scholarly journals Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow

2012 ◽  
Vol 16 (4) ◽  
pp. 1027-1042 ◽  
Author(s):  
Slavica Ristic ◽  
Jelena Ilic ◽  
Djordje Cantrak ◽  
Ognjen Ristic ◽  
Novica Jankovic
Keyword(s):  
Pipe Flow ◽  
Pipe Wall ◽  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Test Rig ◽  
Axial Fan ◽  
Optical Aberrations ◽  
Cylindrical Pipe ◽  
Measuring Volume ◽  
Uncertainty Sources

Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central part of the pipe (r/R < 0.6) exists a small, or negligible pipe wall influence on laser- -Doppler anemometry measuring position, is investigate. The required corrections, for measurements of axial, tangential, and radial velocity components such: shift of measuring volume and its orientation are analyzed and determined for used test rig and for some other pipe geometries.

Errors Due to Turbidity in Particle Sizing Using Laser-Doppler Anemometry

1990 ◽  
Vol 112 (2) ◽  
pp. 142-148 ◽  
Author(s):  
Y. Kliafas ◽  
A. M. K. P. Taylor ◽  
J. H. Whitelaw
Keyword(s):  
Laser Doppler Anemometry ◽  
Particle Diameter ◽  
Laser Doppler Anemometer ◽  
Laser Doppler ◽  
Beam Diameter ◽  
Particle Sizing ◽  
Measuring Volume ◽  
Void Fractions ◽  
Random Fluctuations ◽  
Rms Errors

Flow turbidity, when introduced between the transmitting and receiving optics and the measuring volume of a laser-Doppler anemometer, changes the pedestal amplitude and visibility of the signal. The purpose of this work is to assess the effect on the accuracy of particle sizing, based on measurements of these two quantities, for depths of field of 5 and 10 cm, interrupting particle diameters between 14 to 212 μm in three discrete ranges and void fractions up to 0.1 percent. The turbidity introduces random fluctuations in visibility which increase with void fraction and the resulting rms errors in particle diameter for turbidity introduced on the receiving side of the optics are smaller than 10 percent at void fractions below 0.1 percent. For particles larger than about one third of the beam diameter, the influence of turbidity is largely due to the interruption of the incident beams over the 5 cm nearest to the measuring volume.

Laser Insight Into the Turbulent Swirl Flow Behind the Axial Flow Fan

2014 ◽  
Author(s):  
Đorđe S. Čantrak ◽  
Novica Janković ◽  
Milan R. Lečić
Keyword(s):  
Vortex Core ◽  
High Speed ◽  
Isotropic Turbulence ◽  
Laser Doppler Anemometry ◽  
Measurement Techniques ◽  
Swirl Flow ◽  
Test Rig ◽  
Axial Fan ◽  
Mean Velocity ◽  
Swirl Flows

Complex experimental study of the turbulent swirl flow behind the axial fan is reported in this paper. Axial fan with nine blades, designed to generate Rankine vortex, was positioned in the circular pipe entrance transparent section with profiled free bell mouth inlet. Two test rigs were built in order to study the turbulent swirl flow generated on the axial fan pressure side in the case of axially unrestricted and restricted swirl flows. One-component laser Doppler anemometry (LDA) and stereo particle image velocimetry (SPIV) were used in the first test rig in the measuring section 3.35D, measured from the test rig inlet. One of the latest measurement techniques, high speed SPIV (HSS PIV), was used for the measurements in the second test rig in the section 2.1D downstream the fan’s trailing edge. Achieved Reynolds numbers in the first test rig are Re = 182600 and 277020, while in the second Re = 186463. Turbulent velocity field non-homogeneity and anisotropy is revealed using the LDA system. Calculated turbulent statistical properties, such as moments of the second and higher orders, reveal complex mechanisms in turbulent swirl flow. It is shown for the used axial fan construction that swirl number has almost constant value for two various duty points generated by changing rotation number. Study of the instant and mean velocity fields obtained using SPIV discovers vortex core dynamics. Obtained percentage of the unique positions of the total velocity minimum are 10% for the first regime, while 11.5% for the second regime in the first test rig. HSS PIV experimental results have also shown the three-dimensionality and non-homogeneity of generated turbulent swirl flow. Experimentally determined and calculated invariant maps revealed three-component isotropic turbulence in the vortex core region.

Quantitative measurement of the lifetime of localized turbulence in pipe flow

2010 ◽  
Vol 645 ◽  
pp. 529-539 ◽  
Author(s):  
D. J. KUIK ◽  
C. POELMA ◽  
J. WESTERWEEL
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
Quantitative Measurement ◽  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Transition To Turbulence ◽  
Pressure Measurements ◽  
Indirect Measurements ◽  
Turbulent Spots ◽  
Direct Measurements

Transition to turbulence in a pipe is characterized by the increase of the characteristic lifetimes of localized turbulent spots (‘puffs’) with increasing Reynolds number (Re). Previous experiments are based on visualization or indirect measurements of the lifetime probability. Here we report quantitative direct measurements of the lifetimes based on accurate pressure measurements combined with laser Doppler anemometry (LDA). The characteristic lifetime is determined directly from the lifetime probability. It is shown that the characteristic lifetime does not diverge at finite Re, and follows an exponential scaling for the observed range 1725 ≤ Re ≤ 1955. Over this small Re range the lifetime increases over four orders of magnitude. The results show that the puff velocity is not constant, and the rapid disintegration of puffs occurs within 20–70 pipe diameters.

Micropositioning of a measuring volume in laser Doppler anemometry

1993 ◽  
Vol 16 (1) ◽  
pp. 70-72 ◽  
Author(s):  
C. Bertrand ◽  
P. Desevaux ◽  
J. P. Prenel
Keyword(s):  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Measuring Volume
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