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  • 1
    Electronic Resource
    Electronic Resource
    High resolution measurement of turbulent structure in a channel with particle image velocimetry (1991)
    Springer
    Experiments in fluids 10 (1991), S. 301-312 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract High resolution particle image velocimetry is used to measure the turbulent velocity field for fully developed flow (Re = 2,872) in an enclosed channel. Photographs of particle displacement are obtained in a plane that is parallel to the flow and perpendicular to the walls. These are analyzed to give simultaneous measurements of two components of the velocity at more than 10,000 points. Maps of velocity vectors, spanwise vorticity and Reynolds stress reveal structural aspects of the turbulence. In particular, internal shear layers are observed, in agreement with predictions of direct numerical simulation. Ensemble-averaging of a number of photographs yields statistical properties of the velocity in good agreement with laser-Doppler velocimeter measurements, and with direct numerical simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190246
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Stereoscopic particle image velocimetry applied to liquid flows (1993)
    Springer
    Experiments in fluids 15 (1993), S. 49-60 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A twin-camera stereoscopic system has been developed to extend conventional high image-density Particle Image Velocimetry (PIV) to three-dimensional vectors on planar domains. The stereoscopic velocimeter performs with extremely high accuracy. Translation tests have yielded errors (rms) of 0.2% of full-scale for the in-plane displacement, and 0.8% of full-scale for the out-of-plane component, both of which agree with the errors predicted by an uncertainty analysis. In addition, modified techniques in hardware and software have enabled the stereoscopic system to perform successfully when acquiring images through a thick liquid layer, wherein previously the aberrations arising due to the liquid-air interface have restricted the use of such systems. With these techniques, the stereoscopic system, in combination with a simple method for image-shifting, is able to accurately measure threedimensional velocity fields in liquids. This is demonstrated by measurements of the helical, three-dimensional flow induced by a rotating disk in glycerine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195595
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Stereoscopic particle image velocimetry measurements of the flow around a Rushton turbine (2000)
    Springer
    Experiments in fluids 29 (2000), S. 478-485 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The principles of stereoscopic particle image velocimetry (PIV), including distortion compensation, were applied to the turbulent flow in a vessel stirred by a Rushton turbine. An angular offset configuration was used and tilt-axis lens mounts were incorporated in order to satisfy the Scheimpflug condition, significantly reducing the ordinarily large depth of field requirements of such configurations. A distortion compensation procedure, or in situ calibration, was utilized in place of the ray tracing, or mechanical registration, used in previous studies. The calibration procedure was validated using two tests, one a rigid translation of a speckle target, the other the viscous flow between two concentric cylinders. The results of the tests suggest the success with which the distortion compensation procedure may be applied to real fluid flows. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D velocity fields on a cylindrical shell enclosing the turbine blade. From these fields, the tip vortex pairs and the radial jet documented in previous studies of mixer flows were easily identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480000116
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A particle image velocimetry system for microfluidics (1998)
    Springer
    Experiments in fluids 25 (1998), S. 316-319 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  A micron-resolution particle image velocimetry (micro-PIV) system has been developed to measure instantaneous and ensemble-averaged flow fields in micron-scale fluidic devices. The system utilizes an epifluorescent microscope, 100–300 nm diameter seed particles, and an intensified CCD camera to record high-resolution particle-image fields. Velocity vector fields can be measured with spatial resolutions down to 6.9×6.9×1.5 μm. The vector fields are analyzed using a double-frame cross-correlation algorithm. In this technique, the spatial resolution and the accuracy of the velocity measurements is limited by the diffraction limit of the recording optics, noise in the particle image field, and the interaction of the fluid with the finite-sized seed particles. The stochastic influence of Brownian motion plays a significant role in the accuracy of instantaneous velocity measurements. The micro-PIV technique is applied to measure velocities in a Hele–Shaw flow around a 30 μm (major diameter) elliptical cylinder, with a bulk velocity of approximately 50 μm s-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050235
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  • 5
    Electronic Resource
    Electronic Resource
    Preface (2000)
    Springer
    Experiments in fluids 29 (2000), S. S001 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480070001
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    A Kalman tracker for super-resolution PIV (2000)
    Springer
    Experiments in fluids 29 (2000), S. S034 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We describe a new super-resolution method of particle-image velocimetry (PIV) based on Kalman filtering and χ2-testing. Performance of the “super-resolution KC” method is evaluated by Monte-Carlo simulation and by applying the method to measurements of flow fields recorded in the form of double-pulse/single-frame and single-pulse/double-frame particle images. When the images have good contrast, and depending on the intensity of the velocity gradients present in the flow, the super-resolution KC method is able to extract valid measurements from 80 to 100% of the available image pairs. In these tests, the vector yield is increased by more than five times compared to standard PIV analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480070005
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis and interpretation of instantaneous turbulent velocity fields (2000)
    Springer
    Experiments in fluids 29 (2000), S. 275-290 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Methods of analyzing and interpreting velocity-field data (both two- and three-dimensional) to understand the kinematics, dynamics, and scales of turbulence are discussed. Reynolds decomposition and vorticity are traditionally used; however, several other methods, including Galilean (constant convection velocity) and LES decompositions (low-pass filtering), in conjunction with critical-point analysis of the local velocity gradient tensor, reveal more about the structure of turbulence. Once the small-scale structures have been identified, it is necessary to assess their importance to the overall dynamics of the turbulence by visualizing the motions they induce and the stresses they impose both on other small-scale vortices and on the larger-scale field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003489900087
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Rayleigh-Benard convection: experimental study of time-dependent instabilities (1988)
    Springer
    Experiments in fluids 6 (1988), S. 316-322 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The transition from steady thermal convection to turbulent thermal convection in a horizontal layer of water (Prandtl number=5.8) contained by a square cavity of large aspect ratio (48.5) has been studied using laser Doppler velocimetry. Power spectra of the horizontal velocity fluctuations were measured in the Rayleigh number range from 30,000 and 99,000, wherein periodic, quasi-periodic, and broad-band time-dependent instabilities coexist. At Rayleigh numbers greater than 32,000 a narrow-band spectrum emerges. The frequency of this motion scales with x/d 2 modified by a Prandtl number factor for intermediate values of the Prandtl number. Between 10 Ra c and 30 Ra i the frequency undergoes three abrupt jumps while increasing along an Ra 2/3 power law. A different frequency mode that occurs above 30 Ra c appears to be associated with fully turbulent convection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00538822
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Measurement of velocity vectors with orthogonal and non-orthogonal triple-sensor probes (1989)
    Springer
    Experiments in fluids 7 (1989), S. 228-240 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new method of interpreting the signals from triple-sensor thermal anemometer probes has been developed based on fast solution for all the roots of the non-linear Jorgensen (1971) equations describing the directional response of each cylindrical sensor. The sensors can be oriented at arbitrary angles to each other, but always within a range of probe geometries that keep prong interference and thermal wake interference below acceptable levels. The properties of a class of non-orthogonal symmetric tetrahedral probe geometries are studied in relation to the range of flow vector angles that can be measured, the sensitivity of the probe with respect to changes in flow angle, and the sensitivity of the computed velocity components due to angular errors associated with the construction of the probe. The solutions of Jorgensen's equations are inherently multiple-valued, but if the velocity vector is restricted to be within a cone of angles, they are unique. It is shown that measurements with non-orthogonal triple sensor signals are sensitive to angular deviations of a few degrees of the sensor angles from the nominally orthogonal probe geometry, indicating the need of a non-orthogonal algorithm. The mean, rms, Reynolds stress, and power spectrum of the velocity in fully developed turbulent pipe flow were measured using a specially designed triple sensor probe and the proposed algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198002
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Particle-Imaging Techniques for Experimental Fluid Mechanics (1991)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 23 (1991), S. 261-304 
    Details
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fl.23.010191.001401
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    Paper (German National Licenses)
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