Turbulent Drag Reduction by Biopolymers in Large Scale Pipes (original) (raw)
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Drag reduction induced by polymer in turbulent pipe flows
Chemical Engineering Science, 2013
Equations of the velocity distribution and friction factor in turbulent drag reducing flows are derived. The approach of predicting the onset Reynolds number for drag reduction has been provided. The approach of determining the optimal polymer concentration for the Maximum Drag Reduction is obtained.
Complex Behavior of Polymers as Drag Reducing Agents Through Pipe Fittings
Journal of Applied Fluid Mechanics
Polymer induced turbulent drag reduction has significant industrial importance and finds application in industries, oil and gas, fire-fighting, marine, irrigation, biomedical etc. Most of the reported literature is focused on the skin drag reduction in pipe flow employing drag reducing additives (DRAs) like polymers, surfactants, fibres and suspensions. In this work, the effect of polymeric addition on the total drag reduction (skin and form) is studied for turbulent flow of water through various fittings like 45 degree elbow, 90 degree miter, sudden expansion and sudden contraction. Different polymers like PAM, PEO, HPMC have been employed as DRAs at various concentrations and pressure drops. The results indicate a complex and interesting behavior. When compared to the results reported for pipe flow, even in this case polymers are found to give total drag reduction (TDR) though less relative to skin drag alone. The extent of TDR is found to depend on the nature of fitting, polymer and its concentration and the pressure drop used. From the results, it is also clear that there is a strong need to further investigate the problem using sophisticated analytical tools on rheometry and polymer degradation.
Turbulent drag reduction with polymer additive in rough pipes
Journal of Fluid Mechanics, 2009
Friction factor of drag-reducing flow with presence of polymers in a rough pipe has been investigated based on the eddy diffusivity model, which shows that the ratio of effective viscosity caused by polymers to kinematic viscosity of fluid should be proportional to the Reynolds number, i.e. u∗R/ν and the proportionality factor depends on polymer's type and concentration. A formula of flow resistance covering all regions from laminar, transitional and fully turbulent flows has been derived, and it is valid in hydraulically smooth, transitional and fully rough regimes. This new formula has been tested against Nikuradse and Virk's experimental data in both Newtonian and non-Newtonian fluid flows. The agreement between the measured and predicted friction factors is satisfactory, indicating that the addition of polymer into Newtonian fluid flow leads to the non-zero effective viscosity and it also thickens the viscous sublayer, subsequently the drag is reduced. The investigation ...
An improved diameter scaling correlation for turbulent flow of drag-reducing polymer solutions
Journal of Non-Newtonian Fluid Mechanics, 1999
The friction coefficient was measured for developed flow of drag-reducing polymer solutions in tubes of 2, 5, 10, 20 and 52 mm i.d. Our results were processed along with other authors' data in terms of different parameters in order to investigate the possibility of developing a simple empirical method for the prediction of the pipe diameter effect on friction. We found that the drag-reduction coefficient (DR), if expressed as a function of the fluid bulk velocity (V), becomes independent of the tube diameter in the subcritical region (i.e. without fluid degradation), with the deviations being smaller than about 5% for all the diameters and velocities covered. This correlation proved to be not only better than similar procedures based on friction velocity, but also more convenient and physically more meaningful. It was also found that the logarithmic layer shift in the 3layers velocity profile is also better correlated with the bulk velocity than with the friction velocity. Finally, existing models for drag-reduction involving non-dimensional correlations between the integral flow parameters and the fluid properties were also reevaluated in light of these findings.
A mechanism of polymer induced drag reduction in turbulent pipe flow
2014
Polymer induced drag reduction in turbulent pipe flow was investigated using a non-intrusive laser based diagnostic technique, namely Particle Image Velocimetry (PIV). The drag reduction was measured in a pressure-driven flow facility, in a horizontal pipe of inner diameter 25.3 mm at Reynolds numbers ranging from 35 000 to 210 000. Three highmolecular-weight polymers (polyethylene oxide 2×10 6-8×10 6 Da) at concentrations in the range of 5-250 wppm were used. The results, obtained from the PIV measurements, show that the drag reduction scales with the magnitude of the normalized streamwise and spanwise rms velocity fluctuations in the flow. This scaling seems to universal, and is independent of the Reynolds number and in some cases also independent of the distance from the wall where the velocity fluctuations are considered. Furthermore, the instantaneous PIV observations indicate that as the level of drag reduction increases, the flow in the pipe is separated into a low-momentum flow region near the pipe wall and a high-momentum flow region in the turbulent core. Based on these findings a new mechanism of polymeric drag reduction is proposed in this paper.
AIChE Journal, 2019
In this study, we investigate the hydrodynamics of polymer-induced drag reduction in horizontal turbulent pipe flows. We provide spatiotemporally resolved information of velocity and its gradients obtained with particle image velocimetry (PIV) measurements in solutions of water with dissolved polyethylene oxide (PEO) of three different molecular weights, at various dilute concentrations and with flow Reynolds numbers from 35, 000 to 210, 000. We find that the local magnitudes of important turbulent flow variables correlate with the measured levels of drag reduction irrespective of the flow Reynolds number, polymer weight and concentration. Contour maps illustrate the spatial characteristics of this correlation. A relationship between the drag reduction and the turbulent flow variables is found. The effects of the polymer molecular weight, its concentration and the Reynolds number on the flow are further examined through joint probability distributions of the fluctuations of the streamwise and spanwise velocity components.
Bulk Characteristics of Some Variable Viscosity Polymer Solutions in Turbulent Pipe Flow
As part of a research programme on wall-free turbulent flows of non-Newtonian fluids, aqueous solutions of three different polymers have been extensively investigated in terms of their frictional pressure drop versus flow rate characteristics, after a carefull process of fluid selection and rheological characterisation reported elsewhere (Pereira and Pinho, 1994 and Coelho and Pinho, 1998). All solutions, and in particular those of CMC and more so of xanthan gum, exhibited drag reduction. The total drag reduction was separated into shearthinning (DR v) and elastic (DR e) contributions, with DR v reaching a maximum of about 30% of the total for the thickest xanthan gum solutions.
Journal of Chemical and Petroleum Engineering (JChPE), 2021
It was shown that the concept of drag-reducing in the pipe flow with the aid of macromolecules is of great importance in practical engineering applications. In this study, the drag-reducing the performance of three biological macromolecules including guar gum (GG), xanthan gum (XG), and carboxymethyl cellulose (CMC) was compared with three synthetic macromolecules including polyethylene oxide (PEO), polyacrylamide (PAM), and polyacrylic acid (PAA). Results showed that all the macromolecules enhanced the DR% except for GG. DR% for almost all of the macromolecules deteriorated with increasing fluid flow rate. On the other hand, DR% enhanced with increasing the pipe diameter for the synthetic polymers but this effect is not obvious for biological polymeric solutions. Maximum DR was 44%, which occur at 1000 ppm concentration of XG at 30 °C and flow rate of 6 l/min and diameter ½ inch. Finally, a new correlation was developed for the prediction of friction coefficient based on the Prandtl-Karman relation with the newly adjusted slope which is a linear function of polymer concentration. This correlation was in excellent agreement with the experimental data.
2010
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