摘要:

Drag reduction with polymer additives was measured in a 90° triangular open channel. Also, the laser Doppler technique was employed to measure the velocity profiles in the same flow system. The amount of drag reduction depended on both Reynolds number and polymer concentration in almost the same manner as obtained in a turbulent pipe flow. In addition, a large effect of Froude number on the amount of drag reduction was observed. In supercritical flow, the values of the friction factors were almost constant over a wide range of Reynolds numbers. The results of the velocity measurements showed that the decrease of the eddy diffusivity near the free surface was very significant.

ISSN:0148-6055    

DOI:10.1122/1.549571

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

A disk slowly rotating in a pool of viscoelastic polymer solution experiences a torque lower than it does in an inelastic liquid of the same viscosity. It is suggested that this reduction of frictional drag under laminar flow conditions is due to the reversal of the secondary (radial) flow and a simple model is proposed. Laser Doppler anemometry was used to measure the primary and secondary velocity profiles around a disk rotating in solutions of polyvinylpyrrolidone and polyacrylamid and the experimentally obtained values of radial and tangential velocity gradients were used to predict the reduction of frictional resistance. These predictions are compatible with the experimental data of D. D. Kale, R. A. Mashelkar, and J. Ulbrecht [Rheol. Acta,14, 631 (1975)].

ISSN:0148-6055    

DOI:10.1122/1.549572

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

Detailed studies were made of the drag reduction of poly(ethylene oxide) in water solutions with additions of dyes or sodium dodecyl sulfate. All solutions were well mixed and observations were made in a 2.18 mm tube. Viscosities were also measured as a function of concentration. Several types of behavior were observed. Rhodamine B, Acid Fuschin, Ponceau S, and Fast Green FCF had little or no effect. Evans Blue, Trypan Blue, Aniline Blue, and Congo Red in acid solution all degraded the poly(ethylene oxide). Congo Red in neutral or basic solution, Titan Yellow, and sodium dodecyl sulfate did not degrade the polymer and had similar effects on drag reduction. For this latter group plots of drag reduction versus concentration of dye had a minimum, and the drag reduction approached or exceeded that for polymer alone at dye concentrations over 200 ppm. Specific viscosities were greatly increased by Congo Red but only slightly increased for the other two materials. The results suggest that theSO3group is responsible for bonding and that drag reduction is increased only when molecules bond at a single place and then extend outward into the solution. Effects of mixing time, molecular weight of polymer, and size of dye molecule are also discussed.

ISSN:0148-6055    

DOI:10.1122/1.549573

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

Studies of laminar flow of liquids in curved tubes have shown that the addition of a small amount of high‐molecular‐weight polymer delays departure from Poiseuille flow (straight pipe) behavior and increases the flow rate at higher Dean numbers. Since polymer solutions have high resistance to extension, and since portions of the vortical secondary motion in a curved tube are strongly extensional in nature, the increased flow rate is attributed to attenuation of the secondary motion. Deformation rates at the onset of non‐Newtonian behavior were calculated from the experimental data of Jones and Davies, using the theory of Dean. For these deformation rates, the corresponding non‐Newtonian normal stresses were computed from the constitutive equations for various fluid models. The stress produced by a solution of flexible Rouse‐type macromolecules was found to be several orders below the stress required to retard the secondary motion, and a suspension of long fibers was recognized as ineffective because the particles align with the much stronger primary flow. It was found that the required stress could be produced by networks of fibers, provided the effective aspect ratio of the strands is of order107/2.This size is comparable to estimates made from prior extensional flow rheometry. This work therefore provides some evidence that in dilute solution, macromolecules behave like a network of long fibers.

ISSN:0148-6055    

DOI:10.1122/1.549574

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

The effects of solvent viscosity, bulk velocity, and pipe diameter on drag reduction have been investigated in order to ascertain the feasibility of utilizing polymer drag‐reducing additives to increase the flow rate in the Trans‐Alaska Pipeline. Laboratory screening studies were performed in 1‐ and 2‐in. diam flow loops to determine the best commercially available additive for the application. Field tests in a 14‐in. crude pipeline and in the 48‐in. Trans‐Alaska Pipeline confirmed the material's effectiveness in large‐scale applications. This research program has resulted in the use of drag‐reducing additive in the Trans‐Alaska Pipeline as a temporary replacement for unconstructed pump stations. The effect of additive concentration was investigated over a range of 5 to 25 ppm. The crude‐oil flow conditions that were studied included solvent kinematic viscosities of 9 to50 mm2/sec(9 to 50 cs), Reynolds numbers of 4000 to 300000, wall shear rates of 100 to2000 sec−1,as well as inside pipe diameters from 2.66 to 119.4 cm (1.05 to 47.0 in.). The drag‐reduction results have been correlated based on an extension of a theoretical model available in the literature. The functional form of the model requires a knowledge of the wall shear rate, the friction factor, and the additive concentration as independent variables.

ISSN:0148-6055    

DOI:10.1122/1.549579

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

The ejection of polymer solutions through thin slits, slightly inclined with respect to a wall over which flows a cocurrent stream of water, causes profound changes of the wall pressure distribution downstream of the ejector. Visualizations of the flow show that the polymer jets swell after leaving the slit, and that, depending on the ejection conditions and the main stream velocity, the swollen jet can reach a thickness several times larger than the slit gap. Analysis of the pressure data and the jet visualizations demonstrates that the pressure changes are a direct consequence of the jet swelling effect. A simple model permits one to correlate the swelling of the jet with the ejection velocity, the main stream velocity, and the slit gap.

ISSN:0148-6055    

DOI:10.1122/1.549575

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

Two‐dimensional, laminar, free‐surface water‐table flows of water and dilute poly‐(ethylene oxide) (PEO) solutions have been investigated at high strain rates. Velocity measurements were obtained using both a hot film probe and a laser‐Doppler anemometer (LDA) for water flows, and using the LDA for polymer flows. Measurements of water flows agreed very well with calculations. Provided that the wall strain rate was below750 sec−1,flows of polymer solutions were essentially the same as those of water. Above this value velocity fluctuations coherent over a few cm in the flow direction were observed in the high‐strain‐rate portions of the flow. Velocity spectra showed a pronounced frequency distinct from turbulence which was lowest near the wall where the strain rate is a maximum. A modified dumbbell model of an isolated PEO molecule is proposed which appears to account for many of the observed results. The model allows for partial expansion of the polymer molecule due to the strain field while retaining rotation.

ISSN:0148-6055    

DOI:10.1122/1.549576

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

Economically attractive applications for drag‐reducing polymers include their use in sewers subject to occasional overload. If polymer dosing can be shown to provide the required extra discharge capacity in a particular case, then costly sewer rebuilding can be delayed or avoided. A permanent and fully instrumented dosing station has been constructed on a 305 mm sewer in Bristol and preliminary tests showed that sewer velocities could be increased by up to 60% using 40 wppm Polyox WSR‐301. Further trials have confirmed these results for WSR‐301 but yielded lower velocity increases for a high‐molecular‐weight grade of polyacrylamide. Records of automatic dosing during recent rain storms show a 25% increase in capacity in this sewer. Tests in a 760 mm pumped main sewer at Bath show 20% drag reduction over the pipe's 8 km length. An emulsion‐type liquid polymer containing 50% by weight active polymer was used in this test.

ISSN:0148-6055    

DOI:10.1122/1.549598

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

摘要:

The drag‐reduction effectiveness of a number of high‐polymer additives dissolved in aircraft fuel has been measured in a turbulent‐flow rheometer. These solutions were further subjected to high elongational stress and breakup forces in a jet discharging in air. The jet was photographed using a high‐resolution camera with special lighting. The object of the work was to study the possible spray‐suppression ability of high‐polymer additives to aircraft fuel and to correlate this with the drag‐reducing properties of the additives. It was found, in fact, that the rheometer results indicate the most effective spray‐suppressing additives. Using as a measure the minimum polymer concentration to give a maximum friction‐reducing effect, the order of effectiveness of eight different polymer additives as spray‐suppressing agents was predicted. The photographic results confirm the predictions. The viscoelastic properties of the polymer solutions which reduce drag also seem to be very effective in spray suppression. These results may find application in the development of antimisting additives for aircraft fuel which may increase fire safety in case of crash or accident.

ISSN:0148-6055    

DOI:10.1122/1.549577

出版商:The Society of Rheology    

年代:1980

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549578

出版商:The Society of Rheology    

年代:1980

数据来源: AIP