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This paper aims to analyze the propulsive performance of small-amplitude pitching foils at very high frequencies with double objectives: to find out scaling laws for the time-averaged thrust and propulsive efficiency at very high frequencies; and to characterize the Strouhal number above which the effect of turbulence on the mean values cannot be neglected.

The thrust force and propulsive efficiency of a pitching NACA0012 foil at high reduced frequencies (k) and a Reynolds number Re = 16 000 are analyzed using accurate numerical simulations, both assuming laminar flow and using a transition turbulence model. The time-averaged results are validated with available experimental data for k up to about 12 (Strouhal number, St, up to 0.6). This study also compares the present numerical results with the predictions of theoretical models and existing numerical results. For a foil pitching about its quarter chord with amplitude α₀ = 8^o, the reduced frequency is varied here up to k = 30 (St up to 2), much higher than in any previous numerical or experimental work.

For this pitch amplitude, turbulence effects are found negligible for St ≲ 0.8, and affecting less than 10% to the time-averaged thrust coefficient CT¯ for larger St Linear potential theory fails for very large k, even for the small pitch amplitude considered, particularly for the power coefficient, and therefore for the propulsive efficiency. It is found that CT¯∼St² for large St, in agreement with recent models, and the propulsive efficiency decays as 1/k, in disagreement with the linear potential theory.

Pitching foils are increasingly studied as efficient propellers and energy harvesting devices. Their performance at very high reduced frequencies has not been sufficiently analyzed before. The authors provide accurate numerical simulations to discern when turbulence is relevant for the computation of the time-averaged thrust and efficiency and how their scaling with the reduced frequency is affected in relation to the laminar-flow predictions. This is relevant because some small-amplitude theoretical models predict high propulsive efficiency of pitching foils at very high frequencies over certain ranges of the structural parameters, and only very accurate numerical simulations may decide on these predictions.

Despite estimates that chemical dependency in the workplace is a $100 billion per year problem, many managers are unable or unwilling to recognise it. There are, though, a number of specific job performance related signs that an employee is addicted to drugs or alcohol. Additionally, the informed manager can watch for certain personality and behavioural changes that indicate chemical dependency. Drug testing is sometimes effective, but it has many drawbacks.

Purpose: To examine the refugee women's empowerment and integration component of the pilot program of a Turkish social entrepreneurial organization (SEO) specialized in supporting disadvantaged women's empowerment. Methodology/Approach: The chapter utilizes a comparative qualitative case study approach to investigate the interplay between the dimensions of: business model, knowledge acquisition, and learning experiences, the achievement of goals, and scalability in determining social innovations. Findings: Despite the widespread belief that women's cooperative is an ideal business model for inclusivity, the chapter presents a variance in achieving this goal. The results propose that a strong business model, enhanced with knowledge acquisition and learning, and an inclusive approach to innovation, enable a women's cooperative to offer desirable solutions to community needs, improving its chances for higher impact. Research Limitations/Implications: The chapter adds to social entrepreneurship literature by offering multilevel analysis in examining social innovation, which has been often neglected as a research approach in the field. It asserts that an investigation into the community as a unit of analysis promises to be viable research in social innovation studies. Practical Implications: An inclusive approach that develops relations with the broader community and networking with other cooperatives and social actors is essential for women's cooperatives. Social Implications: The SEO's increasing local reach and impact have made it a strong actor in women's empowerment on the ground and force for institutional change. In the long term, SEOs' actions targeting multiple actors of influence will increase the chances of suggested framework changes accepted by policymakers.

As a result of the COVID-19 pandemic, teacher education in Qatar, similar to many countries around the world, witnessed a succession of disruptions to the way it operated. The disruption continued throughout much of 2020, and the need to adapt to arising changes and concerns permeated all aspects of teacher education, particularly the practicum experience. The chapter presents our attempt to investigate the influence of an adapted practicum experience which was based on the synthesis of qualitative evidence (SQD) model on the development of six student teachers’ technology knowledge and skills. Using a qualitative case study research design, we collected data from multiple data sources, including pre–post-interviews and weekly reflection logs. Quantitative data collected from a pre–post-administration of the SQD survey and TPACK (Technological Pedagogical and Content Knowledge)-practical survey were used to triangulate the qualitative data. Findings from the thematic analysis and descriptive statistical analysis revealed evidence for participants’ increased TPACK-practical knowledge and skills, specifically in the domains of practical teaching and curriculum design. However, an emerging theme revealed that participants considered technology before pedagogy during instructional design. Findings also revealed two challenges to participants’ further development, namely working within a restricted learning environment and experiencing limited mentoring opportunities. We illustrated several implications for the design of the practicum experience and the required institutional support within the context of continued disruption to education and thereafter.

The purpose of this paper is to investigate the development process of the fire whirl in the fixed-frame facility and focus on the impacts of the fire whirl’s vortex core on the formation and flame structure of the fire whirl.

The complex turbulent reacting flame surface is captured by the large eddy simulation turbulence closure coupled with two sub-grid scale (SGS) kinetic schemes (i.e. the chemistry equilibrium and steady diffusion flamelet). Numerical predictions are validated thoroughly against the measurements by Lei et al. (2015) with excellent agreements. A double maximum tangential velocity refinement approach is proposed to quantify the vortex cores’ instantaneous location and region, addressing the missing definition in other studies.

The numerical results show that the transition process of the fire whirl is dominated by the vortex core movement, which is related to the centripetal force. The unsteadiness of the fully developed fire whirl was found depending on the instantaneous fluctuation of heat release rate. The steady diffusion flamelet scheme is essential to capture the instantaneous fluctuation. Furthermore, the axial velocity inside the vortex core is the key to determining the state of fire whirl.

Due to intensive interactions between buoyant fires and ambient rotating flow, the on-set and formation of fire whirl still remain largely elusive. This paper focused on the transition process of fire whirl between different development stages. This paper provides insights into the transition process from the inclined flame to the fire whirls based on the centripetal force.

This paper presented and compared two SGS kinetic schemes to resolve the fire whirl development process and the unsteadiness of its vortical structures. The modelling framework addresses the shortcoming of previous numerical studies where RANS turbulence closure and simplified combustion kinetics was adopted. Numerical results also revealed the fire whirl transition process and its relationship to centripetal force.

This paper aims to present the development of a highly parallel finite-difference computational fluid dynamics code in generalized curvilinear coordinates system. The objectives are to handle internal and external flows in fairly complex geometries including shock waves, compressible turbulence and heat transfer.

The code is equipped with high-order discretization schemes to improve the computational accuracy of the solution algorithm. Besides, a new method to deal with the geometrical singularities, so-called domain decomposition method (DDM), is implemented. The DDM consists of using two different meshes communicating with each other, where the base mesh is Cartesian and the overlapped one a hollow cylinder.

The robustness of the present implemented code is appraised through several numerical test cases including a vortex advection, supersonic compressible flow over a cylinder, Poiseuille flow, turbulent channel and pipe flows. The results obtained here are in an excellent agreement when compared to the experimental data and the previous direct numerical simulation (DNS). As for the DDM strategy, it was successful as simulation time is clearly decreased and the connection between the two subdomains does not create spurious oscillations.

In sum, the developed solver was capable of solving, accurately and with high-precision, two- and three-dimensional compressible flows including fairly complex geometries. It is noted that the data provided by the DNS of supersonic pipe flows are not abundant in the literature and therefore will be available online for the community.

Cantilever plates subject to axial flow can lose stability by flutter and properties such as viscoelasticity and laminar friction affect dynamic stability. The purpose of the present study is to investigate the dynamic stability of viscoelastic cantilever plates subject to axial flow by using the differential quadrature method.

Equation of motion of the viscoelastic plate is derived by implementing Kelvin-Voigt model of viscoelasticity and applying inverse Laplace transformation. The differential quadrature method is employed to discretize the equation of motion and the boundary conditions leading to a generalized eigenvalue problem. The solution is verified using the existing results in the literature and numerical results are given for critical flow velocities

It is observed that higher aspect ratios lead to imaginary part of third frequency becoming negative and causing single-mode flutter instability. It was found that flutter instability does not occur at low aspect ratios. Moreover the friction coefficient is found to affect the magnitude of critical flow velocity, however, its effect on the stability behaviour is minor.

The effects of various problem parameters on the dynamic stability of a viscoelastic plate subject to axial flow were established. It was shown that laminar friction coefficient of the flowing fluid increases the critical fluid velocity and higher aspect ratios lead to single-mode flutter instability. The effect of increasing damping of viscoelastic material on the flutter instability was quantified and it was found that increasing viscoelasticity can lead to divergence instability.

The purpose of this paper is to examine the dimensions of supply management that may contribute to its ability to create value. Based on previous literature, this study proposes that key supplier management (KSM), the strategic level of supply management and supplier relationship management (SRM) capabilities can be supply management factors that significantly influence its ability to create value.

The issue is examined using survey data collected in Finland, and the concepts are tested using regression analysis.

The results show that KSM, the strategic level of supply management and SRM capabilities are significant dimensions of value creation in supply management. The findings support the contemporary understanding of value in which firms endeavour to create value for the company, its customers and its suppliers.

Previously, value creation has received minor attention in supply chain management research. Although previous research clearly shows that strategic supply management plays a significant role in firms’ competitiveness and performance, its role and potential in value creation have been less studied. Thus, this study contributes by empirically examining the factors affecting the ability of a firm’s supply management to create value.