A liquid jet in a crossflow is often used to as a fuel injection method for combustion systems. Parameters such as penetration and core trajectory are used as characterization for the spray and specification of design criteria for combustor geometry. In addition to penetration and core trajectory, mapping the mass flux in space and time is an important part of modeling evaporation and global equivalence ratio throughout the combustor. Accurate prediction of these spray characteristics allows for a stable and robust combustor design. The break up of a liquid jet in a crossflow is an extremely complex phenomenon in both combination of mechanisms and variability of possible paths progressing from a liquid column to a distribution of individual droplets. In each region separate governing forces control the behavior of the liquid phase. Accordingly, different measurement techniques and different factors must be considered in each region. Presented are the results of measurements using Phase Doppler Analyzer, PDA, and a time resolved, digital, particle imaging velocimetry system, TRDPIV. The measurements include instantaneous and time-averaged liquid phase velocity fields, spray penetration and core location in the near field and far field of the spray resulting from the liquid jet breakup. With the TRDPIV system, the holistic properties of all three segments of a jet in crossflow were acquired with a single measurement. This allowed for comparison of system characteristics across not only individual pieces of one segment of the jet, for example PDA measurements of many droplets in one point of the far field spray, but characteristics across the entire system including the liquid column, near field spray, and far field spray simultaneously in a fashion that allowed for direct comparison between the different segments. / Master of Science

In the past 10 years there has been a significant amount of research into two-phase particle transport. The terrorist events of September 11, 2001 sparked a series of studies analyzing particle entrainment and deposition in turbulent airflows. One area of research needing further attention has been the study of particles entrained in axisymmetric air jets. An experimental rig was designed and built to study entrainment properties and deposition of Newtonian particles, after injection into a turbulent axisymmetric free air jet. Newtonian spherical particles, ranging from 1mm to 6mm in diameter, were injected into a turbulent airstream and blown through a nozzle into a large, open space. As the particles fell out of the jet stream, their linear distances, from nozzle to initial-ground-contact, were recorded and analyzed. The experiments conducted indicated particle size and density to be significant factors when considering Newtonian particle entrainment. Additionally, particle deposition distribution revealed a consistent positive skewness, as opposed to an expected Gaussian form. The data presented in this paper provide a starting point for understanding entrainment of Newtonian spherical particles in jets. The simple experimental rig geometry and results also provide an opportunity for computational fluid dynamics models to be validated, answering a call from the 2006 Annual Review of Fluid Mechanics. / Master of Science

En este estudio se han construido dos diferentes instalaciones para investigar primero los chorros de gas horizontales y en segundo lugar los chorros verticales de agua que impactan sobre superficies libres de fluido, también se ha desarrollado un modelo numérico integral para predecir las trayectorias de estos jets y sus parámetros más importantes, validándose con los resultados experimentales obtenidos. En la primera parte de este trabajo, se han realizado experimentos para investigar el comportamiento de chorros de gas horizontales penetrando en agua. Los resultados experimentales indicaron que la longitud de penetración de los chorros de gas está fuertemente influenciada por el diámetro de la boquilla y el número de Froude, así como con el flujo de masa de de entrada y su momento. Aumentar el número de Froude y el diámetro del inyector lleva a aumentar la inestabilidad de jet. Además, la máxima ubicación antes de jet pinch-off se muestra que mantiene una relación logarítmica con el número de Froude para todos los diámetros de jet. Se han desarrollado correlaciones empíricas para predecir estos parámetros. Se ha desarrollado un modelo basado en la integración de las ecuaciones de conservación para que resulte útil en el diseño de aplicaciones en las que participen chorros horizontales así como para asistir a la investigación experimental. Las predicciones del modelo integral se comparan con los datos de los datos experimentales obtenidos con muy buenos resultados. En la segunda parte de este trabajo, se realizaron una serie de experimentos con de chorros de agua, inyectados verticalmente hacia abajo, a través de toberas circulares que impactan sobre una superficie de agua. Los resultados obtenidos mostraron que la profundidad de penetración de la burbuja disminuye con la longitud del chorro, pero que después de ciertas condiciones se mantiene casi constante. Además ésta aumenta con los diámetros de la boquilla y la velocidad del chorro. La velocidad de arrastre / Harby Mohamed Abd Alaal, K. (2012). Experimental and Theoretical Study of the Characteristics of Submerged Horizontal Gas Jets and Vertical Plunging Water Jets in Water Ambient [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18065

Yes / Numerical simulations are carried out to investigate the spreading of two-dimensional plane turbulent aerated and nonaerated jets in a tank filled with finite water depth. A multiphase model is applied to simulate the problem under investigation. The governing equations, their numerical scheme and the boundary conditions are presented. Aerated and non-aerated turbulent jets are simulated for a range of the jet velocity and width at exit, the initial air content at exit and the water depth in tank. The simulated results show that a self-similar Gaussian velocity distribution exists from the distance downstream being larger than five jet slot width for both the aerated and nonaerated jets. Good agreement between the simulated velocity profiles and available laboratory experiments is obtained. The simulated slope of the jet velocity decay along the jet centreline is in good agreement with the experimental measurements. The effect of air content on pressure distribution and the maximum impinging hydrodynamic pressure at the tank bottom is discussed. / the Open Funding from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1302)

In a jet engine air and oil are mixed during removal from the bearing chamber. Before the oil can be recycled back into the system it must be separated from the air. This is accomplished through use of a de-aerator and breather. The oil air mixture enters the de-aerator first. The de-aerator is a vertical cylinder in which the air and oil enter from the top of the system. Gravity then pulls the oil down as it circulates along the outer wall of the de-aerator. The air is forced out through a top hole and sent to the breather where any oil droplets which remain are furthered separated. A pedestal is located near the bottom of the de-aerator. The pedestal creates a gap between itself and the de-aerator wall. Ideally this gap should be large enough to allow oil to flow through the gap without pooling on the pedestal, but small enough so that air does not flow through the gap. The oil will pool up on the pedestal and reduce the efficiency of the system. In this research, a 30° conical pedestal with a gap of 10.7% was tested. The results showed that the pedestal gap of 10.7% is too large and allows air to flow through the gap. The maximum water was 8.5% and the average water thickness was 5.11%. After studying both the previous experimental data and current CFD data, it is recommended further testing be conducted on pedestal gaps between 8.5% and 9.5%. / Master of Science / In jet engines, the turbine provides power and thrust to the aircraft by spinning at high speeds. This spin is created through the expansions of the hot gases leaving the combustion chamber. To prevent the degradation of turbine it spins on lubricated ball bearings. However, the oil which lubricates these ball bearings increases in temperature due to its proximity to the turbine. To prevent the oil from deteriorating it must be recycled from the ball bearings allowing the oil to cool. In process of recycling the oil, air is also pulled out of the system. Before the oil can be reinserted to the ball bearings it must first be separated from the air. This is accomplished in the de-aerator. In the de-aerator the oil and air mixture enter the side of a long cylinder. The oil flows down the side of this cylinder and out vents at the base. The air flows out vents at the top of the cylinder. Towards the base of the de-aerator is a pedestal, which creates a gap between itself and the wall. This gap should create a seal between the oil and the air, so that air does not flow through the gap and oil does not pool on top of the pedestal. Using CFD (Computational Fluid Dynamics), a software which simulates fluid flow, it was determined that pedestal gap should be between 8.5% and 9.5% of the radius of the de-aerator.

The purpose of this study is to numerically investigate the turbulence modulation of polydisperse particles in a square particle-laden jet. Turbulence modulation describes the effects of fluctuating velocity and intensity when the particles and continuous fluid interact in a turbulent flow field. The rate at which turbulence modulation is altered is dependent upon parameters such as particle size, mass loading, Stokes number, coupling, volume fraction and mechanisms of turbulence modulation. This study modifies the analytical model developed by Yarin and Hetsroni (1993) to account for the transitional drag regime for coarse polydisperse particles. The particles under study are dilute, inert and spherical, with relatively high Stokes numbers, and classified as having two-way coupling with the fluid. The new analytical model is compared to numerical results using the Computational Fluid Dynamics (CFD) software FLUENT (ANSYS, Inc.). The turbulence model employed is the standard k-ε model. This study will analyze the effects of varying mass content and particle ratios to investigate how turbulence modulation is influenced. The new model and the CFD results show good agreement in the cases where the mass contents of each particle size are equal. This study will also look into the effects of polydispersion, and the concentration distribution, for indoor air applications. It was found that, in certain cases, the monodisperse assumption slightly over-predicts the concentration distribution in the enclosed region. / Master of Science

No description available.

Recent developments in post-stall maneuverability and thrust vectoring have opened up new possibilities in the field of air combat maneuvering. High angle of attack maneuvers like the Cobra, Herbst Reversal, and Chakra demonstrate that today's cutting edge fighters are capable of exploiting the post-stall flight regime for very dynamic and unconventional maneuvers. With the development and testing of Unmanned Combat Aerial Vehicles, even greater maneuvering ability is expected. However, little work has been done to make use of this increased ability by optimizing a wide range of combat maneuvers. The goal of this thesis was to begin that process by finding several time-optimal air combat maneuvers that could be employed by current and future high performance fighter aircraft.

Pour améliorer les performances aérodynamiques notamment dans le domaine des transports (aéronautique, automobile, ..), le contrôle des écoulements constitue une solution de rupture prometteuse. Il présente à la fois un enjeu majeur pour l'industrie et un défi pour les scientifiques. Les retombées visées par le contrôle (notamment actif) sont d'ordre à la fois économique (réduction de la consommation) et environnemental (diminution des gaz à effet de serre). L'efficacité du contrôle est intimement liée à l'actionneur utilisé. Les actionneurs fluidiques et tout particulièrement le jet synthétique, semblent être une technique prometteuse de progrès. L'objectif de ce travail est le développement, la validation et la mise en œuvre de ce type d'actionneur. Nous avons ainsi conçu un actionneur de type jet synthétique basé sur un haut parleur. Les performances de cet actionneur ont été évaluées dans un milieu au repos en utilisant à la fois l'anémométrie à fil chaud et la PIV. Les effets des différents paramètres ont été analysés (fréquence, amplitude de forçage, …). Une attention particulière a été consacrée à l'étude de l'inclinaison de la fente d'éjection. Trois inclinaisons ont été utilisées (30°, 45° et 90°). Dans chaque cas l'évolution du jet synthétique ainsi que celle des tourbillons ont été caractérisées. Par les mêmes techniques de mesure dans une soufflerie, nous avons étudiés l'interaction du jet synthétique avec un écoulement transverse. Des visualisations par fumée du contrôle du décollement par cet actionneur montrent ses capacités à pouvoir recoller l'écoulement. / To improve the aerodynamic performance particularly in the field of transport (aerospace, automotive, ..), the flow control is a promising solution for rupture. It presents at the same time a major stake for industry and a challenge for the scientists. The fallout aimed by control (particularly active control) are of an at the same time economic (reduction of consumption) and environmental (decrease of greenhouse gases). The effectiveness of control is closely related to the actuator used. The fluidic actuators and particularly the synthetic jet appear to be a promising technique for progress. The objective of this work is the development, validation and implementation of this type of actuator. We thus designed an actuator of the synthetic jet type based on a loudspeaker. The performances of this actuator were estimated in a quiescent environment. Both hot wire anemometer and the Particle Image Velocimetry (PIV) are used. The effects of different parameters were analyzed (frequency, amplitude forcing, ...). Particular attention has been devoted to the study of the inclination of the ejection slot. Three angles were used (30 °, 45 ° and 90 °). In each case the development of synthetic jet and the vortices have been characterized. By the same techniques of measurement in a wind tunnel, we have studied the interaction of the synthetic jet with a transverse flow. Visualizations by smoke control detachment by the actuator to show his ability to pick up the flow.

In this thesis the jet energy scale uncertainty of small and large radius jets at the ATLAS detector is evaluated in-situ using gamma-jet events. The well calibrated photon in the gamma-jet events is used to probe the energy scale of the jets. The studies of the jet energy scale of small radius jets are performed using 4.7 fb^-1 of data collected at sqrt{s} = 7 TeV in 2011. The gamma-jet methods which were developed are then adapted and applied to large radius jets, using 20.3 fb^-1 of data collected at sqrt{s} = 8 TeV in 2012. The new jet energy scale uncertainties are found to be ~1 % for |eta| < 0.8, rising to 2-3 % for |eta| > 0.8. These uncertainties are significantly lower than the 3-6 % precision which has previously been achieved at ATLAS using track jets as a reference object. Due to the increase in precision, uncertainties due to pile-up and the topology of the jet also had to be evaluated. The total energy scale uncertainties for large radius jets are reduced by ~1-2 % (0.5-1 %) for |eta| < 0.8 (> 0.8). This reduction will be beneficial to analyses using large radius jets and it is specifically shown to benefit the t-tbar resonance search in the semi-leptonic channel. The t-tbar search looks for events with two top quarks in the final state, where one decays leptonically and the other hadronically. The hadronically decaying top quark is reconstructed using a large radius jet, and the jet energy scale uncertainty is a dominant source of uncertainty in the analysis. In addition to the studies of the jet energy scale of large radius jets, the first derivation of a calibration, and jet energy scale uncertainties derived with gamma-jet events, are shown for Variable R jets. The Variable R jet algorithm is a new type of jet algorithm with a radius that is inversely proportional to the size of the jet, making it useful for the study of high momentum top quarks. It is shown that similar methods can be used to calibrate and assess the uncertainties of Variable R jets as are used for standard, fixed radius jets at the ATLAS detector, although some adaptations will be necessary. The studies provide a basis for the calibration of Variable R jets in the future.