744 research outputs found
The aerodynamic design and optimization of a wing-fuselage junction fillet as part of a multi-disciplinary optimization process during the early aircraft design stages
Full text linkAn attempt to minimize interference drag in a wing-fuselage junction by means
of inserting a fillet is presented in this thesis. The case of a low-wing com-
mercial transport aicraft at cruise conditions is examined. Due to the highly
three dimensional behaviour of the flow field around the junction, a thin-layer
Navier-Stokes code was implemented to estimate the drag forces at the junc-
tion. Carefully selected design variable combinations based on-the theory of
Design of Experiments constituted the initial group of feasible cases for which
the flow solver had to be run. The drag values of these feasible cases were then
used to create a second order response surface which could predict with rea-
sonable accuracy the interference drag given the value of the design variables
within the feasible region. A further optimization isolated the minimum in-
terference drag combination of design variable values within the design space.
The minimurn interference drag combination of design variable values was eval-
uated numerically by the flow solver. The prediction of the response surface
and the numerical value obtained by the flow solver for the interference drag
of the optimal wing-fuselage combination differed by less than five percent. To demonstrate the ability of the method to be used in an interdisciplinary
analysis and optimization program, a landing gear design module is included
which provides volume constraints on the fillet geometry during the fillet sur-
face definition phase.
The Navier Stokes flow analyses were performed on the Cranfield Cray su-
percomputer. Each analysis required between eight to twelve CPU hours, and
the total CPU time required for the optimization of the six variable model
described in the thesis required thirty Navier Stokes runs implementing the
Design of Experimens and Surface Response Methodology implementation.
For comparison, a typical optimization implementing a classical conjugate di-
rections optimizer with no derivative information available would probably
require more than forty iterations.
Both the optimization and the flow solver results are discussed and some
recommendations for improving the efficiency of the code and for further ap-
plications of the method are given
Patterns of alcohol use in adolescents: early predictors and adulthood outcomes.
No full textAlcohol is one of the leading risk factors for death and disability in young people . Although people usually first start drinking alcohol at around 15-16 years of age, this can vary, and adolescents often follow different patterns or “trajectories” of drinking. The age at which an adolescent first consumes alcohol and how quickly they escalate their alcohol use may be important predictors of alcohol-related problems in early adulthood....
NDARC webinar series presentation: Gen Z: drinking less, but what about alcohol-related harm?
No full textShips Observing Marine Climate: a catalogue of the VOS participating in the VSOP-NA
Full text linkOur present knowledge of the marine climate, as represented by data sets such as COADS (Woodruff et al., 1987), is based on meteorological observations from the Voluntary Observing Ships (VOS). Because the VOS are merchant ships, rather than specially designed meteorological platforms, errors and biases exist in the data. However there is little information readily available to the climatologist either on the nature of the VOS fleet or on the observing practises which are used. This report, describing the forty-six ships that participated in the Voluntary Observing Ships' Special Observing Project - North Atlantic (VSOP-NA), therefore serves two purposes:(i) it provides a reference document to aid analysis of the VSOP-NA data set,(ii) it gives a detailed description of a subset of the VOS, which will be of value in the interpretation of marine climate data sets.This report is in two parts, Part 1 is an overall summary of the ship characteristics, Part 2 is a ship by ship description. The next section will briefly describe the VSOP-NA project, followed by a summary of the characteristics of the VSOP-NA ships (Section 3). Since these ships were specially selected (Section 2.2), the degree to which they are representative of the whole VOS fleet will be carefully considered. The meteorological instrumentation used by the VOS varies depending on which meteorological agency recruited the ships. That used on the chosen VSOP-NA ships is typical of VOS recruited by the countries bordering the North Atlantic, and will be described in Section 4. Section 5 is a summary of Part 1 of the report.Part 2 presents the VSOP-NA ship catalogue. This includes, for each ship, diagrams of the layout (indicating in particular the exposure of the sensors), a summary of the geographical positions at which observations were obtained, and details of the instrumentation used.<br/
Trajectories of alcohol-related harm among young people
Full text linkIn many high-income countries such as Australia, alcohol use has declined in young people since the early 2000s but there is conflicting evidence around reductions in alcohol-related harm. A key issue around quantifying alcohol-related harm is that different data sources can show vastly different patterns due to varying sample characteristics or methods of measurement. The studies comprising this thesis aimed to address these gaps by using a variety of data sources to examine: 1) trends in self-reported harms across age, period, and birth cohort using national surveys (n=121,281); 2) developmental patterns of blackouts, a very common harm, and predictors of high-risk patterns in a recent birth cohort (n=1,821); 3) developmental transitions between different types of alcohol-related harm and predictor of high-risk patterns in a recent birth cohort (n=1,828); and 4) risk factors for experiencing clinical alcohol-related harm for the first time at a younger age and compare rates of subsequent harm by age at first experience of clinical harm in a linked cohort (n=10,300).
Several notable findings were identified. National data indicate that alcohol-related risky behaviours are much less common in recent birth cohorts, though they continue to be most prevalent in young people. Males generally had twice the prevalence of risky behaviours compared to females, but with reduced effect among more recent birth cohorts. Longitudinal cohort data indicated that escalating experience of harms, particularly blackouts and psychosocial harms (e.g., getting into fights) increased risk of early adulthood alcohol use disorder symptoms. Females were at higher risk of experiencing physiological harms such as blackouts earlier in life compared to males. Finally, analyses of linked hospital service data indicated that females were at higher risk of accessing hospital services for an alcohol-related problem for the first time at a younger age. Younger people were more likely to have subsequent injury-related ED presentations but less likely to be hospitalised. Past year hospital service access rates in this cohort were much higher than the same-aged general population.
This thesis highlights important developments in young peoples’ experience of alcohol-related harm. The identification of a closing male-female gap in harms and of female status as a risk factor for early harm warrants future research and shifts to the approach of harm reduction and prevention among young people
Left Wing, Right Wing, People, and Power: The Core Dynamics of Political Action
No full textAvoiding partisan diatribe, Left Wing, Right Wing, People, and Power traces the historical development of the left wing and the right wing to reveal that the core of politics is the conflict over power. Despite specific differences of time and place, political actions are consistently efforts to preserve or change the structure and dynamics of power. With this insight, we can better understand political positions and actions.
Written in an accessible style, this book will inform readers regardless of where they see themselves on the political spectrum. With clear but nuanced definitions of political ideologies and movements, the author shows how politics is people seeking to express and expand their power in the social space around them. Thus, the clash of the left and right wings is not about grand ideologies but instead is about power relations and the flow of power among people
Flapping-wing aerodynamics study on the wake of DelFly II by means of Robotic Volumetric Particle Tracking Velocimetry
No full textThe aim of this investigation is to provide an experimental volumetric visualization of the near wake topology of the vortex structures generated by a flapping-wing Micro Air Vehicle (MAV) by means of large-scale Robotic PIV. This novel technique implements coaxial illumination and imaging in combination with the use of Helium Filled Soap Bubbles (HFSB) as tracing particles to achieve large measurement volumes of the order of 10 liters. Information of different phases throughout the flapping cycle is obtained by means of a phase-locked averaging procedure. The MAV used for this study is called DelFly II. It is a platform composed a two pairs of wings attached to a slip body with horizontal and vertical tailplanes for stability and maneuverability. Measurements are performed at regular free-flight scenarios within the DelFly flying envelope. The configurations selected have different reduces frequencies which allows to analyze the effect of this important parameter. Same configurations are also measured with and without the presence of the tails to see their influence of the wake topology. In addition, experiments in both tethered and free-flight conditions have been performed, yielding an unprecedented comparison between the aerodynamics of the two conditions.The significance of the proposed project lies on the ability of assess the complete three-dimensional wake of the DelFly II. This is the first experimental study performed that can achieve such measuring volumes for any flapping-wing platform, to the knowledge of the present author. Another major benefit of this study is the use of standard flight configuration to observe the wake structures when the MAV is able to sustain level flight. Therefore, the proposed work is expected to be a relevant addition to the understanding of the flapping-wing mechanism.Aerospace Engineerin
A Novel Airframe Design Methodology For Silent Aircraft
Full text linkThe impact of noise on civil aviation is not just a localised airport problem, but a global concern, due
to the ever-increasing demands for passenger travel. The challenge of designing a ‘Silent Aircraft’
lies within the development, integration, and optimisation of efficient airframe-engine technologies.
This research study investigates the design of novel airframes with the aim of producing a
methodology that incorporates airframe noise. Studies investigating the design of Broad Deltas (BD),
Blended Wing Bodies (BWB), and Joined Wing airframe configurations are integrated with
innovative propulsion systems designs to identify key parameters in order to design a Silent Aircraft.
The airframe configuration plays an important role in the total aircraft noise, where the novel
airframes that are analysed, are compared to a datum ‘baseline’ aircraft. All novel configurations
show significant improvements in airframe noise reduction, enhanced by the addition of ultra-efficient
propulsion systems, for which integration studies are discussed. The research into novel airframes
uses a developed design methodology which integrates design considerations such as aerodynamics,
performance, and cost models to complement the noise analysis and identify the most silent airframe
configuration.
The research goal was to identify a silent airframe solution for a future viable short-medium range
airliner, where the final solutions described suggest proposals for the future development of aviation.
The proposals suggested describe a short-term solution to the noise challenge, with a longer-term
solution to aid the development of technologies, maturity in technology release levels (TRLs), and
development of a future 2050 medium capacity civil airliner
The impact of vertical wing placement on the wave drag and sonic-boom performance at supersonic speeds
No full textThis research project aims at obtaining a better understanding of vertically translating the wing and the related wing-body interference effects on the drag and sonic boom. Computational Fluid Dynamics (CFD) analysis using the Euler equations has been used to evaluate an airplane with different vertical wing placements at a lift coefficient of 0.15 at a Mach-number of 1.6 and also in zero-lift conditions. Pressure distributions, drag forces and pressure signatures have been calculated in order to assess the performance in terms of wave drag and sonic booms. These results have been analysed to find out why certain effects are happening for these configurations. The low wing configuration has the highest lift-to-drag ratio due to interference on the upper wing surface close to the fuselage. The lift-to-drag ratio for CL = 0.15 is found to be 4.79% higher compared to the worst performing configuration, the high wing configuration. Due to the local geometry of the low wing configuration it is possible to cre- ate additional suction on the upper wing surface, which positively affects the performance. Pressure signatures are extracted at 1 body-length distance (70푚) from the aircraft for several azimuth angles. These distributions show that the low wing configuration also has the lowest impulse and maximum overpressure. The higher wing configurations show an extra peak in overpressure emanating from the trailing end of the wing, which is created due to interference effects. Below the wing surface there is a large volume of the fuselage, while it is absent for the low wing configuration. Therefore the higher wing configurations show an extra peak in the pressure signature.Next to this discovery, an analysis is presented to relate the geometry of the configurations to the wave drag by assessing the cross-sectional area distribution using different intersection methods. These methods are compared with other methods found in the literature. Two methods which use a single Mach-cone have been analysed, as well as a method incorporating a forward and a backward pointed Mach-cone. One method translates a Mach-cone vertically to align the vertex of the Mach-cone with the centroid of the intersection with the aircraft. This gives an x,z-position which can be used to adjust the area distribution. The drag for the methods using a single Mach-cone was overestimated by a factor of 2, but after multiplying these results by a factor of / the results for the heigh-weighted Mach-cone method approached the wave drag results from CFD within 5%. The double Mach-cone method showed an even better agreement with less variation, while no multiplication factor was applied.A further analysis has taken place to find out why some methods that incorporate a single Mach- cone to evaluate the cross-sectional area to calculate the wave drag, overestimate the drag by a factor of 2. It is found that these methods do not overestimate the drag for a simple shape, such as a Sears- Haack body. The methods simply overestimate the cross-sectional area, which needs smoothing to obtain an area distribution that is suitable for drag calculation. The double Mach-cone method is a method that smoothens the area distribution, since the forward cone lowers the cross-sectional area in the front of an aircraft and adds cross-sectional area in the tail part of the aircraft.Further research is required to find out if these methods using a single Mach-cone can be applied to any geometry or not. Next to that it is recommended to research the sonic boom of other aircraft configurations with wings shifted further back to see if the sonic-boom from the tail can be reduced. Further research is necessary to see if the interference effects on the upper side of the wing of the low wing configuration are present in viscous flows. If the positive interference effects from this thesis are present in a viscous flow, this might see a reduction in fuel burn and maybe contribute to commercial supersonic flight becoming a reality again.Aerospace Engineerin
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