Slug flow characterisation in horizontal annulus

To characterize slug flows in annuli channels and highlight the effect of the eccentricity on the flow behaviors, experiments were conducted in two horizontal annuli setups (a) concentric and (b) fully eccentric using air and water as the testing fluids. The range of air and water superficial velocities investigated were 0.45–3.49 m/s and 0.15–2.77 m/s, respectively. Slug parameters measured using conductance probes designed for this study include slug length, translational velocity, slug frequency, and slug holdup. It is found that the slug translational velocity is unaffected by the annulus eccentricity; however, parameters including slug frequency, slug holdup, and slug lengths have a higher value in the fully eccentric annulus when compared with the concentric one. We introduced a new definition of hydraulic diameter, which reconciles the correlation between the dimensionless mean slug length and the mixture velocity of the horizontal annuli with different setups

Measurement of air distribution and void fraction of an upwards air-water flow using electrical resistance tomography and a wire-mesh sensor

Measurements on an upwards air-water flow are reported that were obtained simultaneously with a dual-plane electrical resistance tomograph (ERT) and a wire-mesh sensor (WMS). The ultimate measurement target of both ERT and WMS is the same, the electrical conductivity of the medium. The ERT is a non-intrusive device whereas the WMS requires a net of wires that physically crosses the flow. This paper presents comparisons between the results obtained simultaneously from the ERT and the WMS for evaluation and calibration of the ERT. The length of the vertical testing pipeline section is 3 m with an internal diameter of 50 mm. Two distinct sets of air-water flow rate scenarios, bubble and slug regimes, were produced in the experiments. The fast impedance camera ERT recorded the data at an approximate time resolution of 896 frames per second (fps) per plane in contrast with the 1024 fps of the wire-mesh sensor WMS200. The set-up of the experiment was based on well established knowledge of air-water upwards flow, particularly the specific flow regimes and wall peak effects. The local air void fraction profiles and the overall air void fraction were produced from two systems to establish consistency for comparison of the data accuracy. Conventional bulk flow measurements in air mass and electromagnetic flow metering, as well as pressure and temperature, were employed, which brought the necessary calibration to the flow measurements. The results show that the profiles generated from the two systems have a certain level of inconsistency, particularly in a wall peak and a core peak from the ERT and WMS respectively, whereas the two tomography instruments achieve good agreement on the overall air void fraction for bubble flow. For slug flow, when the void fraction is over 30%, the ERT underestimates the void fraction, but a linear relation between ERT and WMS is still observed

Political Entrepreneurship in the Field of Māori Sovereignty in Aotearoa New Zealand

Individual actors have the potential to shape political outcomes through creative use of opportunities. Political entrepreneurship identifies how such actors recognise and exploit opportunities, for personal or collective gain. The existing literature focuses on individuals operating within institutional settings, with less attention paid to other types of actors. In this article, I argue for an expansion of the political entrepreneurship framework, by considering individuals in the electoral and protest arenas. An examination of the field of Māori sovereignty, or tino rangatiratanga, in Aotearoa New Zealand allows exploration of prominent actors’ innovative strategies and practices. The findings highlight the actors’ reliance on identity in mobilising support within the community, to press claims. Broadening the application of political entrepreneurship demonstrates the roles of social, cultural and political capital in influencing outcomes, by identifying opportunities available to individuals embedded in the community and according to the context of the arena

Working across boundaries: Science-policy interfaces and international forest politics

If scientific knowledge is to influence international environmental policy it needs to be recognised as authoritative and impartial by key politicians and policy makers. In the case of climate change this is achieved by a boundary organisation, the Intergovernmental Panel on Climate Change (IPCC), which enables climate scientists to demonstrate the veracity of their research to climate policy makers while, for the most part, maintaining scientific integrity and resisting political interference in scientific conclusions. However, in the absence of such an organisation for forest science the international forest science community has come forward and created its own mechanism - the Global Forest Expert Panels - which responds to demands from the forest policy community for knowledge in particular areas and which in some respects is based on the IPCC model. However, even if a more effective forest-science policy boundary organisation were to exist, progress in international forest policy would be constrained by some long standing political divisions, in particular on the financing of sustainable forest management