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Journal articles on the topic 'Laser Doppler velocimeter. Modal analysis'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Arruda, J. R. F. "Spatial Domain Modal Analysis of Lightly-Damped Structures Using Laser Velocimeters." Journal of Vibration and Acoustics 115, no. 3 (July 1, 1993): 225–31. http://dx.doi.org/10.1115/1.2930337.

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Traditional modal identification techniques do not take advantage of the high spatial density of scanning Laser Doppler Velocimeter (LDV) measurements. In this paper, a spatial modal parameter estimation technique, specially adapted for use with LDV measurements, is presented. It is based on a real-mode modal filtering concept and, therefore, is applicable to structures with low damping. From the estimated mode shape surfaces, curve-fitted with two-dimensional Fourier series, angular displacements are calculated. A rectangular plate example illustrates the proposed techniques with both numerically simulated and experimental results.

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2

Lucas, M., and A. C. Smith. "Redesign of Ultrasonic Block Horns for Improved Vibration Performance." Journal of Vibration and Acoustics 119, no. 3 (July 1, 1997): 410–14. http://dx.doi.org/10.1115/1.2889739.

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Ultrasonic block horns are prone to reliability problems associated with modal activity close to the tuned operating frequency. This paper presents an approach to block horn design, which relies on two laser based vibration measurement techniques, electronic speckle pattern interferometry (ESPI) and laser doppler velocimetry (LDV) modal analysis, to validate finite element (FE) models. Block horn vibration characteristics are interpreted from experimental and theoretical data such that successful horn redesign can be achieved from modifications to the FE models.

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3

Kalybek, Maksat, Mateusz Bocian, and Nikolaos Nikitas. "Performance of Optical Structural Vibration Monitoring Systems in Experimental Modal Analysis." Sensors 21, no. 4 (February 10, 2021): 1239. http://dx.doi.org/10.3390/s21041239.

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Image-based optical vibration measurement is an attractive alternative to the conventional measurement of structural dynamics predominantly relying on accelerometry. Although various optical vibration monitoring systems are now readily available, their performance is currently not well defined, especially in the context of experimental modal analysis. To this end, this study provides some of the first evidence of the capability of optical vibration monitoring systems in modal identification using input–output measurements. A comparative study is conducted on a scaled model of a 3D building frame set in a laboratory environment. The dynamic response of the model to an impulse excitation from an instrumented hammer, and an initial displacement, is measured by means of five optical motion capture systems. These include commercial and open-source systems based on laser Doppler velocimetry, fiducial markers and marker-less pattern recognition. The performance of these systems is analysed against the data obtained with a set of high-precision accelerometers. It is shown that the modal parameters identified from each system are not always equivalent, and that each system has limitations inherent to its design. Informed by these findings, a guidance for the deployment of the considered optical motion capture systems is given, aiding in their choice and implementation for structural vibration monitoring.

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4

Filonovich, M. S., R. Azevedo, L. R. Rojas-Solórzano, and J. B. Leal. "Credibility analysis of computational fluid dynamic simulations for compound channel flow." Journal of Hydroinformatics 15, no. 3 (February 18, 2013): 926–38. http://dx.doi.org/10.2166/hydro.2013.187.

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In this paper, verification and validation of a turbulence closure model is performed for an experimental compound channel flow, where the velocity and turbulent fields were measured by a Laser Doppler Velocimeter (LDV). Detailed Explicit Algebraic Reynolds Stress Model (EARSM) simulations are reported. There are numerous methods and techniques available to evaluate the numerical uncertainty associated with grid resolution. The authors have adopted the Grid Convergence Index (GCI) approach. The velocity components, the turbulence kinetic energy (TKE), the dissipation rate and the Reynolds stresses were used as variables of interest. The GCI results present low values for the u velocity component, but higher values in what concerns the v velocity component and w velocity component (representing secondary flows) and for Reynolds stresses RSxy and RSyz. This indicates that the mean flow has converged but the turbulent field and secondary flows still depend on grid resolution. Based on GCI values distribution, the medium and fine meshes were further refined. In addition to GCI analysis, the authors have performed linear regression analysis for estimating the mesh quality in what concerns small value variables. Comparison of numerical and experimental results shows good agreement.

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5

Ribando, R. J., J. L. Palmer, and J. E. Scott. "Flow in a partially filled, rotating, tapered cylinder." Journal of Fluid Mechanics 203 (June 1989): 541–55. http://dx.doi.org/10.1017/s0022112089001588.

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The secondary flow patterns induced by a differentially rotating lid in a partially filled, rapidly rotating, tapered cylinder have been investigated. Using a new laser-Doppler velocimeter system capable of making measurements in the rotor frame of reference, the radial dependence of the azimuthal and axial velocity components was measured at two axial positions in the rotor. A linear, asymptotic analysis and a finite-difference simulation were made for comparison. The latter was performed on a boundary-fitted computational mesh so that the slanted rotor wall and the sagging free surface could be accommodated in the model. The agreement between the experimental and numerical results was excellent for the azimuthal velocity component and good for the axial component. Of particular interest is the modified E½ boundary layer on the slanted wall, a feature which is not present with a vertical sidewall.

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6

Jiang, Hongxu, Yalin Li, Yongwei Liu, and Dejiang Shang. "The system design for calibrating acoustic Doppler current meter in the laboratory." MATEC Web of Conferences 283 (2019): 08001. http://dx.doi.org/10.1051/matecconf/201928308001.

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The Acoustic Doppler Current meter is a most commonly device for the velocity measurement of the seawater in the ocean. We had designed an equipment to calibrate the Acoustic Doppler Current meter in the laboratory, which is mainly composed of a vertical circulating water tank and a system of Laser Doppler Velocimetry. The vertical circulating water tank is the key device of the calibration equipment. The optimization of flow field is carried out by the software, CFD. The optimization of structure intensity, modal analysis and low noise is carried out by the software, ANSYS. We had also used the propeller map to design the power section of the water tank. Through the comparison of the velocity of the flow between Acoustic Doppler Current meter and LDV at the same position in the working section of the water tank, the former can be calibrated, because the wavelength of optics is much less than that of acoustics in the water. After the experimental test, we found that when the fluid flows in the vertical circulating water tank, there exists no resonance phenomenon and the velocity of the flow in the working section is approximately proportional to the rotation speed of the propeller.

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7

Geremew, Africa M., and Ernest K. Yanful. "Role of fines on cohesive behavior of mine tailings inferred from critical shear stress." Canadian Geotechnical Journal 48, no. 4 (April 2011): 568–82. http://dx.doi.org/10.1139/t10-089.

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The significance of fines on the cohesive behavior of mine tailings has been investigated by examining the incipient motion of the tailings. Sixteen laboratory experiments were performed in a Plexiglas laboratory annular column on re-constituted mine tailings under a 50 cm water cover. Re-suspension was produced by a Teflon stirrer and the velocity field in the column was characterized using a laser Doppler velocimeter (LDV). The pressure change in the boundary layer was also measured with a Preston tube. It was observed that the nondimensional critical shear stresses showed deviation from those of the noncohesive model results at a fines content greater than 50%–55%. An empirical relation that shows the relation between the boundary shear stress deviation and the percent fines in the tailings was proposed. Regression analysis of the experimental results showed that a power law relationship could reasonably be used to describe the relation between the measured nondimensional excess bed shear stress and the erosion rate. It is proposed that the value of β (the erosion rate constant) could be taken as 1 for mine tailings that show cohesive behavior.

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8

Zhou Jian, 周健, 冯庆奇 Feng Qingqi, 马曙光 Ma Shuguang, 宋锐 Song Rui, 魏国 Wei Guo, and 龙兴武 Long Xingwu. "Error analysis of reference-beam laser Doppler velocimeter." High Power Laser and Particle Beams 22, no. 11 (2010): 2581–87. http://dx.doi.org/10.3788/hplpb20102211.2581.

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9

Ilic, Jelena, Slavica Ristic, and Milesa Sreckovic. "Laser doppler velocimetry and confined flows." Thermal Science 21, suppl. 3 (2017): 825–36. http://dx.doi.org/10.2298/tsci160720278i.

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Finding the mode, in which two component laser Doppler velocimetry can be applied to flows confined in cylindrical tubes or vessels, was the aim of this study. We have identified principle issues that influence the propagation of laser beams in laser Doppler velocimetry system, applied to flow confined in cylindrical tube. Among them, the most important are influences of fluid and wall refractive indices, wall thickness and internal radius ratio and beam intersection angle. In analysis of the degrees of these influences, we have applied mathematical model, based on geometrical optics. The separation of measurement volumes, that measure different velocity components, has been recognized as the main drawback. To overcome this, we propose a lens with dual focal length ? primary focal length for the measurement of one velocity component and secondary focal length for the measurement of the other velocity component. We present here the procedure for calculating the optimal value of secondary focal length, depending on experimental set-up parameters. The mathematical simulation of the application of the dual focal length lens, for chosen cases presented here, confirmed the accuracy of the proposed procedure.

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10

Liu Zijun, 刘子君, 崔骊水 Cui Lishui, and 谢代梁 Xie Dailiang. "Theory Analysis and Measurement for Interference Fringes of Laser Doppler Velocimeter." Chinese Journal of Lasers 44, no. 8 (2017): 0804001. http://dx.doi.org/10.3788/cjl201744.0804001.

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11

Geng, Ling Xin, Li Jian Zhang, and Qing Xiang Shi. "Fluid Field Analysis for Cyclone Separator Used on Grain Cleaning." Advanced Materials Research 605-607 (December 2012): 1369–71. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.1369.

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Gas velocity in cyclone separator is measured by testing with laser Doppler velocimeter in this paper. The measuring results indicates that tangential velocity, axial velocity, radial velocity of air distribute following some certain rules, reasonable selected structure parameters can improve separating efficiency

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12

El Lababidy, S., N. Bose, P. Liu, and F. Di Felice. "Detailed Analysis of the Wake of a DP Thruster Emphasizing Comparison Between LDV and SPIV Techniques." Journal of Offshore Mechanics and Arctic Engineering 128, no. 2 (November 4, 2005): 81–88. http://dx.doi.org/10.1115/1.2185680.

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To provide experimental data on the hydrodynamic characteristics and features of dynamic positioning (DP) thrusters under variable operating conditions, wake measurements were performed on a DP thruster model using 2D laser Doppler velocimetry (LDV) and stereoscopic particle image velocimetry (SPIV). These tests were performed with and without a nozzle and over a range of advance coefficient values including the bollard pull condition. In this paper, a detailed analysis of the hydrodynamic characteristics of the wake at a plane equal to a distance of 0.5 diameters downstream from the thruster, at advance coefficient values of 0, 0.4, and 0.45 are presented for both the LDV and SPIV measurements showing a comparison between the results of each technique. The effect of the duct and of changes in the advance coefficient values is presented in this paper.

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13

Dura˜o, D. F. G., M. V. Heitor, and A. L. N. Moreira. "Flow Measurements in a Model Burner—Part 2." Journal of Fluids Engineering 115, no. 2 (June 1, 1993): 309–16. http://dx.doi.org/10.1115/1.2910140.

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The isothermal swirling flow in the vicinity of a model oxy-fuel industrial burner is analyzed with laser-Doppler velocimetry together with laser-sheet visualization. The burner consists of a central axisymmetric swirling jet surrounded by sixteen circular jets, simulating the injection of oxygen in practical burners. The results extend those obtained for non-swirling flows, and presented in Part 1 of this paper, to the analysis of the dependence of the mixing efficiency of the burner assembly upon the swirl motion of the central jet and have the necessary detail to allow to assess the accuracy of calculation procedures of the flow in industrial burners. It is shown that swirl attenuates the three-dimensional structure typical of multijet flows in such a way that turbulence production and transport in the near burner zone are dominated by swirl-induced processes.

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14

Wei, Guo, Jian Zhou, and Xingwu Long. "Analysis of signal-to-noise ratio and heterodyne efficiency for reference-beam laser Doppler velocimeter." Optics & Laser Technology 44, no. 1 (February 2012): 108–13. http://dx.doi.org/10.1016/j.optlastec.2011.06.001.

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15

SUGIYAMA, Hitoshi, Mitsunobu AKIYAMA, and Takeo WATANABE. "Experimental Analysis of Developing Turbulent Flow in a Distorted Elliptical Duct by Laser-Doppler Velocimeter." Transactions of the Japan Society of Mechanical Engineers Series B 64, no. 621 (1998): 1335–42. http://dx.doi.org/10.1299/kikaib.64.1335.

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16

KURIHARA, Noboru, Yoshiya TERAO, Shin-ichi NAKAO, and Masaki TAKAMOTO. "Development and Uncertainty Analysis of a Laser Doppler Velocimeter Calibrator for the Flow Velocity Standard." Transactions of the Japan Society of Mechanical Engineers Series B 65, no. 637 (1999): 3029–34. http://dx.doi.org/10.1299/kikaib.65.3029.

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17

Siringoringo, Dionysius M., and Yozo Fujino. "Noncontact Operational Modal Analysis of Structural Members by Laser Doppler Vibrometer." Computer-Aided Civil and Infrastructure Engineering 24, no. 4 (May 2009): 249–65. http://dx.doi.org/10.1111/j.1467-8667.2008.00585.x.

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18

Ronkainen, J., and A. Harland. "Soccer ball modal analysis using a scanning laser doppler vibrometer (SLDV)." Sports Engineering 10, no. 1 (March 2007): 49–54. http://dx.doi.org/10.1007/bf02844201.

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19

Hughes, M. J., S. A. Kinnas, and J. E. Kerwin. "Experimental Validation of a Ducted Propeller Analysis Method." Journal of Fluids Engineering 114, no. 2 (June 1, 1992): 214–19. http://dx.doi.org/10.1115/1.2910018.

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A ducted propeller model was tested in the MIT water tunnel. A hub apparatus was designed which allowed for the duct and propeller forces to be measured separately. The forces on the duct and propeller were measured over a range of advance coefficients. Velocities were measured upstream and downstream from the duct using a Laser Doppler Velocimetry system. Using these velocities the experimental values for the spanwise distribution of circulation on the propeller blades were then calculated. The experimental results were compared to the results from a propeller lifting surface/duct and hub surface panel analysis code over the same range of advance coefficients showing very good agreement for the duct and propeller forces and the circulation in the region of attached flow.

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20

Yao, Xiaobo, and André W. Marshall. "Quantitative Salt-Water Modeling of Fire-Induced Flows for Convective Heat Transfer Model Development." Journal of Heat Transfer 129, no. 10 (February 23, 2007): 1373–83. http://dx.doi.org/10.1115/1.2754943.

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This research provides a detailed analysis of convective heat transfer in ceiling jets by using a quantitative salt-water modeling technique. The methodology of quantitative salt-water modeling builds on the analogy between salt-water flow and fire induced flow, which has been successfully used in the qualitative analysis of fires. Planar laser induced fluorescence and laser doppler velocimetry have been implemented to measure the dimensionless density difference and velocity in salt-water plumes. The quantitative salt-water modeling technique has been validated through comparisons of appropriately scaled salt-water measurements, fire measurements, and theory. This analogy has been exploited to develop an engineering heat transfer model for predicting heat transfer in impinging fire plumes using salt-water measurements along with the adiabatic wall modeling concept. Combining quantitative salt-water modeling and adiabatic wall modeling concepts introduces new opportunities for studying heat transfer issues in basic and complex fire induced flow configurations.

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21

Taylor, Joshua O., Bryan C. Good, Anthony V. Paterno, Prasanna Hariharan, Steven Deutsch, Richard A. Malinauskas, and Keefe B. Manning. "Analysis of Transitional and Turbulent Flow Through the FDA Benchmark Nozzle Model Using Laser Doppler Velocimetry." Cardiovascular Engineering and Technology 7, no. 3 (June 27, 2016): 191–209. http://dx.doi.org/10.1007/s13239-016-0270-1.

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22

Chevrin, P. A., H. L. Petrie, and S. Deutsch. "The Accuracy of a Three-Component Laser Doppler Velocimeter System Using a Single-Lens Approach." Journal of Fluids Engineering 115, no. 1 (March 1, 1993): 142–47. http://dx.doi.org/10.1115/1.2910097.

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An analysis of the effects of misalignment on the on-axis velocity component measurements made with a three-component LDV system using two colors and five beams issuing from a single lens is discussed. A slight misalignment of the center beam from the optical axis is shown to cause large changes in the measured “on-axis” component of velocity. The effect of misalignment on the ensemble averaged velocity statistics in turbulent flows is also considered. The error analysis of Neti and Clark (1979) is applicable to on-axis component of the present system and it shows that even when the system is perfectly aligned, the relative uncertainty of the on-axis component of velocity is much larger than that of the other components of velocity. Measurements taken in a laminar pipe flow support this conclusion.

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23

Савельева, Н. В., Ю. В. Баяндин, А. С. Савиных, Г. В. Гаркушин, С. В. Разоренов, and О. Б. Наймарк. "Формирование упругопластических фронтов и откольное разрушение в сплаве АМг6 при ударных воздействиях." Письма в журнал технической физики 44, no. 18 (2018): 39. http://dx.doi.org/10.21883/pjtf.2018.18.46610.17411.

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AbstractFull wave profiles were monitored by the laser interferometry method by means of a VISAR laser Doppler velocimeter under shock-wave loading of samples of AMg6 aluminum alloy. Analysis of these profiles was used to study the laws of elastic precursor formation and its amplitude variation during elastic–plastic transition front propagation in samples loaded by a shock wave of variable intensity. Critical stresses leading to the spall fracture of samples were determined as dependent on the strain rate under unloading.

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24

Filippov, Andrey V., Vladimir A. Krasnoveikin, Nikolay V. Druzhinin, and Valery E. Rubtsov. "The Use of Laser-Doppler Vibrometry for Modal Analysis of Carbon-Fiber Reinforced Composite." Key Engineering Materials 712 (September 2016): 313–18. http://dx.doi.org/10.4028/www.scientific.net/kem.712.313.

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Both modal analysis procedure and the results obtained on a three-component 3D-printed carbon-fiber reinforced composite (CFRC) are presented. Experimental modal analysis of on the composite has been carried out to obtain the dynamic behavior characteristics. As revealed, the different eigen-oscillations waveforms possess different sensitivity of its amplitude frequency response to structural defects of the composite. For the similar waveforms we observed the differences in eigen-oscuillation frequencies, vibration velocities and damping factors which can be caused by the presence of numerous defects homogeneously distributed in one of the samples.

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25

Cockrill, Martin, and Maximilian Chowanietz. "Detailed experimental modal analysis of a trumpet: An application of laser Doppler vibrometry." Journal of the Acoustical Society of America 142, no. 4 (October 2017): 2543. http://dx.doi.org/10.1121/1.5014297.

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26

Duerinck, Tim, Mathias Kersemans, Ewa Skrodzka, Marc Leman, Geerten Verberkmoes, and Wim Van Paepegem. "Experimental Modal Analysis of Violins Made from Composites." Proceedings 2, no. 8 (July 19, 2018): 535. http://dx.doi.org/10.3390/icem18-05457.

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Six prototype violins made from composite materials are made and investigated using experimental modal analysis with the roving hammer method. The average FRF’s obtained show an influence of the materials on the vibrational response up to 2200 Hz. The A0 breathing mode and B1- mode are identified and are found to be significantly lower than in classical wooden violins. Additional measurements with a Laser Doppler Vibrometer and shaker found the same modes with a small difference in frequency (3–8 Hz).

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27

Zhang, Da, and Ranglei Liu. "Laser Doppler Signal Denoising Based on Wavelet Packet Thresholding Method." International Journal of Optics 2019 (November 14, 2019): 1–11. http://dx.doi.org/10.1155/2019/1097292.

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In laser Doppler velocimeter (LDV), calculation precision of Doppler shift is affected by noise contained in Doppler signal. In order to restrain the noise interference and improve the precision of signal processing, wavelet packet threshold denoising methods are proposed. Based on the analysis of Doppler signal, appropriate threshold function and decomposition layer number are selected. Heursure, sqtwolog, rigrsure, and minimaxi rules are adopted to get the thresholds. Processing results indicate that signal-to-noise ratio (SNR) and root mean square error (RMSE) of simulated signals with original SNR of 0 dB, 5 dB, and 10 dB in both low- and high-frequency ranges are significantly improved by wavelet packet threshold denoising. A double-beam and double-scattering LDV system is built in our laboratory. For measured signals obtained from the experimental system, the minimum relative error of denoised signal is only 0.079% (using minimaxi rule). The denoised waveforms of simulated and experimental signals are much more smooth and clear than that of original signals. Generally speaking, denoising effects of minimaxi and saqtwolog rules are better than those of heursure and rigrsure rules. As shown in the processing and analysis of simulated and experimental signals, denoising methods based on wavelet packet threshold have ability to depress the noise in laser Doppler signal and improve the precision of signal processing. Owing to its effectiveness and practicability, wavelet packet threshold denoising is a practical method for LDV signal processing.

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28

SUGIYAMA, Hitoshi, and Nobuhide HANEDA. "Experimental Analysis of Turbulent Flow in a Rectangular Duct with Arrays of Blocks by using Laser-Doppler Velocimeter." Transactions of the Atomic Energy Society of Japan 1, no. 2 (2002): 119–26. http://dx.doi.org/10.3327/taesj2002.1.119.

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29

El Lababidy, Said A., Neil Bose, Pengfei Liu, and Dan Walker. "Dynamic Positioning Thruster Near Wake Hydrodynamic Characteristics at Near Bollard Pull." Journal of Ship Research 53, no. 01 (March 1, 2009): 48–58. http://dx.doi.org/10.5957/jsr.2009.53.1.48.

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The knowledge of the hydrodynamic characteristics and momentum effects of the flow of dynamic positioning (DP) thrusters are important factors in the design of structures around the DP thrusters and in improving DP system reliability. In the present study, the flow field around a DP thruster model was precisely measured in a cavitation tunnel using a two-component laser Doppler velocimetry (LDV) system. These experiments were carried out with and without a nozzle at three different axial planes up to 1.5 diameters downstream, and the results are presented here for a pitch/diameter ratio of 1.2 at near bollard pull operating conditions (J ¼ 0.4 and J ¼ 0.45). This paper shows and compares the results of the DP thruster near wake hydrodynamic and momentum characteristics when operating with and without a nozzle at two different low advance coefficient values.

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30

Popescu-Cuta, Alina, Georgeta Ionascu, Octavian Donţu, Mihai Avram, Constantin Daniel Comeaga, and Elena Manea. "Modal Analysis of a MEMS Cantilever." Applied Mechanics and Materials 658 (October 2014): 690–93. http://dx.doi.org/10.4028/www.scientific.net/amm.658.690.

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Micro-Electro-Mechanical Systems (MEMS), also known as micromechatronic devices, integrate on the same chip (substrate) both micromechanical structures and microelectronics components. Microcantilevers are miniaturized beams clamped at one end and with the other end suspended freely outwards. They can be used as resonant structures in nano/micro mass detectors, allowing a quantitative assessment of the (substance) mass attached to these devices. An accurate modal analysis makes possible to estimate the sensitivity of the cantilevers or their ability to detect minimum frequencies shifts induced by the substance absorption. In order to obtain a high sensitivity, the structures must present high resonant frequencies (usually bending or torsion), in close correlation with a small equivalent mass. This paper deals with the vibration testing, modeling and simulation of a silicon rectangular microcantilever, micromachined through MEMS technologies. The results of analytical calculations and numerical computation by finite element analysis (FEM) have been compared with those measured through Laser Doppler Vibrometry (LDV) method using MSA-500 system from Polytec.

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31

Tabakoff, W., and M. F. Malak. "Laser Measurements of Fly Ash Rebound Parameters for Use in Trajectory Calculations." Journal of Turbomachinery 109, no. 4 (October 1, 1987): 535–40. http://dx.doi.org/10.1115/1.3262144.

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This paper describes an experimental method used to find particle restitution coefficients. The equations that govern the motion of solid particles suspended by a compressible gas flow through a turbomachine depend on the restitution coefficients. Analysis of the data obtained by a laser-Doppler velocimeter (LDV) system of the collision phenomenon gives the restitution ratios as a function of the incidence angle. From these ratios, the particle velocity components after collision are computed and used as the initial conditions to the solution of the governing equations of motion for particle trajectories. The erosion of metals impacted by small dust particles can be calculated by knowing the restitution coefficients. The alloy used in this investigation was 410 stainless steel.

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32

Johnson, David A. "Analysis of the Immediate Boundary Conditions of an Axial Flow Impeller." Journal of Fluids Engineering 123, no. 4 (August 8, 2001): 771–79. http://dx.doi.org/10.1115/1.1412846.

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The design and analysis of impellers for mixing applications such as stirred tank reactors (STR) have significant application in many engineering processes. In particular, the evaluation of the turbulent flow boundary conditions immediately around a model impeller has been examined using flow visualization, laser Doppler anemometry (LDA) and particle image velocimetry (PIV). Mean and fluctuating velocities are presented for all three velocity components. Good agreement between LDA and PIV measurements was obtained once an optimized PIV arrangement was defined. Turbulence parameters such as kinetic energy, dissipation, and length scales are estimated from the measurements. Several approaches to evaluating dissipation were used. Triggered PIV measurements were used to evaluate the variation in radial and tangential velocities in the entire planes above and below the impeller at constant axial distances. The size and orientation of the vortices shed from the impeller blade tips and the corresponding regions of high kinetic energy and dissipation indicate the importance of these structures in mixing.

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33

Boccazzi, A., A. Perdichizzi, and U. Tabacco. "Flow Field Investigation in a Low-Solidity Inducer by Laser-Doppler Velocimetry." Journal of Turbomachinery 112, no. 1 (January 1, 1990): 91–97. http://dx.doi.org/10.1115/1.2927427.

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The results of an experimental investigation of the flow field within a low-solidity inducer at design and off-design flow rates are presented and discussed; particular attention is devoted to the analysis of the flow field, at the tip in front of the leading edge, for the flow rate close to the back-flow onset. The flow field was measured by means of a laser-Doppler velocimeter at four different axial positions upstream, within, and downstream of the inducer. Axial, tangential, and relative flow angle distributions, in the measuring planes, are presented for three different flow coefficients. At the lower flow rate, the plots show the presence of reverse flow in the region close to the hub downstream of the trailing edge. For the same flow rate, quite low axial velocities are detected at the tip. This is in agreement with pressure probe traverses carried out in a slightly downstream section; these measurements also show radial inward velocities of the same order of magnitude as the axial velocities. Circumferentially averaged losses were evaluated from specific work and total head rise given by pressure probes.

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34

Хрусталёв, А. П., Г. В. Гаркушин, И. А. Жуков, and С. В. Разоренов. "Влияние структуры металломатричного композита магний-нитрид алюминия на его сопротивление деформированию при квазистатическом и динамическом нагружении." Письма в журнал технической физики 44, no. 20 (2018): 21. http://dx.doi.org/10.21883/pjtf.2018.20.46802.17381.

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AbstractThe microstructure of an ML5 commercial magnesium alloy reinforced by aluminum nitride (AlN) nanoparticles with an average size of 80 nm at an amount of 0.5 wt % has been studied. Comparative data on strength and plasticity of the initial ML15 alloy and AlN-reinforced metal-matrix composite were obtained using Instron 3369 universal testing machine. The influence of material microstructure on the resistance of samples to high-rate deformation and fracture was determined by analysis of the full wave profiles measured using a VISAR laser Doppler velocimeter.

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Wilson, C. J., and D. B. Bogy. "An Experimental Modal Analysis Technique for Miniature Structures." Journal of Vibration and Acoustics 118, no. 1 (January 1, 1996): 1–9. http://dx.doi.org/10.1115/1.2889629.

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This paper describes an experimental modal analysis system which can effectively be used to obtain the modal parameters of small structures. The system uses an electromagnetic exciter to produce the excitation force, a piezoelectric transducer to measure this force, and a Laser Doppler Vibrometer to measure the response. Several designs of the magnetic actuator are discussed and evaluated. The system is verified by obtaining the modal parameters of a miniature cantilever plate, using two preferred exciter designs, and comparing the measured parameters with those acquired from a finite element model. Favorable agreement is obtained between the experimental and computational results. Finally, the two preferred exciters are compared and an optimal configuration is discussed.

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Sultanian, B. K., S. Nagao, and T. Sakamoto. "Experimental and Three-Dimensional CFD Investigation in a Gas Turbine Exhaust System." Journal of Engineering for Gas Turbines and Power 121, no. 2 (April 1, 1999): 364–74. http://dx.doi.org/10.1115/1.2817129.

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Both experimental and three-dimensional CFD investigations are carried out in a scale model of an industrial gas turbine exhaust system to better understand its complex flow field and to validate CFD prediction capabilities for improved design applications. The model consists of an annular diffuser passage with struts, followed by turning vanes and a rectangular plenum with side exhaust. Precise measurements of total/static pressure and flow velocity distributions at the model inlet, strut outlet and model outlet are made using aerodynamic probes and locally a Laser Doppler Velocimeter (LDV). Numerical analyses of the model internal flow field are performed utilizing a three-dimensional Navier-Stokes (N-S) calculation method with the industry standard k-ε turbulence model. Both the experiments and computations are carried out for three load conditions: full speed no load (FSNL), full speed mid load (FSML, 57 percent load), and full speed full load (FSFL). Based on the overall comparison between the measurements and CFD predictions, this study concludes that the applied N-S method is capable of predicting complicated gas turbine exhaust system flows for design applications.

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Pershing, Lynn K., Sue Huether, Rebecca L. Conklin, and Gerald G. Krueger. "Cutaneous Blood Flow and Percutaneous Absorption: A Quantitative Analysis Using a Laser Doppler Velocimeter and a Blood Flow Meter." Journal of Investigative Dermatology 92, no. 3 (March 1989): 355–59. http://dx.doi.org/10.1111/1523-1747.ep12277181.

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Zhao, Rong Li, Xin Chen, Ke Tian Li, and Zhou Chang. "Vibration Analysis of Main Shaft of Paper Advance Mechanism Based on Laser Doppler Vibrometer." Applied Mechanics and Materials 215-216 (November 2012): 712–16. http://dx.doi.org/10.4028/www.scientific.net/amm.215-216.712.

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Modal analysis was done to steel shaft and rubber shaft, and their top ten orders of nature frequency were obtained. The lowest nature frequency of steel shaft is 64HZ and the rubber steel’s is 2.2463HZ. Doppler vibration measurement was done to main shaft of paper advance mechanism and the time domain signal and frequency domain signal were obtained when the rotational speed is 80, 160, 240, 320, 400 Rpm. The frequency and amplitude were obtained by signal analysis. It proves that the nature frequency of steel main shaft is much higher than measuring result, but the seventh and eighth order nature frequency of rubber material is in accord with measuring result of laser doppler vibration.

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Martinuzzi, R., A. M. Zaghloul, W. Al-Qaraguli, and R. E. Baddour. "Turbulence Structure of Plane Surface-Jets in a Weak Coflowing Stream for Different Initial Wake Conditions." Journal of Fluids Engineering 120, no. 1 (March 1, 1998): 76–82. http://dx.doi.org/10.1115/1.2819666.

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Plane turbulent surface-jets, in the presence of a weak coflowing ambient current, were experimentally investigated using a single-component Laser Doppler Velocimeter. This study is concerned with the influence on the turbulent mixing characteristics of the relative speed ratio, U′a, and the wake generated behind the plate separating the jet from the ambient stream at the exit. Data were analyzed for similarity characteristics, surface speed decay, jet growth rate, jet momentum flux, jet volume flux, and turbulence decay. An integral analysis of the governing equations was also conducted to examine the turbulent entrainment properties of the surface jets.

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Xu, Y. F., Da-Ming Chen, and W. D. Zhu. "Operational modal analysis using lifted continuously scanning laser Doppler vibrometer measurements and its application to baseline-free structural damage identification." Journal of Vibration and Control 25, no. 7 (February 6, 2019): 1341–64. http://dx.doi.org/10.1177/1077546318821154.

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A continuously scanning laser Doppler vibrometer (CSLDV) system is capable of efficient and spatially dense vibration measurements by sweeping its laser spot along a scan path assigned on a structure. This paper proposes a new operational modal analysis (OMA) method based on a data processing method for CSLDV measurements of a structure, called the lifting method, under white-noise excitation and applies a baseline-free method to identify structural damage using estimated mode shapes from the OMA method. The lifting method enables transformation of raw CSLDV measurements into measurements at individual virtual measurement points, as if the latter were made by use of an ordinary scanning laser Doppler vibrometer in a step-wise manner. It is shown that a correlation function with nonnegative time delays between lifted CSLDV measurements at two virtual measurement points on a structure under white-noise excitation and its power spectrum contain modal parameters of the structure, that is, natural frequencies, modal damping ratios, and mode shapes. The modal parameters can be estimated by using a standard OMA algorithm. A major advantage of the proposed OMA method is that curvature mode shapes associated with mode shapes estimated by the method can reflect local anomaly caused by small-sized structural damage, while those estimated by other existing OMA methods that use CSLDV measurements cannot. Numerical and experimental investigations are conducted to study the OMA method and baseline-free structural damage identification method. In the experimental investigation, effects of the scan frequency of a CSLDV system on the two methods were studied. It is shown in both the numerical and experimental investigations that modal parameters can be accurately estimated by the OMA method and structural damage can be successfully identified in neighborhoods with consistently high values of curvature damage indices.

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Book, Joel M., Samuel F. Asokanthan, and Tian Fu Wang. "Experimental Modal Characterization of MEMS Switches." Advanced Materials Research 403-408 (November 2011): 4598–605. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.4598.

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MEMS devices, Micro Electro-Mechanical Systems, are electrical and mechanical systems with characteristic dimensions on the order of microns. Since these systems have moving mechanical parts, characterization of their dynamics, including their modal parameters, is highly desirable. This paper describes the validation of an existing implementation of the Stochastic Subspace Identification (SSI) algorithm, called MACEC, for experimental modal analysis of a micro-cantilever switch. A white noise signal applied to the built-in electrostatic actuator in the switches excited a response measured using microscanning Laser Doppler Vibrometry (LDV). The modal parameters found using MACEC matched well those predicted by theory, thus validating this combination for experimental modal analysis of MEMS structures.

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Duncan, D. D., C. B. Bargeron, S. E. Borchardt, O. J. Deters, S. A. Gearhart, F. F. Mark, and M. H. Friedman. "The Effect of Compliance on Wall Shear in Casts of a Human Aortic Bifurcation." Journal of Biomechanical Engineering 112, no. 2 (May 1, 1990): 183–88. http://dx.doi.org/10.1115/1.2891170.

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Rigid and compliant casts of a human aortic bifurcation were subjected to physiologically realistic pulsatile fluid flows. At a number of sites near the wall in the approximate median plane of the bifurcation of these models, fluid velocity was measured with a laser Doppler velocimeter, and wall motion (in the case of the compliant cast) was determined with a Reticon linescan camera. The velocity and wall motion data were combined to estimate the instantaneous shear rates at the cast wall. Analysis showed that at the outer walls the cast compliance reduced shear rates, while at the walls of the flow divider the shear rate was increased.

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YAMAGUCHI, Yuzo. "505 A Study on Sources of Error in Laser Doppler Velocimeter : An Analysis of Interference of Diffraction Images near Focal Points." Proceedings of Conference of Kyushu Branch 2001 (2001): 157–58. http://dx.doi.org/10.1299/jsmekyushu.2001.157.

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Chon, W., and R. S. Amano. "Investigation of Flow Behavior around Corotating Blades in a Double-Spindle Lawn Mower Deck." International Journal of Rotating Machinery 2005, no. 1 (2005): 77–89. http://dx.doi.org/10.1155/ijrm.2005.77.

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When the airflow patterns inside a lawn mower deck are understood, the deck can be redesigned to be efficient and have an increased cutting ability. To learn more, a combination of computational and experimental studies was performed to investigate the effects of blade and housing designs on a flow pattern inside a1.1mwide corotating double-spindle lawn mower deck with side discharge. For the experimental portion of the study, air velocities inside the deck were measured using a laser Doppler velocimetry (LDV) system. A high-speed video camera was used to observe the flow pattern. Furthermore, noise levels were measured using a sound level meter. For the computational fluid dynamics (CFD) work, several arbitrary radial sections of a two-dimensional blade were selected to study flow computations. A three-dimensional, full deck model was also developed for realistic flow analysis. The computational results were then compared with the experimental results.

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Rzepecki, Jaroslaw, Anna Chraponska, Sebastian Budzan, Chukwuemeke William Isaac, Krzysztof Mazur, and Marek Pawelczyk. "Chladni Figures in Modal Analysis of a Double-Panel Structure." Sensors 20, no. 15 (July 22, 2020): 4084. http://dx.doi.org/10.3390/s20154084.

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Analysis of the structural vibration, under the sound excitation is an important part of the quality assurance during the design process of devices. One of the most commonly used method is Laser Doppler Vibrometry (LDV). However, under the rapid fluctuations of temperature, structural resonances are shifted into the other frequencies. In such situation LDV method may be inconvenient, due to the scanning time. In this paper the authors proposed Chladni figures to modal analysis of the double-panel structure, excited by the loudspeaker enclosed inside the casing with a rigid frame. Double-panel structure has been proven to be particularly useful for noise and vibration reduction applications. Vision images, obtained during the experiments are converted to binary patterns, using GLCM matrix, and compared with simulations performed in ANSYS.

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Hasheminejad, Navid, Cedric Vuye, Wim Van den bergh, Joris Dirckx, and Steve Vanlanduit. "A Comparative Study of Laser Doppler Vibrometers for Vibration Measurements on Pavement Materials." Infrastructures 3, no. 4 (November 1, 2018): 47. http://dx.doi.org/10.3390/infrastructures3040047.

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A laser Doppler vibrometer (LDV) is a noncontact optical measurement device to measure the vibration velocities of particular points on the surface of an object. Even though LDV has become more popular in road engineering in recent years, their signal-to-noise ratio (SNR) is strongly dependent on light scattering properties of the surface which, in some cases, needs to be properly conditioned. SNR is the main limitation in LDV instrumentation when measuring on low diffusive surfaces like pavements; therefore, an investigation on the SNR of different LDV devices on different surface conditions is of great importance. The objective of this research is to investigate the quality of two types of commercially available LDV systems—helium–neon (He–Ne)-based vibrometers and recently developed infrared vibrometers—on different surface conditions, i.e., retroreflective tape, white tape, black tape, and asphalt concrete. Both noise floor and modal analysis experiments are carried out on these surface conditions. It is shown that the noise floor of the He–Ne LDV is higher when dealing with a noncooperative dark surface, such as asphalt concrete, and it can be improved by improving the surface quality or by using an infrared LDV, which consequently improves the modal analysis experiments performed on pavement materials.

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Darisse, Alexis, Jean Lemay, and Azemi Benaïssa. "Budgets of turbulent kinetic energy, Reynolds stresses, variance of temperature fluctuations and turbulent heat fluxes in a round jet." Journal of Fluid Mechanics 774 (June 5, 2015): 95–142. http://dx.doi.org/10.1017/jfm.2015.245.

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The self-preserving region of a free round turbulent air jet at high Reynolds number is investigated experimentally (at$x/D=30$,$\mathit{Re}_{D}=1.4\times 10^{5}$and$\mathit{Re}_{{\it\lambda}}=548$). Air is slightly heated ($20\,^{\circ }\text{C}$above ambient) in order to use temperature as a passive scalar. Laser doppler velocimetry and simultaneous laser doppler velocimetry–cold-wire thermometry measurements are used to evaluate turbulent kinetic energy and temperature variance budgets in identical flow conditions. Special attention is paid to the control of initial conditions and the statistical convergence of the data acquired. Measurements of the variance, third-order moments and mixed correlations of velocity and temperature are provided (including$\overline{vw^{2}}$,$\overline{u{\it\theta}^{2}}$,$\overline{v{\it\theta}^{2}}$,$\overline{u^{2}{\it\theta}}$,$\overline{v^{2}{\it\theta}}$and$\overline{uv{\it\theta}}$). The agreement of the present results with the analytical expressions given by the continuity, mean momentum and mean enthalpy equations supports their consistency. The turbulent kinetic energy transport budget is established using Lumley’s model for the pressure diffusion term. Dissipation is inferred as the closing balance. The transport budgets of the$\overline{u_{i}u_{j}}$components are also determined, which enables analysis of the turbulent kinetic energy redistribution mechanisms. The impact of the surrogacy$\overline{vw^{2}}=\overline{v^{3}}$is then analysed in detail. In addition, the present data offer an opportunity to evaluate every single term of the passive scalar transport budget, except for the dissipation, which is also inferred as the closing balance. Hence, estimates of the dissipation rates of turbulent kinetic energy and temperature fluctuations (${\it\epsilon}_{k}$and${\it\epsilon}_{{\it\theta}}$) are proposed here for use in future studies of the passive scalar in a turbulent round jet. Finally, the budgets of turbulent heat fluxes ($\overline{u_{i}{\it\theta}}$) are presented.

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Stanbridge, A. B., and D. J. Ewins. "Measurement of Translational and Angular Vibration Using a Scanning Laser Doppler Vibrometer." Shock and Vibration 3, no. 2 (1996): 141–52. http://dx.doi.org/10.1155/1996/737569.

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An experimental procedure for obtaining angular and translational vibration in one measurement, using a continuously scanning laser Doppler vibrometer, is described. Sinusoidal scanning, in a straight line, enables one angular vibration component to be measured, but by circular scanning, two principal angular vibrations and their directions can be derived directly from the frequency response sidebands. Examples of measurements on a rigid cube are given. Processes of narrow-band random excitation and modal analysis are illustrated with reference to measurements on a freely suspended beam. Sideband frequency response references are obtained by using multiplied excitation force and mirror-drive signals.

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Yang, Shifei, and Matthew S. Allen. "Output-only Modal Analysis using Continuous-Scan Laser Doppler Vibrometry and application to a 20kW wind turbine." Mechanical Systems and Signal Processing 31 (August 2012): 228–45. http://dx.doi.org/10.1016/j.ymssp.2012.04.012.

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Tateshima, Satoshi, Fernando Viñuela, J. Pablo Villablanca, Yuichi Murayama, Taku Morino, Kiyoe Nomura, and Kazuo Tanishita. "Three-dimensional blood flow analysis in a wide-necked internal carotid artery—ophthalmic artery aneurysm." Journal of Neurosurgery 99, no. 3 (September 2003): 526–33. http://dx.doi.org/10.3171/jns.2003.99.3.0526.

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Object. The aim of this study was to evaluate axial and secondary flow structures in a wide-necked internal carotid artery—ophthalmic artery aneurysm, one of the most common locations for endovascular coil placement. Methods. A clear acrylic aneurysm model was manufactured from a three-dimensional computerized tomography angiogram. Intraaneurysm blood flow analysis was conducted using an acrylic aneurysm model together with laser Doppler velocimetry and particle imaging velocimetry. The maximal axial blood flow velocities in the inflow and outflow zones at the aneurysm orifice were noted at the peak systolic phase, measuring 46.8 and 24.9% of that in the parent artery, respectively. The mean size of the inflow zone during one cardiac cycle was 44.3 ± 9.8% (range 35.6–58.7%) the size of the axial section at the aneurysm orifice. In the lower and upper planes of the aneurysm dome, the mean size of inward and outward flow areas were 43.3 ± 6.7% and 43.8 ± 6.8% the size of the axial cross-sectional plane, respectively. The axial flow velocity structures were dynamically altered throughout the cardiac cycle, particularly at the aneurysm orifice. The fastest secondary flow at the opening was also noted at the peak systolic and early diastolic phases. Axial blood flow velocity was slower in the upper axial plane of the aneurysm dome than in the lower one. Conversely, the secondary flow component was faster in the upper plane. Conclusions. The side-wall aneurysm in this study did not demonstrate a simple flow pattern as was previously seen in ideally shaped experimental aneurysms in vitro and in vivo. The flow patterns of inflow and outflow zones were very difficult to predict based on the limited flow information provided on standard digital subtraction angiography, even in an aneurysm with a relatively simple dome shape.

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