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Nyberg, Ludwig. "Thrust Allocation for Jet Driven Surface Vessels." Thesis, KTH, Mekatronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-271905.
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Dynamic positioning systems have been under development since the first implementation in the early 1960s. The purpose of a dynamic position system is to allow for automatic positioning of a vessel when circumstances do not allow for mooring or anchoring. Historically the development has been driven forward by the offshore industry, while in recent years such systems have been found useful in other parts of the maritime industry as well. However, very few options exist today for jet driven vessels. One of the main parts of a dynamic positioning system is the control allocation. The purpose of this part is to allocate desired actuation to available actuators. It is often desirable to do this while considering a secondary objective, often energy consumption. One allocation algorithm option is direct allocation, which is considered to be quite a basic solution. More advanced options exist in the literature but implementations of them are still uncommon. An example of a more advanced option, allowing for better tuning, is using model-based allocators. Formulating the allocation problem as a linear quadratic problem and using a linear quadratic regulator is one viable option that has been proven to work well for non-jet driven vessels. A general vessel model is developed and used for simulating and testing different allocators. Furthermore, a method for transforming the allocated actuation into parameters that can control the jet engine is also proposed. This is a necessary step in order to be able to implement the allocation onto a vessel. Comparing the allocation options based on step responses with and without disturbances shows that the linear quadratic regulator preforms better than the direct allocator in almost every way. However, the main drawback of model-based controllers is the needed knowledge about the system. This is something that is not required for the direct allocator and is worth taking into account.<br>Dynamiska positioneringssystem har vart under utveckling sedan den första implementeringen i början av 1960-talet. Syftet med ett dynamiskt positioneringssystem är att möjliggöra automatisk positionering av ett fartyg när omständigheterna inte tillåter förtöjning eller förankring. Historiskt har utvecklingen drivits framåt av behovet inom offshoreindustrin, men under senare år har systemen visat sig vara användbara även i andra delar av den marina industrin. Idag finns dock få alternativ anpassade för jetdrivna fartyg. En av huvuddelarna i ett dynamiskt positioneringssystem är kraftallokering. Syftet med denna del är att fördela önskad styrkraft till tillgängliga ställdon. Ofta är det önskvärt att göra detta samtidigt som ett sekundärt mål tas hänsyn till, vanligtvis energiförbrukning. Ett alternativ för kraftallokering är en direkt allokeringsalgoritm, detta är en ganska enkel algoritm. Mer avancerade alternativ finns i litteraturen, men implementerade exempel är fortfarande ovanliga. Ett exempel på ett mer avancerat alternativ, som möjliggör bättre anpassning, är att använda modellbaserade algoritmer. Att formulera allokeringsproblemet som ett linjärt kvadratiskt problem och använda en linjär kvadratisk regulator är ett alternativ som har visat sig fungera bra för icke jetdrivna fartyg. En generell fartygsmodell utvecklas och anvnnds för att simulera och testa de olika allokeringsalgoritmerna. Vidare föreslås en metod för att omvandla den allokerade styrkraften till parametrar som kan styra jetmotorerna. Detta är ett nödvändigt steg för att, i slutändan, kunna implementera styrkrafterna på ett riktigt fartyg. En jämförelse av allokeringsalgoritmer baserade på stegsvar med och utan störningar visar att den linjära kvadratiska regulatorn hanterar de uppsatta testfallen bättre än den direkta allokeraren. Däremot dras den modellbaserade algoritmen med det problemet att omfattande kunskapen krävs angående systemets dynamik. Detta är något som inte krävs för direktallokeraren och är värt att ta hänsyn till.
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Bergman, Niklas. "Effects of Mach cruise number on conventional civil jet aircraft sizing." Thesis, Mälardalen University, School of Innovation, Design and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-7450.
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<p>This thesis work was executed at Swift Engineering Incorporated located in San Clemente, California during spring in 2009. Placement supervisor from Swift was Mark Page and advisor and examiner from the Division of future products at Mälardalen University, Sweden was Gustaf Enebog.</p><p>The objective with this thesis work was to examine the effects of fitness ratio, lift over drag, lift coefficient at cruise, winglet span, wing sweep angle, wing aspect ratio, wing area and weights with respect to Mach number for a conventional business jet capable of 18 passengers. The cruise speed study range from Mach 0.88 to 0.99.</p><p>The Excel based conceptual design tool Jetsizer 2008c was used to make four models with similar configuration and mission but with different cruise Mach numbers.</p><p>A new Jetsizer module was then created to handle a modification process where the models are optimized for their speed and configuration. The result in this report gives guidelines for the needed values when creating an initial CFD model for this type of airplane.</p>
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Schumacher, Viking Alex. "Jet Stream Velocity fromAzipod on Stadsgården : A Litterature Study of PIANC W.G. 180Application for Stadsgården." Thesis, KTH, Marina system, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-243091.
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The ferry line company VIKING LINE has put in an order for a new vessel with a planned delivery for the year 2020. The vessel will berth and depart daily from the Stockholm port, Stadsgården. The vessel is equipped with two 10 MW Azipod propeller systems. This new propulsion system has the capability of rotating the direction of the propeller thrust 360° which is different from other vessels currently using the same port. The direction and distance of the propeller from the quay has raised concern at the Ports of Stockholm. The integrity and design of the quay wall at Stadsgården is to be related to the guidelines set in place by the World Association for Waterborne Transport Infrastructure (PIANC) Working Group 180: “Guidelines for Protecting Berthing Structures from Scour Caused by Ships.” The guidelines have been compared to the actuator disc theory in order to validate the initial jet stream velocity from the new propeller system. The propagation of the jet stream was later analyzed and a velocity at the quay wall is calculated. A lack of information from certain parameters in the guidelines has led to implementations of assumptions. Uncertainties in the methods and equations presented by the guidelines are discussed. Overall, the guidelines were applicable in the investigation of the new vessel at Stadsgården. The jet stream velocity from the new vessel is compared to the velocity from a similar vessel currently using the same berthing structure. From the comparison it is seen that the berthing structure will be exposed to velocities four times larger than the current jet stream velocities at Stadsgården. A list with recommended action that can be performed by the Ports of Stockholm is presented.<br>Fartygsföretaget VIKING LINE har beställt ett nytt fartyg med planerad leverans år 2020. Fartyget kommer att trafikera dagligen från Stockholm hamnen, Stadsgården. Fartyget är utrustat med två 10 MW Azipod propeller system. Detta nya framdrivningssystem har förmågan att rotera riktningen för propellern 360° vilket skiljer sig från andra fartyg som för närvarande använder samma hamn. Propeller riktning och avstånd från kajen har uppmärksammats hos Stockholms Hamnar. Stabiliteten av kajväggen på Stadsgården ska relateras till de riktlinjer som fastställs av PIANC Arbetsgrupp 180: "Guidelines for Protecting Berthing Structures from Scour Caused by Ships." Riktlinjerna har jämförts med ’actuator disc theory’ för att validera den ursprungliga jetströmhastigheten från den nya propellern. Spridningen av strålströmmen analyserades senare och en hastighet vid kajväggen beräknas. Brist på information från vissa parametrar i riktlinjerna har lett till implementeringar av antaganden. Osäkerheter i de metoder och ekvationer som presenteras i riktlinjerna diskuteras. Jetströmshastigheten från det nya fartyget jämförs med hastigheten från ett liknande fartyg som för närvarande utnyttjar samma hamn. Från jämförelsen framgår det att kajfronten kommer att exponeras för hastigheter fyra gånger större än de nuvarande jetströmshastigheterna på Stadsgården. En lista med rekommenderad åtgärd som kan utföras av Stockholms Hamnar presenteras.
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Fung, Pearl Haiyan. "Flow control over a micro unmanned aerial vehicle using synthetic jet actuators." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/16950.
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Ohanian, Osgar John. "Ducted Fan Aerodynamics and Modeling, with Applications of Steady and Synthetic Jet Flow Control." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/27687.
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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 fanâ 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 fanâ 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.<br>Ph. D.
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Wemming, Hannes. "Validation and integration of a rubber engine model into an MDO environment." Thesis, Linköpings universitet, Fluid och mekanisk systemteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-61028.
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Multidisciplinary design optimization (MDO) is a technique that has found use in the field of aerospace engineering for aircraft design. It uses optimization to simultaneously solve design problems with several disciplines involved. In order to predict aircraft performance an engine performance simulation model, also called “rubber engine”, is vital. The goal of this project is to validate and integrate a rubber engine model into an MDO environment. A method for computer simulation of gas turbine aero engine performance was created. GasTurb v11, a commercial gas turbine performance simulation software, was selected for doing the simulation models. The method was validated by applying it to five different jet engines of different size, different type and different age. It was shown that the simulation engine model results are close to the engine manufacturer data in terms of SFC and net thrust during cruise, maximum climb (MCL) and take off (MTO) thrust ratings. The cruise, take off and climb SFC was in general predicted within 2% error when compared to engine manufacturer performance data. The take off and climb net thrust was in general predicted with less than 5% error. The integration of the rubber engine model with the MDO framework was started and it was demonstrated that the model can run within the MDO software. Four different jet engine models have been prepared for use within the optimization software. The main conclusion is that GasTurb v11 can be used to make accurate jet engine performance simulation models and that it is possible to incorporate these models into an MDO environment.
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Kiran, Amit. "Jet noise : aeroacoustic distribution of a subsonic co-axial jet." Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/3914/.
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The noise generated by aircraft can be easily heard by those living under the flight path of passenger or cargo carriers. It is considered an environmental pollutant and is treated as such by the International Civil Aviation Organization (ICAO) who monitor and review noise levels. The ICAO imposes substantial fines on those carriers who do not adhere to the decibel limitations. With the new limit or `stage' enforced in 2006, aircraft manufacturers (including jet engine manufacturers) are seeking ways to reduce the noise created by an aircraft. A 1/150th scale model, based on the exit geometry typically found on commercial jet engines, was designed and manufactured at Warwick. The laboratory jet flow conditions operated at 0.7 Mach. The work presented in this thesis looks at the noise generated in a subsonic, co- owing jet, with particular focus given to the distribution sound sources from 5 kHz to 80 kHz (0.375 St to 6.0 St). An acoustic mirror mounted on a motorized 3-way traverse measured radiated sound in the co-flowing jet to produce 2D sound source maps. This is done using combinations of smooth cowl and chevrons for the core and bypass nozzles. For frequencies less than 30 kHz, a reduction of noise was observed using the bypass chevron nozzle compared with the bypass smooth cowl nozzle. Laser Doppler Anemometry (LDA) was used to reveal the 2D flow dynamics of the jet, supporting the acoustic distribution results with velocity profiles of the flow. The change in the flow dynamics with different nozzle combinations is discussed and different regions of the flow were identified.
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Muse, Jonathan Adam. "An H-Infinity norm minimization approach for adaptive control." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34830.
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This dissertation seeks to merge the ideas from robust control theory such as H-Infinity control design and the Small Gain Theorem, L stability theory and Lyapunov stability from nonlinear control, and recent theoretical achievements in adaptive control. The fusion of frequency domain and linear time domain ideas allows the derivation of an H-Infinity Norm Minimization Approach (H-Infinity-NMA) for adaptive control architecture that permits a control designer to simplify the adaptive tuning process and tune the uncertainty compensation characteristics via linear control design techniques, band limit the adaptive control signal, efficiently handle redundant actuators, and handle unmatched uncertainty and matched uncertainty in a single design framework. The two stage design framework is similar to that used in robust control, but without sacrificing performance. The first stage of the design considers an ideal system with the system uncertainty completely known. For this system, a control law is designed using linear H-Infinity theory. Then in the second stage, an adaptive process is implemented that emulates the behavior of the ideal system. If the linear H-Infinity design is applied to control the emulated system, it then guarantees closed loop system stability of the actual system. All of this is accomplished while providing notions of transient performance bounds between the ideal system and the true system.
Extensions to the theory include architectures for a class of output feedback systems, limiting the authority of an adaptive control system, and a method for improving the performance of an adaptive system with slow dynamics without any modification terms. Applications focus on using aerodynamic flow control for aircraft flight control and the Crew Launch Vehicle.
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Luo, Xinfu. "Plasma based jet actuators for flow control." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348870/.
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A set of plasma based jet actuators were designed for flow control applications. The characteristics of these actuators and their flow control applications were studied experimentally in a low speed wind tunnel. A dielectric barrier discharge (DBD) based jet actuator is designed, which is made of a covered cavity with two spanwise aligned parallel slots. Two-component particle image velocimetry (PIV) measurements were conducted to determine the effect of actuator in quiescent air and on a canonical zero pressure gradient turbulent boundary layer. It was found that the designed plasma jet actuator produced a transverse jet similar to a continuously blowing jet but with no mass addition into the flow field. The device is different from a traditional alternative blowing-and-suction synthetic jet as the current jet is continuously blown. As such, the DBD based jet actuator is different from either a mass injection blowing jet actuator or a traditional diaphragm based synthetic jet actuator. The impact of the actuation with the designed actuator on the boundary layer characteristics was investigated in detail at different Reynolds numbers. Circular cylinder wake flow control using a newly designed five-electrode plasma jet actuator is also presented in this thesis. This plasma actuator configuration mounted on the cylinder model can easily produce either a downward or upward jet into the flow around the circular cylinder by simply adjusting the same five electrodes’ electrical circuits. The experiments were performed at Reynolds numbers from 7,000 to 24,000. Wake profile measurements were made to evaluate the modification to the mean and fluctuation velocities in the cylinder wake. The results shown that the cylinder wake flow and the turbulence levels in the wake were modified under the actuations, sectional drag reduction and drag increment were obtained by different actuator actuation directions. The study suggested that this new designed five-electrode actuator can be applied to practical separation suppression or enhancement control by adjusting the plasma actuator electric circuits conveniently.
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McLaughlin, Philip. "A contribution to the jet noise installation problem." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/190205/.
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The main objective of this thesis is to understand and predict jet noise installation effects for engines mounted below aircraft wings. This is done through a variety of empirical, analytical and computational methods. Aspects of the jet source are examined and a jet source model, suitable for determining installation effects is derived. As part of this research programme a novel and extensive set of model scale jet noise installation effects experiments were undertaken. These results are presented and analyzed in this thesis. A new semi-empirical method, which can readily predict installation effects for heated coaxial jets is presented and validated using experimental data. A new 3D ray theory jet propagation method for sources in a steady inhomogeneous moving medium is presented. This method is benched marked using an analytical solution of the Lilley equation. The 3-D method is further enhanced by combing it with realistic CFD jet velocity profiles, and bench marked using the data from the experimental programme
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Hu, Xiaowei. "A study of nozzle jet application to winter maintenance vehicles." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447630.
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Whitehead, James Anthony. "Aerodynamics and propulsion of synthetic jet based micro air vehicles." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409883.
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Preston, Giles Andrew. "Modelling sound source regions for the prediction of coaxial jet noise." Thesis, University of Southampton, 1995. https://eprints.soton.ac.uk/173779/.
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Azarpeyvand, Mahdi. "Some aspects of RANS based jet noise prediction." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/66622/.
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Perera, Guruge Elmo Lakshman. "A vertical axis wind turbine generator based on the tangential wall-jet action." Thesis, University of Huddersfield, 1988. http://eprints.hud.ac.uk/id/eprint/7480/.
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Bassetti, Alessandro. "A statistical jet-noise model based on the acoustic analogy and a RANS solution." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/64784/.
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We introduce a hybrid model for the evaluation of jet noise. The model uses the information from a solution of the Reynolds-averaged Navier{Stokes equations (RANS). It evaluates the jet-noise power spectral density (PSD) in the quiescent region outside the turbulent jet. It includes the following components: 1. A propagation model based on the high- and low-frequency approximations of the Lilleyanalogy Green's function. The high-frequency approximation is determined by combining a moving-medium Lighthill analogy and ray acoustics. The low-frequency model is made by using a ow-factor approach on each component of the source two-point CPSD. We use available analytical expressions of ow factors evaluated in the low-frequency limit. 2. A xed-frame source model based on the source terms of the Goldstein (2001) expression for the Lilley analogy. Both the applied-stress and applied-force equivalent acoustic sources are retained. The used acoustic analogy allows for expressing the 2-point covariance of the applied-stress source by using 2-point velocimetry measurements in a turbulent jet. Specically the applied-stress source can be put in correspondence to the unit-density Reynolds-stress statistics. Available measurements of the unit-density Reynolds-stress 2-point statistics are here used to derive an analytical model for the applied-stress 2-point correlation coecient. Also the applied-force 2-point statistics, required for modelling noise source mechanisms at the presence of density inhomogeneities in the ow, is expressed on the basis of the unit-density Reynolds-stress 2-point statistics. Numerical methods are used to derive the frequency{wavenumber expression for a volumetric source-strength tensor. 3. A jet- ow prediction by using a commercial RANS solver and a set of connection relations expressing source-model parameters starting from the RANS solution. The RANS system includes Reynolds Stress modelling (RSM) closure equations. Turbulence anisotropy is then incorporated in the ow-statistics estimation. The proposed connection relations introduce a set of empirical parameters which are evaluated by matching model components to both velocimetry and acoustics measurements. Modelled far-eld jet-noise 1/3-octave spectra are compared to corresponding measurements for isothermal, unheated and hot jets.
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Al, Haddabi Naser Hamood. "Subsonic open cavity flows and their control using steady jets." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/9096/.
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Cavity flow induces strong flow oscillations, which increase noise, drag, vibration, and structural fatigue. This type of flow impacts a wide range of low speed applications, such as aircraft wheel wells, ground transportations, and pipelines. The objective of the current study is to examine the reverse flow interaction inside the cavity, which has a significant impact on the cavity flow oscillations. The study also investigates the impact of steady jets with different-configurations on the time-average field and the oscillations of the cavity separated shear layer. The purpose of the steady jets is suppressing the oscillations of the cavity separated shear layer. The experiments were performed for an open cavity with L/D = 4 at Reθ between 1.28×103 to 4.37×103. The steady jets were applied with different: momentum fluxes (J = 0.11 kg/m.s2,0.44 kg/m.s2 and 0.96 kg/m.s2), slot configurations (sharp edge and coanda), and blowing locations (blowing from the cavity leading and trailing edges). The data were acquired using qualitative (surface oil flow visualisation) and quantitative (hot-wire anemometry, laser Doppler anemometry, particle image velocimetry, and pressure measurements) flow diagnostics techniques. The study found that a low-frequency instability dominates the velocity spectra of the cavity separated shear layer. This instability decreases with increasing Reθ and is related to the reverse flow interaction. This interaction takes place when the reverse flow influences the sensitive separation point of the cavity separated shear layer. As a result, a large amplitude flapping wave is generated and propagates downstream of the cavity separated shear. It was also revealed that increasing J for the leading and trailing edges blowing enhances the reverse flow interaction and increases the broadband level of the unsteady wall pressure spectra. Thus, these types of jet blowing are not suitable for controlling the oscillations of the cavity separated shear layer.
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Toulson, Elisa. "Applying alternative fuels in place of hydrogen to the jet ignition process /." Connect to thesis, 2008. http://repository.unimelb.edu.au/10187/3532.
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Lawrence, Jack. "Aeroacoustic interactions of installed subsonic round jets." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/367059/.
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Additional noise sources are generated when an aircraft engine is mounted beneath a wing. The two main installation sources include: (1) reflection of the exhaust jet mixing noise from the underside of the wing, and (2) interaction between the turbulent jet plume and the trailing edge of the wing, or deployed flap. The strength, directivity and frequency content of these particular sources all serve to increase the time-averaged flyover aircraft noise level heard on the ground by residents beneath the flight path. As the bypass ratio and nacelle diameter of modern turbofan engines continues to increase, constraints on ground clearance are forcing under-wing-mounted engines to be coupled more closely to the wing and flap system, which, in turn, serves to accentuate both of these noise sources. Close-coupled nacelle-airframe designs are now a critical issue surrounding efforts to meet the future environmental targets for quieter civil aircraft. This research is principally aimed at understanding and predicting the groundpropagating noise generated by the latter of these two installed jet noise sources. In order to characterise the jet-surface interaction noise source, however, it is first necessary to isolate it. A small 1/50th model-scale acoustic experiment, therefore, is conducted in a semi-anechoic university laboratory using a single stream jet installed beneath a flat plate. Both far-field acoustic and near-field plate surface pressure data are measured to investigate the jet-surface interaction noise source. Results from this fundamental experiment are then used to help drive a larger, and more realistic, 1/10th modelscale test campaign, at QinetiQ's Noise Test Facility, where 3D wing geometry effects, Reynolds number scaling effects and static-to-flight effects are investigated. A jet-flap impingement tonal noise phenomenon is also identified and investigated at particularly closely-coupled jet-wing configurations. Finally, the first version of a fast, semi-empirical engineering tool is developed to predict the additional noise caused by jet-wing interaction noise, under static ambient flow conditions. It is hoped that this tool will serve to inform future commercial aircraft design decisions and, thus, will help to protect the acoustic environment of residents living beneath flight paths.
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Gildner, Matthew Lee. "Framework for multi-vehicle adaptive sampling of jets and plumes in coastal zones." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80664.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 125-130).<br>This thesis presents a framework for the sampling of thermal and effluent jets and plumes using multiple autonomous surface vehicles. The framework was developed with the goal of achieving rapid and accurate in-situ measurement and characterization of these features. The framework is presented as a collection of simulation, estimation and field tools for use within the Mission Oriented Operations Suite (MOOS) and a novel Acoustic Doppler Current Profiling system that is capable of reorientation and real-time feedback. Key features developed within MOOS include a multi-parameter model of thermal and effluent jet and plume fields, online parameter estimation and sensor fusion. Using these tools, a collaborative adaptive sampling strategy is implemented to efficiently sample an industrial jet and plume. The capabilities of this strategy are demonstrated in realistic mission simulations and in field trials using a fleet of autonomous kayaks equipped with environmental sensors.<br>by Matthew Lee Gildner.<br>S.M.
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Beales, Brian O. "F-22 versus UCAV fixing today's deficiencies leaves questions about tomorrow's dominance." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FBeales.pdf.
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Thesis (M.A. in Security Studies (Homeland Security and Defense))--Naval Postgraduate School, December 2009.<br>Thesis Advisor(s): Looney, Robert E. ; McNab, Robert M. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: F-22, MQ-1, MQ-9, UCAV, homeland defense, aircraft effectiveness, defense spending, manned flight, unmanned flight. Includes bibliographical references (p. 71-76). Also available in print.
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Zakaria, Rami. "Jet fuel spray characterisation using optical methods : an experimental study of high speed fuel injection systems in small rotary engines." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/54103/.
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This thesis was initiated by the need to develop a stable low vibration engine with a high power to weight ratio. A new rotary (Wankel) engine was chosen to meet these requirements. A further operating criterion was that the engine was required to use JP8 (aviation fuel). The difficulty created by the use of JP8 is that its combustion temperature is higher than other conventional fuels, and preheating is necessary, especially in the case of cold start. Thus, the question posed was, could a more appropriate and efficient method of fuel delivery be devised? This thesis presents the design and construction of a fluid spray visualisation system for investigating the macroscopic and microscopic characteristics of fuel sprays using low injection pressure up to 10 bar (1 MPa). Laser imaging techniques have been used for data acquisition. The thesis has been divided into several aspects. Firstly, a background study of fluid sprays and fuel injection strategies was carried out. This has centred on the relationship between droplet size and the combustion process. It further investigated what differentiated the fuel delivery approach to Wankle from that to other engines. Secondly, two families of fuel injector were tested and evaluated within the optical engineering laboratory using deionised water (DI) water for safety reasons. The first family involved conventional gasoline injectors with several nozzle arrangements. The second family involved medical nebulisers with several nozzle diameters. The evaluation of the fuel injectors required developing a fluid delivery circuit, and a specific ECU (Electronic Control Unit) for controlling pulse delivery and imaging instrument. The company associated with the project then set up a test cell for performing experiments on JP8 fuel. The initial global visualisation of the jet spray was made using a conventional digital camera. This gave a measurement of the spray angle and penetration length. However, as the study moved to the more precise determination of the fuel spray particulate size, a specialised Nd:YAG laser based diagnostic was created combined with a long range diffraction limited microscope. Microscopic characterisation of the fuel sprays was carried out using a backlight shadowgraph method. The microscopic shadowgraphy method was applied successfully to resolve droplets larger than 4 microns in diameter. The spray development process during an individual fuel injection cycle was investigated, presenting the frequency response effect of electronic fuel injectors (EFI) on the spray characteristics when operating at high injection frequencies (0.25 -‐ 3.3 kHz). The velocity distribution during the different stages of an injection cycle was investigated using PIV. The influence of the injection pressure on the spray pattern and droplet size was also presented. Novel fluid atomisation systems were investigated for the capability of generating an optimum particulate distribution under low pressure. Finally, it was found that a new electronic medical nebuliser (micro-‐dispenser) could be used to deliver the fuel supply with the relevant particle size distribution at low flow rate and high injection frequency. However, as yet it has not been possible to apply this approach to the engine; it is hoped that it will yield a more efficient method of cold starting the engine. The characteristics of this atomiser can be applied to provide a controllable fuel supply approach for all rotary engines to improve their fuel efficiency. The second part of this research discusses the droplets-‐light interaction using Mie scattering for fluid droplets smaller than the microscope visualisation limit (4 microns). Mie scattering theory was implemented into Three-‐Components Particle Image Velocimetry (3C-‐ PIV) tests to address a number of problems associated with flow seeding using oil smoke. Mie curves were used to generate the scattering profile of the oil sub-‐micron droplets, and therefore the scattering efficiency can be calculated at different angles of observation. The results were used in jet flow PIV system for the determination of the optimum position of the two cameras to generate balanced brightness between the images pairs. The brightness balance between images is important for improving the correlation quality in the PIV calculations. The scattering efficiency and the correlation quality were investigated for different seeding materials and using different interrogation window sizes.
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Hennig, Christian [Verfasser]. "Improvements in thrust and fuel consumption for future jet engines for unmanned aerial vehicles (UAV) using variable cycle technology / Christian Hennig." München : Verlag Dr. Hut, 2017. http://d-nb.info/1139539094/34.
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Krolak, Matthew Joseph. "Optimization of a magnetoplasmadynamic arc thruster." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-042607-155701/.
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Jewkes, James. "An improved turbulent boundary layer inflow condition, applied to the simulation of jets in cross-flow." Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/2372/.
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The jet acting perpendicular to a cross-flow boundary layer is a commonly studied complex turbulent flow. Our research was motivated by their potential application in separation delay devices, where jets can be used to produce streamwise vortices in a similar manner to conventional solid vortex generating vanes. This thesis addresses two problems; firstly the generation of inflow conditions for the simulation of a spatially developing turbulent boundary layer, and secondly the simulation of low velocity ratio jets interacting with the boundary layer. Our approach involved refining a popular turbulent inflow generation technique, validating the accuracy of our improved method against well established direct numerical simulation data. This turbulent boundary layer was used to simulate a low velocity ratio perpendicular jet test-case, which was validated against experimental data. Finally, a pitched and skewed jet model was investigated. Our modifications to the turbulent boundary layer inflow generation method were successful, addressing problems described by various authors regarding the stability and accuracy of the technique. Secondly we have found excellent agreement in our perpendicular jet in cross flow test-case, and have produced what we believe to be the first documented unsteady numerical simulation of the flow field behind a low velocity ratio pitched and skewed jet.
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Littlewood, Rob. "Novel methods of drag reduction for squareback road vehicles." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12534.
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Road vehicles are still largely a consumer product and as such the styling of a vehicle becomes a significant factor in how commercially successful a vehicle will become. The influence of styling combined with the numerous other factors to consider in a vehicle development programme means that the optimum aerodynamic package is not possible in real world applications. Aerodynamicists are continually looking for more discrete and innovative ways to reduce the drag of a vehicle. The current thesis adds to this work by investigating the influence of active flow control devices on the aerodynamic drag of square back style road vehicles. A number of different types of flow control are reviewed and the performance of synthetic jets and pulsed jets are investigated on a simple 2D cylinder flow case experimentally. A simplified ¼ scale vehicle model is equipped with active flow control actuators and their effects on the body drag investigated. The influence of the global wake size and the smaller scale in-wake structures on vehicle drag is investigated and discussed. Modification of a large vortex structure in the lower half of the wake is found to be a dominant mechanism by which model base pressure can be influenced. The total gains in power available are calculated and the potential for incorporating active flow control devices in current road vehicles is reviewed. Due to practicality limitations the active flow control devices are currently ruled out for implementation on a road vehicle. The knowledge gained about the vehicle model wake flow topology is later used to create drag reductions using a simple and discrete passive device. The passive modifications act to support claims made about the influence of in wake structures on the global base pressures and vehicle drag. The devices are also tested at full scale where modifications to the vehicle body forces were also observed.
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Schroeder, Olivia. "Verification and Validation Studies for the KATS Aerothermodynamics and Material Response Solver." UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/122.
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Modeling the atmospheric entry of spacecraft is challenging because of the large number of physical phenomena that occur during the process. In order to study thermal protection systems, engineers rely on high fidelity solvers to provide accurate predictions of both the thermochemical environment surrounding the heat shield, and its material response. Therefore, it is necessary to guarantee that the numerical models are correctly implemented and thoroughly validated. In recent years, a high-fidelity modeling tool has been developed at the University of Kentucky for the purpose of studying atmospheric entry. The objective of this work is to verify and validate this code. The verification consists of the development of an automated regression testing utility. It is intended to both aid code developers in the debugging process, as well as verify the correct implementation of the numerical models as these are developed. The validation process will be performed through comparison to relevant ablation experiments, namely arc-jet tests. Two modules of the code are used: fluid dynamics, and material response. First the fluid dynamics module is verified against both computational and experimental data on two distinct arc-jet tests. The material response module is then validated against arc-jet test data using PICA.
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Serdane, Thierry. "Le jeu vidéo, un art mécanique ? : se réapproprier la contre-culture." Thesis, Montpellier 3, 2014. http://www.theses.fr/2014MON30093/document.
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De la confrontation problématique d’un projet de jeu vidéo aux conditions plurielles desa création, ce travail de thèse tente de mettre à jour les contraintes et les interrogationsqu’elles suscitent. Le jeu vidéo, contemporain de la société de l’information est un témoinde l’évolution complexe du paradigme postmoderne, né avec la cybernétique. De la genèsedu jeu vidéo au temps présent, les technologies, les façons de jouer et les productions serévèlent significatives de visions du monde opposées. La thèse montre que derrière l’imaged’un divertissement et d’une industrie consensuelle, une résistance peut s’exprimer d’unpoint de vue technique, artistique et politique. A travers l’histoire et le devenir du jeuvidéo peuvent se lire certains enjeux de société en lien avec de nouvelles formes de pouvoir.C’est dans un interstice contre culturel que se développe une oeuvre résistante, nourrie d’unexamen critique préalable. Une création originale se construit progressivement en contreculturedu modèle libéral dominant, dans un mouvement d’opposition à l’action irréfléchie,l’accélération et la dématérialisation... Du point de vue plastique, la thèse interroge le retourdes technologies de réalité virtuelle, et élabore deux nouvelles notions, le véhicule expérientielet le leurre suffisant. Profitant de ce nouveau champ d’investigation de création, la thèseinvite le joueur à laisser l’usage pour le faire<br>From the problematic confrontation of a video game project with the multiple conditions ofits creation, the present thesis tries to highlight the constraints and the interrogations whichthey arouse. Contemporary to the information society, the video game is a witness of thecomplex evolution of the postmodern paradigm born from cybernetics. From the genesis ofthe video game to present time, technologies, the ways of playing and the productions revealthe significant oppositions in their visions of the world. The thesis shows that behind theimage of entertainment and of a consensual industry, a form of resistance can express/voiceitself from a technological, artistic and political point of view. Through the history of videogame and its future, one can read some of society’s stakes/challenges linked to new formsof power. It is within a counter cultural interstice, and fed by a prior critical exam, thata resistant work/piece is developed. An original creation is progressively built in reflexivecounter cultural opposition to the mainstream dominant liberal world and its accelerationand dematerialization... From a plastic point of view, the thesis questions the return of thevirtual reality technologies, and elaborates two new notions: the experiential vehicle and thesufficient decoy. Taking advantage of this new field of investigation of creation, the thesisinvites the player to let it be used so as to do so. Keywords: Video games. Counter culture.Experiential vehicle. Counter dematerialization. Sufficient decoy
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Raszka, Aleš. "Klasifikace vozidel s použitím radaru." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2017. http://www.nusl.cz/ntk/nusl-363896.
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This Master thesis deals with usage of radar signal for vehicle classification. The thesis uses radar modules with continuous wave based on Doppler effect. Radar signal is processed by a series of signal processing method finished by Fourier transform. Data produced by FFT is used to create SVM and AdaBoost classifier which can be used to classify vehicles into groups.
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Adler, Martin, Stefanie Peer, and Tanja Sinozic. "Autonomous, connected, electric shared vehicles (ACES) and public finance: An explorative analysis." Elsevier, 2019. http://epub.wu.ac.at/7200/1/main.pdf.
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This paper discusses the implications of autonomous-connected-electric-shared vehicles (ACES) for public finance, which have so far been widely ignored in the literature. In OECD countries, 5-12% of federal and up to 30% of local tax revenues are currently collected from fuel and vehicle taxation. The diffusion of ACES will significantly reduce these important sources of government revenues and affect transport-related government expenditures, unless additional policies are introduced to align the new technological context with the tax revenue requirements. We argue that the realization of socioeconomic benefits of ACES depends on the implementation of tailored public finance policies, which can take advantage of the increase in data availability from the further digitalization of transportation systems. In particular, the introduction of road tolls in line with "user Pays" and "polluter Pays" principles will become more feasible for policy. Moreover, innovation in taxation schemes to fit the changing technological circumstances may alter the relative importance of levels of governance in transport policy making, likely shifting power towards local, in particular urban, governmental levels. We finally argue that, given the risk of path-dependencies and lock-in to sub-optimal public finance regimes if policies are implemented late, further research and near-term policy actions taken during the diffusion process of ACES are required.
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Korzun, Ashley Marie. "Aerodynamic and performance characterization of supersonic retropropulsion for application to planetary entry and descent." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43667.
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Supersonic deceleration has been identified as a critical deficiency in extending heritage technologies to the high-mass systems required to achieve long-term exploration goals at Mars. Supersonic retropropulsion (SRP), or the use of retropropulsive thrust while an entry vehicle is traveling at supersonic conditions, is an approach addressing this deficiency. The focus of this dissertation is aerodynamic and performance evaluation of SRP as a decelerator technology for high-mass Mars entry systems. This evaluation was completed through a detailed SRP performance analysis, establishment of the relationship between vehicle performance and the aerodynamic-propulsive interaction, and an assessment of the required fidelity and computational cost in simulating SRP flowfields, with emphasis on the effort required in conceptual design. Trajectory optimization, high-fidelity computational aerodynamic analysis, and analytical modeling of the SRP aerodynamic-propulsive interaction were used to define the fidelity and effort required to evaluate individual SRP concepts across multiple mission scales.
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Chaligné, Sébastien. "Contrôle du sillage d'un corps non profilé : application expérimentale à une maquette simplifiée de véhicule industriel." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00995837.
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Ce manuscrit présente les travaux de thèse réalisés dans le cadre d'une convention CIFRE entre Renault Trucks et le LMFA. Une stratégie de contrôle d'écoulement, associant un volet déflecteur et des actionneurs de type jets pulsés et synthétiques, est étudiée expérimentalement en vue de réduire la traînée aérodynamique de corps non profilés à culot droit. Une première approche consiste à étudier l'influence de cette stratégie sur une maquette bidimensionnelle. Des mesures de vitesse dans le sillage proche par TR-PIV et par anémométrie à fil chaud démontrent qu'une certaine gamme de fréquence d'actionnement permet à l'écoulement de recoller sur le volet et de diminuer les fluctuations de vitesse dans la zone de recirculation, ce qui engendre une augmentation de la pression au culot. Une analyse par moyenne de phase et la détermination de corrélations spatio-temporelles permettent d'identifier les perturbations induites par le contrôle conduisant à ces modifications de l'écoulement. Un système de jets synthétiques est ensuite intégré à une maquette simplifiée de véhicule poids lourd à l'échelle 1/8e, dont le sillage est représentatif des remorques réelles. Des gains en traînée significatifs sont obtenus et sont associés aux mêmes phénomènes aérodynamiques que pour la maquette bidimensionnelle. Enfin, une étude paramétrique montre la robustesse du contrôle aux caractéristiques de la couche limite incidente aux jets et à la longueur du volet déflecteur.
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Birhanie, Habtamu. "Resource Allocation in Vehicular Fog Computing for an Optimal Use of EVs Electric Vehicles Energy." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK042.
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Résumé : Les progrès technologiques ont permis aux véhicules électriques d’avoir des capacités à la fois de calcul, de communication, de stockage et de perception. Néanmoins, la plupart du temps, ces véhicules électriques sont en stationnement, ce qui engendre une sous utilisation de leurs capacités embarquées. Ainsi, une meilleure gestion et une mise en commun de ces ressources sous-utilisées deviennent fortement recommandées. Les ressources agrégées seraient utiles pour des applications de sécurité routière, des applications liées au confort ou pourraient même être utilisées en tant que centre de calcul distribué. En outre, les véhicules en stationnement pourraient également être utilisés comme plate-forme de fourniture de services. Par conséquent, l’utilisation de ressources abondantes agrégées pour le déploiement de différentes applications mobiles locales a conduit au développement du concept d’informatique en brouillard véhiculaire (an anglais, Vehicular Fog Computing - VFC). Grâce à ce dernier, les véhicules dans les aires de stationnement, les centres commerciaux ou les aéroports vont agir en tant que nœuds fog. Dans un autre contexte, les applications mobiles sont devenues de plus en plus populaires, complexes et gourmandes en ressources. Certaines applications mobiles nécessitent des capacités de calcul intensives et une consommation d'énergie élevée qui transcendent les capacités limitées des appareils mobiles. Tout au long de ce travail, nous abordons les verrous liés au déploiement efficace d’un système VFC agrégeant les ressources inutilisées des véhicules électriques en stationnement pour être utilisées comme nœuds fogs répondants aux demandes de calcul des utilisateurs mobiles à proximité. Notre travail commence par un état de l'art sur les véhicules électriques et l'allocation de ressources dans le système VFC. En outre, nous évaluons le potentiel des ressources agrégées dans les véhicules électriques pour répondre aux demandes d'applications d'utilisateurs mobiles locaux en prenant en compte l'état de santé de la batterie (en anglais, State of Health - SOH) et son état de charge (en anglais, State of Charge - SOC). Notre objectif est de choisir des VEs ayant un état de santé et de charge satisfaisants pour faire partie du VFC tout en permettant aux propriétaires de ces véhicules de disposer d’une quantité d’énergie suffisante pour leur mobilité. Nous abordons, par la suite, le problème d’allocation de ressources avec une nouvelle solution basée sur le processus de décision Markovien (en anglais, Markov Decision Process - MDP) qui vise à optimiser l’utilisation de l’énergie des véhicules électriques pour répondre à la fois à aux demandes de calcul et de mobilité des utilisateurs. Enfin, nous proposons une approche basée sur un jeu stochastique pour montrer la dynamique de la demande de calcul des utilisateurs mobiles et la disponibilité des ressources des véhicules électriques<br>Abstract: Technological advancements made it possible for Electric vehicles (EVs) to have onboard computation, communication, storage, and sensing capabilities. Nevertheless, most of the time these EVs spend their time in parking lots, which makes onboard devices cruelly underutilized. Thus, a better management and pooling these underutilized resources together would be strongly recommended. The new aggregated resources would be useful for traffic safety applications, comfort related applications or can be used as a distributed data center. Moreover, parked vehicles might also be used as a service delivery platform to serve users. Therefore, the use of aggregated abundant resources for the deployment of different local mobile applications leads to the development of a new architecture called Vehicular Fog Computing (VFC). Through VFC, abundant resources of vehicles in the parking area, on the mall or in the airport, can act as fog nodes. In another context, mobile applications have become more popular, complex and resource intensive. Some sophisticated embedded applications require intensive computation capabilities and high-energy consumption that transcend the limited capabilities of mobile devices. Throughout this work, we tackle the problem of achieving an effective deployment of a VFC system by aggregating unused resources of parked EVs, which would be eventually used as fog nodes to serve nearby mobile users’ computation demands. At first, we present a state of the art on EVs and resource allocation in VFC. In addition, we assess the potential of aggregated resources in EVs for serving local mobile users’ applications demands by considering the battery State of Health (SOH) and State of Charge (SOC). Here, the objective is to choose EVs with a good condition of SOH and SOC so that owners secure tolerable amount of energy for mobility. Then, we address the problem of resource allocation scheme with a new solution based on Markov Decision Process (MDP) that aims to optimize the use of EVs energy for both computing users’ demands and mobility. Hence, the novelty of this contribution is to take into consideration the amount of aggregated EVs resource for serving users’ demands. Finally, we propose a stochastic theoretical game approach to show the dynamics of both mobile users’ computation demands and the availability of EVs resources
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Matucha, Tomáš. "Nezávislý nízkonapěťový trakční asynchronní pohon." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233490.
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This work deals with creation of an exact mathematical model of a traction drive with low-voltage induction machine (28 V) which is fed from accumulators. This model was developed in MATLAB – Simulink and consists of induction machine model, inverter model and load model. Vector Control was added to models connected together. This complex model allows considering many effects into simulations. These effects are commonly neglected, although they have significant influence on drive behaviour, especially by using low-voltage machine. It is impact of magnetic circuit saturation, impact of temperature and skin effect on winding resistance, impact of inverter nonlinearities such as on-state voltage drops on switching elements, dead times and transistors switching times. The attention was paid to determination of losses in drive parts. The correctness of the model was verified at laboratory workplace established for this purpose. The laboratory drive can be controlled by a microprocessor or by using MATLAB and dSPACE application. The influence of compensations of inverter nonlinearities and DC-link voltage ripple on higher harmonics of inverter output currents was analyzed. Furthermore, the control, which decreased resistive losses, was solved.
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Tošer, Pavel. "Zkoumání teplotních změn vlastností olověného akumulátoru v režimu hybridních vozidel." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218567.
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The oldest and also most used type of secondary cells is lead-acid accumulator. Basic functional principle stayed same as in foundation time, only operation parameters are still improving (for example one of the most important is lifetime). Significant technical problem is temperature of lead-acid battery and her influence on functionality and running reactions. Master thesis is focused on this section, when is necessary to evaluate new pieces of knowledge in development. The work deals with description existing types of accumulators, further deals with theory of temperature balance and in the end by measured datas and theirs analyzing.
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Mariette, Kevin. "Contrôle en boucle fermée pour la réduction active de traînée aérodynamique des véhicules." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI088.
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Le contrôle actif de l’écoulement à l’arrière des véhicules se déplaçant à grande vitesse est un moyen de diminuer efficacement la consommation énergétique des véhicules par la réduction de la traînée aérodynamique. L’intérêt des méthodes actives est leur possible adéquation avec des conditions environnementales variables pour une modification minimale de la forme des véhicules, contrairement aux systèmes exclusivement passifs (profilage, ailerons aérodynamiques …). Toutefois, le contrôle actif nécessite un apport d’énergie qui réduit sa rentabilité énergétique finale. À l’aide d’essais expérimentaux sur une maquette de véhicule simplifié, cette thèse recherche comment employer un contrôle actif à base de jets pulsés à haute fréquence pour assurer une réduction de traînée de véhicule performante, robuste et énergétiquement rentable. Ces recherches sont axées sur : (i) la compréhension des phénomènes à l’origine de la traînée de pression, (ii) la définition d’un modèle de l’écoulement pour le contrôle, et (iii) l’implémentation expérimentale de méthodes de contrôle de traînée efficaces, robustes et à moindre coût énergétique. Les tests en soufflerie réalisés au cours de cette thèse se basent sur les stratégies de contrôle par mode glissant et de commande par extremum seeking qui permettent de concevoir de nouvelles solutions de réduction de la traînée visant à l’amélioration de la robustesse et de la rentabilité du contrôle par jets pulsés. Cette thèse s’inscrit dans le projet ANR ActivRoad issu de la collaboration de trois laboratoires de recherche : le Laboratoire Ampère (INSA, Lyon), l’Institut Pprime (ENSMA, Poitiers) et le LMFA (Centrale, Lyon) ; et le soutien de deux acteurs industriels : le groupe PSA et Volvo Trucks<br>Active flow control techniques can decrease the aerodynamic drag acting on a vehicle moving at high velocity. Instead of exclusively passive techniques, active control can reduce the pressure drag on a vehicle under a wider range of operating conditions without requiring large modifications of the functional shape of the vehicles. However, active control devices require an additional source of energy, which may decrease the global efficiency of the control. Our work aims to reduce significantly the drag of ground vehicles with efficiency and robustness thanks to high frequency pulsed jet control. We present experimental studies on a simplified bluff body mock-up of a ground vehicle and we seek to understand the phenomena linked to the pressure drag on a vehicle. In this thesis, we propose a modelling methodology of the vehicle’s turbulent wake adapted for control purposes. Finally, we design and test experimentally different closed-loop control methods of the wake with high frequency pulsed air jets. The experimental studies performed in a wind tunnel show the efficient application of sliding mode control and extremum seeking techniques for a robust drag control with energy cost considerations. This thesis was financed by the French National Research Agency (ANR) and contributes to the project ActivRoad involving three French laboratories: Ampère (INSA, Lyon), Pprime Institute (ENSMA, Poitiers), and the LMFA (Centrale, Lyon); and two automotive companies: PSA group and Volvo Trucks
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CHEN, YU-HENG, and 陳昱恆. "The Study on the Performance and Design Analysis of the Pump-Jet for Amphibious Wheel Type Vehicle." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/w2r35u.
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Miller, Warrick Alan. "Reaction Control Jet Actuators for Air-Breathing Hypersonic Vehicles." Thesis, 2019. http://hdl.handle.net/2440/120374.
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Air-breathing hypersonic vehicles have an engine which is tightly integrated with the airframe. This integration leads to complex dynamic characteristics, such as propulsion-pitch coupling. As a result, air-breathing hypersonic vehicles tend to be unstable and high frequency control is required to maintain steady flight. To provide high frequency control, aerodynamic control surfaces may need to be supplemented or replaced by high frequency actuators. Reaction control (RC) jets are an attractive solution, as they are commonly used to supplement aerodynamic control surfaces for exo-atmospheric control of hypersonic vehicles, and can operate at high frequency. If RC jets are operated within the atmosphere, an interaction force is generated in addition to the jet thrust. Understanding this interaction force is important in the design of a control system that implements RC jet actuators for use within the atmosphere. This thesis studies the unsteady interaction between an RC jet, and a hypersonic crossflow. A generic hypersonic vehicle model was used to investigate flight conditions where supplementary control may be required. Due to the instability caused by propulsion-pitch coupling, aerodynamic control surfaces alone are unable to control the vehicle’s rigid-body modes at several flight conditions. To analyse RC jet flow physics, an implicit large-eddy simulation (ILES) methodology was developed, verified and validated using a number of canonical supersonic flow problems, and experimental data for a steady jet in hypersonic crossflow. The steady and pulsed operation of a sonic, round jet issuing from a flat plate into a hypersonic (Mach 5.0) crossflow with a laminar in-flow boundary layer was investigated numerically. The pressure distribution induced on the plate is unsteady, and is influenced by shock and vortex structures that form around the jet. The unsteady and time-averaged behaviour of these structures has been described, leading to an improved understanding of the jet interaction flow physics. When the jet was pulsed, flow structures were influenced by the presence of shocks in the flow, allowing penetration per unit jet mass flow to increase by a maximum of 68% compared with the steady jet. Pulsing also provides a higher jet interaction force per unit jet mass flow compared with a steady jet, with a 52% increase recorded at a 33% duty-cycle. The start-up process for both steady and pulsed jets was also considered. The interaction force during start-up acts as a lightly damped second-order system. An overshoot is observed in the control force, corresponding to expansion of the jet flow behind the initial lead shock, before the flow settles to a quasi-steady state on a timescale related to the time taken for the jet fluid to reach the trailing edge of the flat plate. To assess the effectiveness of RC jets as a supplement to aerodynamic control, jet control was implemented on the generic air-breathing hypersonic vehicle, showing a significant improvement at all supersonic flight conditions. This thesis provides an increased understanding of the unsteady interaction between steady and pulsed sonic jets in hypersonic crossflow, which has applications in reaction jet control of air-breathing hypersonic vehicles.<br>Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2019
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Gangadharan, Sathya Narayan. "Feasibility study of jet propulsion for remote operated underwater vehicles /." 1986. http://collections.mun.ca/u?/theses2,4018.
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Toulson, E. "Applying alternative fuels in place of hydrogen to the jet ignition process." 2008. http://repository.unimelb.edu.au/10187/3532.
Full textAbstract:
Hydrogen Assisted Jet Ignition (HAJI) is an advanced ignition process that allows ignition of ultra-lean mixtures in an otherwise standard gasoline fuelled spark ignition engine. Under typical operating conditions, a small amount of H2 (~ 2 % ofthe main fuel energy or roughly the equivalent of 1 g/km of H2) is injected just before ignition in the region of the spark plug. By locating the spark plug in a small prechamber (less than 1 % of the clearance volume) and by employing a H2 rich mixture, the content of the prechamber is plentiful in the active species that form radicals H and OH on decomposition and has a relatively high energy level compared to the lean main chamber contents. Thus, the vigorous jets of chemically active combustion products that issue through orifices, which connect to the main chamber, burn the main charge rapidly and with almost no combustion variability (less than 2% coefficient of variation in IMEP even at λ = 2.5).<br>The benefits from the low temperature combustion at λ = 2 and leaner are that almost zero NOx is formed and there is an improvement in thermal efficiency. Efficiency improvements are a result of the elimination of dissociation, such as CO2 to CO, which normally occurs at high temperatures, together with reduced throttling losses to maintain the same road power. It is even possible to run the engine in an entirely unthrottled mode, but at λ = 5.<br>Although only a small amount of H2 is required for the HAJI process, it is difficult to both refuel H2 and store it onboard. In order to overcome these obstacles, the viability of a variety of more convenient fuels was experimentally assessed based on criteria such as combustion stability, lean limit and emission levels. The prechamber fuels tested were liquefied petroleum gas (LPG), natural gas, reformed gasoline and carbon monoxide. Additionally, LPG was employed as the main fuel in conjunction with H2 or LPG in the prechamber. Furthermore, the effects of HAJI operation under sufficient exhaust gas recirculation to allow stoichiometric fuel-air supply, thus permitting three-way catalyst application were also examined.<br>In addition to experiments, prechamber and main chamber flame propagation modeling was completed to examine the effects of each prechamber fuel on the ignition of the main fuel, which consisted of either LPG or gasoline. The modeling and experimental results offered similar trends, with the modeling results giving insight into the physiochemical process by which main fuel combustion is initiated in the HAJI process.<br>Both the modeling and experimental results indicate that the level of ignition enhancement provided by HAJI is highly dependent on the generation of chemical species and not solely on the energy content of the prechamber fuel. Although H2 was found to be the most effective fuel, in a study of a very light load condition (70 kPa MAP) especially when running in the ultra-lean region, the alternative fuels were effective at running between λ = 2-2.5 with almost zero NOx formation. These lean limits are about twice the value possible with spark ignition (λ = 1.25) in this engine at similar load conditions. In addition, the LPG results are very encouraging as they offer the possibility of a HAJI like system where a commercially available fuel is used as both the main and prechamber fuel, while providing thermal efficiency improvements over stoichiometric operation and meeting current NOx emission standards.
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Lopez, Mejia Omar Dario. "Computational study of a NACA4415 airfoil using synthetic jet control." 2009. http://hdl.handle.net/2152/10683.
Full textAbstract:
Synthetic jet actuators for flow control applications have been an active topic of experimental research since the 90’s. Numerical simulations have become an important complement of that experimental work, providing detailed information of the dynamics of the controlled flow. This study is part of the AVOCET (Adaptive VOrticity Control Enabled flighT) project and is intended to provide computational support for the design and evaluation of closed-loop flow control with synthetic jet actuators for small scale Unmanned Aerial Vehicles (UAVs). The main objective is to analyze active flow control of a NACA4415 airfoil with tangential synthetic jets via computational modeling. A hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) turbulent model (called Delayed Detached-Eddy Simulation-DDES) was implemented in CDP, a kinetic energy conserving Computational Fluid Dynamics (CFD) code. CDP is a parallel unstructured grid incompressible flow solver, developed at the Center for Integrated Turbulence Simulations (CITS) at Stanford University. Two models of synthetic jet actuators have been developed and validated. The first is a detailed model in which the flow in and out of the actuator cavity is modeled. A second less costly model (RSSJ) was also developed in which the Reynolds stress produced by the actuator is modeled, based on information from the detailed model. Several static validation test cases at different angle of attack with modified NACA 4415 and Dragon Eye airfoils were performed. Numerical results show the effects of the actuators on the vortical structure of the flow, as well as on the aerodynamic properties. The main effect of the actuation on the time averaged vorticity field is a bending of the separation shear layer from the actuator toward the airfoil surface, resulting in changes in the aerodynamic properties. Full actuation of the suction side actuator reduces the pitching moment and increases the lift force, while the pressure side actuator increases the pitching moment and reduces the lift force. These observations are in agreement with experimental results. The effectiveness of the actuator is measured by the change in the aerodynamic properties of the airfoil in particular the lift ([Delta]C[subscript t]) and moment ([Delta]C[subscript m]) coefficients. Computational results for the actuator effectiveness show very good agreement with the experimental values (over the range of −2° to 10°). While the actuation modifies the global pressure distribution, the most pronounced effects are near the trailing edge in which a spike in the pressure coefficient (C[subscript p]) is observed. The local reduction of C[subscript p], for both the suction side and pressure side actuators, at x/c = 0.96 (the position of the actuators) is about 0.9 with respect to the unactuated case. This local reduction of the pressure is associated with the trapped vorticity and flow acceleration close to the trailing edge. The RSSJ model is designed to capture the synthetic jet time averaged behavior so that the high actuation frequencies are eliminated. This allows the time step to be increased by a factor of 5. This ad hoc model is also tested in dynamic simulations, in which its capacity to capture the detail model average performance was demonstrated. Finally, the RSSJ model was extended to a different airfoil profile (Dragon Eye) with good results.<br>text