Hus byggs idag allt tätare för att möta högre miljökrav, ställda av både konsumenter och politiker. När hus byggs täta minskar luftläckaget genom klimatskalet. Tack vare det sänks energiåtgången då nästan all luft styrs genom en värmeväxlare. Tätheten i de nya husen har lett till att utsugande köksfläktar inte fungerar som de ska, beroende på att de behöver mycket luft. I detta projekt utvecklades ett utsugande köksfläktsystem för passivhus, de allra tätaste husen på marknaden. Resultatet blev en utsugande köksfläkt som hela tiden tillförs luft utifrån huset. Tilluften sugs in i huset med hjälp av det undertryck som köksfläkten skapar, luften sprutas in i kåpan och sugs sedan ut ihop med matoset. För att hålla nere energiförbrukningen användes en svag köksfläkt. För att hjälpa fläkten att fånga upp matoset är fläktkåpan utformad för att utnyttja ejektorverkan och coandaeffekten. Under projektet utvecklades även en värmeväxlare som tar tillvara på värmen i frånluften. / Today houses are built more airtight to meet higher environmental standards, initiated by both consumers and politicians. When houses are built airtight it reduces air leakage through the building, which gives reduced energy consumption since almost all air is guided throw a heat exchanger. Since the new houses are very airtight it has caused extractor hoods to work improperly, because they need a lot of air. In this project a extractor hood system has been developed for passive houses, which are the most airtight houses on the market. The result was an extractor hood which is constantly getting air from outside the house. The air from outside is sucked into the house because of the vacuum created by the extractor hood, the air is injected into the hood and then sucked out together with the cooking odors. In order to minimize the energy consumption a weak extractor fan was used. To help the fan capture the cooking fumes, the hood is designed to use ejector- and coandaeffect. During the project a heat exchanger was also developed, which transfer the heat from the cooking odors to the air from the outside.

This research programme explores, theoretically and experimentally, a new liftsystem for Vertical/Short Take-off and Landing (V/STOL) Aircraft. It is based upon an annular wing wrapped around a centrifugal flow generator, potentially creating a vehicle with no external moving parts, reduced vehicle aerodynamic losses compared to previous V/STOL technologies and substantially eliminating induced drag. It is shown that such a wing works best with a thick aerofoil section, and appears to offer greatest potential at a micro-aerial vehicle scale with regard to fundamental performance parameter “lift to weight ratio”. Certain efficiency losses are encountered mainly occurring from annular flow expansion and problems with achieving acceptable blower slot heights. Experimental methods are described along with results, and a comparison shows that the experimental values remain below theoretical values, partly due to flow asymmetry but possibly also other factors. Symmetrical blowing, as initially hypothesised, was found to be impracticable; this suggested use of pure upper surface blowing with Coanda effect. The modified approach was further explored and proved viable. The ultimate goal of this work was to develop an understanding and the facility to integrate the annular-wing into a vehicle to achieve controlled powered flight. To serve the purpose, issues encountered on current and past V/STOL aircraft are being investigated to set a path for further research/development and to validate/justify the design of future V/STOL aircraft. Also, presented is a feasibility study where different physical scales and propulsion systems are considered, and a turbofan has shown to achieve the best performance in terms of Range and Endurance. This privilege allows one to accurately study the V/STOL technologies around.

The ultimate objective of this research is to investigate the effectiveness of cathode gas (air) recirculation for the thermal management of a solid oxide fuel cell (SOFC) stack. SOFCs conventionally operate at high temperatures (>600o C); and recovering heat from stack exhaust is critical to improving the stack and system performance. Prevalent approaches implement bulky and expensive high temperature gas-to-gas heat exchangers. Also, ejectors are being investigated for recirculation of the air; however, an ejector with typically large velocity gradients would incur large viscous losses. An alternative recirculation approach is being developed for distributed entrainment via active flow control. The entrainment would allow recuperative thermal mixing to occur that may be more effective than the preceding two approaches. The ultimate goal of this research thrust is to reduce, or even exclude, the need of an air preheater in a SOFC system. The cathode air preheat contributes to a large portion of the cost of a SOFC system. Verifying and demonstrating the efficacy of the Coand and #259; effect has been the initial focus, and positive results have been demonstrated in a test environment from a fluid mechanics standpoint. This has been based upon three stages of experimental development, inclusive of cross-sectional area and activated blowing degrees-of-freedom. Seed thermal testing of the system has demonstrated legitimate thermal mixing capabilities. EES thermodynamic modeling developments confirm that the approach can reduce or even exclude the air preheat. It is concluded that recuperative thermal mixing with this recirculation approach is indeed feasible and has the potential to greatly reduce the cost and efficiency of the SOFC system.

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on May 20, 2010. Major professor: David Marshall, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Aerospace Engineering." "April 2010." Includes bibliographical references (p. 80-82).

A novel flame spray collar called the Coanda Assisted Spray Manipulation collar (CSM) has been tested for use on the Sulzer Metco 5P II combustion flame spray gun. A comparison study of the stock nozzle and the CSM has been performed by evaluating the porosity, surface roughness, microhardness, tensile strength and microscopy of normal and off-normal sprayed NiAl deposits. The use of the CSM collar resulted in the need to position the sprayed coupons closer to the gun, which in turn affected the particle impact energy and particle temperatures of the NiAl powder. For the CSM, porosities had a larger scatterband, surface roughness was comparably the same, microhardness was lower, and tensile strength was higher. The microscopy analysis revealed a greater presence of unmelted particles and steeper intersplat boundaries for the CSM. For both processes, the porosity and surface roughness increased and the microhardness decreased as the spray angle decreased.

An examination of parameters affecting the control of a jet vectoring technique used in the Coanda-assisted Spray Manipulation (CSM) is presented. The CSM makes use of an enhanced Coanda effect on axisymmetric geometries through the interaction of a high volume primary jet flowing through the center of a collar and a secondary high-momentum jet parallel to the first and adjacent to the convex collar. The control jet attaches to the convex wall and vectors according to known Coanda effect principles, entraining and vectoring the primary jet, resulting in controllable r-θ directional spraying. Several control slots (both annular and unique sizes) and expansion radii were tested over a range of momentum flux ratios to determine the effects of these variables on the vectored jet angle and profile. Two- and three-component Particle Image Velocimetry (PIV) was used to determine the vectoring angle and the profile of the primary jet in each experiment. The experiments show that the control slot and expansion radius, along with the momentum ratios of the two jets, predominantly affected the vectoring angle and profile of the primary jet. The Reynolds number range for the primary jet at the exit plane was between 20,000 and 80,000. The flow was in the incompressible Mach number range (Mach< 0.3).

Active pneumatic flow control methods as applied to aerospace applications have shown noteworthy improvements in lift compared to traditional means. The General Aviation Circulation Control (GACC) concept currently under investigation at NASA's Langley Research Center (LaRC) is an attempt at addressing some of the fundamental obstacles related to the successful development and implementation of such techniques. The primary focus of research in the field of high lift pneumatic devices is to investigate ways of obtaining significant improvements in the lift coefficient without resorting to moving surfaces. Though it has been demonstrated that the lift coefficient can be amplified in a variety of ways, the chosen method for the current work is via enhanced circulation stemming from a trailing edge Coanda jet. A secondary objective is to reduce the amount energy expenditure used in these pneumatic techniques by implementing time-variant flow. This paper describes experimental observations of the flow behavior at the trailing edge of a modified water tunnel based supercritical airfoil model that exploits both steady and pulsed Coanda driven circulation control. A total of 10 sets of data, excluding a baseline case of no Coanda jet, were sampled with five cases each for steady and pulsed flow, the latter at a reduced frequency, f+, of 1. Two cases of equal momentum coefficient but with varying forced frequencies were isolated for further study in an attempt to accurately compare the resultant flow dynamics of each method. All measurements were taken at a zero-lift angle of attack by means of a non-invasive time accurate flow visualization technique (DPIV). Vorticity behavior was investigated using Tecplot® and a MATLAB® program was developed to quantify the Strouhal Number of time-averaged velocity fluctuations moving aft of the Coanda surface for each case. / Master of Science

Notre travail de thèse présente une contribution à l'étude du comportement d'un jet flottant horizontal, représentatif de la dispersion de rejets dans un milieu marin. Il consiste à modéliser ce type d'écoulement par une approche mathématique basée sur la résolution numérique moyennant la méthode des volumes finis, à valider le modèle numérique par des mesures à échelle réduite sur des maquettes expérimentales, et, enfin, à simuler la dispersion de polluants à grande échelle sur un cas réel. Trois cas d’étude ont été abordés:Le premier cas est relatif à l’étude numérique et expérimentale d'un jet flottant turbulent rond et "non-Boussinesq", injecté horizontalement dans un milieu statique et homogène. Les résultats ont permis de décrire la nature du jet et son comportement en fonction des conditions initiales d’éjection. La deuxième étude a concerné un autre cas représentatif des rejets des émissaires de stations d'épuration. Il s’agit d’un jet pariétal admettant l’approximation de Boussinesq en régime de convection mixte. L’objectif ici est d’étudier l'influence de l'effet combiné de la turbulence et de la présence de la paroi sur le comportement du jet. Dans le dernier cas d’étude, on a modélisé, en 2D et en 3D, à grande échelle un processus côtier de dispersion de rejets en surface libre appliqué sur le cas de la pollution de la baie de Tanger. Les résultats ont permis de visualiser le mécanisme de la dispersion et d’avoir des informations précieuses sur l’écoulement généré au voisinage des plages par l’interaction des rejets et des mouvements de flux et de reflux de la marée. / This work is a contribution to the study of horizontal buoyant jet behavior that presents the dispersion of discharges into the marine environment. It consists in the modeling of this flow by a mathematical approach based on numerical simulation by means of the finite volume method, the validation of a numerical model by measurements on experimental model at a small, and, finally, the simulation of pollutant dispersion on a large scale on a real case. Three cases of study were broached: The first case relates to the experimental and numerical study of horizontal round turbulent non-Boussinesq buoyant jet in a static homogeneous environment. The results were used to describe the nature and the behavior of the jet as a function of the initial conditions of ejection. The second study involved another case of discharges from outfalls. We investigated a numerical and experimental study about a horizontal buoyant wall turbulent jet in a static homogeneous environment. The aim was to analyze the influence the effect of both turbulence and wall boundary on the behavior of the jet. The latter case of study focused on numerical simulation in 2D and 3D of the coastal process of discharges dispersion on a free surface. This modeling dealt more precisely with the dispersion of discharges into a marine environment in the presence of cross flows. The bay of Tangier in Morocco was chosen as an application site. The results made it possible to visualize the dispersion mechanism and to gain valuable information on the flow generated by the interaction of discharges and high/low tide movements near the beaches of the bay.

Les oscillateurs fluidiques qui peuvent générer des excitations périodiques sont des actionneurs très prometteurs pour des applications de contrôle actif des écoulements. Les oscillations sont en effet complètement auto-induites et produites en l'absence de parties mobiles ce qui rend ces actionneurs très intéressants en termes de fiabilité et de robustesse. Ce travail de thèse avait pour objectif principal d'identifier les mécanismes physiques qui contrôlent la dynamique de fonctionnement de ce type d'oscillateurs fluidiques et de proposer des lignes directrices pour la conception d'oscillateurs dont les performances soient adaptées aux applications de contrôle d'écoulements envisagées. L'analyse expérimentale de plusieurs prototypes couplée à des simulations numériques a permis de mettre en évidence que le mécanisme de basculement du jet dans ce type d'oscillateurs est contrôlé par les gradients de pression existants au niveau de deux parties critiques de ces actionneurs. A partir de cette analyse, une relation simple a été établie permettant d'estimer la fréquence des oscillations. Deux méthodes de synchronisation, permettant le contrôle du déphasage entre les actionneurs, ont été proposées et validées expérimentalement ainsi qu'à l'aide de simulations numériques. Une matrice de micro­ oscillateurs fluidiques a été conçue, fabriquée et finalement intégrée sur une rampe installée en soufflerie. L'analyse expérimentale de son efficacité pour le contrôle de l'écoulement séparé a mis en évidence un gain important par rapport aux résultats obtenus lors de travaux précédents sur des écoulements de paroi similaires à l'aide d'autres types d'actionneurs fluidiques. / Fluidic oscillators which can generate periodic excitations are very promising for active flow control applications, due to their reliability and robustness, as their internal flow oscillation is totally self-induced and self-sustained. The main objective of this work is to identify the underlying mechanisms controlling the dynamics of this kind of fluidic oscillator and to propose guiding lines for the design of oscillators. Experimental analysis of several oscillator prototypes and associated numerical simulations have permitted to explain that the jet switching in this kind of oscillator is controlled by pressure gradients in two critical parts of the device. From these analyses, a simple function has been proposed to estimate the oscillation frequency. Two synchronization methods, allowing the control of the phase lag between the actuators, have been proposed and validated experimentally and by numerical simulations. An array of micro-fluidic oscillators has then been designed and tested on a ramp separated flow, showing much higher efficiency compared to other kind of fluidic actuators tested on similar wall flows in previous studies.

L'influence des propriétés de surfaces sur un écoulement liquide microscopique au voisinage d'une paroi a été mise en évidence au cours des dernières années. On entend ici par propriétés de surface l'affinité des solides avec les liquides mis en œuvre, caractérisée par l'angle de mouillage formé par une goutte liquide déposée sur la paroi solide. L'usage de surfaces superhydrophobes a permis notamment d'observer un glissement important du liquide sur la paroi solide pour des écoulements de microfluidique. On peut se demander si les propriétés de mouillage ont également une influence dans des situations hydrodynamiques de plus grande échelle, et c'est à cette problématique que l'on tente d'apporter des réponses dans cette thèse.<br>Dans un premier temps, des mesures de forces réalisées sur des solides immergés dans un écoulement montrent que l'application d'un revêtement superhydrophobe ne permet pas d'obtenir la réduction radicale espérée de la traînée hydrodynamique. Par la suite, nous nous intéressons à des situations d'impact solide-liquide, mettant en œuvre des lignes de contact triples : impacts de sphères solides sur une interface liquide-gaz, puis impacts d'un jet liquide sur des impacteurs solides, conduisant à la formation de cloches liquides. Nous mettons en évidence et rationalisons dans ces deux cas le couplage fort qui relie les propriétés des surfaces à l'hydrodynamique macroscopique.