The lift aerodynamic admittances of an airfoil at different angles of attack (AoAs) in turbulent flow are investigated using a combination of theoretical and experimental approaches. Two theoretical one-wavenumber aerodynamic admittances, namely the Sears and Atassi functions, are reviewed and uniformly normalized for comparison with experimental results. In theory, generalized aerodynamic admittances are generated by introducing the spanwise influence into one-wavenumber aerodynamic admittances. The influence of AoA on generalized aerodynamic admittance includes its effect on both the spanwise influence term and one-wavenumber aerodynamic admittances. The experiment indicates that prior to the prestall region, the increase in the spanwise influence factor correlates with the increase in AoA, with the growth rate of the spanwise influence factor likewise accelerating. The Atassi functions demonstrate that the influence of AoA on one-wavenumber aerodynamic admittances is based on the assumption of full correlation in the spanwise direction. Experimental results suggest that one-wavenumber aerodynamic admittances are inapplicable to actual turbulence; however, the Atassi function accurately represents experimental values at the corresponding AoA when taking into account the spanwise effects.

This study obtains expressions for the force and moment coefficients for a finite-span circular cylinder rolling on a plane wall. It is assumed that a small, but finite, gap exists between the cylinder and the wall, as a result of, for example, surface roughness. Using the method of matched asymptotic expansions, the flow is decomposed into an inner solution, valid in the narrow interstice between the cylinder and the wall, and an outer solution, valid far from the interstice. Then, the force and moment coefficients are expressed as the sum of a gap-dependent term, which is computed from the inner solution, and a gap-independent term, which is computed from the outer solution. Solutions to the inner flow are obtained by solving numerically the two-dimensional Reynolds equation for the lubrication flow in the interstice. The inner solution depends only on a single parameter, the cylinder aspect ratio divided by the gap-diameter ratio, and the effects of this parameter on the gap-dependent force and moment coefficients are deduced. Solutions to the outer flow are obtained using thee-dimensional numerical simulations for a range of Reynolds numbers, cylinder aspect ratios and cylinder rotation rates. Then, the variation of the force and moment coefficients against each of these terms is obtained.

Planar entropy waves are commonly assumed for predicting indirect combustion noise. However, the non-planar and turbulent nature of flows found in most practical combustors challenges this assumption. In the present paper, we examine the indirect noise generated by non-planar and turbulent entropy fields through subsonic nozzles. Firstly, we introduce a new transfer function framework that accounts for the contribution of non-planar Fourier modes of the entropy field to the indirect noise spectra. When applied to a turbulent flow field, this method demonstrates a significant improvement in spectral predictions compared with a conventional approach that only considers the planar mode. Secondly, simulations show that non-planar Fourier modes become significant above a threshold frequency $f_{thresh}$, found in the mid- to high-frequency range. This contribution of non-planar modes is explained by two-dimensional shear effects that distort the entropy waves. A scaling relation that uses residence times along streamlines is developed for $f_{thresh}$, showing good agreement with simulation results. Finally, we show that the indirect noise from non-planar entropy modes found in aviation combustors can be significant at frequencies below 1 kHz, which might be relevant in situations of thermo-acoustic instabilities coupled to indirect noise.

In aerodynamic and hydrodynamic devices and locomotive organisms, passive appendages have practical purposes such as drag reduction and flow control. Although these appendages also affect the dynamics of freely falling bodies, underlying principles of their functions remain elusive. We investigate experimentally the dynamics of a falling sphere with a filament appended on its rear side by varying the ratio of filament length to sphere diameter ($l/D=0{-}3.0$) and sphere-to-fluid density ratio ($\rho _s/\rho _f= 1.06{-}1.36$), and maintaining a similar dimensionless moment of inertia ($I^* \approx 0.96$). At the Reynolds number of $O(10^3)$, a sphere without any filament exhibits vertical descent. However, the falling of the sphere with a filament is accompanied by periodic horizontal displacements, and the degree of zigzag motion is maximised under specific filament length. The filament induces periodic rotation of the sphere by shifting the centre of mass of the entire model and through the hydrodynamic interaction of the filament with the surrounding fluid. The rotation of the sphere increases the drag force acting on the model, reducing tangential velocity along the trajectory by 14 % compared to a plain sphere. Furthermore, the sphere rotation enhances the lift force normal to the trajectory, extending trajectory length by 5 %. These combined effects improve falling time over a certain vertical distance by 20 % compared to the plain sphere. With increasing sphere density, the effects of the filament on the falling dynamics weaken, because the offset distance between the centre of mass of the model and the geometric centre of the sphere becomes smaller.

Mining companies are rhetorically committed to corporate social responsibility standards such as human rights, but what really affects their behaviour in the developing world? Communities impacted by mines have become increasingly resistant to them, bolstered and supported by international actors and norms as well as stronger domestic environmental and justice institutions. In this paper, I examine the behaviour of multinational mining companies (primarily Canadian) in two Latin American countries in the face of social resistance, finding that domestic institutional capacity and legal mobilization have an important effect on company decisions and actions. Both are necessary—the legal opportunity structure creates an institutional context in which legal mobilization is encouraged or discouraged. Litigators interacting with competent institutions have a far greater ability to hold firms to account. Thus, company practices adjust to the country’s institutional and legal context, and behaviour varies according to host country conditions.

This article explores the responsibility of wind energy developers for the rights of Indigenous Peoples whose lands are affected by wind energy projects. Applying a rights-based approach and drawing on three landmark court rulings involving the struggle of Indigenous communities against the development of wind energy projects, the analysis explores the insights provided by the cases for clarifying the responsibility of business actors involved in developing such projects. It examines how Indigenous Peoples’ rights are frequently marginalized or overlooked in the planning and siting of wind energy projects and the need to respect the rights of Indigenous Peoples throughout a project in order to attain a transition that is just. Based on the analysis, we argue for a rights-based approach as the theoretical framework and analytical tool to advance justice in the green transition and a means to articulate the responsibilities of corporate actors within that context.

The traditional narrative of Europe’s first wave of democratization is that elites extended the franchise in response to revolutionary threats and reformed majoritarian electoral systems to limit rising working-class parties. This stylized account does not fit early twentieth-century South America, where democratization was driven by internal competition within incumbent parties, without strong working-class parties to contain. I study Argentina’s 1912 electoral reform that introduced elements of democracy (secret and compulsory voting) and simultaneously changed the electoral system from multi-member plurality to the limited vote. To study the motivations behind the electoral system change component of the reform package, I analyze expert surveys, legislative debates, and a 1911 public opinion poll. Granting representation to political minorities was regarded not as an electoral containment strategy to benefit incumbents, but a progressive measure to make opposition parties more competitive. An analysis of roll-call votes shows that legislators who supported the reform were those expecting to not be adversely affected.

This article examines the intersection between forced labour, supply chain risks and environmental, social and governance concerns that pose a threat to the ‘Just Transition’. It addresses how states, businesses and other stakeholders drive or fail Just Transitions and why. Through an application of a ‘policy currents framework’ to the case study of solar panel supply chains originating in China, we analyse states, international organisations and civil society organisations’ framing of modern slavery issues in the context of the ‘Just Transition’. We focus on the framing of challenges and solutions to the nexus of forced labour and climate change. We draw attention to the fact decarbonisation risks are being achieved at the cost of labour rights abuses within supply chains, question whether the concept of renewable sources is ‘Just’ and provide a series of recommendations for stakeholders.

Spanwise wall forcing in the form of streamwise-travelling waves is applied to the suction side of a transonic airfoil with a shock wave to reduce aerodynamic drag. The study, conducted using direct numerical simulations, extends earlier findings by Quadrio et al. (J. Fluid Mech. vol. 942(R2), 2022, pp. 1–10) and confirms that the wall manipulation shifts the shock wave on the suction side towards the trailing edge of the profile, thereby enhancing its aerodynamic efficiency. A parametric study over the parameters of wall forcing is carried out for the Mach number set at 0.7 and the Reynolds number at 300 000. Similarities and differences with the incompressible plane case are discussed; for the first time, we describe how the interaction between the shock wave and the boundary layer is influenced by flow control via spanwise forcing. With suitable combinations of control parameters, the shock is delayed, which results in a separated region whose length correlates well with friction reduction. The analysis of the transient process following the sudden application of control is used to link flow separation with the intensification of the shock wave.

Opposition control (OC) is a reactive flow-control approach that mitigates the near-wall fluctuations by imposing blowing and suction at the wall, being opposite to the off-wall observations. We carried out high-resolution large-eddy simulations to investigate the effects of OC on turbulent boundary layers (TBLs) over a wing at a chord-based Reynolds number (${Re}_c$) of $200 \ 000$. Two cases were considered: flow over the suction sides of the NACA0012 wing section at an angle of attack of $0^{\circ }$, and the NACA4412 wing section at an angle of attack of $5^{\circ }$. These cases represent TBLs subjected to mild and strong non-uniform adverse pressure gradients (APGs), respectively. First, we assessed the control effects on the streamwise development of TBLs and the achieved drag reduction. Our findings indicate that the performance of OC in terms of friction-drag reduction significantly diminishes as the APG intensifies. Analysis of turbulence statistics subsequently reveals that this is directly linked to the intensified wall-normal convection caused by the strong APG: it energizes the control intensity to overload the limitation that guarantees drag reduction. The formation of the so-called virtual wall that reflects the mitigation of wall-normal momentum transport is also implicitly affected by the pressure gradient. Control and pressure-gradient effects are clearly apparent in the anisotropy invariant maps, which also highlight the relevance of the virtual wall. Finally, spectral analyses indicate that the wall-normal transport of small-scale structures to the outer region due to the APG has a detrimental impact on the performance of OC. Uniform blowing and body-force damping were also examined to understand the differences between the various control schemes. Despite the distinct performance of friction-drag reduction, the effects of uniform blowing are akin to those induced by a stronger APG, while the effects of body-force damping exhibit similarities to those of OC in terms of the streamwise development of the TBL although there are differences in the turbulent statistics. To authors’ best knowledge, the present study stands as the first in-depth analysis of the effects of OC applied to TBL subjected to non-uniform APGs with complex geometries.

The transition to renewable energy models to tackle environmental degradation and climate change is one of the most important topics on the international agenda. The energy transition requires a system that is decentralised and democratic, depending more on local energy ownership and the genuine participation of the affected stakeholders. Although different states face various economic and cultural challenges, a common challenge is making the transition as inclusive and equitable as possible so that everyone can benefit equally. The article focuses on South Africa, acknowledging its special place among the Global South countries due to its history and the dependency of its economy on coal. Taking the South African experiences as an example, this article aims to show how the energy transition processes can be more inclusive and just, allowing the affected parties to participate at all levels of the just transition processes and making their voices heard.

The ketogenic diet, initially developed for epilepsy treatment, has gained attention as a potential intervention for neuropsychiatric disorders. A groundbreaking study by Campbell et al highlights its feasibility and potential efficacy in bipolar disorder, shedding light on shared mechanisms across neuropsychiatric disorders and the promise of metabolic treatment approaches.

This paper utilizes neural networks (NNs) for cycle detection in the insurance industry. The efficacy of NNs is compared on simulated data to the standard methods used in the underwriting cycles literature. The results show that NN models perform well in detecting cycles even in the presence of outliers and structural breaks. The methodology is applied to a granular data set of prices per risk profile from the Brazilian insurance industry.