Local drag reduction due to injection of polymer solutions into turbulent flow in a pipe. Part II: Laser-doppler measurements of turbulent structure

AIChE Journal ◽  
1982 ◽  
Vol 28 (4) ◽  
pp. 558-565 ◽  
Author(s):  
W. D. McComb ◽  
L. H. Rabie
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Polymer Solutions ◽  
Turbulent Structure ◽  
Laser Doppler

Use of laser doppler anemometer for the investigation of turbulent flow of polymer solutions

1975 ◽  
Vol 29 (6) ◽  
pp. 1474-1478 ◽  
Author(s):  
N. A. Pokryvailo ◽  
D. A. Prokopchuk ◽  
Z. P. Shul'man
Keyword(s):  
Turbulent Flow ◽  
Polymer Solutions ◽  
Laser Doppler Anemometer ◽  
Laser Doppler

Some Experimental Results on Laser Doppler Velocimetry (LDV) and Birefringence (FIB) Studies of Non-Newtonian Fluids Flow Through Rectangular Channels

2003 ◽  
Author(s):  
Bernhard Gampert ◽  
Thomas Braemer ◽  
Thomas Eich ◽  
Torsten Dietmann
Keyword(s):  
Turbulent Flow ◽  
Laser Doppler Velocimetry ◽  
Xanthan Gum ◽  
Polymer Solutions ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Flow Properties ◽  
Square Channel ◽  
Rectangular Channels ◽  
Fully Developed Turbulent Flow

In the present study, the turbulence behaviour of polymer solutions is investigated using laser-Doppler velocimetry (LDV). At the same time, an attempt is made to determine a possibly occurring extension and orientation of the macromolecules by flow-induced birefringence (FIB). Flow-dynamic and rheo-optical experiments are presented which were performed in a smooth square channel in the area of the fully developed turbulent flow. The turbulent flow properties of aqueous solutions of PAAM and Xanthan Gum were studied. The Reynolds number was 30000. The concentration of the polymer solutions was varied between 300 wppm and 800 wppm for PR2300 and between 30 wppm and 120 wppm in the case of Xanthan Gum. The obtained experimental data indicate a significant dependence of the turbulent flow properties on the molecular structure of the polymers used. Furthermore, the extension and orientation of the macromolecules on the turbulent flow properties was investigated.

Laser-Doppler anemometer measurements of turbulent structure in drag-reducing fibre suspensions

1985 ◽  
Vol 152 ◽  
pp. 455-478 ◽  
Author(s):  
W. D. McComb ◽  
K. T. J. Chan
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Polymer Solutions ◽  
Reynolds Numbers ◽  
Laser Doppler Anemometer ◽  
Laser Doppler ◽  
Energy Spectra ◽  
Circumferential Velocity ◽  
Fibre Suspensions ◽  
Drag Reducing Polymer

A laser-Doppler anemometer (LDA) was used to measure turbulent velocities in drag-reducing fibre suspensions. Measurements of streamwise velocities (and, in one case, the circumferential velocity as well) were made in flow through a straight pipe at x/d = 190, and at Reynolds numbers in the range 1.4 × 104–5.3 × 104. The fibres used were chrysotile asbestos of high aspect ratio (∼ 106), at a concentration of 300 w.p.p.m. They were dispersed in an aqueous solution of a surfactant (0.5% by weight Aerosol OT). In some experiments, the fibre suspensions were supplemented by a drag-reducing polymer (Separan AP30) at a concentration of 150 w.p.p.m. A complete experiment involved passing a quantity of fibre suspension through the apparatus a number of times (at a given Reynolds number) and measuring the velocity distribution across the pipe during each pass. As the amount of drag reduction generally declined with the number of passes (i.e. due to fibre degradation), this provided a convenient way of varying the percentage drag reduction as an experimental parameter. Results were obtained for mean velocity and intensity profiles, autocorrelations, and one-dimensional energy spectra. The mean period of turbulent bursts was determined by measuring autocorrelations with short sampling times.At the lowest Reynolds number (Re = 1.4 × 104), drag reductions of about 70% were obtained during the first two passes. This was accompanied by a reduction in the streamwise intensity below the level obtained in the surfactant solution alone. (Note: The opposite behaviour is found in drag-reducing polymer solutions, where intensity levels are larger than those in the solvent alone.) A measurement of the r.m.s. circumferential velocity showed an increased level (relative to surfactant alone) during this part of the experiment. During further passes, there was a transition to ‘polymer-like’ behaviour, with increased streamwise intensity, which subsequently declined with pass number (and hence drag reduction) towards the result for surfactant alone. This effect had previously been found in preliminary experiments at Re = 9 × 103 (McComb & Chan 1979). Repetition of the experiment a Re = 1.4 × 104, with the addition of Separan AP30, confirmed the existence of this transition from ‘fibre-like’ to ‘polymer-like’ drag reduction. In this case, the drag reduction was smaller (at about 60%), but the mixed suspension was much more resistant to degradation, with transition occurring at the ninth pass. However, such behaviour was not found at higher Reynolds numbers (Re = 3.2 × 104 and 5.3 × 104), in fibre suspensions where increased streamwise intensities occurred, even at high levels of drag reduction (about 70%).Anomalous streamwise autocorrelations were found during ‘fibre-like’ drag reduction but in the ‘polymer-like’ regime they were very similar to those measured in polymer solution, and showed characteristically increased lengthscales. On the other hand, energy spectra were found to be anomalous in all cases and showed an energy deficit at lengthscales of the same order as the fibre length. Finally, mean bursting periods were found to be much increased, with the increases being about the same as those in polymer solutions at the same Reynolds number and percentage drag reduction.

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