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No description available.

No description available.

This research presents improvements to the velocity field reconstruction process achieved through computer vision. The first improvement of the velocity reconstruction process is the automation of the scanning laser Doppler vibrometer (SLDV) pose procedure. This automated process results in superior estimates of the position and orientation of the SLDV. The second improvement is the refinement of the formulation for reconstruction of the velocity field. The refined formulation permits faster computation, evaluation, and interpretation of the reconstructed structural velocity field. Taken together, these new procedures significantly improve the overall velocity reconstruction process which results in better, unbiased out-of-plane velocity estimates in the presence of noise. The automation of the SLDV pose procedure is achieved through a computer vision model of the SLDV. The SLDV is modeled as a projective camera, i.e. an imager which preserves projectivities. This projective camera model permits the precise association of object features with image features. Specifically, circular features in the object space are seen by the SLDV as ellipses in the image space. In order to extract object points, the bitangents among the circular features are constructed and the bitangent points selected. The accuracy and precision of the object points are improved through the use of a calibrated object whose circular features are measured with a coordinate measuring machine. The corresponding image points are determined by constructing the bitangents among the ellipses and selecting the tangent points. Taken together, these object/image bitangent point sets are a significantly improved data set for previously developed SLDV pose algorithms. Experimental verification of this automated pose procedure includes demonstrated repeatability, independent validation of the estimated pose parameters, and comparison of the estimated poses with previous methods. The refinement of the velocity reconstruction formulation is a direct result of the computer vision viewpoint adapted for this research. By viewing the velocity data as images of the harmonically excited structure's velocity field, analytical techniques developed for holographic interferometry are extended and applied to SLDV velocity images. Specifically, the "absolute" and "relative" fringe-order methods are used to reconstruct the velocity field with the "best" set of bases. Full and partial least squares solutions with experimental velocity data are calculated. Statistical confidence bounds of the regressed velocity coefficients are analyzed and interpreted to reveal accurate out-of-plane, but poor in-plane velocity estimates. Additionally, the reconstruction process is extended to recover the velocity field of a family of surfaces in the neighborhood of the "real" surface. This refinement relaxes the need for the exact experimental geometry. Finally, the velocity reconstruction procedure is reformulated so that independent least squares solutions are obtained for the two in-plane directions and the out-of plane direction. This formulation divides the original least squares problem into three smaller problems which can be analyzed and interpreted separately. These refinements to the velocity reconstruction process significantly improve the out-of-plane velocity solution and interpretation of the regressed velocity parameters. / Ph. D.

Turbulent swirling flows are important in many applications including gas turbines, furnaces and cyclone dust separators among others. Although the mean flow fields have been relatively well studied, a complete understanding of the flow field including its dynamics has not been achieved. The work contained in this dissertation attempts to shed further light on the behavior of turbulent swirling flows, especially focused on the dynamic behavior of a turbulent swirling flow encountering a sudden expansion. Experiments were performed in a new isothermal turbulent swirling flow test facility. Two geometrical nozzle configurations were studied. The \cb\ nozzle configuration exhibits a cylindrical \cb\ in the center of the nozzle. The free vortex nozzle configuration is obtained when the cylindrical \cb\ is removed. Detailed laser velocimeter measurements were performed to map out the flow field near the sudden expansion of the 2.9" (ID) nozzle leading to the 7.4" (ID) downstream section. In addition to presenting detailed flow profiles for both nozzle and downstream flow fields, representative frequency spectra of the flow dynamics are presented. Along with the flow time histories and histograms, the wide variety of dynamic behavior was thus described in great detail. The dynamics observed in the experiment can be classified into three main categories: coherent and large scale motion, intermittent motion and coherent periodic motion. Free vortex geometry flows, in the parameter space of the experiments (Swirl number = 0 - 0.21), exhibited mostly coherent and large scale motion. The spectra in these cases were broadband with very light concentration of spectral energy observed in some specific cases. Center--body geometry flows exhibited all three categories of flows as swirl strength was increased from zero. Flows with little or no swirl exhibited broad--band spectra similar to those for the free vortex geometry. Intermediate swirl levels resulted in a large amount of low frequency energy which, with the aid of the time histories, was identified as a large scale intermittence associated with radial movement of the annular jet as it enters the sudden expansion. Large swirl levels resulted in high magnitude coherent oscillations concentrated largely just downstream of the sudden expansion. Linear stability analysis was used to help in the interpretation of the observed dynamics. Although, as implemented here (using the parallel flow assumption), the analysis was not successful in quantitatively matching the experimentally observed dynamics, significant insight into the physical mechanisms of the observed dynamics was obtained from the analysis. Specifically, the coherent oscillations observed for larger swirl levels were able to be described in terms of the interaction between the inner and outer shear layers of the flow field. / Ph. D.

A technique to determine the three-dimensional velocity of a point on a vibrating structure is developed. This technique uses a reference-beam type laser-doppler velocimeter in three independent positions to determine the target velocity in a non orthogonal coordinate system. The transformation from non-orthogonal to orthogonal coordinate systems is analyzed. The sensitivities of the resulting velocity to measurement noise and position errors are also analyzed. Recommendations are made for future testing and applications of this technique. / Master of Science

Denna studie fokuserar på interobservatörsvariabiliteten vid utvärdering av distaltryckmätning, en viktig diagnostisk undersökning vid bedömning av cirkulationeni nedre extremiteterna och upptäcka perifer arteriell sjukdom (PAD) [1]. LaserDoppler Flödesmätning (LDF) användes i klinisk fysiologi och nuklearmedicin i(SUS) Lund och Malmö, för att mäta blodtrycket i ankarna och stortår. Studiensyftade till att utforska överensstämmelsen i resultat mellan olika observatörer,vid distal tryckmätning. Det vill säga, studera om resultaten av distaltryckmätning varierar, med LDF-teknik, beroende på undersökare. Studie krävdeingen etiks ansökan eftersom metoden bestod av avidentifierad och insamladmaterial. Tretton medarbetare med olika erfarenhetsnivåer deltog, ochkvalitetsstudien inkluderade fem patientfall. Resultat visade hög överstämmelsemellan observatörer, vilket indikerar att yrkeserfarenhet inte hade betydandeinverkan på tillförlitligheten i distal tryckmätning. I studiens resultat visadesIntraclass Correlation Coefficient (ICC) för höger tå-index var 0,996, för vänstertå-index 0,987, för höger ankel-index 0,990 och för vänster ankel-index 0,997.Dessa höga ICC-värden indikerar att mätresultaten var mycket tillförlitliga, vilketvisar på en hög grad av överensstämmelse mellan olika observatörers resultat.Studien betonar vikten av standardiserade protokoll och metodbeskrivningar föratt minimera interobservatörsvariabilitet, och säkerställa noggranna diagnostiskametodik.

The structure and behavior of the bimodal flow of the horseshoe vortex at the nose of a wing-body junction flow was studied. The wing consists of a 3:2 elliptic nose and a NACA 0020 tail joined at the maximum thickness (t). Measurements were performed with an approach flow conditions of U_ref = 27.5 m/s, Re_θ = 6700 at x/t=-2.15, and δ/t=0.5. A rapidly-scanning two-velocity-component laser-Doppler anemometer system was developed for use in investigating this flow. U and V velocity components were measured simultaneously with surface pressure measurements at the location of the most bimodal pressure histogram (x/t=-0.26). Mean (U, V) and rms (u’, v’) velocity components were obtained at four x locations, x/t= -0.15, -0.20, -0.25, -0.30, and show the same flow features measured in previous studies at this facility. Cross-correlations between the velocity and the surface pressure fluctuations were obtained. Large correlations were found between the u fluctuations (x/t= -0.15, -0.25, and -0.30) near the wall, y/t < 0.05, and the surface pressure fluctuations. The z fluctuations for y/t > 0.1 at all four x-locations lead the surface pressure fluctuations. Space-time correlations between the velocity fluctuations near the wall with the velocity fluctuations along the scan were also obtained. The correlations at x/t=-0.25 and x/t=-0.30 show that the fluctuations in the outer region, y/t > 0.1, are significantly correlated with and lead the velocity fluctuations near the wall. These measurements support a model of a single primary junction vortex that changes size and location in front of the wing. The strength or circulation of this vortex varies by only 20%. Event-threshold conditional-averages of velocity were obtained based on the surface pressure signal, which is sensitive to the movement of the junction vortex. These show that the junction vortex is concentrated near the nose, with large backflow, when the surface pressure signal is above the mean. The junction vortex is larger, with smaller backflow near the nose, when the surface pressure signal is below the mean. The velocity-pressure cross-correlations and space-time correlations indicate that the behavior of the junction vortex is influenced by fluctuations originating upstream and propagating inward and downward toward the wing. / Ph. D.

An experimental investigation of an incompressible, turbulent junction vortex formed at the base of a streamlined cylinder with a circular leading edge placed normal to a flat surface is documented. The flow environment is characterized by a body Reynolds number of 183,000, based on the diameter of the model. The investigation centered around measurements of mean velocity vectors at over 1,700 locations on the plane of symmetry. In addition, extensive turbulence measurements in regions of interest on the plane of symmetry were also made. All of the measurements are performed with a two-color, two-component, frequency shifted laser Doppler velocimeter. The mean flow field shows the presence of a single vortex on the plane of symmetry and a singular separation point upstream of the vortex. From the measured data, the locations of the vortex center and the singular separation point were determined. The mean velocity field correlates well with previously published surface pressure data and surface flow visualization results. Extensive comparisons were made with earlier Conrad and five-hole pressure probe measurements and hot film measurements. Comparisons with the Conrad probe results were made in a two-dimensional turbulent boundary layer, and with the five-hole probe results for the plane of symmetry junction vortex flow at six stations in the upstream region and four stations inside the separated region. Hot film results were compared at two stations in the upstream region. Excellent agreement was found in the two-dimensional turbulent boundary layer. On the plane of symmetry junction vortex flow, agreement among the three instruments was good, especially for data taken in the upstream region and away from the floor. Turbulence data were also obtained with the laser Doppler velocimeter in conjunction with a minicomputer. Results indicate the turbulence level inside the separated region is significantly higher than in the upstream region. Highest levels of turbulence were found near the singular separation point and near the center of the vortex. Doppler spectra variations in these regions were also shown. In addition, Doppler histograms obtained by a PDP-11 minicomputer were compared to Doppler spectra obtained using an FFT. Excellent agreement was found between the Doppler spectra and the histograms obtained from the two different instruments. / Ph. D.

Approved for public release, distribution is unlimited / Resonant excitation tests of rotor blades in vacuum spin pits using discrete oil jets showed that impact erosion of the blades could limit test times, but lower excitation amplitudes were produced using mist nozzles. Smaller diameter discrete jets might extend test times, but to fully prevent erosion, oil mist droplet size needed to be 30 microns or less. The present study examined both approaches. Prototype nozzles were developed to create 0.005 inch diameter multiple discrete jets using first alumina, then stainless steel tubing, laser and micro-machine drilling. The latter technique was selected and 50 were manufactured for evaluation in HCF spin tests. A vacuum test chamber was built to observe and photograph spray patterns from the prototype nozzles and from commercially available mist nozzles. An LDV system was used successfully to determine the velocity of the oil droplets within the mist. A complete mapping of mist nozzle sprays is required to allow routine design of blade excitation systems. / Lieutenant, United States Navy