Dissertations / Theses: 'High-speed flow'

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Gissen, Abraham Naroll. "Active flow control in high-speed internal flows." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54865.

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Manipulation of high-speed duct flow by streamwise vorticity concentration that are engendered by interactions of surface-mounted passive and active flow control actuators with the cross flow is investigated experimentally in a small-scale wind tunnel. The controlled formation of these streamwise vortices can be a key element in the mitigation of the adverse flow effects in a number of applications including aero-optical aberrations owing to unsteady local transonic shocks, pressure recovery and distortion due to secondary flows in embedded propulsion system, thrusts reversal and augmentation for aerodynamic control. The effects of the actuation are investigated using various converging-diverging inserts along one of the test section walls. Passive actuation includes micro-vanes and active actuation is effected using high-frequency, surface-mounted fluidic oscillators. Hybrid actuation is demonstrated by combining the passive and active actuation approaches to yield a “fail-safe” device with significant degree of controllability. The investigations consider the effects of the surface actuation in three application areas namely, stabilization of transonic shocks, suppression of total-pressure distortion in offset ducts, and mitigation of separation in internal flow turning.

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Crittenden, Thomas M. "Fluid actuators for high speed flow control." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7742.

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In order to extend fluid-based flow control techniques that have been demonstrated at low subsonic speeds to high speed flows, it is necessary to develop actuators having sufficient momentum to control and manipulate high speed flows. Two fluidic actuation approaches are developed where the control jet may reach supersonic velocities and their performance is characterized. The first actuator is a compressible synthetic (zero net mass flux) jet. This is an extension of previous work on synthetic jets with an increase in driver power yielding substantial pressurization of the cavity such that the flow is compressible. The jet is generated using a piston/cylinder actuator, and the effects of variation of the orifice diameter, actuation frequency, and compression ratio are investigated. Operation in the compressible regime uniquely affects the time-dependent cylinder pressure in that the duty cycle of the system shifts such that the suction phase is longer than the blowing phase. The structure of the jet in the near-field is documented using particle image velocimetry and Schlieren flow visualization. In the range investigated, the stroke length is sufficiently long that the jet flow is dominated by a starting jet rather than a starting vortex (which is typical of low-speed synthetic jets). A simple, quasi-static numerical model of the cylinder pressure is developed and is in generally good agreement with the experimental results. This model is used to assess system parameters which could not be measured directly (e.g., the dynamic gas temperature and mass within the cylinder) and for predictions of the actuator performance beyond the current experimental range. Finally, an experiment is described with self-actuated valves mounted into the cylinder head which effectively icrease the orifice area in suction and overcome some of the limitations inherent to compressible operation. The second actuation concept is the combustion-driven jet actuator. This device consists of a small-scale (nominally 1 cc) combustion chamber which is filled with premixed fuel and oxidizer. The mixture is ignited using an integrated spark gap, creating a momentary high pressure burst within the combustor that drives a high-speed jet from an exhaust orifice. At these scales, the entire combustion process is complete within several milliseconds and the cycle resumes when fresh fuel/oxidizer is fed into the chamber and displaces the remaining combustion products. The actuator performance is characterized by using dynamaic measurements of the combustor pressure along with Schlieren flow visualization, limited dynamic thrust measurements, and flame photography. The effects of variation in the following system parameters are investigated: fuel type and mixture ratio, exhaust orifice diameter, chamber aspect ratio, chamber volume, fuel/air flow rate, ignition/combustion frequency, and spark ignition energy. The resulting performance trends are documented and the basis for each discussed. Finally, a proof-of-concept experiment demonstrates the utility of teh combustion-driven jet actuators at low-speed for transitory reattachment of a separated flow over an airfoil at high angles of attack.

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Applebaum, Michael Paul. "Unstructured technology for high speed flow simulations." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40057.

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Accurate and efficient numerical algorithms for solving the three dimensional Navier Stokes equations with a generalized thermodynamic and chemistry model and a one equation turbulence model on structured and unstructured mesh topologies are presented. In the thermo-chemical modeling, particular attention is paid to the modeling of the chemical source terms, modeling of equilibrium thermodynamics, and the modeling of the non-equilibrium vibrational energy source terms. In this work, nonequilibrium thermo-chemical models are applied in the unstructured environment for the first time. A three-dimensional, second-order accurate k-exact reconstruction algorithm for the inviscid and viscous fluxes is presented. Several new methods for determining the stencil required for the inviscid and viscous k-exact reconstruction are discussed. A new simplified method for the computation of the viscous fluxes is also presented. Implementation of the one equation Spalart and Allmaras turbulence model is discussed. In particular, an new integral formulation is developed for this model which allows flux splitting to be applied to the resulting convective flux. Solutions for several test cases are presented to verify the solution algorithms discussed. For the thermo-chemical modeling, inviscid solutions to the three dimensional Aeroassist Flight Experiment vehicle and viscous solutions for the axi-symmetric Ram-II C are presented and compared to experimental data and/or published results. For the hypersonic AFE and Ram-II C solutions, focus is placed on the effects of the chemistry model in flows where ionization and dissociation are dominant characteristics of the flow field. Laminar and turbulent solutions over a flat plate are presented and compared to exact solutions and experimental data. Three dimensional higher order solutions using the k-exact reconstruction technique are presented for an analytic forebody.
Ph. D.

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Ebrinc, Ali Aslan. "High Speed Viscous Plane Couette-poiseuille Flow Stability." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12604769/index.pdf.

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The linear stability of high speed-viscous plane Couette and Couette-Poiseuille flows are investigated numerically. The conservation equations along with Sutherland&
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s viscosity law are studied using a second-order finite difference scheme. The basic velocity and temperature distributions are perturbed by a small-amplitude normalmode disturbance. The small-amplitude disturbance equations are solved numerically using a global method using QZ algorithm to find all the eigenvalues at finite Reynolds numbers, and the incompressible limit of these equations is investigated for Couette-Poiseuille flow. It is found that the instabilities occur, although the corresponding growth rates are often small. Two families of wave modes, Mode I (odd modes) and Mode II (even modes), were found to be unstable at finite Reynolds numbers, where Mode II is the dominant instability among the unstable modes for plane Couette flow. The most unstable mode for plane Couette &
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Poiseuille flow is Mode 0, which is not a member of the even modes. Both even and odd modes are acoustic modes created by acoustic reflections between a will and a relative sonic line. The necessary condition for the existence of such acoustic wave modes is that there is a region of locally supersonic mean flow relative to the phase speed of the instability wave. The effects of viscosity and compressibility are also investigated and shown to have a stabilizing role in all cases studied. Couette-Poiseuille flow stability is investigated in case of a choked channel flow, where the maximum velocity in the channel corresponds to sonic velocity. Neutral stability contours were obtained for this flow as a function if the wave number,Reynolds number and the upper wall Mach number. The critical Reynolds number is found as 5718.338 for an upper wall Mach number of 0.0001, corresponding to the fully Poiseuille case.

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Ebrinç, Ali Aslan. "High speed viscous plane couette-poiseuille flow stability." Ankara : METU, 2004. http://etd.lib.metu.edu.tr/upload/12604769/index.pdf.

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Jadidi, Zahra. "Flow-based Anomaly Detection in High-Speed Networks." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/367890.

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With the advent of online services, the Internet has become extremely busy and demanding faster access. The increased dependency on the Internet obliges Internet service providers to make it reliable and secure. In this regard, researchers are tirelessly working on a number of technologies in order to ensure the continued viability of the Internet. Intrusion detection is one of the fields that enables secure operation of the Internet. An intrusion detection system (IDS) attempts to discover malicious activities in a network. However, with the increasing network throughput, IDSs should be able to analyse high volumes of traffic in real-time. Flow-based analysis is one of the methods capable of handling high-volume traffic. This method reduces the input traffic of IDSs because it analyses only packet headers. Flow-based anomaly detection can increase the reliability of the Internet, provided this method is functional at an early stage and complemented by packet-based IDSs at later stages. Employing artificial intelligence (AI) methods in IDSs provides the capability to detect attacks with better accuracy. Compared with typical IDSs, AI-based systems are more inclined towards detecting unknown attacks. This thesis proposes an artificial neural network (ANN) based flow anomaly detector optimised with metaheuristic algorithms. The proposed method is evaluated using a number of flow-based datasets generated. An ANN-based flow anomaly detection enables a high detection rate; hence, this thesis investigates this system more thoroughly. The ANN-based system is a supervised method which needs labelled datasets; however, labelling of a large amount of data found in high-speed networks is difficult. Semi-supervised methods are the combination of supervised and unsupervised methods, which can work with both labelled and unlabelled data. A semi-supervised method can provide a high detection rate even when there is a small proportion of labelled data; therefore, the application of this method in flow-based anomaly detection is considered.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Information and Cmmunication Technology
Science, Environment, Engineering and Technology
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Schuricht, Paul Hans. "Liquid crystal thermography in high speed flows." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310549.

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Szymczak, Michel. "Flow visualization of cavitating, high-speed, submerged water jets." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5159.

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Osborn, Allan Ray. "Flow control methods in a high-speed virtual channel." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13521.

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Nguyen, Hoang Cuong. "High speed processing for laser doppler blood flow imaging." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517694.

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Bolzmacher, Christian. "Miniaturized piezoelectric actuators for high-speed flow control applications." Palaiseau, Ecole polytechnique, 2010. http://www.theses.fr/2010EPXX0071.

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En français : Cette thèse décrit le développement d'actionneurs piézoélectriques miniaturisés pour le contrôle actif d'écoulement à haute vitesse. L'objectif est de retarder la transition laminaire turbulente par le contrôle actif des ondes de Tollmien-Schlichting par introduction d'ondes artificielles à phase inversée. Le premier concept étudié dans cette thèse est un actionneur amplifié mécaniquement avec une structure de type levier élastique situé au-dessus d'une céramique piézoélectrique. Les avantages de cet actionneur sont le contrôle direct, la fonction de transfert linéaire, et le temps de réponse très rapide, ce qui facilite l'intégration dans un système asservi. Le deuxième concept est basé sur l'utilisation d'une membrane conique actionnée par un anneau piézoélectrique dans un mode propre axisymétrique. La géométrie conique focalise les ondes générées par l'anneau piézoélectrique vers le centre ou les amplitudes sont le plus importantes. Pour le control des ondes de Tollmien-Schlichting, la modulation d'amplitude est appliquée pour atteindre une gamme de fréquence large ou la fréquence porteuse est délivrée par les modes propres. Cet actionneur à l'avantage d'utiliser une membrane robuste fermée et une intégration simple. L'effet des actionneurs sur l'écoulement a été mesuré avec des capteurs film chaud dans une soufflerie en boucle ouverte. Pour les dimensions des actionneurs adaptés sur l'écoulement, l'effet désiré pour le contrôle actif de la transition a été observé. Enfin, il a été démontré que la modulation d'amplitude est une alternative intéressante si la fréquence porteuse est sélectionnée de manière optimale pour qu'elle n'agisse pas sur l'écoulement (> 40kHz)
This work describes the development of miniaturized piezoelectric actuators for high-speed flow control on airfoils. The goal is to delay the laminar-turbulent transition by active wave cancellation of so-called Tollmien-Schlichting waves introducing appropriate counterwaves. The first design concept is based on a mechanically amplified actuator where an external elas-tic lever-type amplification unit is located above a piezoelectric disc. This actuator provides direct control ability, a linear transfer function, and fast response time facilitating its integra-tion in controller systems. The second design concept is based on a tapered membrane driven in one of its axisymmetric eigenmodes, excited by a piezoelectric ring placed at the outer edge. The tapered membrane focuses the induced waves to the centre, where maximum amplitudes can be observed. Ampli-tude modulation allows the actuator to attain a wide frequency range as required for active cancellation of Tollmien-Schlichting waves, where the carrier frequency is provided by the eigenfrequencies. Its robustness, simple fabrication, and closed surface qualify this actuator for aircraft implementation. The effect of both actuators on the airflow around a wing profile at open-loop control has been measured with hot-film anemometers during a wind tunnel experiment. For device di-mensions adapted to the flow conditions both actuators exhibit the desired effect on the air-flow required for active transition control. It has been shown that amplitude modulation is an option for this type of flow control if the carrier frequency is selected adequately (>40 kHz) in order to not disturb the airflow

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Browning, Patrick H. "Transient flow characteristics of a high speed rotary valve." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10543.

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Thesis (Ph. D.)--West Virginia University, 2009.
Title from document title page. Document formatted into pages; contains xv, 138 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 111-115).

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Birckelbaw, Larry Dean. "High speed aerodynamics of upper surface blowing aircraft configurations." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12913.

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Kaupert, Kevin A. "Unsteady flow fields in a high specific speed centrifugal pump /." Zürich, 1997. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12068.

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Guillou, Florian. "CFD Study of the Flow around a High-Speed Train." Thesis, KTH, Aerodynamik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102033.

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This document is a report summering the master thesis work dealing with the Computational Fluid Dynamic (CFD) study of the flow around a high-speed train. The model is a scaled 1:50 generic train with two cars, one inter-car gap and simplified bogies. A platform is set on the side of the train since one of the aim of the study is to look at the consequences of the phenomena in the wake on people or objects standing on the platform. The slipstream is one of this phenomena, it is due to the fact that the viscous air is dragged when the train is passing. If too strong, it can move or destabilize people or objects on the platform. In addition of the slipstream study, a velocity profile study, a drag and lift coefficients analyze as well as a Q-factor study and a frequency study have been realized. Some results of these different studies are compared with the ones obtained on the same model with a Delayed Detached Eddy Simulation (DDES). Since the flow is turbulent, for those different studies, the flow has been simulated with a Reynolds Averaged Navier-Stokes equation model (RANS) which is the k-ω SST model for the turbulence. The study of the slipstream allowed to calculate the Technical Specification for Interoperability (TSI) which must not be higher that the European Union requirement set at 15.5 m/s, the result obtained is 8.1 m/s which is then lower than the limit. The velocity profile shows similarities with the DDES results even though it is less detailed. The same conclusion is done for the Q-plot where is clearly visible the two counter-rotating vortices in the wake. Finally, a Fast Fourier Transform algorithm has been applied to instantaneous velocity results in the wake of the train in order to get the frequency of the aerodynamic phenomena in that wake. The main frequency is 25 Hz and corresponds to a Strouhal number of 0.1, quite closed to the results obtained with DDES which is 0.085. The results of the RANS and DDES are reasonably similar and by regarding at the large difference between the cell numbers (respectively 8 500 000 and 20 000 000) it can be conclude that in some ways the RANS model can be preferred at the DDES to save time for the computation but it does not contain the small scales resolved by the DDES.

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Satija, Aman. "Development of a high speed three-dimensional flow visualization technique." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/SATIJA_AMAN_1.pdf.

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Keshav, Saurabh. "Using Plasmas for High-Speed Flow Control and Combustion Control." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1222026159.

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Lyes, Peter A. "Low speed axial compressor design and evaluation : High speed representation and endwall flow control studies." Thesis, Cranfield University, 1999. http://hdl.handle.net/1826/4251.

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This Thesis reports the design, build and test of two sets of blading for the Cranfield University low speed research compressor. The first of these was a datum low speed design based on the fourth stage of the DERA high speed research compressor C 147. The emphasis of this datum design was on the high-to-low speed transformation process and the evaluation of such a process through comparing detailed flow measurements from both compressors. Area traverse measurements in both the stationary and rotating frame of reference were taken at Cranfield along with overall performance, blade surface static pressure and flow visualisation measurements. These compare favourably with traverse and performance measurements taken on C147 before commencement of the PhD work. They show that despite the compromises made during the transformation process, due to both geometric and aerodynamic considerations, both the primary and secondary flow features can be successfully reproduced in the low speed environment. The aim of the second design was to improve on the performance of the datum blading through the use of advanced '3D' design concepts such as lean and sweep. The blading used nominally the same blade sections as the datum, and parametric studies were conducted into various lean/sweep configurations to try to optimise the blade performance. The final blade geometry also incorporated leading edge recambering towards the fixed endwalls of both the rotor and stator. The '3D' blading demonstrated a 1.5% increase in efficiency (over the datum blading) at design flow rising to around 3% at near stall along with an improvement in stall margin and pressure rise characteristic. The design work was completed using the TRANSCode flow solver for both the blade-to-blade solutions (used in the SI-S2 datum design calculation) and the fully 3D solutions (for the advanced design and post datum design appraisal). The 3D solutions gave a reasonable representation of the mid-span and main 3D flow features but failed to model the corner and tip clearance flow accurately. An interesting feature of the low speed flowfield was the circumferential variation in total pressure observed at exit from all rotors for both designs. This was not present at high speed and represents one of the main differences between the high and low speed flow. Unsteady modelling of mid- height sections from the first stage indicate that part of this variation is due to the potential interaction of the rotor with the downstream stator while the remainder is due to the wake structure from the upstream stator convecting through the rotor passage. Finally, the implications for a high speed design based on the success of the 3D low speed design are considered.

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Lo, I.-Lung. "Data flow description with VHLD." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA246211.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 1990.
Thesis Advisor(s): Lee, Chin-Hwa Second Reader: Cotton, Mitchell L. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Computer Aided Design, High Level Languages, Computerized Simulation, Theses, VHSIC (Very High Speed Integrated Circuits), VHDL (VHSIC Hardware Description Language). Author(s) subject terms: W-4 Computer, PC, TAR, RAM, ACC, ALU, B_REG, IR, Controller, Test_Bench, VHDL. Includes bibliographical references (p. 113). Also available in print.

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Warta, Brett James. "Characterization of High Momentum Flux Combustion Powered Fluidic Actuators for High Speed Flow Control." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19873.

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The performance of a high-power small-scale combustion-based fluidic actuator for high-speed flow control applications is characterized with specific focus on comparisons between premixed and nonpremixed operating modes for the device. Momentary (pulsed) actuation jets are produced by the ignition of a mixture of gaseous fuel and oxidizer within a small (cubic centimeter scale) combustion chamber. The combustion process yields a high pressure burst (1 to 3 ms in duration in the typical configurations) and the ejection of a high-speed exhaust jet. The actuation frequency can be continuously varied by independently controlling the flow rate of the fuel/oxidizer and the spark ignition frequency up to a maximum determined by the operating characteristics of the actuator. The actuator performance is characterized by both its peak thrust and net total impulse, with increases in peak jet momentum often two to three orders of magnitude above the baseline steady jet. Results for operation of the device in both premixed and nonpremixed modes are presented and analyzed, with nonpremixed operation typically yielding higher pressures and greater frequency ranges in the present configurations.

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Meritt, Ryan James. "Skin Friction Sensor Design Methodology and Validation for High-Speed, High-Enthalpy Flow Applications." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54569.

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This investigation concerns the design, build, and testing of a new class of skin friction sensor capable of performing favorably in high-speed, high-enthalpy flow conditions, such as that found in atmospheric re-entry vehicles, scramjets, jet engines, material testing, and industrial processes. Fully understanding and optimizing these complex flows requires an understanding of aerodynamic properties at high enthalpies, which, in turn, requires numerical and analytical modeling as well as reliable diagnostic instrumentation. Skin friction is a key quantity in assessing the overall flight and engine performance, and also plays an important role in identifying and correcting problem areas. The sensor design is founded on a direct-measuring, cantilever arrangement. The design incorporates two fundamental types of materials in regards to thermal conductivity and voltage resistivity properties. The non-conducting material distinction greatly deters the effect of heat soak and prevents EMI transmission throughout the sensor. Four custom fabricated metal-foil strain gauges are arranged in a Wheatstone bridge configuration to increase sensitivity and to provide further compensation for sensitivity effects. The sensor is actively cooled via a copper water channel to minimize the temperature gradient across the electronic systems. The design offers a unique immunity to many of the interfering influences found in complex, high-speed, high-enthalpy flows that would otherwise overshadow the desired wall shear measurement. The need to develop an encompassing design methodology was recognized and became a principal focus of this research effort. The sensor design was developed through a refined, multi-disciplinary approach. Concepts were matured through an extensive and iterative program of evolving key performance parameters. Extensive use of finite element analysis (FEA) was critical to the design and analysis of the sensor. A software package was developed to utilize the powerful advantage of FEA methods and optimization techniques over the traditional trial and error methods. Each sensor endured a thorough series of calibrations designed to systematically evaluate individual aspects of its functionality in static, dynamic, pressure, and thermal responses. Bench-test facilities at Virginia Tech (VT) and Air Force Research Laboratory (AFRL) further characterized the design vibrational effects and electromagnetic interference countermeasure effectiveness. Through iterations of past designs, sources of error have been identified, controlled, and minimized. The total uncertainty of the skin friction sensor measurement capability was determined to be ±8.7% at 95% confidence and remained fairly independent of each test facility. A rigorous, multi-step approach was developed to systematically test the skin friction sensor in various facilities, where flow enthalpy and run duration were progressively increased. Initial validation testing was conducted at the VT Hypersonic Tunnel. Testing at AFRL was first performed in the RC-19 facility under high-temperature, mixing flow conditions. Final testing was conducted under simulated scramjet flight conditions in the AFRL RC-18 facility. Performance of the skin friction sensors was thoroughly analyzed across all three facilities. The flow stagnation enthalpies upward of 1053 kJ/kg (453 Btu/lbm) were tested. A nominal Mach 2.0 to 3.0 flow speed range was studied and stagnation pressure ranged from 172 to 995 kPa (25 to 144 psia). Wall shear was measured between 94 and 750 Pa (1.96 and 15.7 psf). Multiple entries were conducted at each condition with good repeatability at ±5% variation. The sensor was also able to clearly indicate the transient flow conditions of a full scramjet combustion operability cycle to include shock train movement and backflow along the isolator wall. The measured experimental wall shear data demonstrated good agreement with simple, flat-plate analytical estimations and historic data (where available). Numerical CFD predictions of the scramjet flow path gave favorable results for steady cold and hot flow conditions, but had to be refined to handle the various fueling injection schemes with burning in the downstream combustor and surface roughness models. In comparing CFD wall shear predictions to the experimental measurements, in a few cases, the sensor measurement was adversely affected by shock and complex flow interaction. This made comparisons difficult for these cases. The sensor maintained full functionality under sustained high-enthalpy conditions. No degradation in performance was noted over the course of the tests. This dissertation research and development program has proven successful in advancing the development of a skin friction sensor for applications in high-speed, high-enthalpy flows. The sensor was systematically tested in relevant, high-fidelity laboratory environments to demonstrate its technology readiness and to successfully achieve a technology readiness level (TRL) 6 milestone. The instrumentation technology is currently being transitioned from laboratory development to the end users in the hypersonic test community.
Ph. D.

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Bolzmacher, Christian [Verfasser]. "Miniaturized Piezoelectric Actuators for High-Speed Flow Control Applications / Christian Bolzmacher." Aachen : Shaker, 2011. http://d-nb.info/1098039440/34.

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Morgan, Andrew Stacy. "Design Flow Based on Sensitivity Analysis for High-speed Digital Circuits." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-03252004-025959/.

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The purpose of this work is to develop a design flow for high-speed digital circuits that may be used to increase the quality of circuit performance and improve the ability of inexperienced circuit designers. This design flow meshes the use of hand and simulation analysis to increase intuitive understanding of the dominant relationships and most significant circuit parameters that determine performance. The research relies heavily on determining the sensitivity of chosen performance measures to variation in selected circuit parameters, such as transistor gate width. Four detailed examples that follow the generalized design flow are included to illustrate practical application. The examples consist of the following circuits: source-follower, gate-isolated voltage sense-amplifier, Schmidt trigger, and dual-rail domino logic gate. The examples include design specifications, topology advantages and disadvantages, a suggested design approach, and detailed sensitivity analysis including quantitative simulation results supporting drawn conclusions.

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Devito, Anthony. "The combustion of bulk metals in a high-speed oxidizing flow." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123120.

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The ignition of titanium in bulk form when exposed to a supersonic ﬂow of oxygen is studied. Prior studies have shown that the ignition of various bulk metals was possible and suggested that, despite air at ambient conditions (1 bar, 300 K) being outside the ignition envelope of these metals, they are capable of igniting in pure oxygen at elevated pressure and may continue to burn in air once ignited. The data from prior studies were relatively sparse in their measurement of the oxygen partial pressure and ﬂow (or projectile) velocity required to observe bulk metal combustion. The present study focuses on performing a systematic investigation of the envelope of projectile velocities and oxygen pressures for which exothermic reaction is observed to occur for titanium projectiles. Projectiles, consisting of spheres 3.175 mm (0.125 in) in diameter, were launched at speeds of 0.7 to 1.8 km/s (Mach 2.0 to 5.4) using a single-stage light-gas gun into a test section of oxygen with pressure varying between 1 and 5.5 bar in order to determine the conditions necessary to observe combustion. The projectile is observed using a combination of high-speed photography, photodetectors, and spectrometers to quantify the luminosity emitted. The results are correlated with the melting and boiling points of titanium, the adiabatic ﬂame temperature, and the stagnation conditions of the supersonic ﬂow. A model was also developed and successfully reproduced the main experimental trends as well as corroborated the above claim that combustion was occurring.
L'allumage de titane en vrac lorsqu'il est exposé à un écoulement supersonique d'oxyène est étudiée. Des études antérieures on montré que l'allumage de divers métaux en vrac étaient possible et a suggéré que, en depit de l'air dans les conditions ambiantes (1 bar, 300 K) étant à l'extérieur de l'enveloppe de l'allumage de ces métaux, ils sont capables d'allumer dans l'oxygène pur à des pressions élevées et peuvent continuer à brûler dans l'air une fois allumés. Les données provenant d'études antérieures étaient relativement rares dans leur mesure de la pression partielle d'oxygène et la vitesse du projectile requise pour observer la combustion du métal en vrac. La présente étude se concentre sur la réalisation d'une étude systématique de l'enveloppe de vitesses des projectiles et des pressions d'oxygène pour lesquels on observe une réaction exothermique se produire pour les projectiles de titane. Les projectiles, composé de sphères 3,175 mm (0.125 po) de diamètre, ont été lancés à des vitesses de 0,7 à 1,8 km/s (Mach 2,0 à 5,4) par un canon à gaz léger à un seul étage dans une section d'essai de l'oxygène avec une pression variant entre 1 et 5,5 bar afin de déterminer les conditions nécessaires pour observer la combustion. Le projectile est observée à l'aide d'une combinaison de la photographie à haute vitesse, des photodétecteurs, et spectromètres pour quantifier la luminosité émise. Les résultats sont en corrélation avec les points de fusion et d'ébullition de titane, la température de flamme adiabatique, et des conditions de stagnation de l'écoulement supersonique. Un modèle a également été élaboré et reproduit avec succès les principales tendances éxperimentales ainsi que corroboré la demande ci-dessus que la combustion se produisait.

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Stanislaw, Gregory Scott. "Utility of the flow substitution principle for high speed propulsion applications." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/49969.

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Botros, Barbara Brenda. "Impact of unsteady flow processes on the performance of a high speed axial flow compressor." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44880.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references (leaves 66-67).
This thesis examines the unsteady interactions between blade rows in a high Mach number, highly-loaded compressor stage. Two straight vane/rotor configurations with different axial spacing between vane and rotor are considered. The numerical simulations of the two configurations are used to determine the effect of axial blade row spacing on the level of entropy generation and the flow mechanisms that affect stage performance. The rotor shock waves that impinge on the upstream blade row result in shed vortices that convect downstream through the rotor. At the reduced axial spacing, vortices with larger circulation and entropy are formed. Local entropy generation is assessed using a new numerical technique that allows adequate evaluation of spatial derivatives in high gradient regions, such as shock waves. It is found that the main difference in entropy generation between the two configurations studied is associated with the shed vortices. Entropy production and rotor work input depend on the vortex trajectory within the rotor, which in turn depends on the ratio of time scales: the time for vortex convection between blade rows, and the rotor period (i.e. the time for the rotor to move one rotor pitch), for a fixed geometry and inlet Mach number.
by Barbara Brenda Botros.
S.M.

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Pasumarti, Venkata-Ramya. "Large eddy simulation of heated pulsed jets in high speed turbulent crossflow." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37291.

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The jet-in-crossflow problem has been extensively studied, mainly because of its applications in film cooling and injector designs. It has been established that in low-speed flows, pulsing the jet significantly enhances mixing and jet penetration. This work investigates the effects of pulsing on mixing and jet trajectory in high speed (compressible) flow, using Large Eddy Simulation. Jets with different density ratios, velocity ratios and momentum ratios are pulsed from an injector into a crossflow. Density ratios used are 0.55 (CH4/air), 1.0 (air/air) and 1.5 (CO2/air). Results are compared with the low speed cases studied in the past and then analyzed for high speed scaling. The simulations show that the lower density jet develops faster than a higher density jet. This results in more jet spread for the lower density jet. Scaling for jet spread and the decay of centerline jet concentration for these cases are established, and variable density scaling law is developed and used to predict jet penetration in the far field. In most non-premixed combustor systems, the fuel and air being mixed are at different initial temperatures and densities. To account for these effects, heated jets at temperatures equal to 540K and 3000K have been run. It has been observed that, in addition to the lower density of heated jets, the higher kinematic viscosity effects the jet penetration. This effect has been included and validated in the scaling law for the heated jet trajectory.

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28

Lippett, D. A. "The aquisition of three dimensional flow measurements through a muli stage high speed axial flow compressor." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/10721.

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The focus of the thesis is research based around Cranfield University's 3-stage high speed axial compressor test rig. This newly built rig supported by European Commission funding has tested a set of conventionally stacked 2D rotor and stator blades. The results will be used to evaluate the CFD codes; a advanced three dimensional blade set will then be designed by a collaboration of companies. The aim of which is to prove a 2% efficiency gain for the advanced blade set. Due to the limited axial spacing between the measurement planes a unique seven probe assembly and traverse mechanism has been designed. The assembly has the ability to yaw the probes and control the insertion depths. This takes a number of different probes such as cobra probes, fast response (pneumatic) probes and temperature probes. A computer program has been written that completely automates the control of the probes and the data acquisition. This has allowed full area traversing of the compressor between rotor and stator blade rows. Due to the unique design of the seven probes, a high-speed wind turmel section has also been designed and manufactured. This has enabled the probes to be calibrated for mach numbers up to 0.78 as well as for both pitch and yaw. Due to the representative size, blade count and high flow forces of the high-speed compressor, instrumentation to capture the three-dimensional flow field in a high-speed environment has been researched. A small four-hole probe has been designed and used to take three dimensional steady state pneumatic measurements. This combined with a post processing program has provided very detailed results downstream of the stators through the compressor. This includes the complex three-dimensional flow structure and secondary flows associated with tip leakage, end wall boundary layer, wake transportation and blade row interactions. A fast response probe was designed and evaluated to capture the flow field downstream of the rotors but found to be insensitive to yaw angle. The results taken in a high-speed environment at full scale and engine representative speed supports some of the findings taken in a low speed environment. The author considers that the higher turbulence and speeds leads to increased mixing in the blade rows. This leads to almost all the ow being three dimensional in nature, this is not apparent in a low speed representation. The upstream wakes and their interaction with the downstream rows can be clearly seen. This is further demonstrated by the insertion of an upstream probe. The effects of this probe being transported axially downstream through a blade row. The results show the effectiveness and importance of a rigorous mapping procedure. This is particularly useful where the wake thicknesses are small and pressure gradients are high in comparison to the probe size. The size and extent of the areas of loss become more pronounced as results are taken through the compressor. This is true both at peak efficiency as well as near surge. The higher loading at the near surge condition increases these areas of loss still further.

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29

Lippett, David A. "The acquisition of three dimensional flow measurements through a muli stage high speed axial flow compressor." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/10721.

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The focus of the thesis is research based around Cranfield University's 3-stage high speed axial compressor test rig. This newly built rig supported by European Commission funding has tested a set of conventionally stacked 2D rotor and stator blades. The results will be used to evaluate the CFD codes; a advanced three dimensional blade set will then be designed by a collaboration of companies. The aim of which is to prove a 2% efficiency gain for the advanced blade set. Due to the limited axial spacing between the measurement planes a unique seven probe assembly and traverse mechanism has been designed. The assembly has the ability to yaw the probes and control the insertion depths. This takes a number of different probes such as cobra probes, fast response (pneumatic) probes and temperature probes. A computer program has been written that completely automates the control of the probes and the data acquisition. This has allowed full area traversing of the compressor between rotor and stator blade rows. Due to the unique design of the seven probes, a high-speed wind turmel section has also been designed and manufactured. This has enabled the probes to be calibrated for mach numbers up to 0.78 as well as for both pitch and yaw. Due to the representative size, blade count and high flow forces of the high-speed compressor, instrumentation to capture the three-dimensional flow field in a high-speed environment has been researched. A small four-hole probe has been designed and used to take three dimensional steady state pneumatic measurements. This combined with a post processing program has provided very detailed results downstream of the stators through the compressor. This includes the complex three-dimensional flow structure and secondary flows associated with tip leakage, end wall boundary layer, wake transportation and blade row interactions. A fast response probe was designed and evaluated to capture the flow field downstream of the rotors but found to be insensitive to yaw angle. The results taken in a high-speed environment at full scale and engine representative speed supports some of the findings taken in a low speed environment. The author considers that the higher turbulence and speeds leads to increased mixing in the blade rows. This leads to almost all the ow being three dimensional in nature, this is not apparent in a low speed representation. The upstream wakes and their interaction with the downstream rows can be clearly seen. This is further demonstrated by the insertion of an upstream probe. The effects of this probe being transported axially downstream through a blade row. The results show the effectiveness and importance of a rigorous mapping procedure. This is particularly useful where the wake thicknesses are small and pressure gradients are high in comparison to the probe size. The size and extent of the areas of loss become more pronounced as results are taken through the compressor. This is true both at peak efficiency as well as near surge. The higher loading at the near surge condition increases these areas of loss still further.

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30

Muld, Tomas W. "Slipstream and Flow Structures in the Near Wake of High-Speed Trains." Doctoral thesis, KTH, Farkost och flyg, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94182.

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Train transportation is a vital part of the transportation system of today. Asthe speed of the trains increase, the aerodynamic effects become more impor-tant. One aerodynamic effect that is of vital importance for passengers’ andtrack workers’ safety is slipstream, i.e. the induced velocities by the train.Safety requirements for slipstream are regulated in the Technical Specificationsfor Interoperability (TSI). Earlier experimental studies have found that forhigh-speed passenger trains the largest slipstream velocities occur in the wake.Therefore, in order to study slipstream of high-speed trains, the work in thisthesis is devoted to wake flows. First a test case, a surface-mounted cube, issimulated to test the analysis methodology that is later applied to two differ-ent train geometries, the Aerodynamic Train Model (ATM) and the CRH1.The flow is simulated with Delayed-Detached Eddy Simulation (DDES) andthe computed flow field is decomposed into modes with Proper Orthogonal De-composition (POD) and Dynamic Mode Decomposition (DMD). The computedmodes on the surface-mounted cube compare well with prior studies, whichvalidates the use of DDES together with POD/DMD. To ensure that enoughsnapshots are used to compute the POD and DMD modes, a method to inves-tigate the convergence is proposed for each decomposition method. It is foundthat there is a separation bubble behind the CRH1 and two counter-rotatingvortices behind the ATM. Even though the two geometries have different flowtopologies, the dominant flow structure in the wake in terms of energy is thesame, namely vortex shedding. Vortex shedding is also found to be the mostimportant flow structure for slipstream, at the TSI position. In addition, threeconfigurations of the ATM with different number of cars are simulated, in orderto investigate the effect of the size of the boundary layer on the flow structures.The most dominant structure is the same for all configurations, however, theStrouhal number decreases as the momentum thickness increases. The velocityin ground fixed probes are extracted from the flow, in order to investigate theslipstream velocity defined by the TSI. A large scatter in peak position andvalue for the different probes are found. Investigating the mean velocity atdifferent distances from the train side wall, indicates that wider versions of thesame train will create larger slipstream velocities.

QC 20120530

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31

Tanguay, Vincent. "Combustion of reactive metal particles in high-speed flow of detonation products." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32579.

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It is common practice to add reactive metal particles to high-explosive formulations in order to increase the total energy output. The present study is an effort to increase the understanding of metal particle combustion in detonation products. Aluminum and magnesium particles ranging from 2 to 100 μm are subjected to the flow of detonation products of a stoichiometric mixture of hydrogen and oxygen. Luminosity emitted from the reacting particles is used to determine the reaction delay and duration. It is found that the reaction duration increases as d^n with n ≈ 0.5, more consistent with kinetically controlled reaction rather than the classical diffusion controlled regime. Emission spectroscopy is used to estimate the combustion temperature, which is found to be well below the flow temperature. This fact also suggests combustion in the kinetic regime. Finally, the flow field is modelled with a CFD code and the results are used to model analytically the behaviour of the aluminum particles. Furthermore, a simple analytical model is developed to predict ignition of magnesium particles in nitromethane detonation products. The flow field is simplified by considering the detonation products as a perfect gas expanding in a vacuum in a planar geometry. This simplification allows the flow field tobe solved analytically. A single particle is then introduced in this flow field. Its trajectory and heating history are computed. It is found that most of the particle heating occurs in the Taylor wave and in the quiescent flow region behind it, shortly after which the particle cools. By considering only these regions, thereby considerably simplifying the problem, the flow field ca
Il est maintenant courant d'ajouter des particules de métaux réactifs aux formulations d'explosifs pour augmenter l'énergie libérée. Cette étude vise une meilleure compréhension de la combustion de métaux dans les produits de détonation. Des particules d'aluminium et de magnésium de 2 à 100 μm sont exposées à l'écoulement des produits de la détonation d'un mélange d'hydrogène et d'oxygène. La lumière émise par les particules est utilisée pour déterminer le délai et la durée de la réaction. La durée de la réaction augmente selon d^n avec n ≈ 0.5. Ces résultats suggèrent un régime de combustion cinétique plutôt que le régime diffusif classique. La température de combustion est mesurée à l'aide de spectroscopie d'émission. La température mesurée est plus basse que celle de l'écoulement, ce qui est également cohérent avec un régime de combustion cinétique. Finalement, l'écoulement est modélisé avec un code Euler, dont les résultats sont utilisés pour modéliser analytiquement le comportement des particules. Dans un deuxième temps, un modèle analytique simple est développé pour prédire l'ignition de particules de magnésium dans les produits de détonation de nitrométhane. L'écoulement est simplifié en traitant les produits comme gaz parfaits, qui prennent de l'expansion dans le vide dans une géométrie planaire. Ces simplifications permettent de résoudre l'écoulement analytiquement. Ensuite, la trajectoire et la température d'une seule particule introduite dans l'écoulement sont calculées. La particule est chauffée principalement dans le "Taylor wave" et dans la région quiescente derrière celle-ci. En ne

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32

Neale, Samuel. "High speed flow through silicon nitride nanopores as a potential dumb hole." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121513.

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Nanopores with diameters ranging from 30 nm to 50 nm were drilled in siliconnitride membranes using a transmission electron microscope (TEM) electronbeam. High pressures of cold helium gas were applied to one side of themembranes to achieve flow through the nanopores. Mass flows for pressuregradients up to 1000 psi were measured with the goal of achieving transonicflow. Measured mass flows were compared to theoretical choked flow valuesand the flow speeds were deduced analytically. The ultimate goal of this workwas to determine whether or not TEM drilled nanopores can act as de Lavalnozzles and accelerate fluid to, or close to the speed of sound. While the siliconnitride nanopores do present some technical difficulties, we estimated that inour nanopores, Unruh temperatures on the order of 7 10^-3 K were reached,leading to phonons being emitted at a rate in the range of 10^5 to 10^6 Hz.
Des nanopores de diamètres situés entre 30 et 50 nm ont été perçés dans desmembranes de nitrure de silicium (amorphe) à l'aide d'un microscope électroniqueen transmission (MET). De hautes pressions de gaz d'hélium froidont été appliquées d'un côté de la membrane permettant l'écoulement du fluideà travers le nanopore. Le débit de masse a été mesuré pour des differencesde pressions allant jusqu'à 1000 psi, l'objectif étant d'atteindre un écoulementtransonique. Les mesures ont été comparées à un modèle théorique et lesvitesses d'écoulement ont été déduit analytiquement. Le but de ce projet estde déterminer si les nanopores perçés à l'aide du MET peuvent agir commedes tuyères de Laval et accélerer le fluide à des vitesses proches de celle duson. Bien que les nanopores utilisés présentent des difficultés techniques, il aété estimé qu'il permettraient d'observer une température de Unruh de l'ordrede 7 10^-3 K, et les phonons seraient émis à une fréquence de l'ordre de 10^5à 10^6 Hz.

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33

Cutbill, Sue. "A study of the turbulent flow of a high speed Coanda jet." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4743/.

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This thesis presents an experimental investigation into a compressible turbulent wall jet issuing from a slot, and flowing over a surface with streamwise curvature, followed by a plane wall recovery region. The purpose of this data was to provide suitable test cases to aid in the design and validation of turbulence models used for curved flow situations in computational fluid dynamics. The presence of streamwise curvature provides an extra rate of strain to the flow which effects both the mean flow field and the turbulence structure. The effects of curvature are dependent on the ratio of the slot width to the radius of curvature. The effects are increased with the magnitude of this ratio. Hot film anemometry was used to measure the mean flow and Reynolds stresses under six different flow regimes. Four experiments were performed using a constant slot to radius ratio, and the supply pressure ratio was varied. Two further experiments were performed at a constant pressure ratio, but at differing slot to radius ratios. In all cases, the extra rate of strain was found to increase the jet growth and velocity decay rates beyond those of a plane wall jet. 'History effects' were apparent where there was a change from flow with streamwise wall curvature to that without. The turbulence structure was found to require a finite distance along the recovery section before it reverts to a plane wall turbulence structure. The presence of the extra rate of strain, and the history effects at sudden changes in surface curvature, make strong demands on any turbulence model. Various turbulence models have been tested, and although no one turbulence model has proved robust enough for all flow situations, a number of models have been identified to provide superior performance under certain conditions. The use of a higher order numerical scheme has also been found to reduce the effects of numerical diffusion, leading to improvements in the predictions of the flow shock cell structure and the breakaway performance of the jet.

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34

Amaratunga, Shane R. "A numerical study into surface catalytic effects in non-equilibrium reacting viscous laminar hypersonic flow." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266941.

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35

Srinivasan, Ravichandra. "Improved understanding and control of high-speed jet interaction flows." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3055.

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A numerical study of the flow field generated by injection through diamondshaped orifices into a high-speed flow is presented in this document. Jet interaction flows have a wide range of applications in the field of engineering. These applications include the use of jets for fuel injection in scramjets, for reaction control of high-speed aerodynamic bodies and as cooling jets for skins of high-speed vehicles. A necessary requirement in the use of transverse jets for these and other applications is a thorough understanding of the physics of the interaction between the jet and freestream. This interaction generates numerous flow structures that include multiple shocks, vortices, recirculation regions and shear layers. This study involves diamond-shaped orifices that have the advantage of generating weaker or attached interaction shocks as compared to circular injectors. These injectors also negate the effects due to the recirculation region that is formed upstream of the injector. This study was undertaken in order to gain further understanding of the flow features generated by diamond-shaped injectors in a high-speed flow. Numerical simulations were performed using two different levels of turbulence models. Reynolds Averaged Navier-Stokes (RANS) simulations were performed using the GASP flow solver while Detached-Eddy Simulation (DES) runs were performed using the Cobalt flow solver. A total of fifteen diamond injector simulations were performed using the RANS model for a 15 half-angle diamond injector. The fifteen simulations spanned over five different injection angles and three jet total pressures. In addition to these, two circular injector simulations were also performed. In addition, low pressure normal injection through diamond and circular orifices simulations were performed using DES. Results obtained from CFD were compared to available experimental data. The resulting flow structure and the turbulent properties of the flow were examined in detail. The normal injection case through the diamond-shaped orifice at the lowest jet total pressure was defined as the baseline case and is presented in detail. In order to study the effect of different components of the vorticity transport equation, an in-house code was used post-process the results from the RANS runs.

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Che, Idris Azam. "Characterization of high speed inlets using global measurement techniques." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/characterization-of-high-speed-inlets-using-global-measurement-techniques(ca8b687b-aff0-4b50-892f-897a962e22ba).html.

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After the end of the NASA space shuttle programme, there has been resurgence of interest in developing a single stage-to-orbit spacecraft. The key technology to realize this dream is the airbreathing scramjet engine. The scramjet concept has been around for decades, but much work is still needed in order to eliminate the remaining obstacles to develop a practical working prototype of the engine. Many such obstacles are related to the inlet which functions as the main compression unit for the engine. Typically, a high speed inlet is designed to function properly in a single flight condition. Such an inlet would experience adverse flow conditions related to various shock-shock interactions, viscous effects, shock-boundary layer interactions, and many other flow phenomena at off-design conditions. The traditional mechanism to mitigate the adverse flow conditions is by varying the inlet geometry at off-design conditions. There are still gaps in understanding the behaviour of inlets at off-design conditions and the effectiveness of variable geometry as inlet flow control. This is partly due to complex flow diagnostics setup, which limits the type, quantity and quality of information that can be extracted from the inlet flow. The first objective of this thesis was to develop a global inlet measurement system that can provide an abundance of information on inlet flow. The pressure sensitive paint method was employed together with other methods to provide comprehensive understanding on inlet flow characteristics. Calculation of Mach number at the isolator exit using the isolator sidewall pressure map was successfully demonstrated. The measurement of Mach number at the isolator exit has allowed for performance of the inlet to be calculated without the need for intrusive flow diagnostics tools used by previous researchers. The global measurement system was then employed to investigate the characteristics of the scramjet inlet operating at various off-design conditions. Complex shock structures were observed at the inlet cowl entrance as the angle-of-attack was increased. The relationship of flow quality and inlet performance was examined and discussed. General improvements on the inlet performance were obtained if the size of separation on the compression ramp was reduced. The inlet was also observed to perform poorly when compression shocks impinged on the inner cowl surface. Cowl deflections were demonstrated to be effective in controlling the internal flow of the inlet and improving its performance. An exploratory study on the role of micro-vortex generators to control boundary layer separation on scramjet inlets has been included as well. Strategies for optimizing an inlet at off-design conditions were analysed, and it was found that any variable geometry combination must maintain high throat-to-freestream Mach number ratio in order to preserve high inlet performance.

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Crawley, Michael B. "Understanding the Aeroacoustic Radiation Sources and Mechanisms in High-Speed Jets." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1446152138.

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38

Russler, Patrick M. "An investigation of the surge behavior of a high-speed ten-stage axial flow compressor." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040554/.

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Romero, HernaÌndez Sergio. "Determination of windage losses on high-speed enclosed rotating discs with superposed flow." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270488.

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40

Guilbert, A. R. "Modelling of piezoelectric ultrasonic transducers with application to high speed gas flow measurement." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/10402.

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The design and testing of an ultrasonic time of ight Mach number probe for use in the bypass duct of an aircraft gas turbine is presented. Analysis of the time and frequency domain behaviour of the type of thickness mode transducers selected for use in the probe, and the effects of beam profile and attenuation on the transmitted ultrasonic wave in a owing medium are also covered and extended. The results of this analysis are implemented in a computer model which is used to aid in the design of various parts of the probe. Experimental assessment of the transducers designed for the probe is presented together with the results of tests on the performance of the selected probe configuration. A digital signal processing system to control the probe and compensate for the poor signal to noise ratio of the received signal is developed together with analogue circuitry to interface this system to the transducers. A novel method of compensating for the beam sweep encountered at the Mach numbers to b measured using 'ski-ramps' is then developed and implemented. Results from the final configuration including the ski-ramps is then presented.

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Santos, Eduardo Nunes dos. "Development and application of wire-mesh sensors for high-speed multiphase flow imaging." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1410.

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ANP; PETROBRAS, FINEP
Escoamentos multifásicos estão presentes não somente em diversos processos da natureza, mas também são muito comuns em diversas atividades industriais, como na exploração, produção e transporte de petróleo e gás. Na produção de petróleo, a mistura multifásica de gás, petróleo e água é frequentemente encontrada fluindo através de colunas e risers de produção. Nos últimos anos muito progresso no desenvolvimento e aplicação de técnicas de medição em escoamentos multifásicos foi realizado cujo intuito é quantificar com exatidão, prever e/ou controlar o fluxo de misturas multifásicas. Em especial técnicas de imageamento do escoamento multifásico estão em foco atualmente. Sensores de malha de eletrodos (wire-mesh sensors) são dispositivos que produzem imagens da distribuição das fases na seção transversal de uma tubulação com alta resolução espacial e temporal. Em estudos anteriores a utilização desse sensor é explorada em diversas aplicações em escoamentos bifásicos (predominantemente do tipo gás-líquido). O princípio de funcionamento do sensor é baseado na medição de uma única propriedade elétrica (condutividade ou permissividade) da mistura multifásica. Portanto, o objetivo deste trabalho é a aplicação da técnica wire-mesh para visualização de escoamentos multifásicos em alta velocidade para condições de escoamentos diferentes daquelas utilizados até o momento, bem como prover a técnica com melhorias, adicionando a capacidade de operar em dupla modalidade (medição simultânea condutiva/capacitiva). Assim, novos algoritmos e rotinas de processamento de dados para a investigação de escoamentos gás-líquido e sólido-líquido (suspensão) foram desenvolvidos e testados. A fim de continuar com o aprimoramento da técnica xiii de medição, uma nova eletrônica capaz de medir simultaneamente a permissividade e condutividade através da medição (vetorial) de amplitude e fase é introduzido. Além disso, um algoritmo baseado em um modelo da permissividade elétrica complexa realiza a fusão dos dados de condutividade e permissividade gerados pela técnica desenvolvida. Assim, esta fusão permite obter distribuições individuais das frações de fase de misturas de óleo-água-gás. A principal contribuição deste trabalho no campo de medição e investigação de escoamentos multifásicos é, por conseguinte, o desenvolvimento e aplicação soluções em software e processamento de dados para extração de parâmetros do fluxo multifasico a partir de dados do sensor wire-mesh, bem como a melhoria no sistema de medição com adoção de medidas vetoriais. Desta forma, a gama de aplicação do sensor wire-mesh é ampliada, permitindo a investigação de escoamentos gás-líquido e gás-sólido, assim como escoamentos trifásicos gás-líquido-líquido através de visualização em alta velocidade da distribuição de fases em escoamentos.
Multiphase flows are present not only in nature but also are very common in industrial activities such as in exploration, production and transport of oil and gas. In oil production, the mixture of gas, oil and water is often found streaming through production columns and flow risers. A lot of progress has been made in recent years in the development and application of measurement techniques applied to multiphase flow measurement in order to accurately quantify, predict and control the flow of multiphase mixtures. Especially, high-speed imaging of multiphase flows has received much attention in recent years. Wire-mesh sensors are flow-imaging devices and allow the investigation of multiphase flows with high spatial and temporal resolution. In the past, such sensors have found widespread application in gas-liquid flows. Its operating principle is based on measurement of a single electrical property (conductivity or permittivity) of flowing mixture. The objective of this work is the application of the wire-mesh technique for high-speed multiphase flow imaging in different flow conditions as applied so far, as well as the further development of this technique by adding the capability of dual-modality (simultaneous conductive/capacitive) operation. Hence, novel routines and data processing algorithms for the investigation of two-phase flows of the type gas-liquid and solid-liquid (slurry) were developed and tested. As a step towards the further development of the wire-mesh sensor technique, a novel dual- modality electronics being able to simultaneously evaluate the conductivity and permittivity component of a fluid through vector measurements (amplitude and phase) is introduced. Further, a model-based algorithm to fuse the data of dual-modality wire xi mesh sensor is developed to obtain individual phase fraction distributions in gas-oil- water three-phase flows. Hence, this thesis’ main contribution to the field of flow measurement and investigation is the development and application of software solutions for extracting flow parameters from wire-mesh sensor data, as well as the improvement in the hardware of measuring electronics. As a result, the range of application of wire-mesh sensors is enhanced being capable to investigate two-phase gas-liquid and slurry flows as well as gas-liquid-liquid three-phase flow problems through high-speed flow imaging.

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42

Garcia, Robert Gordon. "CFD simulation of flow fields associated with high speed jet impingement on deflectors." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31675.

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Computational Fluid Dynamics is used to analyze the formation of under-expanded jets and to investigate the three-dimensional flow field associated with the impingement of free jets onto stationary deflectors. This investigation was performed to develop a verified modeling ability for such problems. Predictions were compared with the experimental results obtained by Donaldson and Snedeker [1]. Computational models for free and impinging jets were created according to the data provided in Ref. 1. Numerical results for each of the experiments performed in this benchmark report are presented.

Three different turbulent free jets produced by a simple convergent nozzle were analyzed. These include a subsonic jet with p₁/pâ =1 and M₁=0.57, a moderately under-expanded jet with p₁/pâ =1.42 and M₁=1, and a highly under-expanded jet with p₁/pâ =3.57 and M₁=1. The reflecting shocks associated with the moderately under-expanded jet as well as the shock disk associated with the highly under-expanded jet were fully resolved. Velocity profile data predicted at locations downstream of the nozzle exit agreed very well with the experimental results.

The impingement of a moderately under-expanded jet with p₁/pâ =1.42 and M₁=1 was also investigated. The interaction of the high speed jet with circular flat plates at angles of 60Â° and 45Â° relative to the center axis of the jet are presented. Wall jet velocity profiles on the surface of the flat plate are fully resolved and compare well with experimental results. The CFD solver controls and method used to obtain these results are summarized and justified.
Master of Science

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43

Choi, Woong-Sik. "Flame stabilization by a plasma driven radical jet in a high speed flow." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29780.

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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Zinn, Ben; Committee Co-Chair: Jagoda, Jeff; Committee Member: Glezer, Ari; Committee Member: Jeter, Sheldon; Committee Member: Neumeier, Yedidia. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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44

Mizo, Viktor R. "Investigation of inertia controlled bubble departure mechanism in subcooled flow boiling using high speed photography /." Online version of thesis, 1995. http://hdl.handle.net/1850/12084.

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45

Perret, Matias Nicholas. "Local optical phase detection probes with an application to a high speed boundary layer." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2129.

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This thesis presents the continued development of micro optical phase detection instrumentation capable of measuring void fraction, interfacial area density, interfacial velocity and bubble sizes and their application to measurements in a high speed boundary layer. The instrumentation consists of micro sized sapphire tipped probes tailored to measure in the two-phase flow of air bubbles in water. Probe tips with geometries intended to maximize field life while minimizing intrusiveness were designed, fabricated and characterized. The characterization revealed that the active region of a probe tip can go beyond the highly sensitive 45 degree tip. Controlling the active length of the tips can be achieved through a combination of taper angles and 45 degree tip size, with larger tips having shorter active lengths. The full scale bubbly flow measurements were performed on a 6 m flat bottom survey boat. The aforementioned quantities were measured on bubbles naturally entrained at the bow of the boat. Probes were positioned at the bow of the boat, near the entrainment region and at the stern where the bubbles exit after having interacted with the high shear turbulent boundary layer. Experiments were conducted in fresh water, at the Coralville Lake, IA, and salt water, at the St. Andrews Bay and Gulf Coast near Panama City, FL. The results indicate that the bubbles interact significantly with the boundary layer. At low speeds, in fresh water, bubble accumulation and coalescence is evident by the presence of large bubbles at the stern. At high speeds, in both fresh and salt water, bubble breakup dominates and very small bubbles are produced near the hull of the boat. It was observed that salt water inhibits coalescence, even at low boat speeds. Void fraction was seen to increase with boat speeds above 10 knots and peaks near the wall. Bubble velocities show slip with the wall at all speeds and exhibit large RMS fluctuations, increasing near the wall.

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46

Courtiade, Nicolas. "Experimental analysis of the unsteady flow and instabilities in a high-speed multistage compressor." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00838695.

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The present work is a result of collaboration between the LMFA (Laboratoire de Mécanique des Fluides et d'Acoustique, Ecole Centrale de Lyon - France), Snecma and the Cerfacs. It aims at studying the flow in the 3.5-stages high-speed axial compressor CREATE (Compresseur de Recherche pour l'Etude des effets Aérodynamique et TEchnologique - rotation speed: 11543 RPM, Rotor 1 tip speed: 313 m/s), designed and built by Snecma and investigated at LMFA on a 2-MW test rig. Steady measurements, as well as laser velocimetry, fast-response wall static and total pressure measurements have been used to experimentally investigate the flow. The analysis focuses on two main aspects: the study of the flow at stable operating points, with a special interest on the rotor-stator interactions, and the study of the instabilities arising in the machine at low mass flow rates.The description of the unsteady flow field at stable operating points is done through measurements of wall-static pressure, total pressure and velocity, but also total temperature, entropy and angle of the fluid. It is shown that the complexity and unsteadiness of the flow in a multistage compressor strongly increases in the rear part of the machine, because of the interactions between steady and rotating rows. Therefore, a modal analysis method developed at LMFA and based on the decomposition of Tyler and Sofrin is presented to analyze these interactions. It is first applied to the pressure measurements, in order to extract the contributions of each row. It shows that all the complex pressure interactions in CREATE can be reduced to three main types of interactions. The decomposition method is then applied to the entropy field extracted from URANS CFD calculations performed by the Cerfacs, in order to evaluate the impact of the interactions on the performance of the machine in term of production of losses.The last part of this work is devoted to the analysis of the instabilities arising in CREATE at low mass flows. It shows that rotating pressure waves appear at stable operating points, and increase in amplitude when going towards the surge line, until reaching a critical size provoking the onset a full span stall cell bringing the machine to surge within a few rotor revolutions. The study of these pressure waves, and the understanding of their true nature is achieved through the experimental results and the use of some analytical models. A precise description of the surge transient through wall-static pressure measurements above the rotors is also provided, as well as a description of a complete surge cycle. An anti-surge control system based on the detection of the amplitude of the pressure waves is finally proposed.

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47

Lauer, Eric [Verfasser]. "Numerical simulation and investigation of high-speed bubble-dynamics in cavitating flow. / Eric Lauer." München : Verlag Dr. Hut, 2013. http://d-nb.info/1045989126/34.

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48

Kunt, Cengiz O. "Analysis of high speed pneumatic actuation systems under rotary directional on-off flow control /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487596807822691.

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49

O'Neill, Collin James. "Understanding Flow Physics and Control in an Aggressively Offset High-Speed Inlet/Diffuser Model." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu158765763256521.

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50

Kearney-Fischer, Martin A. "The Noise Signature and Production Mechanisms of Excited High Speed Jets." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1318961517.

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Dissertations / Theses on the topic 'High-speed flow'

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