Statistical estimation of trailing edge noise from finite wall-mounted airfoils

The 2016 Joint Conference of The Australian Acoustical Society and The Acoustical Society of New Zealand. Acoustics2016 - The Second Australasian Acoustical Societies ConferenceIt is important to be able to accurately model the flow and noise generated by finite wall-mounted airfoil flows because of the many engineering applications in which these flows occur. One method for predicting turbulent trailing edge noise is the Reynolds-averaged Navier-Stokes based statistical noise model (RSNM) of Doolan et al. (Proceedings of 20th International Congress on Acoustics, ICA 2010). The RSNM method has previously been used successfully on a range of two-dimensional geometry-flow cases. In this paper a new turbulent velocity cross-spectrum model and improved implementation are proposed to allow the RSNM method to be used to effectively and efficiently predict turbulent trailing edge noise from more complex three-dimensional cases. Reynolds-averaged Navier-Stokes (RANS) simulations of a series of wing-in-junction cases are used in combination with the developed acoustic model to predict the far-field noise and compared against experimental noise measurements.Jesse Coombs, Con Doolan, Anthony Zander, Danielle Moreau and Laura Brook

Stiffness and energy losses in cylindrically symmetric superconductor levitating systems

Stiffness and hysteretic energy losses are calculated for a magnetically levitating system composed of a type-II superconductor and a permanent magnet when a small vibration is produced in the system. We consider a cylindrically symmetric configuration with only vertical movements and calculate the current profiles under the assumption of the critical state model. The calculations, based on magnetic energy minimization, take into account the demagnetization fields inside the superconductor and the actual shape of the applied field. The dependence of stiffness and hysteretic energy losses upon the different important parameters of the system such as the superconductor aspect ratio, the relative size of the superconductor-permanent magnet, and the critical current of the superconductor are all systematically studied. Finally, in view of the results, we provide some trends on how a system such as the one studied here could be designed in order to optimize both the stiffness and the hysteretic losses.Comment: 8 pages; 8 figure

Sceptical Employees as CSR Ambassadors in Times of Financial Uncertainty

This chapter offers new insights into the understanding of internal (employee) perceptions of organizational corporate social responsibility (CSR) policies and strategies. This study explores the significance of employees’ involvement and scepticism upon CSR initiatives and focuses on the effects it may have upon word of mouth (WOM) and the development of employee–organisation relationships. Desk research introduces the research questions. Data for the research questions were gathered through a self-completion questionnaire distributed in a hardcopy form to the sample. An individual’s level of scepticism and involvement appears to affect the development of a positive effect on employees’ WOM. Involvement with the domain of the investment may be a central factor affecting relationship building within the organization, and upon generation of positive WOM. The chapter offers a conceptual framework to public relations (PR) and corporate communications practitioners, which may enrich their views and understanding of the use and value of CSR for communication strategies and practices. For-profit organisations are major institutions in today’s society. CSR is proffered as presenting advantages for (at macro level) society and (micro level) the organization and its employees. Concepts, such as involvement and scepticism, which have not been rigorously examined in PR and corporate communication literature, are addressed. By examining employee perceptions, managers and academic researchers gain insights into the acceptance, appreciation and effectiveness of CSR policies and activities upon the employee stakeholder group. This will affect current and future CSR communication strategies. The knowledge acquired from this chapter may be transferable outside the for-profit sector

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields

Crossed magnetic field effects on bulk high-temperature superconductors have been studied both experimentally and numerically. The sample geometry investigated involves finite-size effects along both (crossed) magnetic field directions. The experiments were carried out on bulk melt-processed Y-Ba-Cu-O (YBCO) single domains that had been pre-magnetized with the applied field parallel to their shortest direction (i.e. the c-axis) and then subjected to several cycles of the application of a transverse magnetic field parallel to the sample ab plane. The magnetic properties were measured using orthogonal pick-up coils, a Hall probe placed against the sample surface and Magneto-Optical Imaging (MOI). We show that all principal features of the experimental data can be reproduced qualitatively using a two-dimensional finite-element numerical model based on an E-J power law and in which the current density flows perpendicularly to the plane within which the two components of magnetic field are varied. The results of this study suggest that the suppression of the magnetic moment under the action of a transverse field can be predicted successfully by ignoring the existence of flux-free configurations or flux-cutting effects. These investigations show that the observed decay in magnetization results from the intricate modification of current distribution within the sample cross-section. It is also shown that the model does not predict any saturation of the magnetic induction, even after a large number (~ 100) of transverse field cycles. These features are shown to be consistent with the experimental data.Comment: 41 pages, 9 figures, accepted in Phys. Rev. B Changes : 8 references added, a few precisions added, some typos correcte

A geometrically-exact Finite Element Method for micropolar continua with finite deformations

Micropolar theory is a weakly non-local higher-order continuum theory based on the inclusion of independent (micro-)rotational degrees of freedom. Subsequent introduction of couple-stresses and an internal length scale mean the micropolar continuum is therefore capable of modelling size effects. This paper proposes a non-linear Finite Element Method based on the spatial micropolar equilibrium equations, but using the classical linear micropolar constitutive laws defined in the reference configuration. The method is verified rigorously with the Method of Manufactured Solutions, and quadratic Newton-Raphson convergence of the minimised residuals is demonstrated

The influence of defined ante-mortem stressors on the early post-mortem biochemical processes in the abdominal muscle of the Norway lobster, Nephrops norvegicus (Linnaeus, 1758)

The effects of four different ante-mortem stressors (exercise, emersion, starvation and a patent infection with the parasite Hematodinium sp.) on post-mortem processes have been investigated in the abdominal muscle of Norway lobster Nephrops norvegicus by measuring changes in the pH, the levels of glycogen, l-lactate, arginine phosphate, ATP, ADP, AMP, IMP, HxR, Hx and the adenylate energy charge (AEC) over a time course of 24 h with samples being taken at 0, 3, 6, 12 and 24 h. The acute stresses of intense exercise and 2 h emersion resulted in a premature onset of anaerobic glycolysis, leading both to an enhanced glycogen depletion rate and an early accumulation of l-lactate. The chronic stressors, starvation and parasite infection, resulted in a complete ante-mortem depletion of muscle glycogen and consequently the failure of post-mortem glycolytic fermentation. Post-mortem pH and ATP inter-conversion were significantly altered in chronically stressed animals. Ante-mortem, a rapid, almost complete depletion of arginine phosphate was observed in all stress groups. The AEC was altered significantly by all stresses, indicating a strong energy demand. The findings suggest that ante-mortem stressors strongly influence the post-mortem biochemical processes. The laboratory-based results are compared to 'field' data and effects on post-harvest product quality are discussed

Microbiological influences on fracture surfaces of intact mudstone and the implications for geological disposal of radioactive waste

The significance of the potential impacts of microbial activity on the transport properties of host rocks for geological repositories is an area of active research. Most recent work has focused on granitic environments. This paper describes pilot studies investigating changes in transport properties that are produced by microbial activity in sedimentary rock environments in northern Japan. For the first time, these short experiments (39 days maximum) have shown that the denitrifying bacteria, Pseudomonas denitrificans, can survive and thrive when injected into flow-through column experiments containing fractured diatomaceous mudstone and synthetic groundwater under pressurized conditions. Although there were few significant changes in the fluid chemistry, changes in the permeability of the biotic column, which can be explained by the observed biofilm formation, were quantitatively monitored. These same methodologies could also be adapted to obtain information from cores originating from a variety of geological environments including oil reservoirs, aquifers and toxic waste disposal sites to provide an understanding of the impact of microbial activity on the transport of a range of solutes, such as groundwater contaminants and gases (e.g. injected carbon dioxide)