This work studies the effects of radial flow on the aerodynamic phenomena occurring on a retreating blade with a focus on dynamic stall and reverse flow as applied to both a helicopter rotor in forward flight and a wind turbine operating at a yaw angle. While great progress has been made in understanding the phenomenon of two-dimensional dynamic stall, the effect of rotation on the dynamic stall event is not well understood. Experiments were conducted on a rigid two bladed teetering rotor at high advance ratios in a low speed wind tunnel. Particle image velocimetry (PIV) measurements were used to quantify the flow field at several azimuthal angles on the rotating blade during the dynamic stall event. The effect of centrifugal forces induced ``pure'' radial velocity on the dynamic stall event at 270 degrees azimuth was studied in detail. Further investigation of the radial flow field suggested that the mean radial velocity attenuated on moving outboard due to an apparent shear layer instability and it was demonstrated to be of first order importance in the flow field. These radial flow results prompted an exploration of the flow over a rotating disk to establish similarities of the radial flow over rotating blade in separated flow to that over a rotating disk in separated flow. While a greater part of this work focused on aspects of dynamic stall on the retreating blade, the final parts focus on the exotic flow regime of reverse flow (characterized by flow from the trailing edge to the leading edge of the blade). Aerodynamic loads measurement and surface flow visualization via tufts are used to first quantify the behavior of a static yawed blade in reverse flow. PIV measurements are then used on a static yawed blade and a rotating blade in reverse flow conditions to ascertain the effects of rotation on reverse flow.

This thesis numerically studied mass transfer during fully confined liquid jet impingement on a rotating target disk of finite thickness and radius. The study involved laminar flow with jet Reynolds numbers from 650 to 1500. The nozzle to plate distance ratio was in the range of 0.5 to 2.0, the Schmidt number ranged from 1720 to 2513, and rotational speed was up to 325 rpm. In addition, the jet impingement to a stationary disk was also simulated for the purpose of comparison. The electrochemical fluid used was an electrolyte containing 0.005moles per liter potassium ferricyanide (K3(Fe(CN6)), 0.02moles per liter ferrocyanide (FeCN6?4), and 0.5moles per liter potassium carbonate (K2CO3). The rate of mass transfer of this electrolyte was compared to Sodium Hydroxide (NaOH) and Hydrochloric acid (HCl) electrochemical solutions. The material of the rotating disk was made of 99.98% nickel and 0.02% of chromium, cobalt and aluminum. The rate of mass transfer was also examined for different geometrical shapes of conical, convex, and concave confinement plates over a spinning disk. The results obtained are found to be in agreement with previous experimental and numerical studies. The study of heat transfer involved a microchannel for a composite channel of trapezoidal cross-section fabricated by etching a silicon wafer and bonding it with a slab of gadolinium. Gadolinium is a magnetic material that exhibits high temperature rise during adiabatic magnetization around its transition temperature of 295K. Heat was generated in the substrate by the application of magnetic field. Water, ammonia, and FC-77 were studied as the possible working fluids. Thorough investigation for velocity and temperature distribution was performed by varying channel aspect ratio, Reynolds number, and the magnetic field. The thickness of gadolinium slab, spacing between channels in the heat exchanger, and fluid flow rate were varied. To check the validity of simulation, the results were compared with existing results for single material channels. Results showed that Nusselt number is larger near the inlet and decreases downstream. Also, an increase in Reynolds number increases the total Nusselt number of the system.

Bladed disks are critical structural components in jet engines and other turbomachinery. The nominal design for a bladed disk is typically assumed to have identical blades. However, there are always small, random variations in the blade properties due to manufacturing tolerances, material defects, and operational wear. These blade-to-blade discrepancies, called mistuning, can have a dramatic effect on bladed disk vibration. In particular, mistuning can cause localization of the response in a small region of the bladed disk, leading to higher blade stress and high-cycle fatigue concerns. While comprehensive analytical and computational studies of mistuning have been performed, relatively few experimental investigations have been conducted. The primary objective of this research is to experimentally investigate the fundamental structural dynamics of mistuned bladed disks, and to achieve a physical understanding of mistuning effects by accounting for the influence of important phenomena that have been largely neglected in previous mistuning models and system identification algorithms. First, a systematic experimental approach is presented to validate a new mistuning identification and model updating algorithm for single-piece bladed disks, or blisks. It is shown that only a few system response measurements taken at resonant frequencies are required to identify the blade stiffness mistuning parameters and the model updating parameters referred to as cyclic modeling error. By incorporating a model updating procedure, the accuracy of the mistuning identification results are significantly improved. Second, an alternative approach for vibration testing of many mistuning patterns is proposed and validated. In particular, varying the external forcing function provided to the blades is used to mimic the influence of structural blade property mistuning on the vibration response. Since it is much easier and more efficient to vary the external excitation than to physically alter the blades, this work opens the possibility of running an experimental analogue of a Monte Carlo simulation. Finally, the mistuning identification method is extended to also identify the forcing amplitude and phase applied to each blade. This approach shows promise as a powerful tool for accelerating calibration procedures, as well as for improving the accuracy and capability of experimental methods for bladed disks.

Šio darbo tikslas buvo ištirti Galaktikos storojo disko žvaigždžių cheminę evoliuciją. Devynių F-G-K spektrinės klasės žvaigždžių spektrai buvo gauti SOFIN spektrografu su Šiaurės šalių teleskopu. Iš spektrų nustačiau pagrindinius žvaigždžių atmosferų fizikinius parametrus: efektinę temperatūra Teff., gravitacinį pagreitį žvaigždės paviršiuje lg g, mikroturbulencijos greitį vt. ir deguonies, geležies, α, r- ir s-procesų elementų gausas devyniose storojo Galaktikos disko žvaigždėse. Rezultatus palyginau su kitų mokslininkų grupių darbais: tai Tautvaišienės ir kt. darbas (2001 m.); Bensby ir kt. darbai (2004, 2005, 2007 m.); Reddy ir kt. darbas (2006 m.). Geležies gausai [Fe/H] esant intervale nuo ≈ –0,9 iki ≈ –0,3 dešimtųjų žvaigždės, pasižyminčios storojo Galaktikos disko kinematika, yra turtingesnės deguoniu, magniu ir alfa-proceso elementais, nei plonojo disko žvaigždžių populiacija. Kitų cheminių elementų gausos storajame ir plonajame Galaktikos diskų žvaigždėse yra panašios. / The aim of this research is to study the Galactic thick disk chemical evolution. Using high-resolution spectra I have derived the chemical composition of a sample of Galactic thick disk stars. High resolution spectra of 9 F-G-K spectral type stars in the Galactic thick disk have been obtained by the SOFIN spectrograph on the Nordic Optical Telescope. From these stellar spectra I determined the basics stellar atmosphere parameters: effective temperatures Teff [K], surface gravities lg g, microturbulent velocities vt [km/s], and abundances of oxygen, iron, α, r- and s-process elements in the Galactic thick disk. The results are similar to those of other investigations: Tautvaišienė et al., 2001; Bensby et al., 2004, 2005, 2007; Reddy et al., 2006. For a given [Fe/H] the stars with kinematics typical of the thick disk are more enriched in oxygen and α- process elements (Mg, Si, Ca, Ti) than the stars with kinematics typical of the thin disk. The abundance of other elements (Al, Na, Cr, Ni, V, Sc, Mn, Co, Cu, Y, Zr, Ba, La and Nd) is similar for the two disks. The abundance ratios of oxygen, α, r- and s-process elements to iron provide further evidence that the thick disk star population have a different chemical history compared to the thin disk. The stars formation rate was probably higher in the Galactic thick disk than in the Galactic thin disk.

The relining of deteriorated gravity flow and pressure pipes with polymeric liners is now popular practice. In the water industry, health concerns and challenges associated with re-opening water services in a lined small diameter pipe have limited the use of liners. Sanexen Environmental Services Inc. in Montreal, Canada, manufactures a cured-in-place liner system which can restore water service connections after lining from within the pipe, using a remote controlled robot. The installation of the liner within cast iron water pipes can result in the formation of geometric imperfections (wrinkles) as the external diameter of the liner often exceeds the internal diameter of the host pipe. Previous studies have suggested that the wrinkles have a detrimental effect on the structural performance of the liner. In this study, experimental and analytical investigations were conducted to evaluate further the effect of the wrinkles on the circumferential (hoop) strength of the liner. The experimental investigation involved testing 33-25 mm wide ring samples of the liner with and without wrinkles, using the split-disk test method which is defined by ASTM Standard D2290. The laboratory tests were conducted to examine the effects on the response of the liner of loading rate, cyclic loading, and presence of different wrinkle configurations. A series of two-tailed Mann-Whitney statistical tests were conducted on the obtained test data. The analytical investigation examined the behavior of two of the three types of wrinkles observed in the liner using finite element models. The results from the models were evaluated using the experimental results. This study confirmed that the wrinkles were a source of weakness in the liner as failure was initiated at the wrinkle in all the test samples. It also showed that their presence may or may not result in a reduction in the ultimate hoop tensile capacity of the liner depending on wrinkle pattern. The loading rate had no significant effect on the first cracking load of the resin within the wrinkle. However, lower ultimate hoop tensile capacities were observed at very slow loading rates. Under the 50-year cyclic loading, the resin within the wrinkle was susceptible to cracking while the jackets of the wrinkle remained intact. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-09-16 22:38:10.234

No description available.

Ce mémoire a pour but d'étudier les propriétés des solutions à l'équation aux valeurs propres de l'opérateur de Laplace sur le disque lorsque les valeurs propres tendent vers l'in ni. En particulier, on s'intéresse au taux de croissance des normes ponctuelle et L1. Soit D le disque unitaire et @D sa frontière (le cercle unitaire). On s'inté- resse aux solutions de l'équation aux valeurs propres f = f avec soit des conditions frontières de Dirichlet (fj@D = 0), soit des conditions frontières de Neumann ( @f @nj@D = 0 ; notons que sur le disque, la dérivée normale est simplement la dérivée par rapport à la variable radiale : @ @n = @ @r ). Les fonctions propres correspondantes sont données par : f (r; ) = fn;m(r; ) = Jn(kn;mr)(Acos(n ) + B sin(n )) (Dirichlet) fN (r; ) = fN n;m(r; ) = Jn(k0 n;mr)(Acos(n ) + B sin(n )) (Neumann) où Jn est la fonction de Bessel de premier type d'ordre n, kn;m est son m- ième zéro et k0 n;m est le m-ième zéro de sa dérivée (ici on dénote les fonctions propres pour le problème de Dirichlet par f et celles pour le problème de Neumann par fN). Dans ce cas, on obtient que le spectre SpD( ) du laplacien sur D, c'est-à-dire l'ensemble de ses valeurs propres, est donné par : SpD( ) = f : f = fg = fk2 n;m : n = 0; 1; 2; : : :m = 1; 2; : : :g (Dirichlet) SpN D( ) = f : fN = fNg = fk0 n;m 2 : n = 0; 1; 2; : : :m = 1; 2; : : :g (Neumann) En n, on impose que nos fonctions propres soient normalisées par rapport à la norme L2 sur D, c'est-à-dire : R D F2 da = 1 (à partir de maintenant on utilise F pour noter les fonctions propres normalisées et f pour les fonctions propres quelconques). Sous ces conditions, on s'intéresse à déterminer le taux de croissance de la norme L1 des fonctions propres normalisées, notée jjF jj1, selon . Il est vi important de mentionner que la norme L1 d'une fonction sur un domaine correspond au maximum de sa valeur absolue sur le domaine. Notons que dépend de deux paramètres, m et n et que la dépendance entre et la norme L1 dépendra du rapport entre leurs taux de croissance. L'étude du comportement de la norme L1 est étroitement liée à l'étude de l'ensemble E(D) qui est l'ensemble des points d'accumulation de log(jjF jj1)= log : Notre principal résultat sera de montrer que [7=36; 1=4] E(B2) [1=18; 1=4]: Le mémoire est organisé comme suit. L'introdution et les résultats principaux sont présentés au chapitre 1. Au chapitre 2, on rappelle quelques faits biens connus concernant les fonctions propres du laplacien sur le disque et sur les fonctions de Bessel. Au chapitre 3, on prouve des résultats concernant la croissance de la norme ponctuelle des fonctions propres. On montre notamment que, si m=n ! 0, alors pour tout point donné (r; ) du disque, la valeur de F (r; ) décroit exponentiellement lorsque ! 1. Au chapitre 4, on montre plusieurs résultats sur la croissance de la norme L1. Le probl ème avec conditions frontières de Neumann est discuté au chapitre 5 et on présente quelques résultats numériques au chapitre 6. Une brève discussion et un sommaire de notre travail se trouve au chapitre 7. / The goal of this master's thesis is to explore the properties of the solutions of the eigenvalue problem for the Laplace operator on a disk as the eigenvalues go to in nity. More speci cally, we study the growth rate of the pointwise and the L1 norms of the eigenfunctions. Let D be the unit disk and @D be its boundary (the unit circle). We study the solutions of the eigenvalue problem f = f with either Dirichlet boundary condition (fj@D = 0) or Neumann boundary condition ( @f @nj@D = 0; note that for the disk the normal derivative is simply the derivative with respect to the radial variable: @ @n = @ @r ). The corresponding eigenfunctions are given by: f (r; ) = fn;m(r; ) = Jn(kn;mr)(Acos(n ) + B sin(n )) (Dirichlet) fN (r; ) = fN n;m(r; ) = Jn(k0 n;mr)(Acos(n ) + B sin(n )) (Neumann) where Jn is the nth order Bessel function of the rst type, kn;m is its mth zero and k0 n;m is the mth zero of its derivative (here we denote the eigenfunctions for the Dirichlet problem by f and those for the Neumann problem by fN). The spectrum of the Laplacian on D, SpD( ), that is the set of its eigenvalues, is given by: SpD( ) = f : f = fg = fk2 n;m : n = 0; 1; 2; : : :m = 1; 2; : : :g (Dirichlet) SpN D( ) = f : fN = fNg = fk0 n;m 2 : n = 0; 1; 2; : : :m = 1; 2; : : :g (Neumann) Finally, we normalize the L2 norm of the eigenfunctions on D, namely: R D F2 da = 1 (here and further on we use the notation F for the normalized eigenfunctions and f for arbitrary eigenfunctions). Under these conditions, we study the growth rate of the L1 norm of the normalized eigenfunctions, jjF jj1, in relation to . It is important to mention that the L1 norm of a function on a given domain corresponds to the iv maximum of its absolute value on the domain. Note that depends on two parameters, m and n, and the relation between and the L1 norm depends on the regime at which m and n change as goes to in nity. Studying the behavior of the L1 norm is linked to the study of the set E(D) which is the set of accumulation points of log(jjF jj1)= log : One of our main results is that [7=36; 1=4] E(B2) [1=18; 1=4]: The thesis is organized as follows. Introduction and main results are presented in chapter 1. In chapter 2 we review some well-known facts regarding the eigenfunctions of the Laplacian on the disk and the properties of the Bessel functions. In chapter 3 we prove results on pointwise growth of eigenfunctions. In particular, we show that, if m=n ! 0, then, for any xed point (r; ) on D, the value of F (r; ) decreases exponentially as ! 1. In chapter 4 we study the growth of the L1 norm. Eigenfunctions of the Neumann problem are discussed in chapter 5. Some numerical results are presented in chapter 6. A discussion and a summary of our work could be found in chapter 7.

In high density magnetic hard disk drives, both fast track seeking and extremely accurate positioning of the read/write head are required. A new piezoelectric microactuator with transverse and lateral control of the head positioning system for high density hard disk drives is proposed. First, the structure of the new piezoelectric microactuator is illustrated. Design of the new microactuator is based on the axial deformation of piezoelectric elements for lateral motion and the bimorph actuation of piezoelectric elements for transverse motion. Next, a mathematical model of the microactuator system is defined. Static properties associated with the displacement of the system are evaluated and then dynamic system equations of the system are evaluated. Frequency response of the system is studied based on the dynamic system equations of the actuator system. Dynamic properties of the system with a variety of system parameters are evaluated. Finally, the controller design for the actuator is presented. Simulation results show that the new actuator achieves a maximum stroke of displacement of more than 0.2m with servo bandwidth of more than 5 kHz in the lateral direction and the flying height is decreased to less than 6 nm with resonance frequency of more than 100 kHz under the 0.5 % damping assumption. The new piezoelectric microactuator improves performance of high density hard disk drives by increasing servo bandwidth and decreasing flying height.

Nous avons étudié des circuits supraconducteurs bi-dimensionnels en mesurant la température critique, le courant critique et l'aimantation en fonction du champ magnétique. Ces mesures peuvent être reliées aux propriétés du spectre d'énergie d'une particule quantique chargée confinée dans la structure bidimensionnelle considérée.<br />Les circuits submicroniques ont été réalisés par lithographie électronique utilisant un procédé bicouche PMMA/MAA. L'optimisation de ce procédé a permis d'obtenir des lignes de 100nm de large.<br />Nous avons étudié pour la première fois un disque supraconducteur en mesurant sa température critique, son aimantation ainsi que la dérivée de son aimantation avec la température. Ces résultats sont parfaitement expliqués par un modèle théorique considérant une particule quantique chargée confinée dans un disque et soumise à un champ magnétique.<br />Nous avons aussi mesuré le courant critique d'un réseau carré de fils supraconducteurs. Ce dernier a été interprété comme étant le courant de « dépairage ». Ces propriétés s'expliquent très précisément par un modèle théorique utilisant le spectre d'énergie d'une particule dans un réseau carré. <br />Deux régimes de dissipation apparaissent au delà du courant critique. A champ magnétique nul, des sauts de tensions comparables à des « phase slip centre » dans un fil unique sont observés. Sous champ magnétique, un régime comparable au « flux flow » apparaît dans le réseau dont la viscosité mesurée a pu être expliquée par un modèle théorique simple.

Crack initiation and propagation in the bladed disks of aero-engines caused by high-cycle fatigue under cyclic loads could result in the breakdown of the engines if not detected at an early stage. Although a number of fault detection methods have been reported in the literature, it still remains very challenging to develop a reliable online technique to accurately diagnose defects in bladed disks. One of the main challenges is to characterize signals contaminated by noises. These noises caused by very dynamic engine operation environment. This work presents a new technique for engine bladed disk crack detection, which utilizes advanced analysis of clearance and time-of-arrival signals acquired from blade tip sensors. This technique involves two stages of signal processing: 1) signal pre-processing for noise elimination from predetermined causes; and 2) signal post-processing for characterizing crack initiation and location. Experimental results from the spin rig test were used to validate technique predictions.