Computational study of rotorcraft aerodynamics in ground effect and brownout

When helicopters operate close to the ground in desert conditions, the rotor wake can entrain large amounts of dust into the flow field surrounding the aircraft. This entrainment of dust can result in the potentially dangerous condition known as brownout where the pilot loses situational awareness. Understanding the physics that governs the entrainment of dust from the ground may eventually allow the condition of brownout to be avoided completely. To enable the formation of dust clouds around helicopters to be investigated, Brown's Vorticity Transport Model~(VTM) has been enhanced to include the ability to model the entrainment of dust from the ground and the transport of this dust once in the flow field. Comparison of the predictions of the VTM with experimental results has shown the VTM to be capable of capturing the general characteristics of the dust clouds. Close examination of the formation of the dust clouds revealed that the general physics that governs the entrainment process is the same for different rotors and a universal model of this process is described. Differences in the size and density of the dust clouds that form around different rotors result from differences in the overall behaviour of the wakes that are generated. The design of a rotor can have a significant effect on the size and density of the dust cloud that is produced. The tip vortices have been identified as the main cause of the changes to the dust cloud. However, the behaviour of these tip vortices, when the rotor is operating in ground effect, is dependent on the rotor design and also on the advance ratio of the rotor. Thus, to determine the size and density of the dust cloud that would form around any particular rotor, the behaviour of the wake of that rotor must first be known

The flow physics of helicopter brownout

The formation of the dust cloud that is associated with low-level helicopter operations in desert environments has been simulated using the Vorticity Transport Model together with a coupled model to represent the entrainment and subsequent transport of particulate matter through the flow. A simple thin-layer theory, supported by simulations performed using the more physically-representative numerical model, is used to explain the formation of characteristic sheet- and filament-like structures in the dust cloud in terms of the interactions between individual vortical filaments and the ground. In parts of the flow, for instance near the ground vortex that is formed under the leading edge of the rotor when in forward flight, the dust cloud becomes more space-filling than sheet-like in character, and the theory suggests that this is a result of the dust distribution having been processed by multiple vortices over a significant period of time. The distribution of the regions on the ground plane from which significant entrainment of dust into the flow takes place is shown to be influenced strongly by the unstable nature of the vortical structures within the flow. It is suggested that the effect of this vortical instability, when integrated over the timescales that are characteristic of the formation of the dust cloud, is to de-sensitize the gross characteristics of the dustcloud to the details of the wake structure at its inception on the rotor blades. This suggests that the formation of the brownout cloud may be relatively insensitive to the detailed design of the blades of the rotors and may thus be influenced only by less subtle characteristics of the helicopter system

The effect of rotor design on the fluid dynamics of helicopter brownout

Helicopters operating close to the ground in dusty environments tend to generate large clouds of dust in the surrounding air. These clouds can obscure the pilot's view of the ground and lead to a dangerous condition known as brownout. Given the intimate relationship between the induced flow feld around the rotor and the process through which the particulate matter becomes airborne and is subsequently transported, it has been speculated that the design of its rotor may influence the shape and size of the dust clouds that are produced by any particular type of helicopter. This paper presents a study of the influence of two key geometric properties of the rotor on the development of these dust clouds. A particle transport model is coupled to Brown's Vorticity Transport Model to represent the dynamics of the particulate-air system surrounding a generic helicopter rotor under various flight conditions. The number of blades on the rotor is altered, whilst keeping the solidity constant, thus altering the distribution of vorticity that is released onto the ground. In addition, the twist of the blades is varied in order to investigate the effect of the resultant changes in the distribution of induced downwash on the evolution of the dust cloud. The study suggests that, in general, the larger the number of blades, and the higher the blade twist, the less dense the dust clouds that are produced under brownout conditions. It appears thus that the characteristics of the dust clouds are indeed sensitive to the geometry of the rotor and hence that careful aerodynamic design may allow the severity of brownout to be ameliorated

Helicopter brownout - can it be modelled?

Significant progress has been made to date in modelling, computationally, the formation and development of the dust cloud that forms in the air surrounding the rotorcraft under brownout conditions. Modern computational methods are able to replicate not only the development of the dust cloud in appropriate operational scenarios, but also the sensitivity of the shape and density of the dust cloud to the detailed design of the rotorcraft. Results so far suggest that attempts to ameliorate brownout by aerodynamic means, for instance by modifying the rotor properties, will be frustrated to some extent by the inherent instability of the °flow field that is produced by the helicopter. Nonetheless, very recent advances in understanding the fundamental mechanisms that lead to the formation of the dust cloud may allow substantial progress to be made once certain elements of the basic physics of the problem are more fully understood and better quantified

Applying rotorcraft modelling technology to renewable energy research

The perceived need to reduce mankind's impact on the global climate motivates towards a future society in which a significant proportion of its energy needs will be extracted from the winds and the tides of the planet. This paper shows several examples of the application of Brown's Vorticity Transport Model, originally developed to perform simulations of helicopter aeromechanics and wake dynamics, to the analysis of the performance of renewable energy devices and their possible impact on the environment. Prediction of the loading on wind turbines introduces significant additional challenges to such a model, including the need to account fully for the effects of radial flow on blade stall. The wake-mediated aerodynamic interactions that occur within a wind farm can reduce its power output significantly, but this problem is very similar to that where the aerodynamic unsteadiness of the coupled wake of the main and tail rotors of a helicopter can result in significantly increased pilot workload. The helicopter-related problem of brownout, encountered during operations in desert conditions, has its analogue in the entrainment of sediment into the wakes of tidal turbines. In both cases it may be possible to ameliorate the influence of the rotor on its environment by careful and well-informed design. Finally, calculations of the distortion and dispersal of the exhaust plumes of a helicopter by the wake of its rotor allow insight into how wind turbines might interfere with the dispersal of pollutants from nearby industrial sites. These examples show how cross-disciplinary information transfer between the rotorcraft field and the renewable energy community is helping to develop the technologies that will be required by our future society, as well as helping to understand the environmental issues that might need to be faced as these technologies become more prevalent

Montessori, the White Cross and Trauma-Informed Practice

Childhood adversity and trauma are pervasive and have powerful, far-reaching consequences for health and well-being. Recent years have seen increased recognition of the need for trauma-informed practice, which aims to promote understanding, healing, and the prevention of retraumatization. Historical data show that the early Montessori schools were known internationally as healing schools, wherein children affected by adversity or trauma were apparently healed on a considerable scale. This study presents the findings from a documentary analysis of three primary sources, namely, Maria Montessori’s own original accounts, eyewitness accounts, and media reports pertaining to this healing aspect of the early Montessori schools. The findings demonstrate that, first, from the beginning of her career, Montessori worked with children who had experienced significant exposure to adversity or trauma, second, that her Montessori Method was shown to affect healing or recovery in these children, and third, that her long involvement with trauma-affected children directly led to her later attempts to set up an organization to be called the White Cross, which was to incorporate, among other things, a trauma-informed course for teacher–nurses. In this innovative approach to Montessori studies, we argue that Montessori was ahead of her time, that her work is even more relevant today in the context of adversity and trauma research, and that her methods, principles, and approaches may be harnessed and used in ways that promote trauma-informed practice in contemporary education settings

Whole genome sequencing of Salmonella Typhimurium illuminates distinct outbreaks caused by an endemic multi-locus variable number tandem repeat analysis type in Australia, 2014

Phylogeny of the outbreak A and M strains in the context of national and international STM isolates. Genome data analysed in Octavia et al. representing five STM outbreaks in Australia [25]; Kingsley et al. representing ST313 outbreak in Malawi [30]; Leekitcharoenphon et al. representing six STM outbreaks in Denmark [15] and Hawkey et al. representing STM DT135a outbreak in Australia [21] were also included as comparisons and marked as the corresponding study/outbreak. Other branches that are not labelled are background isolates from the above studies; draft genomes from Pang et al. [29] which include five diverse Australian STM isolates; Fu et al. representing Salmonella reference collection A; [28] and other fully sequenced STM genomes available from GenBank including LT2 (Accession No. NC003197), 798 (Accession No. CP003386), DT2 (Accession No. HG326213), DT104 (Accession No. HF937208), 14028S (Accession No. CP001363), SL1344 (Accession No. FQ312003), UK-1 (Accession No. CP002614), T000240 (Accession No. AP011957), U288 (Accession No. CP003836) and ST4/74 (Accession No. CP002487). Bootstrap values if greater than 50 %, are presented on the internal branches. (PPTX 74 kb

Systematic review of the evidence on orthotic devices for the management of knee instability related to neuromuscular and central nervous system disorders

Objectives To assess the effectiveness of orthotic devices for the management of instability of the knee in adults with a neuromuscular disorder or central nervous system disorder. Design A systematic review of primary studies. Setting Community. Participants Adults with a neuromuscular disorder or central nervous system disorder and impaired walking ability due to instability of the knee. Interventions Orthoses with the clinical aim of controlling knee instability, for example, knee-ankle-foot orthoses, ankle-foot orthoses and knee orthoses or mixed design with no restrictions in design or material. Primary and secondary outcome measures Conditionspecific or generic patient-reported outcome measures assessing function, disability, independence, activities of daily living, quality of life or psychosocial outcomes; pain; walking ability; functional assessments; biomechanical analysis; adverse effects; usage; patient satisfaction and the acceptability of a device; and resource utilisation data. Results Twenty-one studies including 478 patients were included. Orthotic devices were evaluated in patients with postpolio syndrome, poststroke syndrome, inclusion body myositis and spinal cord injury. The review included 2 randomised controlled trials (RCTs), 3 non-randomised controlled studies and 16 case series. Most were small, single-centre studies with only 6 of 21 following patients for 1 year or longer. They met between one and five of nine quality criteria and reported methods and results poorly. They mainly assessed outcomes related to gait analysis and energy consumption with limited use of standardised, validated, patient-reported outcome measures. There was an absence of evidence on outcomes of direct importance to patients such as reduction in pain and falls. Conclusions There is a need for high-quality research, particularly RCTs, of orthotic devices for knee instability related to neuromuscular and central nervous system conditions. This research should address outcomes important to patients. There may also be value in developing a national registr

Eulerian simulation of the fluid dynamics of helicopter brownout

A computational model is presented that can be used to simulate the development of the dust cloud that can be entrained into the air when a helicopter is operated close to the ground in desert or dusty conditions. The physics of this problem, and the associated pathological condition known as ‘brownout’ where the pilot loses situational awareness as a result of his vision being occluded by dust suspended in the flow around the helicopter, is acknowledged to be very complex. The approach advocated here involves an approximation to the full dynamics of the coupled particulate-air system. Away from the ground, the model assumes that the suspended particles remain in near equilibrium under the action of aerodynamic forces. Close to the ground, this model is replaced by an algebraic sublayer model for the saltation and entrainment process. The origin of the model in the statistical mechanics of a distribution of particles governed by aerodynamic forces allows the validity of the method to be evaluated in context by comparing the physical properties of the suspended particulates to the local properties of the flow field surrounding the helicopter. The model applies in the Eulerian frame of reference of most conventional Computational Fluid Dynamics codes and has been coupled with Brown’s Vorticity Transport Model. Verification of the predictions of the coupled model against experimental data for particulate entrainment and transport in the flow around a model rotor are encouraging. An application of the coupled model to analyzing the differences in the geometry and extent of the dust clouds that are produced by single main rotor and tandem-rotor configurations as they decelerate to land has shown that the location of the ground vortex and the size of any regions of recirculatory flow, should they exist, play a primary role in governing the extent of the dust cloud that is created by the helicopter