An experimental investigation of the recirculation zone formed downstream of a forward facing step

An experimental investigation of the recirculation zone formed downstream of a forward facing step immersed in a turbulent boundary layer has been undertaken using particle image velocimetry. Bluff body flow is observed with the fixed separation point located at the leading edge of the step. The recirculation region dimensions are characterised over a range of Reynolds numbers (1400–19 000), with Reh based on the step height and the free stream velocity. Turbulent perturbations are produced in the free shear layer which develops between the recirculating flow close to the step and the free stream flow. Contour maps of amplification factor, streamwise perturbation velocity and Reynolds stresses are constructed, providing insight into optimal placement of structures within such topographical features. The mechanisms affecting the reattachment distance, namely the turbulent mixing within the boundary layer and the velocity deficit in the boundary layer, are discussed

Characterisation of a horizontal axis wind turbine’s tip and root vortices

The vortical near wake of a model horizontal axis wind turbine has been investigated experimentally in a water channel. The objective of this work is to study vortex interaction and stability of the helical vortex filaments within a horizontal axis wind turbine wake. The experimental model is a geometrically scaled version of the Tjæreborg wind turbine, which existed in western Denmark in the late 1980s. Here, the turbine was tested in both the upwind and downwind configurations. Qualitative flow visualisations using hydrogen bubble, particle streakline and planar laser-induced fluorescence techniques were combined with quantitative data measurements taken using planar particle image velocimetry. Vortices were identified using velocity gradient tensor invariants. Parameters that describe the helical vortex wake, such as the helicoidal pitch, and vortex circulation, were determined for three tip speed ratios. Particular attention is given here to the root vortex, which has been investigated minimally to date. Signatures of the coherent tip vortices are seen throughout the measurement domain; however, the signature of the root vortex is only evident much closer to the rotor plane, irrespective of the turbine configuration. It is postulated that the root vortex diffuses rapidly due to the effects of the turbine support geometries

Multi-rate demodulator architecture

A unique digital multi-rate demodulator (MRD) architecture is presented for onboard satellite communications processing. The multi-rate feature enables the same demodulator hardware to process either one wideband channel (WBC), or process up to thirty-two independent narrowband channels (NBC) that are time division multiplexed (TDM). The MRD can process many quadrature modulation format such as offset quadrature phase shift keying (OQPSK). Possible applications include voice and data transmission for commercial or military users

Examining the Contributions of Glacial Till Water to Storm Runoff using Two- and Three-Component Hydrograph Separations

Two- and three-component hydrograph separations based on 18O and dissolved silica are used to investigate the contributions of glacial till water to the storm runoff of a headwater stream on the Canadian Shield. Two-component isotopic hydrograph separations based on 18O indicate that the volume and flux of event water could be accounted for by direct precipitation onto saturated areas. Three-component hydrograph separations distinguish between event water, preevent soil water, and preevent till water. These results show that groundwater flow through coarse-textured glacial tills can make a significant contribution to stream discharge during runoff events (29 and 62% in this study) despite the lower hydraulic conductivities of the tills compared to the overlying soils. The three-component hydrograph separations also demonstrate that the relative contributions of preevent soil water and preevent till water changed during one runoff event such that the average water chemistry of the preevent component varied during the event. Two-component hydrograph separations using dissolved silica indicate that seasonal changes in the till water contributions also occur and are related to groundwater levels. Measurements of vertical hydraulic gradients during runoff events indicate that the increase in flow from the tills to the soils is minimal and cannot account for the large and rapid increase in till water flow into the stream. Till water that has discharged to the soils prior to the event is probably being flushed from the soils into the stream during events

Commentary on Household Hardships, Public Programs, and Their Associations with the Health and Development of Very Young Children: Insights from Children\u27s HealthWatch

This commentary, written in response to the article Household Hardships, Public Programs, and Their Associations with the Health and Development of Very Young Children: Insights from Children\u27s HealthWatch , highlights the importance of the research done by Children\u27s HealthWatch in relation to childhood food insecurity. Childhood food insecurity has been linked with various adverse health effects, including undernutrition, poor or delayed child development, and social and psychological consequences. Children\u27s HealthWatch provides important data that can be used to monitor threats to our children\u27s well-being and address problems with effective interventions

Optimal Rebuilding of Fish Stocks in Different Nations: Bioeconomic Lessons for Regulators

Under the rubric of sustainable fisheries, nations are mandated to rebuild overfished stocks. Although rebuilding strategies are almost universally directed by the available biological information, approaches vary depending on fishery laws, management objectives, and technical guidelines. For example, rebuilding schedules in the United States are primarily designed to achieve rapid rebuilding of biomass and spawning stocks consistent with the biological characteristics of the resource. In contrast, New Zealand has greater flexibility in rebuilding stocks in order to consider economic, social, and cultural needs. In this paper we investigate potential economic costs to the fishery that result by limiting the US manager’s flexibility in choosing a recovery trajectory. Using numerical models for moderate- and long-lived stocks, the analysis reveals that depending on productivity of the stock and the discount rate, extending the rebuilding timeframe can substantially increase annual harvests and economic benefits. The results underscore the importance of economic analysis in crafting flexible rebuilding schedules that account for the unique characteristics of the fisheries, including economic and social needs.Fisheries economics, fisheries management, K-selective species, rebuilding., Resource /Energy Economics and Policy, Q22, C61,

Why do home-owners do better?

Australians who own their own home display favourable outcomes on a range of socio-economic indicators when compared to renters, and substantial benefits of home-ownership also appear to accrue to their children. Whether such effects are causal or simply reflect pre-existing characteristics associated with selection into home-ownership has important implications for decisions to be made by individuals and families, and for policy in light of recent declines in home-ownership rates for younger adults. The literature primarily attributes the better outcomes of those in home-ownership to greater residential stability, particularly in the case of children’s educational attainment, and a greater incentive to invest in the local community, but there is little empirical evidence on the sources of benefits from home-ownership in Australia. Using longitudinal data from the Household, Income and Labour Dynamics in Australia survey (HILDA) this paper employs a range of strategies to test competing hypotheses relating to causal mechanisms and selection effects associated with home-ownership. We focus on indicators of physical and mental health, life satisfaction and, for youth, educational attainment. The results suggest the better physical and mental health outcomes of home-owners reflect selection effects rather than any causal impact of home-ownership on health. However, there is evidence that home-ownership promotes higher life-satisfaction, and of residential stability and parental community engagement associated with parental home-ownership impacting beneficially on outcomes for youth

Welcome from the Co-Chairs. Knowledge Community for Student Leadership Programs Innovation Newsletter

On behalf of our entire SLPKC Leadership Team, we\u27d like to be the first to welcome you to another academic year. We hope that the summer has allowed you the opportunity to unwind, rejuvenate, and come back ready to serve your students. Be assured that the SLPKC has been busy over the summer offering webinars, conducting research, representing our members at a national leadership collaborative summit, recognizing outstanding leadership programs, and much more. We are fortunate to have many of these summer projects highlighted within this newsletter

The interaction of helical tip and root vortices in a wind turbine wake

Analysis of the helical vortices measured behind a model wind turbine in a water channel are reported. Phase-locked measurements using planar particle image ve- locimetry are taken behind a Glauert rotor to investigate the evolution and breakdown of the helical vortex structures. Existing linear stability theory predicts helical vortex filaments to be susceptible to three unstable modes. The current work presents tip and root vortex evolution in the wake for varying tip speed ratio and shows a breaking of the helical symmetry and merging of the vortices due to mutual inductance between the vortical filaments. The merging of the vortices is shown to be steady with rotor phase, however, small-scale non-periodic meander of the vortex positions is also ob- served. The generation of the helical wake is demonstrated to be closely coupled with the blade aerodynamics, strongly influencing the vortex properties which are shown to agree with theoretical predictions of the circulation shed into the wake by the blades. The mutual inductance of the helices is shown to occur at the same non-dimensional wake distance

Farewell from the Co-Chairs

Has it been three years already?!?!? Indeed it has. We have been honored to serve as Co-Chairs for the Student Leadership Programs Knowledge Community. As a farewell, we would like to reflect on our time as Co-Chairs and revisit our mission and strategic goals. The mission of the Student Leadership Programs Knowledge Community is to serve as a resource for higher educationprofessionals who have a professional interest in young-adult (i.e., college students) leadership training, education, and development. The Community will share best practices, provide critical evaluation of the field, examine standards for leadership programs, support national and regional efforts to develop student leadership programs, make contributions to the literature, recognize exemplary programs, and cultivate a forum for the presentation of new ideas. Our 2012-2014 Strategic Goals are outlined below