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High-Speed Railway (HSR) technology requires the deployment of noise barriers to mitigate noise pollution affecting nearby residents. As train speeds increase, so does the magnitude of aerodynamic effects such as aerodynamic noise and the pressure on these barriers, meaning that these structures require robust sound insulation and structural load-bearing capacities. Train-induced aerodynamic loads must therefore be accounted for in the structural design of HSR noise barriers, and accurate characterization of these loads is vital for ensuring noise barrier performance and safety. Current European standards primarily evaluate aerodynamic loads on noise barriers based on train speed and the distance to the track centre. However, geometric differences between high-speed trains (HSTs) from different countries and regions necessitate the validation and potential revision of existing load calculation models. This thesis aims to enhance the characterization of train-induced aerodynamic pressure on HSR noise barriers and develop more accurate models for its calculation, focusing on the most common barrier type—vertical noise barriers. Initially, a thorough literature review was conducted to assimilate current knowledge on this topic and pinpoint existing gaps and challenges. Multiple factors including the geometric properties of trains and the heights of noise barriers were then analysed using computational fluid dynamics (CFD) simulations to evaluate their impact on the train-induced aerodynamic pressure on vertical noise barriers. Finally, the suitability of existing pressure calculation models was evaluated using literature data and a modified calculation model building on the EN 14067-4 model was developed.  A key finding is that the general applicability of existing pressure calculation models is limited because of the wide variation in HST geometries and noise barrier heights. The amplitude of train-induced aerodynamic pressure on vertical noise barriers increases with train height and width but decreases as nose length increases. While taller noise barriers experience greater aerodynamic pressures, the in-crease in pressure with barrier height is not significant. The proposed modified pressure calculation model that accounts for train geometry and the height distribution coefficient predicts the train-induced aerodynamic pressure on vertical noise barriers more accurately than existing models and could thus improve the structural design and safety of HSR noise barriers across a wide range of conditions.

Ducted fan vehicles possess a superior ability to maximize payload capacity while minimizing vehicle size. Their ability to both hover and fly at high speed is a key advantage for information-gathering missions, particularly when close proximity to a target is essential. However, the ducted fan's aerodynamic characteristics pose difficulties for stable vehicle flight and therefore require complex control algorithms. In particular, they exhibit a large nose-up pitching moment during wind gusts and when transitioning from hover to forward flight. Understanding ducted fan aerodynamic behavior and how it can be altered through flow control techniques are the two prime objectives of this work. This dissertation provides a new paradigm for modeling the ducted fan's nonlinear behavior and new methods for changing the duct aerodynamics using active flow control. Steady and piezoelectric synthetic jet blowing are employed in the flow control concepts and are compared. The new aerodynamic model captures the nonlinear characteristics of the force, moment, and power data for a ducted fan, while representing these terms in a set of simple equations. The model attains excellent agreement with current and legacy experimental data using twelve non-dimensional constants. Synthetic jet actuators (SJA) have potential for use in flow control applications in UAVs with limited size, weight, and power budgets. Piezoelectric SJAs for a ducted fan vehicle were developed through two rounds of experimental designs. The final SJA design attained peak jet velocities in the range of 225 ft/sec (69 m/s) for a 0.03â x 0.80â rectangular slot. To reduce the magnitude of the nose-up pitching moment in cross-winds, two flow control concepts were explored: flow separation control at the duct lip, and flow turning at the duct trailing edge using a CoandÄ surface. Both concepts were experimentally proven to be successful. Synthetic jets and steady jets were capable of modifying the ducted fan flow to reduce pitching moment, but some cases required high values of steady blowing to create significant responses. Triggering leading edge separation on the duct lip was one application where synthetic jets showed comparable performance to steady jets operating at a blowing coefficient an order of magnitude higher. / Ph. D.

The study of the flow of a fan blade was conducted to improve tonal fan noise reduction by optimizing an existing flow control configuration. The current configuration consisted of a trailing edge Slot with a flow control area of 0.045 in² per inch span with an exit angle of -3.3° with respect to the blade exit angle. Two other flow control configurations containing discrete jets were investigated. For the first configuration, the trailing edge jets (TEJ), the fan blade was modified with discrete jets spaced 0.3 inches apart with a flow control area of 0.01 in² per inch span positioned on the trailing edge aimed at -3.3° with respect to the blade exit angle. Similarly, discrete jets were also placed on the suction surface at 95.5% chord aimed at 15° with respect to the local blade surface. This configuration is referred to as the suction surface jet (SSJ). The discrete jets for both configurations were designed to be choked while injecting a mass flow rate of 1.00% of the fan through-flow. Computational Fluid Dynamics (CFD) was used to model new configurations and study subsequent changes in total pressure deficit using a blade design inlet Mach number of 0.73, Reynolds number based on chord length of 1.67 à 106, and design incidence angle of 0°. Experimental testing was later conducted in a 2D cascade tunnel. The TEJ and SSJ were tested at design blowing of 1.00% and at off-design conditions of 0.50%, 0.75%, and 1.25% fan through-flow. Results between the different flow control configurations were compared using a blowing coefficient. CFD showed the TEJ and SSJ offered aerodynamic improvement over the Slot configuration. Testing showed the SSJ outperformed the TEJ, as validated in CFD, producing wider and shallower wakes. SSJ area-averaged pressure losses were 25% less than TEJ at design. Noise predictions based on CFD findings showed that both TEJ and SSJ provided additional tonal sound power level attenuation over the Slot configuration at similar blowing coefficients, with the SSJ providing the most attenuation. Noise prediction based on experimental results concurred that the SSJ provided more total attenuation than the TEJ. Experimental results showed that the SSJ performed better aerodynamically and, based on analytical prediction, provided 2 dB more total attenuation than the TEJ. / Master of Science

<p dir="ltr">This article-based research traces the evolution and advancements of vehicular aerodynamic concepts and emphasizes on the significance of vehicle aerodynamics for high-performance vehicles. The thesis further explores the scope of integrating advanced vehicle aerodynamic concepts into consumer vehicles. The thesis aims to point out the significant improvements achieved with the integration of active aerodynamic concepts in terms of both vehicle performance as well as efficiency figures for consumer vehicles. Additionally, exploring the scope for the development of these advanced active aerodynamic systems as third-party modifications is the secondary objective of the presented research. The thesis also highlights the development and integration of unique active aerodynamic systems featured in performance vehicles and analyzes the performance gains achieved using MATLAB program-based simulations supported by a graphical representation of analyzed output data. The study of Active aerodynamic systems for both performance/track-oriented and consumer vehicles remains to be the primary emphasis for the presented thesis.</p>

<p dir="ltr">This work seeks to study a novel, actively cooled aerodynamic probe nacelle with integrated optics to enable short focal length laser diagnostics in high-temperature supersonic flows, especially relevant for Hot Jet wind tunnels. The nacelle has been designed to: i.) survive the thermal loads generated at Mach 6 and total conditions of 1700 K, 44 bar, and ii.) minimize the flow disturbance generated by the front bow shock. By enabling measurements at shorter focal lengths, higher irradiance is achieved at the focal point for the same laser power.</p><p dir="ltr">The thermal survivability of the nacelle is studied first via a 1D conjugate heat transfer model including effusion cooling effects. The coolant pressure predicted by the model is used as boundary condition in 3D Steady RANS numerical simulations, where spatially resolved cooling effectiveness contours are extracted. Flow distortion is also studied from the numerical simulations. Modelling accurately the effusion holes allows to study the coolant jets-bow shock interaction and its effect on the shape of the shock. The distance between the focusing lens and the bow shock is studied and compared to the focal length achieved if the optics were placed outside the facility. The shift in laser trajectory due to refractive index gradients across the flow is predicted using ray propagation models.</p><p dir="ltr">The cooling jacket of the nacelle is tested experimentally in an Open Jet wind tunnel at low supersonic (Mach~1.1), long duration, heated conditions. “In-situ” calibrated infrared thermography is used to obtain temperature and cooling effectiveness contours in the front faces and Atomic Layer Thermopiles (ALTPs) are used to measure heat flux and adiabatic heat transfer coefficient, enabling validation of the numerical models. High-frequency accelerometer data and Camera-Based vibrations data are collected to identify vibration frequencies and peak to peak amplitudes in the nacelle, allowing to correlate them with the momentum of the Open Jet and study their impact on the location of the focal point.</p>

This thesis is based around examination of three mainstream inhaled drugs Formoterol, Budesonide and Beclomethasone for treatment of asthma and COPD. The areas investigated are these which have been raised in reports and studies, where there are concern, for drug use and assessment of their use. In reporting this work the literature study sets out a brief summary of the background and anatomy and physiology of the respiratory system and then discuses the mechanism of drug deposition in the lung, as well as the methods of studying deposition and pulmonary delivery devices. This section includes the basis of asthma and COPD and its treatment. In addition, a short section is presented on the role of the pharmacist in improving asthma and COPD patient's care. Therefore the thesis is divided into 3 parts based around formoterol, budesonide and beclomethasone. In the first case the research determines the in-vitro performance of formoterol and budesonide in combination therapy. In the initial stage a new rapid, robust and sensitive HPLC method was developed and validated for the simultaneous assay of formoterol and the two epimers of budesonide which are pharmacologically active. In the second section, the purpose was to evaluate the aerodynamic characteristics for a combination of formoterol and the two epimers of budesonide at inhalation flow rates of 28.3 and 60 L/min. The aerodynamic characteristics of the emitted dose were measured by an Anderson cascade impactor (ACI) and the next generation cascade impactor (NGI). In all aerodynamic characterisations, the differences between flow rates 28.3 and 60 were statistically significant in formoterol, budesonide R and budesonide S, while the differences between ACI and NGI at 60 were not statistically significant. Spacers are commonly used especially for paediatric and elderly patients. However, there is considerable discussion about their use and operation. In addition, the introduction of the HFAs propellants has led to many changes in the drug formulation characteristics. The purpose of the last section is to examine t h e performance of different types of spacers with different beclomethasone pMDIs. Also, it was to examine the hypothesis of whether the result of a specific spacer with a given drug/ brand name can be extrapolated to other pMDIs or brand names for the same drug. The results show that there are different effects on aerodynamic characterisation and there are significant differences in the amount of drug available for inhalation when different spacers are used as inhalation aids. Thus, the study shows that the result from experiments with a combination of a spacer and a device cannot be extrapolated to other combination.

<p>The energy exchange in the soil-snow-vegetation-atmospheresystem was studied to improve the quantitative knowledge of thegoverning processes. The lack of such knowledge contributes tothe uncertainty in the applicability of many existing modelsindependent of the temporal or spatial scale. The theoreticalbackground and available methods for measurements and numericalsimulations were reviewed. Numerical simulation models andavailable data sets representing open land and boreal forestwere evaluated in both diurnal and seasonal time-scales.Surface heat fluxes, snow depth, soil temperatures andmeteorological conditions were measured at an agriculturalfield in central Sweden over two winters, 1997-1999. Twoone-dimensional simulation models of different complexity wereused to simulate the heat and water transfer in thesoil-snow-atmosphere system and compared with the measurements.Comparison of simulated and observed heat fluxes showed thatparameter values governing the upper boundary condition weremore important than the formulation of the internal mass andheat balance of the snow cover. The models were useful toevaluate the lack of energy balance closure in the observedsurface heat fluxes, which underlined the importance ofimproved accuracy in eddy correlation measurements of latentflow during winter conditions.</p><p>The representation of boreal forest in the land surfacescheme used within a weather forecast model was tested with athree-year data set from the NOPEX forest site in centralSweden. The formulation with separate energy balances forvegetation and the soil/snow beneath tree cover improvedsimulation of the seasonal and diurnal variations of latent andsensible heat flux compared with an older model version.Further improvements of simulated surface heat fluxes could beexpected if the variation of vegetation properties within andbetween years and a new formulation of the boundary conditionsfor heat flux into the soil is included.</p><p><strong>Keywords</strong>: Surface energy balance, Snow, Boreal forest,SVAT models, Eddy-correlation Measurements, Latent heat flux,Sensible heat flux, Net radiation, Soil temperature,Aerodynamic roughness, Surface resistance</p> / QC 20100614

L’étude effectuée au cours de cette thèse a permis de caractériser numériquement les instabilités d’origine aérodynamique rencontrées dans un compresseur centrifuge dessiné par Turbomeca. Ce compresseur est composé d’une roue directrice d’entrée, d’un rouet centrifuge, d’un diffuseur radial et de redresseurs axiaux. Le module expérimental, dénommé Turbocel, sera accueilli au LMFA courant 2016. Le contenu de cette étude repose donc exclusivement sur des résultats numériques dont certains sont cependant comparés à des résultats expérimentaux partiels obtenus par Turbomeca sur une configuration proche. _ Le fonctionnement du compresseur est analysé à différentes vitesses de rotation, à partir de simulations RANS et URANS menées avec le code elsA. Du point de vue de la méthodologie, deux points importants sont à retenir :- Du fait du caractère transsonique de l’écoulement dans le rouet et le diffuseur radial à haut régime de rotation, les simulations RANS stationnaires ne permettent pas d’accéder à une description satisfaisante des phénomènes physiques. Cela est dû à l’utilisation d’un plan de mélange aux différentes interfaces rotor-stator qui a pour effet d’empêcher les ondes de choc de remonter à l’amont, et qui affecte tant la physique de l’écoulement que l’étendue de la plage de fonctionnement stable.- En-dessous d’un certain débit, les calculs URANS sur période machine révèlent que le comportement de l’étage n’obéit plus à la périodicité spatio-temporelle mono-canal. Une plage instable est alors obtenue à toutes les iso-vitesses simulées. A bas régime de rotation, une autre plage stable existe lorsque le compresseur est suffisamment vanné. L’étage retrouve alors une périodicité spatio-temporelle, à condition d’étendre le domaine de calcul dans le stator à deux canaux inter-aubes. En ce qui concerne les limites de stabilité de Turbocel, différentes évolutions sont décrites selon la vitesse de rotation considérée :- A haut régime de rotation, une basse fréquence commence à émerger près du point de rendement maximal et son intensité ne fait qu’augmenter jusqu.au pompage.- A bas régime, une signature basse fréquence comparable se manifeste près du point de rendement maximal mais disparaît passé un certain vannage, et n’est donc présente que sur une plage de débit délimitée. La seconde zone stable peut alors être numériquement parcourue jusqu.au pompage proprement dit. La signature basse fréquence est imputée à l’instauration d’une recirculation dans l’inducteur qui une fois établie est quasi-stationnaire. Les résultats numériques mettent en évidence que la source d’instabilité sévère sur Turbocel provient du diffuseur aubé. En fonction du point de fonctionnement, ce composant adopte des comportements différents, entre lesquels une certaine continuité existe, et ses performances chutent progressivement lorsque le débit diminue. Au final, les domaines de stabilité de l’étage de compression peuvent être reliés au type d’écoulement qui se développe dans le diffuseur radial, et apparaissent dictés par le diffuseur semi-lisse à haut régime de rotation. Enfin, afin d’étendre les plages de fonctionnement stable, une stratégie de contrôle basée sur l’aspiration de couche limite dans le diffuseur aubé a également été déterminée dans le cadre de cette thèse. Son évaluation fera l’objet d’études ultérieures sur Turbocel. / The present study aims at characterizing the aerodynamic instabilities involved in a centrifugal compressor designed by Turbomeca, by means of numerical simulation. This compressor is composed of inlet guide vanes, a centrifugal impeller, a radial vaned diffuser and axial outlet guide vanes. The test module, named Turbocel, will be delivered to the LMFA in 2016. Thus, the results presented in this manuscript are only based on CFD, although some of them are compared to experimental results obtained by Turbomeca on a close configuration.RANS and URANS simulations are performed for several rotational speeds, using the elsA software.Two methodological key points are to be emphasized:- As the flow in both the impeller and the radial diffuser is transonic at high rotational speed, steady RANS simulations cannot provide a satisfactory description of the physical phenomena taking place. This can be explained by the use of the mixing plane approach which prevents shock waves to extend upstream the rotor-stator interfaces, and which impacts the flow field predicted as well as the prediction of the stable operating range.- Below a given massflow rate, URANS simulations covering the spatial period of the compressor prove that the stage behavior does not obey to the single passage spatio-temporal periodicity anymore. An unstable operating range then appears at all the simulated rotational speeds. At low rotational speed, another stable range is however obtained if the compressor is further throttled’ A new periodicity arises on this massflow range, provided that the stator domain is extended to two neighboring blade passages. Concerning the stability domains of Turbocel, different evolutions are obtained depending on the rotational speed:- At high rotational speed, a low frequency phenomenon starts to develop near the peak efficiency point and its intensity keeps increasing until surge happens.- At low rotational speed, a low frequency signature also appears near the peak efficiency point, but it then vanishes when the compressor is further throttled, so that only a restricted operating range exhibits this instability. It then gives rise to a second stable operating range which can be described numerically, ending with surge itself. The low frequency signature is attributed to the enhancement of a flow recirculation in the inducer which, once fully established, is quasi-steady. The numerical results underline that the source of severe instability in the compressor comes from the vaned diffuser. Depending on the operating point, this component can adopt different behaviors, between which a relative continuity exists, and its performances decrease when the massflow rate decresases. The overall stage performances prove that at high rotational speed, the global stability is driven by the semi-vaneless diffuser and depends on the flow developing in the radial diffuser. Finally, in order to extend the stable operating range of the compressor, a flow control strategy based on boundary layer suction has also been determined in the diffuser. Its impact on the performances of Turbocel will be deeply studied later on.