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This paper aims to conduct, a detailed investigation of various Reynolds averaged Navier–Stokes (RANS) models to study their performance in attached and separated flows. The turbulent flow over two airfoils, namely, National Advisory Committee for Aeronautics (NACA)-0012 and National Aeronautics and Space Administration (NASA) MS(1)-0317 with a static stall setup at a Reynolds number of 6 million, is chosen to investigate these models. The pre-stall and post-stall regions, which are in the range of angles of attack 0°–20°, are simulated.

RANS turbulence models with the Boussinesq approximation are the most commonly used cost-effective models for engineering flows. Four RANS models are considered to predict the static stall of two airfoils: Spalart–Allmaras (SA), Menter’s k – ω shear stress transport (SST), k – kL and SA-Bas Cakmakcioglu modified (BCM) transition model. All the simulations are performed on an in-house unstructured-grid compressible flow solver.

All the turbulence models considered predicted the lift and drag coefficients in good agreement with experimental data for both airfoils in the attached pre-stall region. For the NACA-0012 airfoil, all models except the SA-BCM over-predicted the stall angle by 2°, whereas SA-BCM failed to predict stall. For the NASA MS(1)-0317 airfoil, all models predicted the lift and drag coefficients accurately for attached flow. But the first three models showed even further delayed stall, whereas SA-BCM again did not predict stall.

The numerical results at high Re obtained from this work, especially that of the NASA MS(1)-0317, are new to the literature in the knowledge of the authors. This paper highlights the inability of RANS models to predict the stall phenomenon and suggests a need for improvement in modeling flow physics in near- and post-stall flows.

This study aims to validate the linear flow theory with computational fluid dynamics (CFD) simulations and to propose a novel shape for the airfoil that will improve supersonic aerodynamic performance compared to the National Advisory Committee for Aeronautics (NACA) 64a210 airfoil.

To design the new airfoil shape, this study uses a convex optimization approach to obtain a global optimal shape for an airfoil. First, modeling is conducted using linear flow theory, and then numerical verification is done by CFD simulations using ANSYS Fluent. The optimization process ensures that the new airfoil maintains the same cross-sectional area and thickness as the NACA 64a210 airfoil. This study found that an efficient way to obtain the ideal airfoil shape is by using linear flow theory, and the numerical simulations supported the assumptions inherent in the linear flow theory.

This study’s findings show notable improvements (from 4% to 200%) in the aerodynamic performance of the airfoil, especially in the supersonic range, which points to the suggested airfoil as a potential option for several fighter aircraft. Under various supersonic conditions, the optimized airfoil exhibits improved lift-over-drag ratios, leading to improved flight performance and lower fuel consumption.

This study was conducted mainly for supersonic flow, whereas the subsonic flow is tested for a Mach number of 0.7. This study would be extended for both subsonic and supersonic flights.

Convex optimization and linear flow theory are combined in this work to create an airfoil that performs better in supersonic conditions than the NACA 64a210. By closely matching the CFD results, the linear flow theory's robustness is confirmed. This means that the initial design phase no longer requires extensive CFD simulations, and the linear flow theory can be used quickly and efficiently to obtain optimal airfoil shapes.

The proposed airfoil can be used in different fighter aircraft to enhance performance and reduce fuel consumption. Thus, lower carbon emission is expected.

The unique aspect of this work is how convex optimization and linear flow theory were combined to create an airfoil that performs better in supersonic conditions than the NACA 64a210. Comprehensive CFD simulations were used for validation, highlighting the optimization approach's strength and usefulness in aerospace engineering.

Active flow control on the NACA 0024 airfoil defined as suction-injection jet at the chord-based Reynolds number of 1.5 × 1e + 5 is studied.

The three-dimensional incompressible unsteady Reynolds-averaged Navier–Stokes equations with the SST k-ω turbulence model are used to study the effects of coflow-jet (CFJ) on the dynamic and static stall phenomena. CFJ implementation is conducted with several momentum coefficients to investigate their turnover. Furthermore, the current work intends to analyze the CFJ performance by varying the Reynolds number and jet momentum coefficient and comparing all states to the baseline airfoil, which has not been studied in prior research investigations.

It is observed that at the momentum coefficient (Cµ) of 0.06, the lift coefficients at low attack angles (up to a = 15) dramatically increase. Furthermore, the dynamic stall at the given Reynolds number and with the lowered frequency of 0.15 is explored. In the instance of Cµ = 0.07, the lift coefficient curve does not show a noticeable stall feature compared to Cµ = 0.05, suggesting that a more powerful stronger jet can entirely control the dynamic stall.

Furthermore, the current work intends to analyze the CFJ performance by varying the jet momentum coefficient and comparing all states to the baseline airfoil, which has not been studied in prior research investigations.

The purpose of this paper is the examination of fluid flow around NACA0012 airfoil, with the aim of the numerical validation between the experimental results in the wind tunnel and the Lattice Boltzmann method (LBM) analysis, for the medium Reynolds number (Re = 191,000). The LBM–large Eddy simulation (LES) method described in this paper opens up opportunities for faster computational fluid dynamics (CFD) analysis, because of the LBM scalability on high performance computing architectures, more specifically general purpose graphics processing units (GPGPUs), pertaining at the same time the high resolution LES approach.

Process starts with data collection in open-circuit wind tunnel experiment. Furthermore, the pressure coefficient, as a comparative variable, has been used with varying angle of attack (2°, 4°, 6° and 8°) for both experiment and LBM analysis. To numerically reproduce the experimental results, the LBM coupled with the LES turbulence model, the generalized wall function (GWF) and the cumulant collision operator with D3Q27 velocity set has been used. Also, a mesh independence study has been provided to ensure result congruence.

The proposed LBM methodology is capable of highly accurate predictions when compared with experimental data. Besides, the special significance of this work is the possibility of experimental and CFD comparison for the same domain dimensions.

Considering the quality of results, root-mean-square error (RMSE) shows good correlations both for airfoil’s upper and lower surface. More precisely, maximal RMSE for the upper surface is 0.105, whereas 0.089 for the lower surface, regarding all angles of attack.

This paper presents the results of a survey of perceptions on sustainable procurement (SP) in the United Nations (UN). It is the first of its kind to systematically analyse the issue of SP in the UN system. While the UN has a tremendous opportunity to support their objective of sustainable development through SP practices, significant obstacles still block the full implementation of this goal. The purpose of this study is to investigate the barriers to implementing SP practices in the UN system. Based on an online survey that yielded 282 responses, we identified a framework of SP measures and barriers, and conducted a regression analysis to identify underlying correlations. We find significant correlation between good SP practices and low demand, performance measurement and tool barriers.

This study theoretically investigates the extant literature published about circular economy and sustainable development to identify significant research themes, the most relevant authors, countries and journals.

Bibliometric analysis is used, followed by cluster formation using co-citation analysis. The clusters are discussed in-depth to identify emerging themes and future research areas.

By systematically reviewing 596 research articles, significant themes of research in this field were found. These include frameworks and indicators to define and assess the circular economy, circular business models and use cases, global and industrial contexts of application of circular economy and different dimensions of the circular economy.

Publications from only one database have been used. Only articles published in relevant academic journals have been used for the bibliometric analysis. For co-citation analysis and cluster formation, only articles with a high number of citations were selected.

The analysis of the various clusters revealed research areas that can be explored in future research to understand the circular economy better and implement its practices to attain sustainability.

This article presents an exploratory analysis of perceived information needs for managing fixed public sector assets in South-Eastern Europe (SEE).

The analysis was carried out from a user needs perspective. A questionnaire was administered to government officials in SEE. Respondents were queried about what categories of information they need to make or to recommend five typical decisions concerning fixed public sector assets. Respondents also provided assessments on current availability and quality of information on fixed public sector assets, cost-benefit considerations regarding data collection and suitability of information for routine collection and updating.

The findings of this study indicate that the information collected for financial reporting purposes is recognized as insufficient to support decision-making on fixed public sector assets. However, perceived information needs by respondents are still rather basic. The need for more “sophisticated” and “strategic” information is found to be rather low, more so when the cost of collecting and processing such information is considered.

The findings of this study raise concerns about the persistently insufficient attention paid to the potential benefits that well-compiled and appropriately used asset registries could produce. The findings of this study might be useful to governments initiating the identification and measurement of their fixed assets, establishing fixed asset registries and instituting relevant regulation.

This study adds to the scant literature on the management of fixed public sector assets. It provides evidence on the perceived information needs of public sector officials, and it contributes to the ongoing debate on what good public sector asset management is and how it should be pursued.

The purpose of this paper is to investigate the financial determinants of local government debt in New Zealand.

To investigate the financial determinants of local government debt in New Zealand, the authors analyse the relationship between key financial variables with local government debt in New Zealand based on the theories of fiscal accountability and moral hazard using a panel data methodology, specifically the pooled ordinary least squares regression model.

The findings suggest that council income is the major financial determinant of local government borrowing in New Zealand rather than infrastructural spending and that during the global financial crises (GFC) borrowing levels of New Zealand local councils was not significantly impacted. However, the findings indicate that post the GFC, low interest rates have stimulated increased borrowing activity by New Zealand local governments to fund infrastructure.

This paper is the first to examine the determinants of local government debt in New Zealand. The findings of this study contribute to better understanding of local government/municipality debt in New Zealand and internationally by providing evidence on the financial determinants of debt of local governments and the indirect use of government policy to control local government borrowing. The findings of this study are anticipated to affect local government practices and national government policies in relation to local government finances.

New Zealand (NZ) has no reporting standard or guidance for management commentary (MC) that accompanies financial reports. This is unusual, considering MC is provided by many entities and valued by users. Further, the guidance on MC provided by the International Accounting Standards Board (IASB) in their Management Commentary Practice Statement 1 (MCPS1), which was issued in 2010, is currently under review. Thus, the purpose of this paper is to examine the views of NZ’s financial reporting stakeholders, particularly users, preparers and auditors of financial reports for insights regarding the usefulness of MC.

To gain insights into the views of NZ’s financial reporting stakeholders on MC, this paper surveyed users, preparers and auditors of financial statements. This paper includes an analysis of their views on the objectives, content and principles that should underlie MC in financial reporting, based on the IASB’s MCPS1 with consideration of recent work by the IASB on the revision of MCPS1. In addition, the analysis provides insights as to whether the reporting of MC should be made mandatory, and whether assuring MC would increase its usefulness.

This study found that auditors generally view MC as less useful and more in need of assurance than do preparers and users. Respondents’ ratings indicate that the most important objective for MC is “to enable the assessment of the quality of management’s stewardship”. “Assessing the entity’s future prospects”, and “assessing future cash flows” are also highly rated objectives. The most important principle in preparing MC is identified as “focus on the most important and relevant information”, while the most important content element identified is “the entity's financial performance and position, and cash flows”.

This paper highlights the views of various stakeholders regarding MC reporting, particularly preparers and auditors whose views have not been noted previously in the literature. Also, this study should be of interest to both international and national financial reporting standard setters and regulators. It is particularly timely in view of the current IASB work towards revision and updating of MCPS1, as it provides current insights into what users, preparers and auditors perceive as the most important considerations for MC. This study also has implications for the XRB in NZ, where there is no prior research on stakeholders’ views on MC.