This thesis documents trailing edge blowing research performed to reduce rotor / stator interaction noise in turbofan engines. The existing technique of filling every velocity deficit requires a large amount of air and is therefore impractical. The purpose of this research is to investigate new blowing configurations in order to achieve noise reduction with lesser amounts of air. Using the new configurations air is not injected into every fan blade, but is instead varied circumferentially. For example, blowing air may be applied to alternating fan blades. This type of blowing configuration both reduces the amount of air used and changes the spectral shape of the tonal interaction noise. The original tones at the blade passing frequency and its harmonics are reduced and new tones are introduced between them. This change in the tonal spectral shape increases the performance of acoustic liners used in conjunction with trailing edge blowing. This thesis presents numerical predictions performed to estimate the sound power reductions due to these concepts, as well as experimental results taken on the ANCF rig at NASA Glenn for validation purposes. The results show that the new concepts are successful in increasing the efficiency of trailing edge blowing. / Master of Science

The adaptation to a new country is a complex and stressful process that is compounded when changes in status and identity have to be made. This exploratory study examined the adaptation of international company transferee spouses when they decide to follow the transferee on overseas assignments. Research to date indicates that the spouses’ dissatisfaction with life abroad is the leading cause of transferees breaking contract and prematurely returning home. The causes of this dissatisfaction are still not clear and this study sought greater clarification, particularly examining the experiences of male as well as female trailing spouses. The study, thus, takes gender as a main variable to consider. It explores how gendered expectations inherent in the structures of society inflect and inform the decisions, attitudes, and behaviors that affect the adaptations of trailing spouses living in a foreign habitus. The study is based on eight months of ethnographic research in two culturally different locations, Kuala Lumpur, Malaysia and Brussels, Belgium. Forty-two American international company transferee spouses were recruited (seven males and thirty-five females). The data analysis revolved around five main themes: (1) the comparison of male with female trailing spouses’ experiences, (2) the effect of location on spouses’ adaptation, (3) the communities that spouses integrate into, (4) variations in personal work and family histories, and (5) conditions of exit. The analysis engaged multiple theories regarding gender, sociological adaptation, and psychological adaptation. Results indicate that both socio-cultural and psychological factors affect adaptation and that gender matters very significantly, particularly along two axes: (1) gendered structures in our society create different reasons why males and females become trailing spouses, (2) the gendered social constructions of role expectations make the experience of being a trailing husband different from being a trailing wife. In addition spouses’ status as parents (or not) and their “readiness for change” were found to be important predictors of positive spousal adaptation. In contrast, significant ties with families in the home country and strong professional identity with career projections were important predictors of negative spousal adaptation.

The design, implementation, management and the evaluation of sound conservation practices, is often dependent on the availability of reliable estimates of animal abundance. Large carnivores often pose particular problems in this regard, due to their low densities and wide-ranging behaviour, so the true abundance of such species are seldom able to be reported in literature . As a result, the use of indices of abundance, mostly for relative abundance, has been investigated. However, before these indices can be reliably utilized for conservation purposes , there is a pressing need to calibrate them. As of yet, calibration studies have primarily been performed on demarcated conservation areas, where individuals could be individually identified. Not all these calibrations studies reported indices to be a function of true density. Nevertheless , spoor frequency has been reported to be a function of true density for carnivores in certain Parks in Namibia . Precisely , cheetah spoor density was reported to correlate with visuals in the Kgalagadi Transfrontier Park. The majority of these studies elucidate a species spatial organization, animal behaviour, as the paramount factor determining the relationship between densities estimated via different censusing methods. Thus, the efficiency of spoor frequency to estimate and monitor relative abundance for wild cheetahs is yet to be empirically tested . Despite the lack of a true density estimate for the free-ranging cheetahs in the study area, evaluated spoor tracking as a possible index to monitor relative cheetah abundance using radiotelemetry densities estimates as representative of true abundance for the area, for the 1995 to 2000 period. The study is considered to be opportunistic , and a pillar for future research, as transects where spoor tracking was conducted were layout primarily for ungulates strip counts. Least-linear regression and Spearman's correlation were used to evaluate the relationship between density estimates derived by the two methods. Percentages of change on annual densities were also regressed as a mean to test spoor frequency sensitivity to density changes. The calibration of spoor frequency with estimates of density produced using radio-telemetry, without the ascription of imprints to individual animals, was poor (rs=17.4, y=0.36+0.20). The sensitivity analysis also showed spoor tracking poor reliability to monitor cheetah population. This can be attributed, in order of importance, to the discrepancies on the spatial extent sampled by the two methods, the species large home ranges, substrate quality , habitat preferences, the availability of farm road networks and the transect design, i.e., cyclic. However, the paramount factor limiting the study conclusions was the lack of a more local density estimate at a farm level. Therefore, the use of spoor frequency to estimate wild cheetah relative abundance requires further research, particularly using a different sampling design, longer straight transects and the acquisition of local densities estimates. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

A wind tunnel based investigation into the effects of unsteady yaw angles on the aerodynamics of a simple automotive body has been carried out to increase the understanding of the effects of unsteady onset conditions similar to those experienced in normal driving conditions. Detailed flow field measurements have been made using surface pressure tappings and PIV around a simple automotive model in steady state conditions and these have been compared to measurements made whilst the model was oscillating in the yaw plane. The oscillating motion was created by a motored crank which was used to produce consistent and repeated motion which produced a reduced frequency that indicated that a quasi-static response should be expected. The PIV data are used to compare the wake flow structures and the surface pressures are used to infer aerodynamic loads and investigate the development of the flow structures across the surfaces of the model. This includes a comprehensive comparison of the surface pressures on the sides of the model during a transient and quasi-static yaw angel oscillation. These results show differences between the two test conditions with the oscillating model results containing hysteresis and the greatest differences in the flow field occurring on the leeside of the model. Two configurations of the same model with different rear pillar geometries were used to isolate model specific effects. Square rear pillars create strong and stable trailing vortices which are less affected by the model motion whereas radiused rear pillars created weaker and less steady vortices that mixed with the quasi-2D wake behind the model base and were affected to a greater extent by the model motion. The unsteadiness in the trailing vortex separation feeds upstream into the A-pillar vortex demonstrating that small geometry changes at the rear can affect the entire flow field around the model.

In modern gas turbine engines, film cooling is extensively used to cool the components exposed to the hot mainstream gas path. In implementing film cooling on modern gas turbine engines, the trailing edge film poses a particularly challenging design problem. From an aerodynamic point of view, the trailing edge of a blade is designed to be as thin as possible. However, this conflicts with the implementation of the cooling design. The most common method of film cooling the trailing edge is via late pressure surface discrete film cooling holes. Another method of cooling the trailing edge is by using discrete pressure surface slots. This thesis documents a comparative aerodynamic and heat transfer study of three trailing edge cooling configurations. The study was carried out using a large scale, low speed wind tunnel situated at the Southwell Laboratory. The three trailing edge cooling configurations considered were as follows. First is the common late pressure film cooling of the trailing edge via discrete film cooling holes. This configuration is designated as datum configuration. Second is the pressure surface slot coolant ejection. This configuration was designated as cast cutback configuration. The third is the pressure surface ejection via discrete film cooling holes within a step cutback. This configuration was designated the machined cutback configuration. The above configurations were incorporated into three flat plates manufactured using stereolithography. In the aerodynamic study, the static pressure distribution and discharge coefficient for the three configurations were compared. Furthermore, two dimensional total pressure measurements were carried out using a traverse mechanism downstream of the test plates. The total pressure measurements were used to compute the mixed out losses for the three configurations. It was found that the datum and machined cutback configurations have similar discharge coefficients and mixed out losses whilst the cast cutback configuration produces greater mixed out loss. The film effectiveness and heat transfer coefficient on the pressure surface downstream of the coolant ejection was obtained using a steady state heat transfer technique. The effectiveness measurements were compared with those from the literature and correlated against the two dimensional slot model. The heat transfer measurements show that the cast cutback configuration has the potential to give higher effectiveness at the trailing edge.

In this thesis we explore several topics with applications to both aero and hydroacoustics. Due to the much larger speed of sound in water compared to in air, several of the approximations used in aeroacoustics are not applicable underwater over the range of frequencies of interest. Specifically, we study the finite-chord effects on two broadband noise mechanisms: the trailing edge noise and the ingested noise problems. We start by investigating the acoustic wave diffraction by a finite rigid plate using three different methods. We compare the behaviour of the different solutions as a function of the reduced acoustic wavenumber. Our results reveal that the Mathieu function expansion is the most appropriate method as long as the reduced acoustic wavenumber is not too large. Finally, we show how the Mathieu functions can be used to build a Green's function tailored to an elliptic cylinder of arbitrary aspect ratio without relying on addition theorems. The results obtained in chapter two motivated the search for an exact solution to the trailing edge noise problem using a Mathieu function expansion. It is shown that the approximate methods used in aeroacoustics are not accurate enough for reduced acoustic wavenumbers less than unity, and for all wavenumbers near cut-off. Furthermore it is shown that, even at low Mach numbers, it is crucial to take into account the effects of convection at low frequency. Finally Lighthill's analogy is used, combined with the tailored Green's function introduced previously, to recover the two asymptotic Mach number scalings of the acoustic power for a flat plate at high frequency and low frequency. In chapter four, we introduce a novel method to solve the ingested noise problem by decomposing the pressure field into a singular part whose functional form can easily be found, and a regular part that we express using a Mathieu function expansion. It was found that finite-chord effects do have a strong impact for reduced acoustic wavenumbers less than unity, and for all wavenumbers near cut-off. The following chapter focuses on the trailing edge noise mechanism and details how the theory for a single stationary aerofoil can be applied to a rotating propeller. Due to the general geometry of a blade, we extended Amiet's model to take into account a mean flow misaligned with the blade chordline. Different semi-analytical models of wall pressure spectra are introduced and compared. We make extensive use of Brooks' data for a NACA 0012 aerofoil to obtain realistic inputs in the semi-analytical models. Finally, we introduce and compare two models of rotating blade trailing edge noise. The effects of both the angle of attack and the number of strips are then investigated. The final chapter is distinct from the rest of the thesis. We propose a model for studying the low Mach number flow noise from a 2D circular cylinder with small roughness. The method is based on using the Green's function tailored to a smooth cylinder in Curle's acoustic analogy. It was found that the main source of noise was the tonal low frequency scattering by the smooth geometry. However, it is suggested that roughness elements might be the dominant source of noise at higher frequency.

Rotary wing aircrafts in any flight conditions suffer from excessive vibration which makes the passengers feel uncomfortable and causes fatigue failure in the structure. The main sources of vibration are the rotor harmonic airloads which originate primarily from the rapid variation of flow around the blade due to the vortex wake. In this thesis, a mathematical model is developed for rotor blades to compute the harmonic airloads at rotor blades for two flight conditions vertical takeoff and landing, and forward flight. The sectional lift, drag, and pitching moment are computed at a radial blade station for both flight conditions. The lift at a particular radial station is computed considering trailing and shed vortices and summing over each blade. The results for airloads are obtained after considering zeroth, first, and second harmonics. The calculated results for airloads are compared to the experimental flight-test data.

The dropped objects are identified as one of the top ten causes of fatalities and serious injuries in the oil and gas industry. It is of importance to understand dynamics of dropped objects under water in order to accurately predict the motion of dropped objects and protect the underwater structures and facilities from being damaged. In this thesis, we study nondimensionalization of dynamic equations of dropped cylindrical objects. Nondimensionalization helps to reduce the number of free parameters, identify the relative size of effects of parameters, and gain a deeper insight of the essential nature of dynamics of dropped cylindrical objects under water. The resulting simulations of dimensionless trajectory confirms that drop angle, trailing edge and drag coefficient have the significant effects on dynamics of trajectories and landing location of dropped cylindrical objects under water.

This thesis will describe the works had been done by the author in the Flying Crane aircraft group design project and the new design of a novel swing arm mechanism which can be applied in the trailing edge high lift devices for this aircraft concept. Flying Crane aircraft is a new generation commercial airliner concept as the result of group design project conducted by China Aviation Industry Corporation I (AVIC I) and Cranfield University. At the end of the group design project, parameters such as take-off and landing distance, trailing edge flap type and deflection in take-off and landing configuration of the Flying Crane concept have been determined. These parameters are design input of the novel trailing edge high lift device mechanism for this aircraft concept. The idea of this innovative mechanism comes from the research achievement of a previous MSc student, Thomas Baxter, which applied swing arm mechanism into a passenger aircraft's leading edge slat. This thesis applied this idea to trailing edge flap and modeled the mechanism on CATIA software to yield a kinematic simulation for the purpose of check motion trail and force transfer in this mechanism. Relevant works such as actuation, mass and stress analysis are also involved. As the result of this research project, it was found that swing arm mechanism trends to require relatively small fairings for supports and attachments due to its high stowed space utilizing efficiency. Initial mass estimation carried out in this thesis also indicates that the new design takes advantage in terms of weight comparing with traditional trailing edge flap mechanisms. Thus. swing arm mechanism is supposed to show great competitive potential for commercial airliner's trailing edge flaps after further analysis has been done in the detail design phase.

Alleviating loads on a wind turbine blades would allow a reduction in weight, and potentially increase the size and lifespan of rotors. Trailing edge flaps are one technology proposed for changing the aerodynamic characteristics of a blade in order to limit the transformation of freestream wind fluctuations into load fluctuations within the blade structure. An instrumented wind turbine test rig and rotor were developed to enable a wide-range of experimental set-ups for such investigations. The capability of the developed system was demonstrated through a study of the effect of stationary trailing edge flaps on blade load and performance. The investigation focused on measuring the changes in flapwise bending moment and power production for various trailing edge flap parameters. The blade was designed to allow accurate instrumentation and customizable settings, with a design point within the range of wind velocities in a large open jet test facility. The wind facility was an open circuit wind tunnel with a maximum velocity of 11m/s in the test area. The load changes within the blade structure for different wind speeds were measured using strain gauges as a function of flap length, location and deflection angle. The blade was based on the S833 airfoil and is 1.7 meters long, had a constant 178mm chord and a 6o pitch. The aerodynamic parts were 3D printed using plastic PC-ABS material. The total loading on the blade showed higher reduction when the flap was placed further away from the hub and when the flap angle (pitching towards suction side) was higher. The relationship between the load reduction and deflection angle was roughly linear as expected from theory. The effect on moment was greater than power production with a reduction in moment up to 30% for the maximum deflection angle compared to 6.5% reduction in power for the same angle. Overall, the experimental setup proved to be effective in measuring small changes in flapwise bending moment within the wind turbine blade.