around a supercritical airfoil at chord Reynolds number Rec = 3 × 106, with the aim of…

Abstract

Purpose

This paper aims to show results of numerical simulations of transonic flow around a supercritical airfoil at chord Reynolds number Rec = 3 × 106, with the aim of elucidating the mechanisms responsible for large-scale shock oscillations, namely, transonic buffet.

Design/methodology/approach

Unsteady Reynolds-averaged Navier–Stokes simulations and detached-eddy simulations provide a preliminary buffet map, while a high fidelity implicit large-eddy simulation with an upstream laminar boundary layer is used to ascertain the physical feasibility of the various buffet mechanisms. Numerical experiments with unsteady RANS highlight the role of waves travelling on pressure side in the buffet mechanism. Estimates of the propagation velocities of coherent disturbances and of acoustic waves are obtained, to check the validity of popular mechanisms based on acoustic feedback from the trailing edge.

Findings

Unsteady RANS numerical experiments demonstrate that the pressure side of the airfoil plays a marginal role in the buffet mechanism. Implicit LES data show that the only plausible self-sustaining mechanism involves waves scattered from the trailing edge and penetrating the sonic region from above the suction side shock. An interesting side result of this study is that buffet appears to be more intense in the case that the boundary layer state upstream of the shock is turbulent, rather than laminar.

Originality/value

The results of the study will be of interest to any researcher involved with transonic buffet.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 29 May 2009

Carola Raab, Karl Mayer, Stowe Shoemaker and Steve Ng

This paper aims to demonstrate how activity‐based pricing can be applied in a restaurant setting by combining the use of price sensitivity measurement with activity‐based costing.

Abstract

Purpose

This paper aims to demonstrate how activity‐based pricing can be applied in a restaurant setting by combining the use of price sensitivity measurement with activity‐based costing.

Design/methodology/approach

Data are collected at a Hong Kong buffet restaurant, based on guests' price perceptions and the establishment's detailed cost structure. These data are analyzed by using price sensitivity measurement techniques and activity‐based costing methods, separately, and then combined to create an activity‐based pricing analysis of the restaurant's menu.

Findings

The use of activity‐based pricing techniques reveals that, although the guests are relatively price‐insensitive, drastic measures were needed to reduce costs for the restaurant to become profitable. Without the benefit of this study, the restaurant's management would not have been able to see clearly the nature of the challenges that they faced, since a single pricing study, or cost study, would have missed the combined cost and pricing effects that were captured by activity‐based pricing.

Research limitations/implications

Activity‐based pricing is shown to be a powerful technique that can be applied effectively in a restaurant. Utilizing this method allows a restaurant truly to understand both its operating cost structure and the price perceptions of it guests. Since this study involved only a single buffet restaurant, further research should be conducted to confirm that activity‐based pricing can also be applied in other restaurant and hospitality industry settings.

Practical implications

The findings from this study suggest that activity‐based pricing may be a viable way for restaurant managers to gain a better understanding of both their guests' price perceptions and the true cost structure of their restaurants. Use of activity‐based pricing allows restaurant managers to set price levels that cover all operating costs and profits, while still meeting guests' expectations of value.

Originality/value

This study is the first of its kind in the hospitality literature, since no prior research has applied activity‐based pricing in a hospitality research setting. This study represents an important new addition to the existing body of hospitality cost and pricing literature.

Details

International Journal of Contemporary Hospitality Management, vol. 21 no. 4
Type: Research Article
ISSN: 0959-6119

Keywords

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Article
Publication date: 13 February 2007

Carola Raab and Karl Mayer

This research paper aims to examine whether using menu engineering (ME) together with activity‐based costing (ABC) for menu analysis gives new insights about true menu…

Abstract

Purpose

This research paper aims to examine whether using menu engineering (ME) together with activity‐based costing (ABC) for menu analysis gives new insights about true menu profitability. The traditional ME approach only uses food cost to determine the contribution margin of individual menu items. This combined approach uses both food and traceable operating costs to estimate contribution margins more accurately.

Design/methodology/approach

An improved menu engineering model was developed and tested in a buffet restaurant in Hong Kong. Direct observation of restaurant activities allowed most costs to be traced (not simply allocated) to individual menu items.

Findings

The results found that only three of 20 dinner menu entrées were profitable. This unique insight would not have been possible using traditional ME methods alone. The results also showed that ABC methods are applicable to a buffet‐style restaurant.

Research limitations/implications

Only a single restaurant and only the dinner menu were examined in this study. Future research should apply the model used herein to other restaurant types located in different geographical areas in an effort in order to validate the approach.

Practical implications

The paper suggests that ME can be improved upon by first assessing variable costs using ABC methods. Thus, the extra effort required to apply ABC in a restaurant appears to be worthwhile.

Originality/value

The paper combines two disparate analytic techniques (ME and ABC) in a new approach that reveals a menu's true profit and loss picture. The paper also makes several modifications to the traditional ME approach.

Details

International Journal of Contemporary Hospitality Management, vol. 19 no. 1
Type: Research Article
ISSN: 0959-6119

Keywords

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Article
Publication date: 5 September 2016

Fulvio Sartor and Sebastian Timme

The purpose of this paper is to discuss a numerical study of the flow over a wing representative of a large civil aircraft at cruise condition. For each Mach number…

Abstract

Purpose

The purpose of this paper is to discuss a numerical study of the flow over a wing representative of a large civil aircraft at cruise condition. For each Mach number considered, the numerical simulations indicate that critical angle of attack exists where the separated region increases in size and begins to oscillate. This phenomenon, known as transonic shock buffet, is reproduced by the unsteady simulation and much information can be extracted analysing location, amplitude and frequency content of the unsteadiness.

Design/methodology/approach

Reynolds-averaged Navier-Stokes simulations are conducted on a half wing-body configuration, at different Mach numbers and angles of attack. Different turbulence models are considered, and both steady-state results and time-accurate simulations are discussed.

Findings

The high number of cases presented in this study allows the creation of a database which, to the authors’ knowledge, has not been documented in literature before. The results indicate that, while high-fidelity approaches can improve the quality of the results, the URANS approach is capable of describing the main features of the buffet phenomenon.

Research limitations/implications

The presence of a turbulence model, despite allowing the description of the main unsteady phenomenon, might be insufficient to fully characterise the unsteadiness present in a transonic flow over a half wing-body configuration. Therefore, researchers are encouraged to verify by means of experimental investigation or high-fidelity approach the results issued from a Reynolds-averaged Navier-Stokes equations.

Practical implications

The results presented clearly indicate that, despite what proposed in recent research papers, transonic buffet can be described by means of time-accurate Reynolds-averaged Navier-Stokes equations. Such an approach is popular in the aeronautical industry because of its reduced costs, and could be used for wing design.

Originality/value

In this paper, the authors used a classical approach to tackle the known problem of transonic buffet in three-dimensional configurations. The large number of results presented can be used as a database for future numerical simulations and experiments, and allow to describe the flow-physics of the buffet unsteadiness on a half wing-body configuration.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 6 November 2017

Mojtaba Tahani, Mehran Masdari, Hamidreza Eivazi and Massoud Tatar

This paper aims to investigate numerical solution of transonic flow around NACA0012 airfoil under sinusoidal pitch oscillation. Accordingly, effects of the amplitude and…

Abstract

Purpose

This paper aims to investigate numerical solution of transonic flow around NACA0012 airfoil under sinusoidal pitch oscillation. Accordingly, effects of the amplitude and frequency of oscillations on aerodynamic coefficients are evaluated and the efficiency of the turbulent models, K-ω shear-stress transport (SST), scale adaptive simulation (SAS) and delayed detached eddy simulation (DDES), in simulation of the nonlinear phenomena – i.e. the interaction between shock and boundary layer and the shock oscillations – is studied.

Design/methodology/approach

K-ω SST, SAS and DDES models are used as turbulence approaches. The numerical results are compared with available experimental and numerical information.

Findings

According to the results inside the buffet boundaries, the DDES turbulent model expresses results that are more appropriate; however, SAS and SST models are not efficient enough in evaluating the characteristics of nonlinear flow.

Originality/value

In this research study, hybrid RANS-LES turbulence model is engaged to simulate transonic flow around pitching NACA0012 airfoil, and results are compared to the SAS and Reynolds Average Navier–Stocks simulations as well as available numerical and experimental data. In addition, effects of the amplitude and frequency of oscillations on aerodynamic coefficients are evaluated in buffet regions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 11
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 February 1931

THE Accidents Investigation Sub‐Committee of the Aeronautical Research Committee has issued a detailed technical report on the accident to the Junkers F.13‐type aeroplane…

Abstract

THE Accidents Investigation Sub‐Committee of the Aeronautical Research Committee has issued a detailed technical report on the accident to the Junkers F.13‐type aeroplane G‐AAZK which occurred at Meopham, Kent, on July 21, 1930. The report, which fills ninety‐two pages, gives a complete account of the researches and technical investigations that were made at the instigation of the Sub‐Committee, much of which is of great technical interest. It is impossible here to do more than give a brief summary of the circumstances of the accident and the inquiries which led to the rejection of a number of theories of the cause, leading to the final conclusion that it was due to a phenomenon called “Buffeting,” which is defined as “an irregular oscillation of the tail unit, in which the tail‐plane bends rapidly up and down and the elevators move in an erratic manner.” It is caused by the eddies given off by the wings at large angles of incidence and is, the Sub‐Committee state, quite distinct from flutter, which, in the case of machines of the Junkers F.13‐type would develop only at speeds above 250 m.p.h.

Details

Aircraft Engineering and Aerospace Technology, vol. 3 no. 2
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 10 October 2008

Jane Lu Hsu and Vikki Wei‐Ting Chiu

Complaint handling has the great influence on customer retention and provides a chance for businesses to improve service quality. This study intended to reveal the…

Abstract

Purpose

Complaint handling has the great influence on customer retention and provides a chance for businesses to improve service quality. This study intended to reveal the complaint actions of adolescent customers and perceptions of failure recovery in buffet restaurants with a linkage of family communication patterns.

Design/methodology/approach

A consumer survey was administered in the metropolitan area of Taipei. Quota sampling procedure was applied following the age and gender distribution of the population between the ages of 13 and 19. Consent from parents was obtained prior to the survey.

Findings

Based on the results of the study, adolescent customers with high concept‐ and high socio‐orientation were prone to complain for dissatisfaction. Private actions were preferred by adolescent customers to express dissatisfaction, followed by using the internet or through actions of parents. For service recovery, adolescents preferred to have discounts, followed by free desserts. The results indicated that adolescents were more straightforward and they wanted to have compensations immediately. Furthermore, service recovery satisfaction showed a positive relationship with repeat purchases. Adolescent customers who were satisfied with service or food compensations would be likely to have repeat purchases. Nevertheless, adolescents who were unsatisfied with the service or food recovery did not totally cease purchasing.

Practical implications

Buffet managers should give inducements to encourage adolescents to complain spontaneously. Buffet managers may offer discounts for the current consumption rather than coupons for next patronage. Adolescent customers with concept‐ and socio‐orientation will provide useful information for buffet managers to improve their service quality.

Originality/value

This study provides new insights into the area that has not been studied exclusively, complaint behavior of adolescent customers in buffet restaurants.

Details

Chinese Management Studies, vol. 2 no. 4
Type: Research Article
ISSN: 1750-614X

Keywords

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Article
Publication date: 3 May 2017

Knut Boge and Anjola Aliaj

Given the premise of de facto universal standards for FM, this paper aims to investigate development of facilities management (FM) at an Albanian and a Norwegian…

Abstract

Purpose

Given the premise of de facto universal standards for FM, this paper aims to investigate development of facilities management (FM) at an Albanian and a Norwegian university hospital through examination of two hypotheses: the university hospital has recognised FM and established a designated FM organisation (H1) and the university hospital provides adequate food and catering services at ward kitchens and buffets (H2).

Design/methodology/approach

This is an exploratory and descriptive comparative case study based on a diverse cases’ designs.

Findings

There is limited and strong support for H1 at the Albanian and Norwegian university hospitals, respectively. Both the Albanian and the Norwegian university hospitals rely on in-house production of facilities services, but the Albanian university hospital has outsourced food and catering services. FM and provision of facilities services are deeply integrated within the Norwegian university hospital’s core activities. There is also limited and strong support for H2 at the Albanian and Norwegian university hospitals, respectively. Hence, the Albanian Ministry of Health and the Albanian university hospital’s top management have a comprehensive, but not impossible, task, if the aim is to catch up with the Norwegian university hospital concerning FM.

Research limitations/implications

This is an exploratory and descriptive comparative case study. Large N studies should be carried out both in Albania and Norway and preferably also in other countries to corroborate and develop the findings.

Originality/value

This is the first comparative study of FM at an Albanian and a Norwegian university hospital.

Details

Facilities, vol. 35 no. 7/8
Type: Research Article
ISSN: 0263-2772

Keywords

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