To see the other types of publications on this topic, follow the link: NACA 0018.
Dissertations / Theses on the topic 'NACA 0018'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'NACA 0018.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Oliveira, Thiago Fernandes. "Estudo experimental do estol dinâmico em um aerofólio naca 0018." reponame:Repositório Institucional da UnB, 2011. http://repositorio.unb.br/handle/10482/9388.
Full textAbstract:
Dissertação (mestrado)—Universidade de Brasília, Departamento de Engenharia Mecânica, 2011.<br>Submitted by Shayane Marques Zica (marquacizh@uol.com.br) on 2011-09-13T19:13:31Z
No. of bitstreams: 1
2011_ThiagoFernandesOliveira.pdf: 4245386 bytes, checksum: 1a6804b340c8e4f82fe6c1591dffe1e9 (MD5)<br>Approved for entry into archive by LUCIANA SETUBAL MARQUES DA SILVA(lucianasetubal@bce.unb.br) on 2011-10-04T16:16:42Z (GMT) No. of bitstreams: 1
2011_ThiagoFernandesOliveira.pdf: 4245386 bytes, checksum: 1a6804b340c8e4f82fe6c1591dffe1e9 (MD5)<br>Made available in DSpace on 2011-10-04T16:16:42Z (GMT). No. of bitstreams: 1
2011_ThiagoFernandesOliveira.pdf: 4245386 bytes, checksum: 1a6804b340c8e4f82fe6c1591dffe1e9 (MD5)<br>O objetivo deste trabalho é o estudo experimental de um perfil aerodinâmico NACA 0018 em movimento angular em túnel de água. Os coeficientes de sustentação, arrasto e momento de arfagem foram medidos estaticamente e dinamicamente (durante a movimentação angular do perfil) através de uma célula de carga desenvolvida especificamente para este estudo. O software LabView foi utilizado para a aquisição de dados e controle do experimento. Os ensaios foram realizados para os números de Reynolds iguais a 97.000, 124.000 e 150.000 para os casos estáticos e 124.000 e 150.000 para os casos dinâmicos com velocidades angulares do perfil iguais a 0,06, 0,13 e 0,19 rad/s. Os resultados dos ensaios estáticos foram comparados com a literatura apresentando boa concordância. Os ensaios dinâmicos foram realizados para a verificação do fenômeno de estol dinâmico. Os resultados foram comparados entre os diferentes números de Reynolds. A influência das diferentes velocidades angulares nos casos dinâmicos também foi evidenciada comparando-se inclusive com o caso estático. A visualização do escoamento também foi realizada para complementar a análise. _______________________________________________________________________________ ABSTRACT<br>The objective of this work is the experimental study of a NACA 0018 airfoil in angular movement in a water tunnel. The lift, drag and pitching moment coefficients were measured statically and dynamically (along the airfoil's angular movement) through a load cell specifically designed for this study. The LabView software was used for the data acquisition and control of the experiment. The tests were performed for Reynolds numbers equal to 97,000, 124,000 and 150,000 for the statics cases and 124,000 and 150,000 for the dynamics cases with angular velocities of the airfoil equal to 0.06, 0.13 e 0.19 rad/s. The results of the statics tests were compared with the literature with good agreement. The dynamic tests were performed to verify the phenomenon of dynamic stall. The results were compared between the different Reynolds numbers. The influence of the angular velocities in the dynamics cases was also evidenced comparing including with the static case. The flow visualization was also performed to complement the analysis.
2
Bonavita, Gianluca. "Ottimizzazione costruttiva e di montaggio di un aerogeneratore ad asse verticale privo di fondazione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3666/.
Full text
3
Yu, Hongtao. "A Validation Study of SC/Tetra CFD Code." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1399896316.
Full text
4
Islam, Md Monirul. "Nonlinear normal force indicial responses for a 2-D NACA 0015 airfoil." Ohio : Ohio University, 1991. http://www.ohiolink.edu/etd/view.cgi?ohiou1183730957.
Full text
5
Fang, Kuan-Chieh. "Nonlinear aerodynamic responses in tow tank study for a two dimensional NACA 0015 airfoil." Ohio : Ohio University, 1992. http://www.ohiolink.edu/etd/view.cgi?ohiou1172265691.
Full text
6
Li, Sihao. "Effect of aeroelasticity in tow tank strain gauge measurements on a NACA 0015 airfoil." Ohio : Ohio University, 1993. http://www.ohiolink.edu/etd/view.cgi?ohiou1175713922.
Full text
7
Fernie, Robert Mark. "Low frequency shock motion on a NACA 0012 aerofoil." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614936.
Full text
8
Jensen, Christopher Douglas. "Global Pressure and Temperature Surface Measurements on a NACA 0012 Airfoil in Oscillatory Compressible Flow at Low Reduced Frequencies." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331075431.
Full text
9
Digavalli, Sasi K. (Sasi Kumar). "Dynamic stall of a NACA 0012 airfoil in laminar flow." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12206.
Full text
10
Castañeda, Vergara David Armando. "Active Control of Flow over an Oscillating NACA 0012 Airfoil." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587420875168203.
Full text
11
Heyd, Darrick Vaughn. "Photodissociation of methyl bromide adsorbed on LiF(001), NaCl(001), and MgO(001)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0001/NQ27950.pdf.
Full text
12
Sahoo, Dipankar. "Experimental analysis of the vorticity and turbulent flow dynamics of a pitching airfoil at realistic flight (helicopter) conditions." Diss., Texas A&M University, 2008. http://hdl.handle.net/1969.1/85893.
Full textAbstract:
Improved basic understanding, predictability, and controllability of vortex-dominated and unsteady aerodynamic flows are important in enhancement of the performance of next generation helicopters. The primary objective of this research project was improved understanding of the fundamental vorticity and turbulent flow physics for a dynamically stalling airfoil at realistic helicopter flight conditions. An experimental program was performed on a large-scale (C = 0.45 m) dynamically pitching NACA 0012 wing operating in the Texas A&M University large-scale wind tunnel. High-resolution particle image velocimetry data were acquired on the first 10-15% of the wing. Six test cases were examined including the unsteady (k>0) and steady (k=0) conditions. The relevant mechanical, shear and turbulent time-scales were all of comparable magnitude, which indicated that the flow was in a state of mechanical non-equilibrium, and the expected flow separation and reattachment hystersis was observed. Analyses of the databases provided new insights into the leading-edge Reynolds stress structure and the turbulent transport processes. Both of which were previously uncharacterized. During the upstroke motion of the wing, a bubble structure formed in the leading-edge Reynolds shear stress. The size of the bubble increased with increasing angle-of-attack before being diffused into a shear layer at full separation. The turbulent transport analyses indicated that the axial stress production was positive, where the transverse production was negative. This implied that axial turbulent stresses were being produced from the axial component of the mean flow. A significant portion of the energy was transferred to the transverse stress through the pressure-strain redistribution, and then back to the transverse mean flow through the negative transverse production. An opposite trend was observed further downstream of this region.
13
Nowak, Lisa M. "Computational investigations of a NACA 0012 airfoil in low Reynolds number flows." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1992. http://edocs.nps.edu/npspubs/scholarly/theses/1992/Sep/92Sep_Nowak.pdf.
Full textAbstract:
Thesis (Degree in Aeronautical and Astronautical Engineer)--Naval Postgraduate School, Sept. 1992.<br>Thesis advisor(s): M.F. Platzer and M. Chandrasekhara. "September 1992." Includes bibliographical references. Also available online.
14
Debien, Antoine. "Étude électromécanique et optimisation d'actionneurs plasmas à décharge à barrièrediélectrique – Application au contrôle de décollement sur un profil d'aile de type NACA0015." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2253/document.
Full textAbstract:
Cette thèse est effectuée dans le cadre du projet Européen "PlasmAero" dont le but est de développer et d'étudier des actionneurs plasmas, et de démontrer leur capacité à contrôler des écoulements aérodynamiques. L'actionneur plasma à Décharge à Barrière Diélectrique (DBD) de surface est un moyen innovant pour contrôler un écoulement en utilisant le vent électrique induit par la force électrohydrodynamique (EHD) générée au sein du gaz ionisé. Une première partie est dédiée à l'étude des actionneurs plasmas. L'influence de la géométrie de l'électrode active d'une DBD est précisée par des mesures électriques, optiques et mécaniques. Les régimes de la décharge de surface peuvent être totalement modifiés, tout commel'évolution de la force EHD en fonction du temps, calculée ici par bilan intégral. Une géométrie optimisée permet de supprimer le régime de décharge streamer et d'augmenter l'efficacité de l'actionneur de 0,65 à 0,97 mN/W. De plus, des configurations à multi-électrodes (sliding discharge et multi-DBD) sont étudiées et développées. Une multi-DBD à potentiels alternés a permis d'obtenir un vent électrique record de 10,5 m/s.L'étude du contrôle d'un écoulement décollé à mi-corde ou en bord de fuite sur l'extrados d'un profil NACA 0015 fait l'objet de la seconde partie de la thèse. Une DBD standard à deux électrodes, une multi-DBD à six électrodes et une DBD de type "nanoseconde" sont utilisées pour agir sur une séparation à des nombres de Reynolds atteignant 1,3μ106, avec une transition naturelle ou déclenchée. Les résultats démontrent que le contrôle permet de repousser efficacement la séparation, améliorant ainsi les performances aérodynamiques du profil<br>This work is conducted in the framework of the European PlasmAero project that aims to demonstrate how plasma actuators can be used to control aircraft aerodynamic. Surface Dielectric Barrier Discharge (DBD) is an innovative solution to control a flow with the electric wind induced by the electrohydrodynamic (EHD) force produced by a surface discharge. A first part is dedicated to plasma actuators study. The exposed electrode shape of a DBD actuator is investigated by electrical, optical and mechanical characterization. Discharges properties and EHD force evolution is fully dependent of exposed electrode shape. With an optimized active electrode shape, streamer discharge is cancelled while actuator effectiveness is increased from 0.65 to 0.97 mN/W. Flow field induced by multiple electrode design is also investigated. An innovative multi-DBD design is proposed. Inhibition of mutual interaction between successive DBD actuators and exposed electrode shape optimization conduct to an electric wind velocity of 10.5 m/s. In a second part, the control of boundary layer separation on a NACA 0015 airfoil is investigated. An ac DBD, a multi-DBD and a nanosecond DBD are used to manipulate separation at a Reynolds number Re = 1.3μ106, with tripped and natural boundary layer. Results show that actuators can effectively remove the separation existing without actuation
15
Clifford, Christopher J. "An Investigation of Physics and Control of Flow Passing a NACA 0015 in Fully-Reversed Condition." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440156651.
Full text
16
Singhal, Achal Sudhir. "Unsteady Flow Separation Control over a NACA 0015 using NS-DBD Plasma Actuators." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu148217512319911.
Full text
17
Sinha, Roy Arijit. "Analysis and control of boundary layer transition on a NACA 0008 wing profile." Thesis, KTH, Mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-239931.
Full textAbstract:
The main aim of this thesis was to understand the mechanism behind the classical transition scenario inside the boundary layer over an airfoil and eventually attempting to control this transition utilizing passive devices for transition delay. The initial objective of analyzing the transition phenomenon based on TS wave disturbance growth was conducted at 90 Hz using LDV and CTA measurement techniques at two different angles of attack. This was combined with the studies performed on two other frequencies of 100 and 110 Hz, in order to witness its impact on the neutral stability curve behavior. The challenges faced in the next phase of the thesis while trying to control the transition location, was to understand and encompass the effect of adverse pressure gradient before setting up the passive control devices, which in this case was miniature vortex generators. Consequently, several attempts were made to optimize the parameters of the miniature vortex generators depending upon the streak strength and stability. Finally, for 90 Hz a configuration of miniature vortex generators have been found to successfully stabilize the TS wave disturbances below a certain forcing amplitude, which also led to transition delay.
18
Audier, Pierre. "Etude d'une décharge à barrière diélectrique surfacique. Application au contrôle d'écoulement autour d'un profil d'aile de type NACA 0012." Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00843633.
Full textAbstract:
Dans un contexte de croissance du trafic aérien et dans le but de réduire la consommation de carburant ainsi que les émissions de polluants dans l'atmosphère, l'avion de demain se doit d'être plus respectueux de l'environnement. Dans un objectif d'optimisation de ses performances aérodynamiques,d'importantes activités de recherche sont menées dans le monde pour étudier de nouveaux dispositifs de contrôle actif des écoulements en temps réel. Depuis une dizaine d'années, l'utilisation de la décharge à barrière diélectrique surfacique comme actionneur plasma pour le contrôle d'écoulements suscite un intérêt grandissant. Ce type d'actionneur permet de créer un plasma non-thermique capable de générer un écoulement basse vitesse, appelé vent ionique, qui interagit avec l'écoulement naturel en proche paroi pour l'amener dans un état souhaité. Les études expérimentales présentées dans cette thèse portent, d'une part, sur la caractérisation de l'actionneur plasma sous atmosphère contrôlée pour étudier le rôle de l'azote et de l'oxygène sur le comportement de la décharge et d'autre part, sur l'évaluation des potentialités de cet actionneur à contrôler le décollement massif naissant au bord d'attaque d'un profil d'aile placé à forte incidence. Les résultats mettent en évidence l'importance du rôle joué par O2 dans l'amorçage des filaments de plasma et dans la production de vent ionique. Le taux de production d'ozone de l'actionneur plasma a été quantifié en fonction de la puissance électrique. Les essais en soufflerie, réalisés dans le cadre du projet européen PLASMAERO, montrent l'effet de la fréquence de pulsation du signal d'alimentation haute tension sur la réponse de l'écoulement décollé et des ses instabilités naturelles. Il est ainsi possible, pour le profil placé à des incidences au-delà de l'incidence de décrochage naturel, d'augmenter la portance du profil en supprimant le décollement ou en favorisant la formation de tourbillons portants à l'extrados du profil.
19
Beck, Paulo Arthur. "Análise metodológica de simulações de escoamentos turbulentos sobre seções de perfis aerodinâmicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/28925.
Full textAbstract:
Este trabalho apresenta o resultado da aplicação do Método dos Volumes Finitos, adotado pelo software comercial Star-CCM+ na simulação para o regime permanente de escoamentos turbulentos incompressíveis e compressíveis sobre seções de aerofólios. Para o caso incompressível modelam-se seções do aerofólio NACA 0012 com ângulo de ataque zero. Para o caso compressível, uma seção do aerofólio supercrítico OAT15A em pequeno ângulo de ataque é modelada. Os domínios computacionais são discretizados por malhas não estruturadas de células poliédricas ou por malhas estruturadas de geração hiperbólica para diferentes topologias e parâmetros construtivos determinados pela estimativa de grandezas do fenômeno físico, como a altura da primeira camada de células quadrilaterais junto à parede. A qualidade e adequação dessas malhas para as simulações são verificadas por estudo de dependência quanto ao nível de refinamento e também quanto à posição do contorno onde o escoamento é livre no caso de escoamento compressível. Na metodologia de verificação, o índice de convergência de malha GCI e a ordem observada de convergência do método (dos Volumes Finitos) são obtidos para três níveis de refinamento com o propósito de selecionar uma malha de trabalho que concilie precisão e esforço computacional com os recursos disponíveis. As simulações são conduzidas para dois modelos de turbulência – o modelo Spalart-Allmaras e o modelo k-ω/SST. Os resultados obtidos pela aplicação desses modelos são interpretados sob o ponto de vista fenomenológico e comparados com os resultados experimentais disponíveis em literatura.<br>The Finite Volumes Method adopted by the commercial software Star-CCM+ is applied to the simulation of the steady state regime of incompressible and compressible turbulent flows over selected airfoil’s sections. The physical model used with the incompressible flow case is a NACA 0012 airfoil section at zero angle of attack. The ONERA’s OAT15A supercritical airfoil section at small angle of attack applies to the compressible flow case. The computational domains are discretized by structured and unstructured meshes for different topologies and far field configurations. The structured meshes are of the quadrilateral type with hyperbolic node distribution whilst the unstructured meshes use polyhedral cells. The grids are generated by applying a methodology where estimates of the flow variables are used as input for the grid’s constructive parameters like the near wall cell thickness. Grid dependency studies are carried out in order to verify the grid’s quality and suitability to represent the physical phenomena. The grid’s asymptotic convergence index GCI and its observed order of convergence are evaluated for three refinement levels and far field position for the compressible flow cases. The objective is to select the most suitable grid taking into account the accuracy requirements and the computational resources available. The one-equation Spalart-Allmaras turbulence model and the two-equation k-ω/SST turbulence models are used. The numerical results are discussed from the physical point of view and compared with the experimental ones available in literature.
20
Sullivan, Taylor D. "REDUCED ORDER MODELING OF FLOW OVER A NACA 0015 AIRFOIL FOR FUTURE CONTROL APPLICATION." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1407295741.
Full text
21
Song, Longfei. "Leading-edge flow separation control over a NACA 0012 aerofoil with DBD plasma actuators." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49841/.
Full textAbstract:
An experimental investigation has been conducted in a low-speed wind tunnel at the University of Nottingham to study the flow separation control capability of a wall-normal plasma jet by DBD plasma actuator over a NACA 0012 aerofoil. As an active flow separation control technique, DBD plasma actuators could be applied when required to manipulate a flow. They are surface-mounted and require no moving parts, ducts, holes or cavities, so no profile drag penalty will be caused. Moreover, they are fast responding since they are purely electrical devices and could be operated at a higher frequency relative to other flow control techniques. DBD plasma actuators are easy to manufacture, low in weight, low energy consuming and can be easily fitted to aerofoils. Therefore, they are ideal tools to control the flow separation around aerofoil. Up to date, wall plasma jet was used to add momentum to flow directly so that flow becomes more energetic and capable of withstanding adverse pressure gradient. In this study, a wall-normal plasma jet by steady actuation of plasma actuator was investigated and PIV results show that it has the capability of controlling the separation around aerofoil at post-stall angles of attack. The wall-normal jet is bent towards freestream direction and some small-scale vortical structures are created due to the interaction between the wall-normal plasma jet and freestream. These vortical structures could promote mixing and transport high-momentum fluids into the boundary layer, which affects the flow above the suction surface significantly. Moreover, unsteady actuation of plasma actuator was also utilised to control the flow separation around aerofoil. It was found that it has a stronger ability to control flow separation even at a much lower energy consumption than steady actuation of plasma actuator. PIV measurements demonstrate that separated flow could be reattached at post-stall angle of attack of 14° with only 10% of the energy consumption by steady actuation. Flow is well organized and a series of large-scale vortices are created with periodic activation of plasma actuator, these vortices enhance entrainment and the outwards transport of fluids from aerofoil surface leads to a favourable pressure gradient, resulting in a control of flow separation.
22
Hu, Wei. "Monte Carlo simulations of the CO¦2/NaCI(001) and CH¦3Br/LiF(001) systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25989.pdf.
Full text
23
Métivier, Vincent. "Étude des oscillations auto-excitées d'un profil d'aile NACA 0012 à des nombres de Reynolds transitionnels." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/28696/28696.pdf.
Full text
24
Tsiachris, Fotios K. "Retreating blade stall control on a NACA 0015 aerofoil by means of a trailing edge flap." Thesis, University of Glasgow, 2005. http://theses.gla.ac.uk/5109/.
Full textAbstract:
Trailing edge flaps may provide a mechanism for alleviating retreating blade stall. In the present investigation numerical simulations were conducted involving a NACA 0015 aerofoil section fitted with a plain trailing edge (TE) flap. All simulations were conducted using DIVEX, a tool being developed at the University of Glasgow, Department of Aerospace Engineering. In summary, the code uses a surface shedding discrete vortex method (DVM) for the simulation of 2-D incompressible flows around pitching aerofoils. The aero-foil is oscillating in pitch about its quarter chord axis and the clap undergoes negative pitch inputs, i.e. upward. An interesting feature appears to be that the cause of the severe nose down pitching movement introduced during dynamic stall is due to the cortical pair of the DSV and TEV where it is shown that the former feeds the latte in the case of the clean aerofoil for the range of reduced frequencies varying between k = 0.128 and k = 0.180. This fact suggests that manipulation of the vorticity in the vicinity of the trailing edge may be a mechanism for modification of the dynamic stall vortex (DSV) trajectory. This was found to relieve the aerofoil from severe pitching moment undershoot occurring during dynamic stall under appropriately phased flap actuations. Results obtained so far encourage the employment of a flap with fairly small size, 15% of the aerofoil chord. A parametric study is described which identifies the proper aerodynamic and actuation parameters for the current problem. In addition a simple open loop control scheme is developed based purely on rotor and flap related quantities.
25
L'Esperance, Alan M. "Experimental Study of Delay of Separation on a NACA 0015 Wing Model Using Synthetic Jet Actuators." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1287.
Full textAbstract:
An experimental study has been conducted in the Cal Poly ME 0.61 m x 0.61 m (2 ft x 2 ft) subsonic wind tunnel of the effect of a piezoelectric synthetic jet actuator at 10% chord on a NACA 0015 finite wing up to α = 20° at ReC = 100,000. It was observed that the actuation is able to delay the separation over the NACA 0015 finite wing model up to α = 20°. For all the Cμ values tested, the synthetic jet excitation is effective at F+ = 1, 2.8, and 13.9 at α = 16°, but only at F+ = 13.9 at α = 20°. At α = 16°, the Cp suction peak under the synthetic jet excitation at F+ = 1, 2.8, and 13.9 all gradually reduce from Cp ≅ -4 at in the inboard area to about Cp ≅ -3 near the wingtip, about 25% reduction. The situation is similar for F+ = 13.9 at α = 20° except at 2y/b = 0.30, the most inboard testing position, where the excitation shows almost no effect. The surprising result is that slit is not the only actuation influencing the flow. For F+ from 1 to 2.8, the synthetic jet is indeed the most effective configuration and is successful in causing flow attachment as seen in previous experiments. For F+= 13.9, however, the flow is successfully attached with the model vibration caused by the actuators alone without the slit at 16°. At 20°, this configuration was not successful in delaying separation.
26
Siauw, Wei Long. "Transient process of separation and attachment over a NACA 0015 airfoil controlled by fluidic vortex generators." Poitiers, 2008. http://www.theses.fr/2008POIT2313.
Full textAbstract:
Ce travail expérimental est consacré à l’étude du décollement et du recollement transitoire sur profil NACA 0015 contrôlé par des Générateurs de Vortex Fluidique (FVG). Des essais sont effectués à un nombre de Reynolds de 1 million, et à une incidence de 11o. L’écoulement sans contrôle est caractérisé par une zone décollée qui commence à xA-c=0,7 à partir du bord d'attaque (soit 30% de la corde) avec un minimum de vibrations. Pour effectuer le contrôle de l’écoulement, 44 FVG sont installés à xA-c=0,3. Les effets de la FVG sont caractérisés par une augmentation de 16% du coefficient de portance et réduction de 30% du coefficient de traînée. Ces conditions permettent de déterminer des processus transitoires dans l’écoulement pendant que les FVG pulsent à une fréquence de 1 Hz. Ils sont déterminées, par Décomposition Orthogonale aux Valeurs Propres (POD) de la PIV données obtenues à partir de moyennes en référence de phases; l’échelle de temps caractéristique du décollement (_T+~20) est deux fois celle du recollement (_T+~10). Un système dynamique a été modélisé à partir des quartes premières modes, qui représente 98% de l’énergie, temporelles de la POD. Dans une seconde expérience, des signaux de pression sur le profil dan la zone décollée, sont utilisés pour estimer l'évolution des fluctuations de vitesse par une technique d'Estimation Stochastique Linéaire (LSE). Les vitesses sont obtenues à partir d'un fil chaud en croix dans le sillage à xA-c=2 et l’autre dans la couche de cisaillement à xA-c=0,91. Les grandes structures de l’écoulement sont bien estimées pour les cas sans contrôle. Dans le cas du processus transitoire pendant l’activation de la FVG, il y d’abord a une augmentation de la taille des structures dans le sillage puis une diminution. A l’arrêt du contrôle, la taille du sillage réaugmente progressivement. Un comportement similaire est observé dans la couche de cisaillement<br>This is an experimental study dedicated to the transient processes of flow separation and attachment over a NACA 0015 airfoil. Tests are performed at a Reynolds number of 1 million with the airfoil pitched at an incidence of 11o. The uncontrolled state is characterised by a separation size of 30% upstream from the trailing edge with minimal model vibration. A spanwise array of 44 angled fluidic vortex generators (FVG) is positioned at 30 percent of chord from the leading edge to control flow separation. Effects of the FVG are characterized by 16% improvement in CL and 30% reduction in Cd during the controlled steady state. These conditions allow deterministic changes in the wake and shear layer when operating the FVG in an “on-off” manner at a frequency of 1 Hz. It is estimated from the Proper Orthogonal Decomposition (POD) of the conditional averaged PIV data in the wake that the time taken for the separation (ΔT+~20) is twice that of attachment (ΔT+~10). A reduced order model has been realized based on the first four temporal modes, which represent 98% of the energy, of the POD. In a second experiment, pressure signals in the separated zone of the airfoil, are used as conditional signals to estimate the evolution of the fluctuating velocities using technique of Linear Stochastic Estimation (LSE). The velocities are acquired from a crosswire traversing in the wake at xA/c=2 and the shear layer at xA/c=0. 91. A double and single vortex streets has been estimated in the wake and shear layer, respectively for the baseline uncontrolled case. In the case of the transient process in the wake during FVG deployment, there is an increase in the size of the vortex streets followed by a decrease in size. In the reverse process, there is a gradual re-establishment of the shear layer and gradual enlargement of the wake. The ability of the pressure signals in describing evolution of coherent structures motivates the use of its moving rms, after being filtered to retain the energy containing scales of the flow, to anticipate the onset of flow separation
27
Lundberg, Marcus. "Aerodynamics of Insect Flight : Effects of wind gusts on a rigid flapping NACA 0012 airfoil at Re = 3000." Thesis, KTH, Mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-167123.
Full textAbstract:
Insects and small flyers operate at Reynolds numbers ranging from approximately 10-105 , where viscous forces are important. Due to their small size and weight, they are sensitive to small changes in the free stream during flight, such as wind gusts. First, the aerodynamics of flapping flight is briey explained. Then the lift, drag and power usage for a flapping NACA 0012 airfoil is simulated in ANSYS Fluent for different oncoming wind directions. The aim of the report is to understand how the pitching amplitude, the apping frequency and the plunging amplitude can be adjusted to compensate for oncoming wind gusts. The simulation is modelled as quasistatic since the time scale of the flapping wings of the insect is much shorter than the time scale of the wind gusts.<br>Insekter och andra små flygande djur flyger vid låga Reynolds tal som sträcker sig från cirka 10-100 000. Det medför att viskösa krafter är viktiga. På grund av sin ringa storlek och vikt är de känsliga för små förändringar i den friströmmen under flygningen, till exempel vindbyar. Först förklaras teorin bakom aerodynamiken vid flaxande flygning. Sedan simuleras lyftkraft, dragkraft och effektförbrukning för en flaxande NACA 0012 vingprofil vid olika riktningar på friströmmen med hjälp av ANSYS Fluent. Syftet med rapporten är att förstå hur pitching-amplitud, vingslagsfrekvens och vingslagsamplitud kan justeras för att kompensera för inkommande vindbyar. Simuleringen modelleras som kvasistatisk eftersom tidsskalan hos insekters flaxande vingar normalt är mycket kortare än tidsskalan hos vindbyar.
28
Goffert, Bruno. "Análise numérica e experimental de escoamento transônico sobre o aerofólio NACA 0012 no túnel transônico piloto do IAE." Instituto Tecnológico de Aeronáutica, 2012. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2140.
Full textAbstract:
Experimentos em escoamentos transônicos sobre aerofólios em túneis de vento podem apresentar reflexões de ondas de choque, entupimento aerodinâmico e alteração das linhas de corrente devido à presença das paredes da seção de testes. Para inibir estes fenômenos físicos, projetistas desenvolveram seções de testes com paredes perfuradas ou fendidas. O objetivo deste trabalho é analisar numericamente e experimentalmente escoamento transônico sobre o aerofólio NACA 0012 no Túnel Transônico Piloto (TTP) do Instituto de Aeronáutica e Espaço (IAE). As análises foram realizadas com número de Mach 0,6 a 0,85 e variações de ângulo de ataque de 0 a 8. As simulações numéricas são baseadas nas Equações de Euler, resolvidas pelo método de diferenças finitas centradas, proposto por Beam e Warming e modificado para algoritmo diagonal. Foi gerada algebricamente a malha computacional da seção de testes fendidas do TTP com o aerofólio NACA 0012 fixado nas paredes superior e inferior, e por equações diferenciais parciais os pontos próximos ao perfil foram redistribuídos. As distribuições de pressão obtidas pelas simulações numéricas foram comparadas entre escoamentos em paredes sólidas e paredes com fendas, das quais se verificaram a importância das fendas em escoamentos transônicos. Dos experimentos no TTP foram realizadas medições de distribuição de pressão por tomadas de pressão estática e pela técnica PSP ("Pressure Sensitive Paint"), das quais foram obtidas distribuições de pressão sobre toda a corda aerodinâmica do perfil. Os resultados experimentais e numéricos com paredes fendidas foram comparados com o trabalho de Harris, onde se observaram curvas de distribuição de pressão e posicionamento de ondas de choque mais próximas do que as encontradas em trabalhos realizados em túneis de vento renomados.
29
Mikat, Jürgen E. R. "Optische und schwingungsspektroskopische Hochdruckuntersuchungen von Ladungsträgereigenschaften in herkömmlich und nach der Template-Methode synthetisierten leitfähigen Polypyrrolschichten." [S.l. : s.n.], 2001. http://pub.ub.uni-potsdam.de/2001/0013/mikat.pdf.
Full text
30
Hustedt, Michael. "Zur Adsorption von CO2 auf NaCl(001)- und KCl(001)-Einkristallspaltflächen höchstauflösende Polarisations-Fouriertransform-Infrarot-Spektroskopie, Diodenlaserspektroskopie, Beugung langsamer Elektronen und Spektrensimulationen /." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=955904102.
Full text
31
Mish, Patrick F. "Mean Loading and Turbulence Scale Effects on the Surface Pressure Fluctuations Occurring on a NACA 0015 Airfoil Immersed in Grid Generated Turbulence." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33751.
Full textAbstract:
Detailed surface pressure measurements have been made on a NACA 0015 immersed in two grid generated homogenous flows at Re = 1.17 x 10^6 for a = 0°, 4°, 8°, 12°, 16°, and 20°. The goal of this measurement was to reveal and highlight mean loading and turbulence scale effects on surface pressure fluctuations resulting from turbulence/airfoil interaction. Also, measurements are compared with the theory of Amiet (1976a,b). The surface pressure response shows a dependance on angle of attack, the nature of which is related to the relative chord/turbulence scale. The dependance on turbulence scale appears to be non-monotonic at low reduced frequencies, wr = Pi*f*c/U with both an increase and decrease in unsteady pressure magnitude occuring with increasing mean load. A reduced frequency overlap region exists at wr > 10 where the two different scale flows begin to produce similar effects on the surface pressure with increasing angle of attack manifesting as a rise in unsteady surface pressure magnitude. Also, the interaction of the full 3-dimensional wavenumber spectrum affects the distance over which pressure fluctuations correlate and the extent of correlation is affected by angle of attack as demonstrated in the chordwise and spanwise pressure correlation. Amietâ s theory is shown to agree favorably with measurements in the leading edge region although demonstrates insufficiencies in predicting unsteady pressure phasing.<br>Master of Science
32
Van, Dyken Robert D. "Experimental and computational analysis of separation bubble behavior for compressible, steady and oscillatory flows over a NACA 0012 airfoil at M=0.3 and a reynolds number of 540,000." Thesis, Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8365.
Full textAbstract:
Approved for public release; distribution is unlimited<br>In this thesis, the separation bubble behavior and its effect on the steady and dynamic stall characteristics of a thin airfoil in a compressible flow at a transitional Reynolds number was studied. For such flows, laminar separation occurs near the airfoil leading edge, but turbulent reattachment occurs within a short distance downstream, forming a separation bubble in the underlying region. Two experimental techniques, point diffraction interferometry (PDI) and laser doppler velocimetry (LDV), were used to acquire detailed flowfield information that showed the development of the leading-edge separation bubble and its subsequent bursting at higher angles of attack. The initiation of the stall process from the leading-edge separation bubble as opposed to trailing-edge flow reversal pointed to the need for transitional flow analysis. Both in the boundary layer and Reynolds-averaged, Navier-Stokes (N-S) analysis methods, transition models were incorporated to determine the location and extent of the transition zone that best modeled the measured separation bubble behavior. Computed results for steady flow gave remarkable agreement with the measurements
33
Gertz, Roman Johannes [Verfasser]. "Effekt unterschiedlicher Conditioning-Strategien auf myokardiale Funktion und Prognose nach ST-Strecken-Hebungs-Myokardinfarkt / Roman Johannes Gertz." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2021. http://nbn-resolving.de/urn:nbn:de:gbv:7-21.11130/00-1735-0000-0008-5901-3-1.
Full text
34
Benda, Stefan [Verfasser]. "Einfluss von salzreicher Ernährung auf die hyperperfundierte Niere nach Uninephrektomie bei hereditären Nierenerkrankungen wie dem Alport-Syndrom im Mausmodell / Stefan Benda." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2021. http://nbn-resolving.de/urn:nbn:de:gbv:7-21.11130/00-1735-0000-0008-58DD-D-4.
Full text
35
Traeger, Franziska. "Streuexperimente mit Wasserstoff- und Heliumstrahlen zur Untersuchung der Wechselwirkung von H2, N2 und C2H2 mit den (001)-Oberflächen von LiF, NaCl, KCl und MgO." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963022342.
Full text
36
Oelze, Christiane Verfasser], Hermann [Akademischer Betreuer] [Staats, Dirk [Akademischer Betreuer] Wedekind, and Patricia [Akademischer Betreuer] Virsik-köpp. "Bestimmung Zentraler Beziehungskonfliktthemen (nach Luborsky) bei Patienten mit generalisierter Angststörung : Vergleich der Qualität unterschiedlicher Auswertungsmethoden und Therapieverfahren / Christiane Oelze. Gutachter: Hermann Staats ; Dirk Wedekind ; Patricia Virsik-Köpp. Betreuer: Hermann Staats." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://nbn-resolving.de/urn:nbn:de:gbv:7-11858/00-1735-0000-0019-859F-4-4.
Full text
37
Ramalho, Diogo Almeida. "Desempenho das ferramentas cfMesh e snappyHexMesh para geração da malha em torno de perfis alares." Master's thesis, 2015. http://hdl.handle.net/10316/38984.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra<br>O objetivo do trabalho apresentado é o estudo da eficiência do gerador de malha cfMesh na criação da malha em torno de um perfil alar, NACA 0018. Os geradores de malha são, tal como o nome indica, responsáveis pela geração da malha usada nos estudos de dinâmica dos fluidos computacional (CFD). Este gerador, ou algoritmo, é relativamente recente mas que segundo alguns estudos, este apresenta resultados interessantes na forma como gera a malha em torno de um perfil alar. Para comprovar a eficiência deste algoritmo foram efetuados cálculos das características aerodinâmicas no software livre OpenFOAM e comparadas com as características já conhecidas deste perfil (obtidos experimentalmente). Para além da comparação dos valores experimentais, foram ainda calculados e comparados com os valores obtidos com um gerador de malha diferente, o snappyHexMesh, com o objetivo de verificar as diferenças obtidas nos cálculos efetuados com diferentes malhas.<br>The objective of this work is to study the efficiency of a mesh generator named cfMesh, which in this case will be responsible to create a mesh around an airfoil, the NACA 0018. The mesh generator is, as the name implies, responsible for generating the mesh used in studies of computational fluid dynamics (CFD). This generator, or algorithm, is relatively recent but according to some studies, the way it generates the mesh around an airfoil is very interesting. To prove the efficiency of this algorithm were made calculations of the aerodynamic characteristics in the open source software OpenFOAM and comparing the results with the already known characteristics of this profile (obtained experimentally). In addition to comparing the experimental values it was also calculated and compared the values obtained with a different mesh generator, the snappyHexMesh, in order to verify the differences obtained in the calculation performed with different meshes.
38
Boutilier, Michael Stephen Hatcher. "Experimental Investigation of Transition over a NACA 0018 Airfoil at a Low Reynolds Number." Thesis, 2011. http://hdl.handle.net/10012/6044.
Full textAbstract:
Shear layer development over a NACA 0018 airfoil at a chord Reynolds number of 100,000 was investigated experimentally. The effects of experimental setup and analysis tools on the results were also examined.
The sensitivity of linear stability predictions for measured separated shear layer velocity profiles to both the analysis approach and experimental data scatter was evaluated. Analysis approaches that are relatively insensitive to experimental data scatter were identified. Stability predictions were shown to be more sensitive to the analysis approach than to experimental data scatter, with differences in the predicted maximum disturbance growth rate and corresponding frequency of approximately 35% between approaches.
A parametric study on the effects of experimental setup on low Reynolds number airfoil experiments was completed. It was found that measured lift forces and vortex shedding frequencies were affected by the end plate configuration. It was concluded that the ratio of end plate spacing to projected model height should be at least seven, consistent with the guideline for circular cylinders. Measurements before and after test section wall streamlining revealed errors in lift coefficients due to blockage as high as 9% and errors in the wake vortex shedding frequency of 3.5%.
Shear layer development over the model was investigated in detail. Flow visualization images linked an observed asymmetry in wake velocity profiles to pronounced vortex roll-up below the wake centerline. Linear stability predictions based on the mean hot-wire profiles were found to agree with measured disturbance growth rates, wave numbers, and streamwise velocity fluctuation profiles. Embedded surface pressure sensors were shown to provide reasonable estimates of disturbance growth rate, wave number, and convection speed for conditions at which a separation bubble formed on the airfoil surface. Convection speeds of between 30 and 50% of the edge velocity were measured, consistent with phase speed estimates from linear stability theory.
39
Bernardo, André Rodrigues. "Estudo das características aerodinâmicas de perfis alares." Master's thesis, 2017. http://hdl.handle.net/10316/83064.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia<br>Esta dissertação de mestrado tem como objectivo estudar as forças que actuam sobre asas com diferentes alongamentos, quando sujeitas a um escoamento subsónico. As asas estudadas têm um perfil simétrico NACA 0012. Este estudo foi realizado no Laboratório de Mecânica dos Fluidos do Departamento de Engenharia Mecânica.Foi estudada a variação da intensidade e direcção das forças e momentos aplicados na asa, e dos respectivos coeficientes aerodinâmicos, com a variação do ângulo de ataque, do alongamento e do número de Reynolds.Estes coeficientes aerodinâmicos foram determinados por via computacional e experimental. Os coeficientes obtidos computacionalmente surgiram da implementação de métodos teóricos num programa destinado a programação, designado por MatLab.Efectou-se uma comparação entre os resultados experimentais e os obtidos através de modelos teóricos. Com isto, é possível efectuar a sua validação, ou seja, estudar a aproximação que estes resultados possuem em relação aos obtidos experimentalmente. Verificou-se que apesar de os modelos teóricos considerarem o fluido como invíscido, estes permitem, ainda assim, obter resultados próximos das medições.Relativamente aos métodos tridimensionais, verificou-se que os resultados obtidos pela Teoria da Superfície Sustentadora possuem um maior grau de fiabilidade, pelo facto destes serem representados sob a forma de um conjunto de coeficientes distribuídos na superfície da asa. Enquanto que a Teoria Clássica da Linha Sustentadora, apenas permite obter, para uma dada asa e ângulo de ataque, um só coeficiente.Ao longo da realização dos trabalhos experimentais, verificou-se que a medição da força de arrasto não apresentava valores consistentes. Tal facto, levou ao estudo de possíveis interferências entre as componentes de arrasto e de sustentação, como também entre o arrasto e o momento.<br>This dissertation aims to study the forces that act on wings with different aspect ratios, when subjected to a subsonic flow. The studied wigs have a symmetric airfoil NACA 0012. This study was carried out in the Laboratory of Fluid Mechanics of the Department of Mechanical Engineering.In was studied the variation of the intensity and direction of the forces and moments applied in the wing, and of the respective aerodynamic coefficients, with the variation of the angle of attack, the aspect ratio and the Reynolds number.These aerodynamic coefficients were determined computationally and experimentally. The coefficients, that were obtained computationally, emerged from the implementation of theoretical methods in MatLab.The various results, obtained computationally and experimentally, were subsequently compared. With this, it is possible to carry out its validation. In other words, it is possible to study the approximation that these results have in relation to those obtained experimentally. It was verified that the theoretical methods, which consider the fluid as being inviscid, obtain good results in relation to those obtained by the measurements.With respect to the three-dimensional methods, it was verified that the results obtained by the Lifting Surface Theory have a higher degree of reliability, due to the fact that they are represented by a set of coefficients distributed along the lifting surface. Whereas the Prandtl Lifting Line Theory only allows to obtain, for a given wing and angle of attack, a single coefficient.During the experimental work, it was verified that the measurement of the drag force didn’t present consistent values. So, this led to the study of possible interferences between the drag and lift components, as also between the drag and momentum components.
40
Pruski, Brandon. "Leading Edge Flow Structure of a Dynamically Pitching NACA 0012 Airfoil." Thesis, 2012. http://hdl.handle.net/1969.1/148372.
Full textAbstract:
The leading edge flow structure of the NACA 0012 airfoil is experimentally investigated under dynamic stall conditions (M = 0.1; α = 16.7◦, 22.4◦; Rec = 1× 10^6) using planar particle image velocimetry. The airfoil was dynamically pitched about the 1/4 chord at a reduced frequency, k = 0.1. As expected, on the upstroke the flow remains attached in the leading edge region above the static stall angle, whereas during downstroke, the flow remains separated below the static stall angle. A phase averaging procedure involving triple velocity decomposition in combination with the Hilbert transform enables the entire dynamic stall process to be visualized in phase space, with the added benefit of the complete phase space composed of numerous wing oscillations. The formation and complex evolution of the leading edge vortex is observed. This vortex is seen to grow, interact with surrounding vorticity, detach from the surface, and convect downstream. A statistical analysis coupled with instantaneous realizations results in the modification of the classical dynamic stall conceptual model, specifically related to the dynamics of the leading edge vortex.
41
Hu, Wei. "Monte Carlo simulations of the CO₂/NaCl(001) and CH₃Br/LiF(001) systems." Thesis, 1997. http://spectrum.library.concordia.ca/188/1/MQ25989.pdf.
Full textAbstract:
Metropolis Monte Carlo simulations were used to examine the stable structures, phase coexistence and mechanism of nucleation and growth of films of CO$\sb2$ molecules adsorbed on the (001) surface of NaCl. This was done for submonolayer, monolayer, and multilayer coverages. The results show that the monolayer has two stable structures, a (2 x 1) herringbone structure and a (1 x 1) structure while the bilayer system has three stable structures: the (2 x 1), the (1 x 1) and the c(2 x 2). The trilayer system adopts a c(2 x 2) structure owing to the instability of the (2 x 1) structure. Multilayers most likely grow in the Stranski-Krastanov fashion whereby multilayer islands on top of a monolayer adopt a bulk-like crystalline structure $\{c$(2 x 2)$\}.$ At low coverages the CO$\sb2$ molecules behave like a 2D gas which aggregates into low density islands but finds it hard to nucleate the denser 2D solid phase directly, even in the presence of a surface step. This suggests that the adsorption of CO$\sb2$ molecules on the low density islands nucleates the 2D solid phase. The 2D gas-solid phase coexistence was found to obey the (2D) van der Waals equation of state. The critical coverage $\Theta\sb{c}$ and temperature T$\sb{\rm c}$ were found to be 0.162 and 142.9K respectively, close to the theoretical values of $\Theta\sb{c}$ = 1/6 and $T\sb{c}=151.2$K. For the CH$\sb3$Br/LiF(001) system, submonolayer and monolayer coverages were examined. The results show that for low coverages the molecules are tilted by 60$\sp\circ$ from surface normal while at monolayer coverage a stable (2 x 1) herringbone structure was found with a molecular tilt of 39.2$\sp\circ$ in agreement with experiment. An alternative incommensurate monolayer structure was found where the molecules are antiferroelectrically ordered perpendicular to the surface.
42
Hung, Wei-Chia, and 洪偉家. "The Effects of Surface Roughness on the Characteristics of Surface Pressure of NACA 0015 Airfoil." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/68260099098319045875.
Full textAbstract:
碩士<br>國立中興大學<br>機械工程學系<br>93<br>The present study was intended to investigate the surface pressure of NACA 0015 airfoil at upper and lower surface due to the sandblast roughness. The experiment was proceeded in an low-speed and open-type wind tunnel. The dynamic behavior of surface pressure of NACA 0015 airfoil was analyzed at various angle of attack, Reynolds number, number of sandblast, and width of sandblast. The freestream velocity was operated at 5~20 m/s and the corresponding Reynolds number at 3.8×104~1.5×105 which based on the chord of the wing. The purpose of this study was intended to understand the relation between surface pressure of the airfoil and parameters. The surface pressure of NACA 0015 had measured and analyzed the aerodynamic performance and flow field characteristics of NACA 0015 airfoil.
The experimental results was shown that a parameter of sandblast was one of important parameters to affect the flow field. The parameter of sandblast was not apparent to affect the flow field at low Reynolds number, but it appeared gradually dominated at higher Reynolds number. The general phenomena of the surface pressure drop increased with more sandblast width was not shown in this study. Moreover, the pressure drop phenomenon and the pressure lift dynamic behavior respectively near the leading edge when angle of attack were 5° and 10°, freestream velocity was 20 m/s, number of sandblast was #100. The pressure drop phenomenon beacame large with increasing the freestream velocity and width of sandblast, and the pressure lift dynamic behavior moved forward to the leading edge obviously. However, the phenomenon of rising pressure for sandblast number #150 wasn’t shown apparently. The present results can be provided to the references for the defense industry.
43
Knabke, Diana. "Sportfähigkeit nach vorderer Kreuzbandplastik." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-001D-AFA5-B.
Full textAbstract:
Die Ruptur des vorderen Kreuzbandes ist die häufigste Verletzung des Kniegelenkes. Ziel dieser prospektiven klinischen Studie ist es, Kriterien wie Operationsmethode- und zeitpunkt, subjektive Patientenzufriedenheit, Alltagsfähigkeit und betriebene Sportarten nach der Kreuzbandersatzplastik in verschiedenen Abhängigkeiten voneinander zu diskutieren.
Um eine möglichst allgemeingültige Aussage treffen zu können, umfasst die Studie ein nicht-selektives Patientenkollektiv, das Männer und Frauen, Sportler und Nicht-Sportler, Schüler, Studenten und Berufstätige beinhaltet. Außerdem handelt es sich um eine Multicenterstudie, bei der Operationen und Untersuchungen von verschiedenen Personen durchgeführt werden und die Studie so eine höhere wissenschaftliche Aussagekraft bekommt. Der standardisierte Fragebogen, mit dem die Untersuchungen an allen drei Zentren durchgeführt wurden, ermöglicht dennoch eine gute Vergleichbarkeit aller Ergebnisse.
Es wird ein Patientenkollektiv von 160 Patienten untersucht und nach dem standardisierten Fragebogen befragt. Kriterien der Sportfähigkeit (sportliches Leistungsniveau, Aktivitätsniveau und Zeitpunkt der vollen Sportfähigkeit), prä- und postoperativ betriebene Sportarten und Lysholm-Score, Operationsmethode und –zeitpunkt sowie die subjektive Patientenzufriedenheit werden
miteinander in Verbindung gesetzt.
Nach einem Zeitraum von durchschnittlich etwa 17 Monaten nehmen 90 Patienten an den Nachuntersuchungen teil.
Etwa ein Jahr nach der Operation kann ca. die Hälfte der Patienten von einer komplett wieder erreichten Sportfähigkeit berichten. Auch bei der Befragung nach dem
sportlichen Leistungsniveau in Wochenstunden berichtet ca. die Hälfte der nachuntersuchten Patienten von einer unveränderten sportlichen Leistungsfähigkeit im Vergleich zum Leistungsniveau vor der Operation.
Hinsichtlich des Bezuges zwischen Sportfähigkeit und Operationsmethode ergibt sich, dass Patienten, die ein Double-Bundle-Transplantat erhielten, ihr sportliches Leistungsniveau am schnellsten und mit den geringsten Einschränkungen wieder erreichen. Patienten aus der Bone-Tendon-Bone-Gruppe erzielen die schlechtesten Ergebnisse hinsichtlich des Zeitpunktes und des Niveaus der Sportfähigkeit.
Betrachtet man das gesamte Patientenkollektiv unabhängig von der Operationsmethode in Bezug auf den Lysholm-Score, ist der postoperativ erhobene Wert signifikant höher als der präoperative. Aufgeschlüsselt nach Operationsmethoden zeigt sich diese Signifikanz bei der Bone-Tendon-Bone- sowie bei der Semitendinosusgruppe. Nach der Operation mit einem Double-Bundle-Transplantat findet sich kein signifikant erhöhter Lysholm-Score.
Der Operationszeitpunkt in Zusammenhang gesetzt mit dem in dieser Arbeit erhobenen postoperativen Lysholm-Score ergibt keine statistisch signifikante Korrelation.
Auch die subjektive Patientenzufriedenheit korreliert nicht mit dem Zeitpunkt der Operation.
Unabhängig vom Operationszeitpunkt ist eine große subjektive Patientenzufriedenheit zu finden. Mehr als 80 % der operierten Patienten bewerten ihr behandeltes Kniegelenk gut oder sehr gut. Hier findet sich eine Korrelation zwischen positiver Bewertung und einer möglichst vollständigen und zeitnahen Rückkehr zur ursprünglichen Sportfähigkeit.
Durch diese Korrelationen bestätigt sich die These dieser Arbeit, dass die Wiedererlangung der Sportfähigkeit für den Patienten mit einer Ruptur des vorderen Kreuzbandes im Mittelpunkt steht.
44
Sallabi, Abdulwahab K. "Computer simulations of the structure, stability and phase transitions of diatomic molecules physisorbed on ionic surfaces : the CO/MgO(001), N2/MgO(001) and N2/NaCl(001) systems." Thesis, 2002. http://spectrum.library.concordia.ca/1715/1/NQ68200.pdf.
Full textAbstract:
Metropolis Monte Carlo simulations, using semiempirical potentials, are performed to study the structures, stability, and phase transitions of layers of CO and N 2 molecules physisorbed on the MgO(100) surface as well as a monolayer of N 2 physisorbed on NaCl(001) surface. In agreement with experiments [35-37], our simulations show that the c (4 x 2) structure of CO on the MgO(001) surface is the most stable structure below 41 K. The unit cell contains three CO molecules; two bridging molecules tilted in opposite directions by the same polar angle of 31 ̕with respect to the surface normal and a third molecule perpendicular to the surface. At 41 K the c (4 x 2) phase undergoes a transition into a less dense disordered phase accompanied by the desorption of some molecules. The density of this disordered phase is the same as for the p (3 x 2) phase. A model to compare the stability of the c (4 x 2) and the p (3 x 2) phases is constructed and suggests that at sufficiently high pressures and temperatures the p (3 x 2) phase is more stable than the c (4 x 2) phase as found by Panella et al . [35]. We propose that a sequence of transitions to a set of (n x 2) structure with ever decreasing density is possible under suitable conditions of temperature and pressure. This sequence of transitions is an example of the devil's staircase phenomenon as has been suggested by LEED experiments. Nitrogen molecules adsorbed on MgO(001) were studied and were also found to form a sequence of structures. A ([Special characters omitted.] ) R 33.7 ̕structure is found to form the most stable phase at low temperatures (below 20 K). This structure undergoes a phase transition into a less dense phase at 20 K and in all likelihood evolves into the less dense ([Special characters omitted.] ) R 36.9 ̕structure. The ([Special characters omitted.] )R36.9 ̕structure is stable up to 25 K. These results are in agreement with HAS results. This system might also prove to be an example of the devil's staircase phenomena. A monolayer of nitrogen molecules adsorbed on an NaCl(001) surface are used to test the validity of the theory of critical phenomena and its applicability to molecular systems. The simulations predict that this system undergoes a continuous order-disorder transition near 25 K with a logarithmically divergent heat capacity. The values of the critical exponents for the order parameter and susceptibility are calculated and found to deviate significantly from the Ising values but still satisfy Rushbrooke's scaling law. This behaviour is typical of the universality class containing the XY model with cubic anisotropy where the critical exponents are functions of the anisotropy and are thus "nonuniversal"
45
Otten, Birte. "Zeit/Geschichte: Amerikanische Alternate Histories nach 9/11." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0028-8697-8.
Full textAbstract:
Zeit/Geschichte: Amerikanische Alternate Histories nach 9/11 untersucht die Entwicklung kontrafaktischer Geschichtstexte, sogenannter alternate histories, vor dem Hintergrund des öffentlichen Diskurses in den USA nach dem 11. September 2001. Dabei konzentriert sich die Studie auf die formalen und generischen Eigenschaften neuerer „Mainstream-alternate histories“ seit den Terroranschlägen. Obwohl keiner der drei untersuchten Texte – Philip Roths The Plot Against America, Michael Chabons The Yiddish Policemen's Union sowie Quentin Tarantinos Inglourious Basterds – von den 9/11-Anschlägen handelt, geben doch alle drei Einblicke in die Beziehungen zwischen dem 9/11-Diskurs und jüngeren Entwicklungen im literarischen bzw. kulturellen Feld. Dabei erweist sich alternate history als ein Genre, das mit seiner thematischen, strukturellen und medialen Variabilität ermöglicht, 9/11-spezifische Veränderungen darzustellen und gleichzeitig den 9/11-Diskurs selbst zu beeinflussen. Die vorliegende Studie zeigt auf, wie sich die untersuchten Texte aktiv in den 9/11-Diskurs einschreiben, um nicht nur zeitgenössische Erfahrungen, Entwicklungen und Empfindungen, sondern auch Fragen nach Geschichte und Vergangenheitsdarstellungen zu beantworten.
46
Knust, Elisabeth. "Histopathologische Veränderungen im zentralen Nervensystem nach peripherer Stammzelltransplantation." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-86EC-A.
Full text
47
Oelze, Christiane. "Bestimmung Zentraler Beziehungskonfliktthemen (nach Luborsky) bei Patienten mit generalisierter Angststörung." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0019-859F-4.
Full text
48
Beltrán, Varas Víctor Javier. "Bewertung endoskopischer Verfahren in der Oralchirurgie nach 15 Jahren Anwendung." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-86FD-6.
Full textAbstract:
Ziel der vorliegenden Arbeit war eine Analyse der Entwicklung der Endoskopie im Bereich der dentoalveolären Chirurgie am Zentrum ZMK-Heilkunde der Universitätsmedizin Göttingen. Zu diesem Zwecke wurden die im OP - Register verzeichneten endoskopischen Eingriffe der Jahre 1997-2012 ausgewählt. In dieser Gesamtgruppe (Kohorte) wurden demografische Parameter und die anatomische Lokalisation der Eingriffe ermittelt. Aus dem Archiv wurden videoendoskopische Aufzeichnungen für weitergehende Auswertungen ausgewählt und ausgewertet: Klinisch diagnostische Maßnahmen (Subgruppe A, Stützendoskopie, n = 54), therapeutische Maßnahmen (Subgruppe B, endoskopisch assistierte Enukleation, Stützendoskopie, n = 10) und mikromorphometrische Diagnostik (Subgruppe C, Nahfeld-Stützimmersionsendoskopie, n = 16). Es ergaben sich in der Gesamtgruppe 1017 Alveoloskopien bei 525 Patienten und 1690 Implantoskopien bei 676 Patienten. Die am häufigsten untersuchte Region waren bei Alveoloskopien die dritten Molaren, bei Implantoskopien die Prämolaren / Eckzahnregion. Eine diagnostische Endoskopie (Stützendoskopie) wurde bei 54 Eingriffen an 35 Patienten ausgewertet. Die lateralen und apikalen Bereiche der Alveolen unterschieden sich nicht signifikant hinsichtlich der Häufigkeit pathologischer Befunde (p = 0,423). Im posterioren Bereich des Zahnbogens wurden absolut und relativ mehr pathologische Befunde beobachtet. Bei der endoskopisch assistierten Chirurgie konnten 10 verschiedene Teilschritte bei der Entfernung von verlagerten dritten Molaren videoendoskopisch definiert werden.
Daneben wurde eine quantitative Definition der Komplexität der Wurzelanatomie über die Lage der Furkation beschrieben.
Eine gröβere Furkationshöhe war signifikant mit einer höheren Anzahl von operativen Teilschritten verbunden (p = 0,040) und ein kleinerer Abstand Furkation – Apex zeigte eine Tendenz zu mehr operativen Teilschritten (p = 0,087). Die mikromorphometrische Analyse von Knochenoberflächen mittels Nahfeld-Stützimmersionsendoskopie wurde erstmals quantitativ unter Verwendung des Programms „Image J“ beschrieben. Im Vergleich von repräsentativen Arealen der Implantatkavitäten und Extraktionsalveolen zeigte sich, dass Implantatkavitäten mit 22,19% einen signifikant höheren Anteil an nicht-mineralisierten Arealen aufweisen im Vergleich zu 9,46% bei Extraktionsalveolen. Hingegen ist die Gefäβquerschnittsfläche bei Extraktionsalveolen mit 1,81% im Vergleich zu Implantakavitäten (0,58%) größer.
Schlussfolgernd kann man sagen, dass sich die Endoskopie als Routineverfahren etabliert hat. Die endoskopische Bildgebung erlaubt über eine präzise Visualisierung der Furkationsstelle die sytematische Entfernung von Zahnwurzeln ohne laterale Osteotomie. Eine neue mikromorphometrische Untersuchungstechnik mit der NF-SIE hat erhebliches Potential als Fenster zur In-vivo-Histologie von Knochenstrukturen.
49
Nowak, Kathrin Annelore. "Korrektur der Fallotschen Tetralogie nach vorhergehender Palliativoperation- Langzeitergebnisse aus einem historischen Patientenkollektiv." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-874D-A.
Full textAbstract:
Korrektur der Fallotschen Tetralogie nach vorhergehender Palliativoperation - Langzeitergebnisse aus einem
historischen Patientenkollektiv
Hintergrund:
Die Fallotschen Tetralogie ist ein komplexer zyanotischer Herzfehler, der erst mit dem Einsatz der Herz-Lungen-Maschine korrigiert werden kann. Zuvor erfolgte eine palliativ Operation. Seit 1960 werden Patienten mit Fallotscher Tetralogie in der Klinik für Thorax, -Herz- und Gefäßchirurgie der Universität Göttingen operiert. Ziel der Arbeit ist es, die Langzeitergebnisse eines historischen Patientenkollektivs, die zwischen 1960 und 1984 zuerst mit einer palliativen Operation behandelt und im Anschluss die Korrektur-Operation erhalten haben, zu analysieren.
Methoden:
Von 1960 bis 1984 erhielten 324 Patienten mit Fallotscher Tetralogie eine Korrektur-Operation nachdem zuvor eine Palliativ-Operation durchgeführt wurde. Die Datenanalyse erfolgte retrospektiv. Drei Gruppen wurden anhand der primären Palliativ-Operation gebildet: BTA-Gruppe (Blalock-Taussig-Anastomose, n=250), WCA-Gruppe (Waterstone-Cooley-Anastomose, n=57) und AD-Gruppe (verschiedene andere palliative Verfahren, n=17).
Ergebnisse:
Das mittlere Patientenalter war zur Korrektur-Operation in der BTA-Gruppe signifikant höher (8,45 ± 4,62 Jahre vs. 6,89 ± 2,96 Jahre in der WCA-Gruppe; p=0,0015). Die Operationsdauer war in der BTA-Gruppe mit 283 ± 105 Minuten kürzer im Vergleich zur WCA-Gruppe 314 ± 114 Minuten (p=0,32 ???). Intraoperativ wurde unter anderem eine Erweiterungsplastik mit Patch bei 64,5% durchgeführt (BTA: 63,2%, WCA: 70,2%), von diesen waren 48,8% transannulär (BTA: 44,3%, WCA: 75%). Postoperativ war eine Rethorakotomie nach der Korrektur-Operation in der WCA-Gruppe seltener (11% vs. 25% in der BTA-Gruppe; p=0,002). Die Korrektur-Operation führte in allen Gruppen zu einer effektiven, signifikanten Reduktion des rechtsventrikulären Druckes (BTA: von 96,01 ± 21,17 mmHg auf 52,75 ± 15,79 mmHg, WCA: von 97,78 ± 34,73 mmHg auf 59,05 ± 15,04 mmHg; p <0,001). Die Dauer der mechanischen Ventilation nach der Korrektur-Operation war in der BTA-Gruppe signifikant kürzer als in der WCA-Gruppe (46 ± 57 Stunden vs. 108 ± 207 Stunden; p=0,002), ebenso dauerte der Intensivaufenthalt in der BTA-Gruppe signifikant kürzer (117 ± 100 Stunden vs. 189 ± 205 Stunden in der WCA-Gruppe; p<0,001). Die Frühletalität betrug im Gesamtkollektiv 15,1%, Unterschiede zwischen den Gruppen???. Im weiteren Verlauf starben 12 weitere Patienten, so dass die Gesamtletalität 18,8% beträgt. Beim letzten Kontakt befanden sich die meisten Patienten im NYHA-Stadium II und III (NYHA-Stadium des Gesamtkollektivs: 2,3 ± 1,0; BTA-Gruppe: 2,2 ± 1,0; WCA-Gruppe: 2,7 ± 0,8).
Schlussfolgerung:
Die Datenanalyse zeigt, dass von den Palliativ-Operationen vor einer Korrektur-Operation bei Fallotscher Tetralogie, die BTA die vorteilhaftere Variante darstellt. Bei der Korrektur-Operation hatten die Patienten nach vorheriger BTA-Shunt-Operation eine kürzere OP-Dauer, weniger Blutungen postoperativ, sowie kürzere Beatmungs- und Intensivaufenthaltsdauer. Nach Korrektur der Fallotschen Tetralogie zeigen alle Patienten eine effiziente Verbesserung der hämodynamischen Parameter und ein gutes klinisches Langzeitergebnis. Da das optimale Operationsverfahren von mehreren Faktoren abhängt (u.a. Alter des Patienten, klinischen Zustand und anatomische Gegebenheiten), muss eine individuelle Entscheidung erfolgen und falls eine Palliativ-Operation notwendig ist, sollte die Anlage einer BTA bevorzugt werden.
50
Peitsch, Werner Karl Josef. "Komplikationen nach endoskopisch-laparoskopischer Hernioplastik (TAPP) als Regeloperation zur Versorgung von Leistenhernien." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-001D-BF71-8.
Full text