Dissertations / Theses: 'Laser Doppler Velocimetry'

1

Pannell, C. N. "Fibre-optic laser Doppler velocimetry." Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383370.

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Liu, Chengxin. "Applications of laser- and phase-Doppler velocimetry." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/8390.

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3

Collins, Patrick M. "Point Doppler velocimetry measurements in circular jets." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1304.

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Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains vii, 120 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 40-42).

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Utschig, Joseph M. "Laser Doppler velocimetry in a low speed multistage compressor." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA274836.

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Thesis (M.S. in Engineering Science (with a Major in Aeronautical Engineering) Naval Postgraduate School, September 1993.
Thesis advisor(s): Garth V. Hobson. "September 1993." Includes bibliographical references. Also available online.

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Bell, John R. "Application of laser doppler velocimetry to rotor vibration measurement." Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/7563.

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Vibration measurement is of fundamental importance in many machinery applications including for the development and monitoring of rotating machinery. In such applications, measurement of the vibration transmitted from the rotor into a non-rotating part of the structure is the most common arrangement but this cannot always be relied upon because vibration transmission may be low. In such cases, the use of a non-contacting vibration transducer capable of measuring vibration directly from the rotor itself is desirable. Laser Doppler Velocimetry (LDV) is a non-contacting vibration technique capable of such measurements but vibration measurements on rotating structures using LDV have been shown to be ambiguous. The sensitivity of the measured velocity to other rotor vibration components can be significant enough to mask the intended vibration measurement entirely. This thesis examines the use of LDV for vibration measurements on rotating structures more comprehensively than in any previous study. A new and completely general theory is developed to allow the velocity sensitivity of LDV measurements taken from rotating structures to be described for laser beam incidence in an arbitrary direction on a target element requiring 6 degrees of freedom to define its vibratory motion fully. Extension of the' theory to optical configurations incorporating multiple laser beams is also included with a number of useful instrument configurations established. The theory enables some fundamental questions regarding the use of LDV on rotating structures to be answered. Of particular importance is the confirmation that direct measurement of radial or pitch and yaw vibration is not possible because the measurements will always be unavoidably cross-sensitive to other motion components. Resolution of these components is possible, however and a new method of resolving steady state, non-synchronous radial, pitch and yaw vibrations is presented enabling a range of measurements to be made for the first time using LDV. Several of these measurements were made on a running IC engine and of special note are the angular vibration measurements made using a novel instrument incorporating 3 beams, the laser angular vibrometer, designed specifically for the task. Errors within the resolution technique are considered in detail and, looking forward, a number of promising means by which to reduce error magnitudes are introduced and recommended for further investigation. LDV has great potential for rotating machinery diagnostics and such developments are key to achieving this potential.

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Maeda, Shigenori. "Characterization of aerosols with laser doppler velocimetry for LC/ICPMS." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/27110.

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Egan, D. A. "In-line fibre optic laser Doppler velocimetry for turbomachinery applications." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323879.

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Fawcett, Philip Andrew. "An investigation on planar velocimetry by spatial cross correlation." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/15731.

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Rothberg, Steven Joseph. "Laser speckle studies for vibration and torque measurement." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241481.

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10

Bagnera, Carlo. "Development of a Doppler Global Velocimetry system in view of turbomachinery applications." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210548.

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The development of a Doppler Global Veocimetry (DGV) system is described. An argon ion laser has been modified to suit the requirements of DGV. An etalon with high precision tilting control has been mounted in the laser cavity. The backward mirror of the laser cavity has been mounted on a piezotranslator for controlling the laser cavity length. Two iodine cells have been designed and manufactured: one with a bead of iodine in the cell volume, the other with a limited amount of iodine. The iodine absorption line of both cells has been calibrated with good repeatibility. The laser has been stabilized in frequency, so that operations during a measurement session in the lab are simplified. The capabilities of DGV measurements have been tested in two jets, at low and at high speeds. Velocity fluctuations of the jet could be followed, in spite of the highly noisy signals. The first steps towards three velocity component measurements with a single camera in a difficult environment such as the geometry of a turbomchinery cascade have been made. Imaging two views of a target on the same camera sensor is discussed, along with the spatial and luminosity calibration required.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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Perretta, David Arthur. "Laser Doppler velocimetry measurements across a normal shock in transonic flow." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA267240.

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Shao, Zhenzhi. "Seeding particle impact on Laser Doppler Velocimetry in-cylinder flow measurement." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/MQ40978.pdf.

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Starn, Andrew Douglas. "Doppler global velocimetry measurements in a wing flow field with tip blowing." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=24.

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Thesis (M.S.)--West Virginia University, 2004.
Title from document title page. Document formatted into pages; contains vi, 101 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 41-45).

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Webb, David L. "Development of and measurements using a point Doppler velocimetry (PDV) system." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1027.

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Thesis (M.S.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains vii, 98 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 62-66).

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15

Shapley, Nina C. "Laser Doppler velocimetry measurements of particle velocity fluctuations in a concentrated suspension." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/32699.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2000.
Includes bibliographical references (p. 246-251).
Recent statistical constitutive models of suspensions of neutrally buoyant, non-Brownian, non-colloidal, solid spheres in Newtonian fluids suggest that the particles nijgrate in response to gradients in "suspension temperature," defined as the average kinetic energy contained in the particle velocity fluctuations. These models have not yet been compared systematically with experimental data. In addition, the "temperature" models assume isotropic particle velocity fluctuations, since the "suspension temperature" is given as a scalar, in analogy to molecular systems. However, highly anisotropic particle velocity fluctuations have been observed in settling suspensions, which suggests that a "suspension temperature" tensor would be more realistic. We used laser Doppler velocimetry (LDV) to make a set of experimental observations of particle velocity fluctuations arising from inter-particle collisions in a concentrated non-colloidal suspension under nearly homogeneous shear flow in a narrow-gap concentric cylinder Couette device. We compared the relative sizes of the fluctuating velocity components and observed the variation of each component with particle volume fraction, shear rate, and radial position. In addition, we assessed the implications of these observations for suspension temperature models. The data indicate that the suspension temperature is anisotropic. The flow direction component is overwhelmingly the largest at every concentration and shear rate, followed by the neutral and then the gradient components. Meanwhile, each fluctuating velocity component demonstrates a distinct variation with the shear rate and with the particle volume fraction, but only slight variation with radial position, over the region of the flow accessible to measurement. Comparison between model predictions and measured shear rate and particle volume fraction profiles shows that several models capture the measured profiles qualitatively but not quantitatively, with better agreement for moderately concentrated suspensions than for highly concentrated suspensions. Also, comparison between predicted scalar suspension temperature profiles and the sum of the measured velocity fluctuation components demonstrates that most of the models underpredict the sum of the temperature components by a large factor. Finally, comparison among the models shows that the models are quite sensitive to the choice of transport coefficients that are functions of the particle volume fraction.
by Nina Claire Shapley.
Ph.D.

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He, Lingfeng. "ULTRASONIC STRESS MEASUREMENT BY USE OF LASER DOPPLER VELOCIMETRY FOR RAYLEIGH WAVES." Kyoto University, 1999. http://hdl.handle.net/2433/181801.

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Koehler, Timothy Philip. "Quantification of initial conditions in turbulent liquid sheets using laser-doppler velocimetry." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131234/unrestricted/koehler%5Ftimothy%5Fp%5F200405%5Fms.pdf.

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Machado, Pedro Miguel Borges do Canto Mota. "Characterization of the Dynamics of the Atmosphere of Venus with Doppler velocimetry." Observatoire de Paris, 2013. http://www.theses.fr/2013OBSP0270.

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L’objectif principal de cette thèse est de contribuer à une meilleure compréhension de la dynamique de l’atmosphère vénusienne, contraignant sa caractérisation au niveau du sommet des nuages , en complément des observations de la sonde Venus Express à des observations au sol. Afin d’atteindre cet objectif d’étudier la super-rotation atmosphérique, j’ai mesuré la vitesse du vent zonal (vent de travers allant d’Est en Ouest) et sa variabilité spatiale et temporelle, à l’aide de la spectroscopie de haute précision et de la vélocimétrie Doppler. Les observations ont été effectuées avec le spectrographe à haute résolution UVES monté sur le Very Large Telescope de l’ESO (VLT) et avec le spectropolarimètre à haute résolution ESPaDOnS au télescope Canada-France-Hawaii (CFHT) à l’Observatoire de Mauna Kea. J’utilise une méthode de mesure directe des vents planétaires basée sur la spectroscopie haute résolution dans le visible. L’atmosphère de Vénus contient des aérosols très dispersants en suspension, surtout dans la couche supérieure de nuages. Cette couche de nuages recouvre entièrement la planète, imposant un albédo inhabituellement élevé. Ces particules sont transportées par le vent, emportant avec eux les informations sur la dynamique atmosphérique. La couche nuageuse supérieure est située à environ 70 km d’altitude qui correspond à la vitesse maximale de la superrotation zonale. La méthode utilisée, dans le cas des observations avec une fente longue obtenues avec VLT/UVES, ont permis de caractériser les variations spatiales de vent zonal en fonction de la latitude (car la fente est mince par rapport à la taille de l’image du disque de Vénus). Une comparison entre les vents obtenus par la méthode de suivi de nuages avec l’intrument VEx/VIRTIS et ceux obtenus avec la méthode de vélocimétrie Doppler à l’aide du CFHT/ESPaDOns a également été réalisée
The main purpose of this thesis is to contribute to a better understanding of the dynamics of the Venusian atmosphere, constraining its characterization at cloud top level, complementing the observations of the Venus Express spacecraft with ground-based observations. In order to achieve this objective of studying the atmospheric super-rotation, I measured the zonal wind velocity (crosswind the planet from East to West) and its spatial and temporal variability, by means of high precision spectroscopy and Doppler velocimetry. The observations were made with the high-resolution spectrograph UVES with ESO’s Very Large Telescope (VLT) and with the high-resolution ESPaDOnS spectropolarimeter at the Canada-France-Hawaii telescope (CFHT) at Mauna Kea observatory. I use a method of direct measurement of the planetary winds based on high resolution spectroscopy in the visible range. The atmosphere of Venus contains highly scattering aerosols in suspension, mostly at cloud top layer. This cloud deck covers entirely the planet, imposing an unusually high albedo. These particles are carried by the wind, carrying with them the information on atmospheric dynamics. The upper cloud layer is located about 70 km altitude. This altitude corresponds to the maximum velocity of zonal superrotation. The method used, in the case of long-slit observations obtained with VLT/UVES, allowed to characterize the spatial variations of zonal wind as a function of latitude (since the slit is thin compared to the size of the disk image of Venus), and a comparison with VEx/VIRTIS cloud tracking was also performed using CFHT/ESPaDOnS

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19

Southward, James D. "Laser doppler velocimetry in the space-shuttle main engine high-pressure fuel turbopump." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA342224.

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Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, March 1998.
Thesis advisor(s): Garth V. Hobson. "March 1998." Includes bibliographical references (p. 145-147). Also available online.

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20

Stock, Joel. "Untersuchung der Hochviskosströmung in der Umgebung gleichsinnig rotierender Doppelschneckenelemente mittels dreidimensionaler Laser-Doppler-Velocimetry /." Hamburg : Helmut-Schmidt-Univ., Inst. für Mechanik, 2009. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=018003617&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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21

Fitzgerald, Kevin D. "Examination of flow around second-generation controlled diffusion compressor blades in cascade at stall." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FFitzgerald.pdf.

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22

Lee, Eung S. "D J. ." "Investigation of hydrodynamics in bubble columns and three-phase fluidized beds by particle image velocimetry and laser doppler velocimetry techniques /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu148819563351998.

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23

Sriram, P. "Whole field optical methods for structural mechanics : digital speckle correlation and laser Doppler velocimetry." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/11751.

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24

Harland, Andrew R. "The application of laser Doppler velocimetry to the measurement of underwater acoustic pressure fields." Thesis, Loughborough University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272669.

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25

Danitz, David Joseph. "Experimental investigation of the mixing of an axial jet within a swirling flow, utilizing laser Doppler velocimetry and particle image velocimetry." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38729.

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Williams, Andrew John Harold. "Laser-Doppler velocimetry and viscous computation of the flow through a compressor cascade near stall." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA303750.

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27

Felis, Carrasco Francisco Ignacio. "Instalación y Pruebas de un Sistema de Medición de Velocidad por LDV (Laser Doppler Velocimetry)." Tesis, Universidad de Chile, 2009. http://www.repositorio.uchile.cl/handle/2250/103561.

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Autorizada por el autor, pero con restricción para ser publicada a texto completo hasta el año 2014
El principal objetivo de este trabajo de título fue instalar un sistema de medición de velocidades de flujo en fluidos por anemometría láser Doppler (LDV). Esto se realizó en el marco del proyecto Fondecyt N°1085015, cuyos estudios apuntan a la caracterización de los flujos de transporte de calor y momentum a través de dispositivos de cortinas de aire doble jet-doble flujo. Parte de estos estudios se realizan en un montaje experimental, el cual simula el calor generado por un incendio en un túnel a escala, donde el objetivo de las cortinas de aire es contener el calor, generado por una fuente térmica, aislándolo de las zonas que se quiere proteger, y que deberán mantenerse a una temperatura moderada. Dentro de este montaje experimental, se instaló el dispositivo LDV junto con un sistema de medición de temperaturas por termocupla fina. La operación de estos instrumentos permitió la medición simultánea del campo de velocidad y temperatura, promedio y fluctuante, al interior del túnel donde evoluciona el doble jet-doble flujo. Para probar los instrumentos se consideraron tres casos de estudio. El primero fue un caso base de prueba, donde se obtuvieron perfiles de velocidad y temperatura de manera simultánea, lo que permitió posteriormente calcular el factor de correlación velocidad-temperatura, el cual corresponde al transporte de calor turbulento. Posteriormente, el caso dos y tres corresponde al análisis de las correlaciones velocidad-temperatura en la dirección vertical y horizontal del jet respectivamente. Se obtuvieron los valores de esta correlación en perfiles horizontales a distintas alturas del jet, encontrando que el transporte de calor turbulento aumenta considerablemente de magnitud, a medida que el jet se ensancha en los niveles inferiores más cercanos a la zona de impacto. Sin embargo, la dirección neta de este transporte de calor no pudo determinarse claramente, debido a una alta dispersión de los datos obtenidos. Se concluye que las condiciones de medición son determinantes al momento de obtener los datos de temperatura y velocidad simultáneamente. Especial cuidado debe tenerse en el sembrado de partículas y alineación de los instrumentos, para así obtener resultados concordantes con la teoría del fenómeno.

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28

DeVlaminck, James Raymond. "Extracting the Rotational Degrees of Freedom From a Reconstructed Three-Dimensional Velocity Field Along With an Analytical Demonstraton and a Proposed Method for Experimental Verification." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34173.

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A theoretical method for extracting the rotational degrees of freedom from a reconstructed three-dimensional velocity field has been developed. To extract the angular velocities the curl of the translational velocities must be performed. The three-dimensional velocity field is to be equally spaced so that the DFT-IDFT technique of taking partial derivatives of the translational velocities is used. A program was written in C along with MATLABÂ® which performed the theoretical calculations. Two proposed methods of experimentally verifying the angular velocity data is developed using a Kistler translational/angular piezobeam accelerometer to compare against the DFT-IDFT partial derivative technique for calculating the angular velocities.
Master of Science

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Varano, Nathaniel David. "Fluid Dynamics and Surface Pressure Fluctuations of Turbulent Boundary Layers Over Sparse Roughness." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/26918.

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Turbulent boundary layers over rough surfaces are a common, yet often overlooked, problem of practical engineering importance. Development of correlations between boundary layer parameters that can be used in turbulence models and the surface geometry is the only practical option for solving these problems. Experiments have been performed on a two-dimensional zero pressure gradient turbulent boundary layer over sparsely spaced hemispherical roughness elements of 2 mm diameter. Laser Doppler velocimetry was used to measure all three components of velocity. The friction velocity was calculated using an integral momentum balance. Comparisons were made with various fitting methods that assume the von KÃ¡rmÃ¡n constant is appropriate for rough walls. Results indicate that this is not the case, and that the slope of the semi-logarithmic portion of the mean streamwise profile may be a function of the ratio of inner and outer length scales. Comparisons were also made between various correlations that relate the surface geometry to the behavior of the mean velocity profile. In general, the existing correlations achieved a reasonable agreement with the data within the estimated uncertainties. A detailed study of the local turbulent structure around the roughness elements was performed. It was found that, in contrast to `sharper-edged' elements such as cylinders, an elevated region of TKE and Reynolds shear stress was found downstream of the element below the peak. This can be explained by the delay in separation of the flow coming over the top of the element due to the smooth curvature of the element. Surface pressure fluctuation measurements were made as well using a dual microphone noise reduction technique. There have only been a few past experiments on the surface pressure fluctuations under rough wall boundary layers. However, it has been shown that the spectra of the wall fluctuations can be used to predict the far-field noise spectrum [1,2]. Therefore it is been the goal of this research to verify existing correlations between the surface pressure fluctuation spectrum and the surface geometry as well as develop new correlations that provide insight into the interactions between the turbulent motions in the flow surface pressure.
Ph. D.

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Derlaga, Joseph Michael. "An Experimental Study of Longitudinally Embedded Vortices in a Turbulent Boundary Layer via the Non-Invasive Comprehensive LDV Technique." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32776.

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This report documents the measurements of turbulence quantities resulting from vortices embedded in a zero pressure gradient turbulent boundary layer. Turbulent boundary layers are found in most flow regimes over large scale vehicles and have been studied for many years. Various systems to control separation of boundary layers have been proposed, but vortex generators have proven to be an economical choice as they are often used to fix deficiencies in a flow field after large scale production of a vehicle has commenced. In order to better understand the interaction between vortex generators and the boundary layer in which they are embedded, an experiment has been performed using through non-invasive Comprehensive Laser Doppler Velocimeter. The results show that normalization on edge velocity is appropriate for comparison with previous work. The 1/S parameter and vq^2 parameter were found to be most appropriate to correlate the Reynolds stresses and triple products, respectively. The higher inflow edge velocity and greater momentum thickness, creating a lower vortex generator to boundary layer height ratio, result in a more diffuse vortex as compared to previous work conducted in the same wind tunnel, with the same geometry, but with different inflow conditions.
Master of Science

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Xu, Hanjiang. "Measurement of fiber suspension flow and forming jet velocity profile by pulsed ultrasonic doppler velocimetry." Diss., Available online, Georgia Institute of Technology, 2005, 2003. http://etd.gatech.edu/theses/available/ipstetd-1071/.

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32

Reyt, Ida. "Écoulements induits en guide d'onde acoustique fort niveau." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2292/document.

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La propagation d'une onde acoustique en guide est associée, pour de forts niveaux, à un certain nombre de phénomènes de l'acoustique non linéaire. Parmi ces phénomènes, les écoulements redressés (ou vent acoustique), l'effet d'une discontinuité et la transition à la turbulence, à l'étude dans ce mémoire, sont associés à la génération d'écoulements induits. L'étude expérimentale de ces phénomènes repose sur l'adaptation des méthodes de vélocimétrie Laser : Vélocimétrie Laser par effet Doppler (VLD) et Vélocimétrie par Images de Particules (PIV) à la mesure des différents écoulements. Ainsi, des mesures PIV en sortie de convergent, viennent compléter des mesures VLD réalisées antérieurement. Dans l'espoir de mieux appréhender les spécificités de la transition à la turbulence en guide d'onde acoustique, l'évolution de la couche limite de Stokes est étudiée pour des amplitudes de vitesse acoustique croissantes. Une étude expérimentale des écoulements redressés dans un guide d'onde à section carrée est proposée et les spécificités liées à cette géométrie sont recherchées. En outre, l'évolution des tourbillons du vent acoustique en guide d'onde cylindrique est analysée lorsque le vent devient rapide et certains facteurs pouvant être à l'origine de cette évolution sont modifiés. La répartition harmonique dans le guide est ainsi modifiée, puis l'influence des conditions thermiques est abordée en couplant les mesures de vitesses à des mesures de température moyenne dans le guide et en paroi. Une comparaison avec des résultats issus de simulations numériques permet de conforter l'évolution des écoulements redressés observée
High amplitude acoustic propagation in a guide is associated with several non linear phenomena including acoustic streaming, discontinuity effects and transition to turbulence. Those phenomena are studied in this work and are all associated with acoustically induced flows. The present experimental study therefore is based on velocimetry laser techniques: Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV), wich are fitted to the measurement of the different flow velocity components. Firstly, PIV measurements at the exit of a convergent enable to complement previous LDV measurements. Then, in order to a better understanding of the specificity of transition to turbulence in acoustics, the evolution of the Stokes boundary layer is studied for increasing acoustic velocity amplitudes. Then an experimental study of acoustic streaming in a square channel is reported, and the influence of the geometry is examined. Moreover, the evolution of acoustic streaming vortices in a cylindrical waveguide is analyzed for fast streaming and some parameters that could control such evolution are modified. The harmonicdistribution inside the guide is changed and then the influence of thermal conditions is studied by coupling velocity measurements and mean temperature measurements inside the waveguide and along the wall. Some comparisons between measured streaming velocities and numerical simulation results are presented

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33

Brooks, Donald Ray. "Development of Specialized Laser Doppler Velocimeters for High Resolution Flow Profile and Turbulence Spectral Measurements." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78089.

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Fluid dynamicists are always in need of innovative instruments for flow velocity measurements. An ideal instrument would be non-intrusive, have a very fine spatial resolution as well as a very fine temporal resolution, be able to measure three-components of velocity, and be compact. Through recent advancements, laser Doppler velocimetry can now meet all of those requirements making it an important part of aerodynamicist's research toolbox. The first paper presented in this manuscript style thesis explains the development of an advanced three-velocity component, spatially-resolving laser-Doppler velocimetry (LDV) system for highly resolved velocity measurements in situations with limited optical access. The new instrument, a next generation version of the previously developed 'comprehensive' LDV technology, enables measurements of three components of velocity and particle position in the axial direction all through a single transceiving lens. Described here is the design process and the final design for the 'compact, comprehensive' LDV (Comp²LDV). The probe was designed to achieve ± 10 micron root-mean-square uncertainties in axial particle position, which combined with the long measurement volume, allow researchers to obtain a three-velocity-component velocity statistics profiles over a span of approximately 1.5mm without the need for traversing. Results from measurements in a flat plate turbulent boundary layer very near the wall have compared favorably to data from previous studies. The second paper focuses on the motion and evolution of coherent structures in supersonic jet flows and how that relates to the intense noise the flows generate. As a preliminary study to experimentally address these relationships, novel non-intrusive measurements using two-component laser Doppler velocimetry (LDV) have been conducted at exceptionally high data rates to lend insight into the statistical behavior of noise-generating flow structures. A new heated supersonic jet facility has been constructed to provide supersonic flow at total temperatures ratios (T₀/Tₐ) up to 3. In the present work, the instrumentation is validated via comparison of LDV measurements along the centerline of a screeching cold jet with microphone and high-speed shadowgraph results. Reynolds stress spectra are presented for an over-expanded case (nozzle pressure ratio of 3.2) of a design Mach number 1.65 nozzle operated cold (T₀/Tₐ = 1). A preliminary study was then conducted in the near-nozzle shear layer, up to x/d = 4.0, at design nozzle pressure ratio (4.58) and total temperature ratio of 2.0. Results are presented for Reynolds stress time-delay correlations and power spectra at Re_d = 1.1M for this case. The stream-wise Reynolds normal stress spectra are compared with published spectral behavior reported by other researchers, indicating a similar spectral shape in the downstream stations as previously measured with LDV and hot wire anemometry for cold jets, but which differ in shape from density-based techniques.
Master of Science

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34

Schober, Peter. "Berührungsfreie Erfassung beschleunigter schubspannungsgetriebener Kraftstoffwandfilme unter Druckeinfluss." Berlin Logos-Verl, 2009. http://d-nb.info/997220376/04.

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Acheson, S. K. "An experimental investigation of the flow field in the turbine stator of a variable geometry turbocharger using laser Doppler velocimetry." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403440.

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Talioua, Abdessamad. "Etude expérimentale et analyse statistique de la transition vers les rouleaux turbulents dans l’écoulement de Couette-Taylor." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMLH18/document.

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Dans ce travail, nous représentons des résultats expérimentaux sur la transition vers les rouleaux turbulents dans l’écoulement de Couette-Taylor, l’écoulement produit entre deux cylindres coaxiaux tournant indépendamment l’un par rapport à l’autre. Une fois la géométrie et la nature du fluide sont fixes, l’écoulement est gouverné par deux paramètres de contrôle, les nombres de Reynolds intérieur et extérieur 〖Re〗_o et 〖Re〗_i associés à la rotation des cylindres extérieur et intérieur respectivement. La variation de ces paramètres confère à l’écoulement une variété de régimes, décrits par Coles [7] et par Andereck et al. [13]. Dans le cas de la contra-rotation, nous avons identifié trois régimes principaux sur le diagramme d'Andereck et al. [13] En considérant la variation de 〖Re〗_i pour une valeur fixe de〖 Re〗_o, l’écoulement est laminaire pour des faibles〖 Re〗_i. Il devient instable pour des valeurs plus élevées de〖 Re〗_i. Avant d'atteindre la turbulence, l'écoulement passe par un régime de coexistence laminaire-turbulent [7 13 14 16]. Pour notre série de mesures, nous avons fixé le nombre de Reynolds extérieur à 〖Re〗_o=-4368 et nous avons varié 〖Re〗_i du régime laminaire vers le régime turbulent. Pour 3000 < 〖Re〗_i < 4000, les diagrammes spatio-temporels indiquent la présence de structures cohérentes désordonnées. Ces structures sont bien organisées dans le temps et dans l’espace pour 4000 <〖 Re〗_i < 10000, et deviennent stationnaires pour des 〖Re〗_i plus grands [35]. Cette étude a été réalisée à l’aide d’une technique de visualisations à l'aide du kalliroscope, ainsi que par des mesures de vitesse par PIV stéréoscopique et LDV. Ceci nous permet ensuite de calculer les différentes quantités moyennes (énergie cinétique, contrainte de Reynolds, temps et longueur de corrélation, ...)
In this work we report experimental results on the transition to the turbulent vortices in the Couette-Taylor flow, the flow produced between independently rotating coaxial cylinders. Once the geometry and the nature of the fluid are fixed, the flow is gouverned by two control parameters, the outer and the inner Reynolds numbers 〖Re〗_o and 〖Re〗_i associated with the rotation of the outer and inner cylinders respectively. The variation of these parameters produces a large variety of regimes, which have been described by Coles [7], and Andereck et al. [13]. In the counter-rotating case, we have identified three main regimes on the diagram of Andereck et al. [13] When considering the variation of 〖Re〗_ifor a fixed value of〖 Re〗_o, the flow is laminar for low〖 Re〗_i. It becomes unstable for higher values of 〖Re〗_i. Before reaching turbulence, the flow passes by a regime of laminar-turbulent coexistence [7 13 14 16]. For our series of measurements, we fixed the outer Reynolds number at 〖Re〗_o=-4368, and varied 〖Re〗_ifrom the laminar to the turbulent regime. For 3000 < 〖Re〗_i< 4000, the space-time diagrams indicate the occurrence of disordered coherent structures. These structures are then well organized in time and space for 4000 < 〖Re〗_i< 10000, and become stationnary for the highest 〖Re〗_i [35]. These regimes are studied by visualizations using kalliroscope, as well as measurements of the velocity by stereoscopic PIV and LDV. This later allows us to calculate the various mean quantities (kinetic energy, Reynolds stress, time and length of correlation, etc…)

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Simon, Helene A. "Influence of the implant location on the hinge and leakage flow fields through bileaflet mechanical heart valves." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04012004-192539/.

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Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2004.
Sambanis Athanassios, Committee Member ; Sotiropoulos Fotis, Committee Member ; Yoganathan Ajit, Committee Chair. Includes bibliographical references (leaves 239-243).

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Lena, Andrea. "Misure di turbolenza finalizzate alla stima della tensione tangenziale di parete in una corrente idraulica." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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Il presente elaborato mira a definire lo studio e il calcolo degli sforzi tangenziali che una corrente idraulica crea al passaggio presso una parete piana. Più specificatamente, il lavoro di tesi consiste nella raccolta di informazioni sul moto turbolento e sui principali strumenti per la misurazione della velocità del flusso, concludendosi con l'analisi di alcuni dati misurati con un LDV a due componenti nel canale sperimentale situato presso il laboratorio di Ingegneria Idraulica dell'università di Bologna, durante la Summer School nel Workshop on Advanced measurement Techniques and Experimental Research - W.A.T.E.R., 24-28 giugno 2019. Inizialmente si andrà ad approfondire il moto turbolento, definendo più precisamente il fenomeno con le principali proprietà e si analizzerà un caso specifico di moto, che è quello in prossimità di una parete. Successivamente si elencheranno i principali strumenti di misurazione della velocità di un flusso, in particolare i metodi ottici ed a ultrasuoni. Infine verrà descritto il canale sperimentale utilizzato in laboratorio e l'analisi dei dati raccolti con le conseguenti considerazioni sui risultati ottenuti.

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Boualia, Hassan. "Etude numérique et expérimentale des champs dynamiques et scalaires dans un écoulement turbulent fourni par un brûleur coaxial. Effet de la stratification." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR129/document.

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De nos jours, l’énergie délivrée par la combustion dépasse 80% de l‟énergie totale dans le monde, et ce pourcentage restera probablement élevé le long des 100 prochaines années. La plupart des systèmes réactifs qui génèrent la combustion turbulente sont utilisés dans la fabrication, le transport et l‟industrie pour la génération des puissances. Comme résultat, l‟émission des polluants est parmi les problèmes majeurs qui sont devenus des facteurs critiques dans notre société. Dans ce cadre, une étude détaillée des systèmes réactifs est alors nécessaire pour la conception de systèmes de haute performance qui s‟adaptent aux technologies modernes. L'optimisation des performances de ces systèmes énergétiques permet d‟une part d‟économiser l'énergie et d‟autre part de réduire la pollution. Les jets turbulents sont impliqués dans l'efficacité de ces divers systèmes. Dans le cas isotherme, la complexité des écoulements turbulents résulte principalement de la coexistence des structures de tailles très différentes et de l‟interaction non linéaire entre ces structures. Les plus grandes structures dépendent fortement de la géométrie du domaine considéré, elles sont donc anisotropes. De plus, elles ont une grande durée de vie et elles sont responsables du transport de la quasi-totalité de l'énergie. Les plus petites structures, quant à elles, ont souvent un caractère beaucoup plus "universel" (dû à leur comportement relativement isotrope) et sont à l'origine du processus de dissipation visqueuse. Prédire numériquement la dispersion et le mélange d‟un scalaire non réactif dans un écoulement turbulent est considéré comme un problème primordial et reste toujours actuel. Plusieurs recherches sont attachés à ce sujet afin d‟approfondir de plus à la connaissance de différents phénomènes pour pouvoir les mieux prédire. La prédiction numérique du mélange turbulent existant dans plusieurs applications industrielles et environnementales, a un important intérêt en génie chimique. Il est nécessaire donc de bien comprendre la majorité de propriétés du mélange et de l‟écoulement. En combustion, la complication du comportement des jets résulte de l‟interaction entre le dégagement de la chaleur, les processus de mélange, l'entraînement et la recirculation des gaz. Pour bien comprendre la complexité de ce phénomène, il est nécessaire de connaître parfaitement l'évolution dynamique et scalaire des jets turbulents isothermes en présence d'importantes différences de densité, comme elles peuvent lors de la combustion. Cette optimisation passe par la compréhension de l'effet de la variation des conditions d'entrée sur les processus de mélange dans le cas non réactif et sur la stabilité et la nature de la flamme dans le cas réactif. Ainsi, des études théoriques, expérimentales et numériques, doivent être menées en parallèle pour mieux identifier les effets d'une telle intervention. Bien des questions demeurent ouvertes dans le but de mieux caractériser les différents écoulements turbulents réactifs. Les objectifs des études menées dans ce domaine sont la réduction des émissions de polluants et l‟amélioration du rendement de combustion. Une compréhension du mélange et leur interaction avec les différents processus chimiques traduit donc un enjeu majeur. Elle est considéré alors comme un facteur déterminant la qualité des variétés des procèdes. Ce travail de thèse se base sur les jets coaxiaux qui constituent un cas particulier de jet axisymétrique. Ils sont communément rencontrés dans des différents brûleurs industriels qui assurent le contact entre le comburant et le carburant sous une forme de jets coaxiaux. Cette technique est le siège d‟une amélioration du mélange et de la stabilité des flammes
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40

Parisot-Dupuis, Hélène. "Application de l'holographie acoustique en soufflerie par mesures LDV." Thesis, Toulouse, ISAE, 2012. http://www.theses.fr/2012ESAE0035/document.

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L’ Holographie acoustique de champ proche (NAH) est une méthode d’imagerie acoustique robuste, mais son application en écoulement peut être limitée par l’utilisation de mesures intrusives de pression ou de vitesse acoustique. Dans cette étude, une procédure holographique applicable en écoulement utilisant des mesures de vitesse non-intrusives est proposée. Cette méthode est basée sur le théorème intégral de Kirchhoff-Helmholtz convecté. La fonction de Green convectée est alors utilisée pour déterminer des propagateurs spatiaux convectés définis dans l’espace réel et incluant l’effet d’un écoulement subsonique uniforme. Les transformées de Fourier discrètes de ces propagateurs permettent alors d’évaluer les champs acoustiques à partir de la mesure du champ de pression ou de vitesse acoustique normale. Le but étant de développer une méthode de caractérisation de sources aéroacoustiques à partir de mesures de vitesse non-intrusives, cette étude se concentre essentiellement sur les propagateurs réels convectés basés sur la mesure de vitesse acoustique. Afin de valider cette procédure,des simulations ont été menées dans le cas de combinaisons de sources monopolaires et dipolaires convectées corrélées ou non. La procédure holographique développée donne de bons résultats par comparaison aux champs acoustiques théoriques. Une comparaison des résultats obtenus par les propagateurs convectés réels, développés dans cette thèse, avec ceux obtenus par leurs formes spectrales, développés par Kwon et al. fin 2010 pour des mesures de pression acoustique, montre l’intérêt d’utiliser la forme réelle pour la reconstruction de la pression acoustique à partir de la mesure de vitesse acoustique normale. L’efficacité de la procédure développée est confirmée par une campagne de mesure en soufflerie avec un haut-parleur affleurant rayonnant au sein d’un écoulement à Mach 0.22, et des mesures non-intrusives effectuées par Vélocimétrie Laser Doppler (LDV). Les champs de vitesse acoustique utilisés pour la procédure holographique sont dans ce cas extraits des mesures LDV par corrélation avec un microphone de référence. La faisabilité de prendre en compte des variations de l’écoulement dans la direction de reconstruction holographique est également vérifiée
Nearfield Acoustic Holography (NAH) is a powerful acoustic imaging method but its application in flow can be limited by intrusive measurements of acoustic pressure or velocity. In this work, a moving fluid medium NAH procedure using non-intrusive velocity measurements is proposed. This method is based on the convective Kirchhoff-Helmholtz integral formula. The convective Green’s function is then used to derive convective realspace propagators including uniform subsonic airflow effects. Discrete Fourier transforms of these propagators allow then the assessment of acoustic fields from acoustic pressure or normal acoustic velocity measurements. As the aim is to derive an aeroacoustic sources characterisation method from non-inrusive velocity measurements, this study is especially focused on real convective velocity-based propagators. In order to validate this procedure, simulations in the case of combinations of monopolar and dipolar sources correlated or not, radiating invarious uniform subsonic flows, have been performed. NAH provides very favorable results when compared to the theoretical fields. A comparison of results obtained by real convective propagators, developed in this work, and those obtained by the spectral ones, developed by Kwon et al. at the end of 2010 for acoustic pressure measurements, shows the interest of using the real-form for NAH acoustic pressure reconstruction from normal acoustic velocity measurements. The efficiency of the developed procedure is confirmed by a wind tunnel campaign with a flush-mounted loudspeaker radiating in a flow at Mach 0.22 and non-intrusive Laser Doppler Velocimetry (LDV) measurements. Acoustic velocity fields used for the NAH procedure are in this case extracted from LDV measurements by correlation with a reference microphone. The feasibility of taking into account mean flow variations in the direction of NAH reconstruction is also checked

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Petery, Christian von. "Experimentelle Bestimmung des Geschwindigkeitsfeldes bei der Kohlenstaubfeuerung in O_tn2-CO_tn2-Atmosphäre /." Aachen : Shaker, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016478121&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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42

Lowe, Kevin Todd. "Design and application of a novel Laser-Doppler Velocimeter for turbulence structural measurements in turbulent boundary layers." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29257.

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An advanced laser-Doppler velocimeter is designed to acquire fully-resolved turbulence structural measurements in high Reynolds number two- and three-dimensional turbulent boundary layers. The new instrument combines, for the first time, new techniques allowing for the direct measurement of particle acceleration and sub-measurement-volume-scale position resolution so that second-order 3D particle trajectories may be measured at high repetitions. Using these measurements, several terms in the Reynolds stress transport equations may be directly estimated, giving new data for modeling and understanding the processes leading to the transport of turbulence in boundary layer flows. Due to the unique performance of the probe, many aspects of LDV instrumentation development were addressed. The LDV configuration was optimized for lowest uncertainties by considering the demanding applications of particle position and acceleration measurements. Low noise light detection and signal conditioning was specified for the three electronic channels. A high-throughput data acquisition system allows for exceptional burst rate acquisition. Signal detection and processing algorithms have been implemented which draw from previous techniques but also address distinctive problems with the current system. In short, the instrument was designed to advance the state-of-the-art in LDV systems. Measurements presented include turbulence dissipation rate and fluctuating velocity-pressure gradient correlations that have been measured in 2D and 3D turbulent boundary layers using the unique capabilities of the CompLDV--many of these measurements are the first of their kind ever acquired in high Reynolds number turbulent flows. The flat-plate turbulent boundary layer is studied at several momentum thickness Reynolds numbers up to 7500 to examine Reynolds numbers effects on terms such as the velocity-pressure gradient correlation and the dissipation rate in the Reynolds transport equations. Measurements are also presented in a pressure-driven three-dimensional turbulent boundary layer created upstream from a wing-body junction. The current results complement the extensive data from previous studies and provide even richer depth of knowledge on the most-completely-documented 3D boundary layer flow in existence. Further measurements include the wakes of three circular-cylinder protuberances submerged in a constant pressure turbulent boundary layer.
Ph. D.

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43

Moreno, Oscar Ray. "Investigation and development of oil-injection nozzles for high-cycle fatigue rotor spin test." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FMoreno.pdf.

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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2005.
Thesis Advisor(s): Raymond Shreeve, Garth Hobson. Includes bibliographical references (p. 91-93). Also available online.

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Soni, Abhishek. "Experimental Investigation of Flame Aerodynamics for Confined and Unconfined Flow for a Novel Radial-Radial Novel Injector using 2D Laser Doppler Velocimetry." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552656922178471.

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Hollnagel, Dorothea Ilse. "Hemodynamics in cerebral arteries and aneurysms : comparative velocity investigations with 3D phase-contrast magnetic resonance angiography, laser doppler velocimetry and computational fluid dynamics." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17658.

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Hopkins, Andrew. "Fluid Dynamics and Surface Pressure Fluctuations of Two-Dimensional Turbulent Boundary Layers Over Densely Distributed Surface Roughness." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/26919.

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Measurements were made in two-dimensional zero pressure gradient turbulent boundary layers over 5 geometries of three-dimensional densely distributed surface roughness. A 3-velocity component laser Doppler velocimeter was used to measure instantaneous velocities. These measurements permitted an independent estimate of skin friction on the surfaces using a momentum balance approach, and the validity of the von Karman constant for rough walls was tested. Five roughness fetches were evaluated: three sandpaper roughness fetches of varying grit size and two cases of uniformly distributed hemispheres of different spacing. Optical surface profilometry was used to characterize the geometry of the sandgrain surfaces. It was found that the smooth wall von Karman constant can not be assumed for densely distributed rough wall flows in order to determine the skin friction for these flows. This requires an independent measure of skin friction using more than a single boundary layer profile. Near wall flow structure measurements found that the hemispherical elements do not have high TKE or Reynolds shearing stress regions at the trailing edge of elements as had been shown for sparsely spaced cylindrical elements. This is likely due to the sharp trailing corner of the cylindrical elements, as opposed to an effect of spacing. Rather, hemispherical roughness has a periodically occurring high stress and TKE region located between two element centers in the stream-wise direction at a height of approximately 1.5 times the roughness element height. The periodic nature of the near wall flow extends to approximately 4 roughness element heights. The traditional roughness function f(λ) did not correlate well with λ or the modified Λ for the experimental data. However, it was found that the friction coefficient for the current dense roughness cases is a constant 0.004, within the experimental uncertainty. Traditional inner wall scalings, outer wall scalings, and roughness scalings were not able to collapse surface pressure fluctuation spectra for the various rough wall surfaces tested. However, the data do collapse for individual geometries based on Reynolds number. This gives rise to the ability to predict pressure fluctuation spectra at other Reynolds numbers.
Ph. D.

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Stewart, Devin O. "Effects of Spacing and Geometry of Distributed Roughness Elements on a Two-Dimensional Turbulent Boundary Layer." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/35481.

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This thesis is a study of the effects of distributed roughness elements on a two-dimensional turbulent boundary layer. Measurements were taken on a total of ten rough wall configurations: four involving Gaussian spikes, and six with circular cylindrical posts. Rough wall flows are particularly suited to study with Laser Doppler Velocimetry (LDV) due to the fact that measurements are required near a solid surface, as well has in highly turbulent fluid. The LDV system used in this study is a fine resolution (~50 micron), three-component, fiber optic system. All mean velocities, Reynolds stresses, and triple products are measured. This study is unique in the range and variety of roughness cases for which data was taken.

The data show that the flow over a rough wall is characterized by high levels of turbulence near the roughness element peaks at the interface between low-speed, near-wall fluid and the higher speed fluid above. Behind an element, high-momentum fluid sweeps toward the wall, and there is a small region of ejection of low-momentum fluid. Cylindrical elements typically have larger magnitudes of turbulent stresses at their peaks compared to Gaussian elements. Trends in mean velocity profile parameters such as displacement height, roughness effect, and wake parameter are examined with respect to roughness element geometry and spacing.
Master of Science

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48

Hertel, Daniela. "Flow of polyethylene melts within and into rectangular ducts investigated by laser : Doppler velocimetry = Strömungsverhalten verschiedener Polyethylenschmelzen im Einlauf und im Inneren von Schlitzdüsen /." Göttingen : Sierke, 2008. http://d-nb.info/989056228/04.

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Kalpakli, Athanasia. "Experimental study of turbulent flows through pipe bends." Licentiate thesis, KTH, Linné Flow Center, FLOW, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93316.

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This thesis deals with turbulent flows in 90 degree curved pipes of circular cross-section. The flow cases investigated experimentally are turbulent flow with and without an additional motion, swirling or pulsating, superposed on the primary flow. The aim is to investigate these complex flows in detail both in terms of statistical quantities as well as vortical structures that are apparent when curvature is present. Such a flow field can contain strong secondary flow in a plane normal to the main flow direction as well as reverse flow. The motivation of the study has mainly been the presence of highly pulsating turbulent flow through complex geometries, including sharp bends, in the gas exchange system of Internal Combustion Engines (ICE). On the other hand, the industrial relevance and importance of the other type of flows were not underestimated. The geometry used was curved pipes of different curvature ratios, mounted at the exit of straight pipe sections which constituted the inflow conditions. Two experimental set ups have been used. In the first one, fully developed turbulent flow with a well defined inflow condition was fed into the pipe bend. A swirling motion could be applied in order to study the interaction between the swirl and the secondary flow induced by the bend itself. In the second set up a highly pulsating flow (up to 40 Hz) was achieved by rotating a valve located at a short distance upstream from the measurement site. In this case engine-like conditions were examined, where the turbulent flow into the bend is non-developed and the pipe bend is sharp. In addition to flow measurements, the effect of non-ideal flow conditions on the performance of a turbocharger was investigated. Three different experimental techniques were employed to study the flow field. Time-resolved stereoscopic particle image velocimetry was used in order to visualize but also quantify the secondary motions at different downstream stations from the pipe bend while combined hot-/cold-wire anemometry was used for statistical analysis. Laser Doppler velocimetry was mainly employed for validation of the aforementioned experimental methods. The three-dimensional flow field depicting varying vortical patterns has been captured under turbulent steady, swirling and pulsating flow conditions, for parameter values for which experimental evidence has been missing in literature.
QC 20120425

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Amara, Mohamed Kamel Eddine. "Applications de l'effet photoréfractif en métrologie optique : velocimetrie holographique par imagerie de particules & vélocimétrie Doppler laser." Rouen, 1998. http://www.theses.fr/1998ROUES019.

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La PIV permet de cartographier des distributions de vitesses dans les écoulements divers, flammes, jets, elle n'est cependant pas adaptée à l'étude de distributions de vitesses à trois composantes dans un volume d'étude. Des systèmes associant l'holographie à la PIV ont permis d'étendre l'étude aux volumes en utilisant des plaques photosensibles. Ils sont donc lents à cause du développement chimique et souffrent d'un RSB moyen. Dans la première partie de ce travail, un système de HPIV utilisant un cristal photoréfractif, support dynamique totalement recyclable, a été réalisé. Il se base sur l'enregistrement holographique instantané de plusieurs nappes dans le volume d'un cristal BSO. L'exploitation des puissances spectrales, via un calcul d'auto-corrélation, permet de déterminer les composantes de vitesses transversales. Une méthode de calcul de phase a été élaborée pour déterminer la composante axiale des vecteurs vitesses. Les tests de faisabilité se sont avérés encourageants. Dans la seconde partie de ce travail, on a procédé à une étude théorique de faisceaux non-diffractants produits par diffraction d'une onde convergente sur une ouverture annulaire. Pour compenser la faible efficacité de conversion, on a eu recours à une amplification optique des faisceaux par mélange à deux ondes dans un cristal photoréfractif Batio#3. On a montré aussi que, dans la LDV avec des faisceaux gaussiens, des erreurs d'estimations de vitesses de particules peuvent être induites à cause de la variation de l'interfrange dans le volume d'étude. Celles-ci peuvent être réduites par l'utilisation de faisceaux non-diffractants.

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Dissertations / Theses on the topic 'Laser Doppler Velocimetry'

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