Effect Of Drag-reducing Polymers Research Articles

Effects of Drag-Reducing Polymers on Hemodynamics and Whole Blood-Endothelial Interactions in 3D-Printed Vascular Topologies.

Most in vitro models use culture medium to apply fluid shear stress to endothelial cells, which does not capture the interaction between blood and endothelial cells. Here, we describe a new system to characterize whole blood flow through a 3D-printed, endothelialized vascular topology that induces flow separation at a bifurcation. Drag-reducing polymers, which have been previously studied as a potential therapy to reduce the pressure drop across the vascular bed, are evaluated for their effect on mitigating the disturbed flow. Polymer concentrations of 1000 ppm prevented recirculation and disturbed flow at the wall. Proteomic analysis of plasma collected from whole blood recirculated through the vascularized channel with and without drag-reducing polymers provides insight into the effects of flow regimes on levels of proteins indicative of the endothelial-blood interaction. The results indicate that blood flow alters proteins associated with coagulation, inflammation, and other processes. Overall, these proof-of-concept experiments demonstrate the importance of using whole blood flow to study the endothelial response to perfusion.

Effects of drag-reducing polymers on the flow patterns, pressure gradients, and drag-reducing rates of horizontal oil–water flows

The effects of drag-reducing polymers on the flow patterns, pressure gradients, and drag-reducing rates of oil–water two-phase flows were investigated using a horizontal acrylic pipe with an inner diameter of 25.4 mm and No. 7 white oil with a viscosity of 10.6 mPa∙s and a density of 888.9 kg/m3 at 25 °C. An aqueous solution of polyacrylamide (PAM), with a molecular weight of 19 million Daltons and a concentration of 100 ppm, was used. In the experiment, the oil and water velocities were 0.1-1.5 m/s and 0.1-1.6 m/s, respectively. The DRPs were found to extend the transition boundaries of stratified flow (ST), ST with mixing at the interface (ST&MI), dispersion of oil in water and water (Do/w&w), and oil and dispersion of oil in water (o&Do/w) but did not change the transition boundaries of dispersion of water in oil (Dw/o). The maximum drag reduction rate could be obtained by adding the DRPs to the dispersion of oil in water (Do/w). The drag reduction effect was closely related to the oil and water velocities. An empirical model for the friction factor was established.

Effect of drag-reducing polymer on blood flow in microchannels

Drag-reducing polymers (DRPs) can significantly improve blood circulation when added to blood at a nanomolar concentration, manifesting great potential for application in the biomedical field. In this work, hyaluronic acid (HA) was selected as a natural DRP, and its effects on blood microcirculation at different concentrations, flow rates, and channel geometry were studied in microchannels. The experimental results show that adding a small dose of HA can increase the velocity and shorten the thickness of the cell-free layer (CFL or cell depletion layer (CDL)) near the wall. After considering efficiency, our experiments determined 50 ppm addition of HA to be the most suitable amount for improving blood circulation. Our results demonstrate that HA has high efficiency in improving the circulation of blood flow and shed light on unveiling the mechanism of using natural DRPs to cure some cardiovascular diseases.

Transient dynamics of turbulence growth and bursting: Effects of drag-reducing polymers

The transient process of turbulence development and vortex breakdown from a marginal flow state dominated by streaky velocity patterns is not only essential for understanding the bypass transition into turbulence, but – in the context of viscoelastic fluids – also offers unique insight into the dynamics at high-extent and maximum drag reduction (HDR and MDR). Shooting trajectories connecting the edge state and following its unstable manifold to the turbulent basin are generated. In Newtonian flow, the growth of turbulence starts with the intensification of velocity streaks and a sharp rise in the Reynolds shear stress. It is followed by a quick breakdown into high-intensity small-scale fluctuations before entering the basin of statistical turbulence. Adding drag-reducing polymers does not affect the initial growth of turbulence but stabilizes the primary streak-vortex structure. As a result, the vortex breakdown stage is circumvented. Polymer deformation is insignificant until the vortex breakdown, after which polymer stress rapidly shoots up. At high Weissenberg number Wi, loss of turbulent kinetic energy through polymer elastic conversion is comparable to viscous dissipation. Beyond bypass transition, the transient process studied here closely resembles the bursting phase of the self-sustaining cycle of turbulence. Our results indicate that at high Wi (i.e., HDR) polymer effects can significantly reduce bursting by rerouting the trajectory of turbulent dynamics.

Production of copper powder from synthetic wastewaters by cementation on a longitudinal finned rotating zinc cylinder

This study aims to the enhancement of Cu2+ ions removal from wastewaters and recovery of the metal value by cementation on a longitudinal finned rotating zinc cylinder. The effect of different parameters such as cylinder rotational speed (rpm), initial Cu2+ ions concentration and the effect of the fin height to cylinder diameter (e/d) on the rate of Cu2+ ions cementation was investigated. In addition, the effect of drag reducing polymer on the rate of Cu2+ cementation was examined. The rate of cementation was expressed in terms of the mass transfer coefficient. The results revealed that the mass transfer coefficient increases with increasing rpm, initial Cu2+ concentration and e/d ratio. The present results show that finned rotating cylinder enhances rate of cementation compared to smooth rotating cylinder by percentage ranges from 28.79 to 134.85 depending on the operating conditions. On the other hand, the presence of drag reducing polymer retards the rate of cementation. The present data fit the following dimensionless equations: For smooth cylinder: Sh = 0.74 Re0.69 Sc0.33. For finned rotating cylinder: Sh = 0.38 Re0.9 Sc0.33 (e/d)0.25. The importance of the above correlations in the design and operation of industrial-scale rotating cylinders cementation reactors was pointed out.

Drag-reducing polymers increase exercise tolerance in an ischemic hind-limb rat model

Drag-reducing polymers are long-chain, blood soluble macromolecules that can improve microcirculation invivo. This study aimed to examine the effects of drag-reducing polymers on exercise tolerance in a rat model of hind-limb ischemia. After adaptive running training, bilateral femoral artery ligation models were established in 64 Wistar rats. During an exhaustive exercise, polyethylene oxide or normal saline was intravenously injected to each group (n = 32) at 4 mL/h for 10 min. The exhaustive exercise time was recorded, and lactic acid levels in gastrocnemius muscle and serum were measured. Serum levels of nitric oxide, creatine kinase and lactate dehydrogenase were measured as biomarkers of physical fatigue. Compared with saline-treated control group, rats in polyethylene oxide-treated group had longer exhaustive exercise time (774.7 ± 171.5 s vs. 687.6 ± 166.1 s, p = 0.043), and lower lactic acid level in gastrocnemius muscle (p < 0.01) but no significant difference in serum lactic acid level between two groups was observed (p > 0.05). Nitric oxide level was higher in polyethylene oxide group than in controls (p < 0.05), but no significant differences in serum creatine kinase and lactate dehydrogenase levels between two groups were observed (p > 0.05). Drag-reducing polymers contribute to the enhancement of exercise endurance and exert anti-fatigue effect.

Effect of drag reducing polymer on horizontal liquid–liquid flows

The effect of adding a drag reducing polymer in the water phase during horizontal oil–water flows was studied experimentally. Experiments were carried out in a 14mm ID acrylic pipe using tap water and kerosene oil (Exxsol D140: density 828kg/m3; viscosity 5.5mPas at 23°C) as test fluids. An initial master solution of the polymer (Magnafloc 1011, a copolymer of polyacrylamide and sodium acrylate) at 1000ppm concentration was added at different flowrates into the water phase to give polymer concentrations in the test section between 2.5 and 50ppm. Flow patterns were investigated with high speed imaging while conductivity probes were used to obtain interface properties in separated flows. It was found that as little as 20ppm polymer in the water phase could give maximum drag reduction of about 45% during two-phase flow. When polymer was added, the region of stratified oil–water flow extended to higher superficial oil and water velocities. In separated flows, the polymer addition resulted in a decrease in the interface height and increase in average water velocity. In addition, interfacial wave amplitudes decreased while wave lengths and celerities increased. Velocity measurements in single phase water flows with particle image velocimetry showed that the addition of polymer changed the axial velocity profile and decreased the Reynolds stresses to almost zero values.

Mechanical Energy Losses in Horizontal, Inclined and Vertical Intermittent Two-Phase Flows with Drag-Reducing Polymer

Mechanical energy loss is usually considered to be generated from frictional pressure drop in pipe flow. An analytical equation was derived from hydrodynamic model to estimate the mechanical energy loss in intermittent two-phase flow. This equation indicates that only part of energy loss is generated from frictional pressure drop in inclined and vertical intermittent flows. Experiments were conducted in a gas–liquid pipeline to investigate the different effects of drag-reducing polymer (DRP) on the mechanical energy losses of turbulent intermittent flows in pipes. The inside diameter of the pipeline is 0.04 m. Whether or not DRP is used, the results show that the mechanical energy loss is highest in the vertical case and is lowest in the horizontal case among horizontal, inclined, and vertical intermittent flows. The energy loss reduction induced by DRP in horizontal intermittent flow is greater than the one in either vertical or inclined intermittent flow.

Effects of Drag-Reducing Polymers on Stratified and Slug Gas–Liquid Flows in a Horizontal Pipe

This paper presents experiments in which the effect of drag-reducing polymers (DRP) on the frictional pressure drop of stratified flow and slug frequency of a slug flow of air and water flow in 2.54 cm diameter horizontal pipe is explained. The effect of DRP on the liquid holdup is also identified. The reduction in the frictional pressure drop by DRP in the stratified flow happened only at certain operational conditions. The reduction in the slug frequency also happened at certain operational condition, and the reduction is pronounced at certain range of superficial liquid and gas velocities. Liquid holdup for air–water flows was less than that for air–water with DRP.

Experimental study on the effect of drag reducing polymer on flow patterns and drag reduction in a horizontal oil–water flow

In this study, a HMW anionic co-polymer of 40:60wt/wt NaAMPS/acrylamide was used as a drag reducing polymer (DRP) for oil–water flow in a horizontal 25.4mm ID acrylic pipe. The effect of polymer concentration in the master solution and after injection in the main water stream, oil and water velocities, and pipe length on drag reduction (DR) was investigated. The injected polymer had a noticeable effect on flow patterns and their transitions. Stratified and dual continuous flows extended to higher superficial oil velocities while annular flow changed to dual continuous flow. The results showed that as low as 2ppm polymer concentration was sufficient to create a significant drag reduction across the pipe. DR was found to increase with polymer concentration increased and reached maximum plateau value at around 10ppm. The results showed that the drag reduction effect tends to increase as superficial water velocity increased and eventually reached a plateau at Usw of around 1.3m/s. At Usw>1.0m/s, the drag reduction decreased as Uso increased while at lower water velocities, drag reduction is fluctuating with respect to Uso. A maximum DR of about 60% was achieved at Uso=0.14m/s while only 45% was obtained at Uso=0.52m/s. The effectiveness of the DRP was found to be independent of the polymer concentration in the master solution and to some extent pipe length. The friction factor correlation proposed by Al-Sarkhi et al. (2011) for horizontal flow of oil–water using DRPs was found to underpredict the present experimental pressure gradient data.

The Effect of Drag-Reducing Polymer on Heat Transfer in Gas-Liquid Two-Phase Flow

An experimental loop was established with API X52 steel pipes to investigate the effect of drag-reducing polymer on heat transfer in gas-liquid two-phase flow. The inner diameter of the steel pipe is forty millimeter and the test loop has four different test sections such as horizontal, inclined upward, inclined downward and vertical upward sections. The experimental results were presented. The relationship between the drag reduction efficiency and heat transfer reduction was analyzed. When the drag reduction induced by drag-reducing polymer is about 60~70%, the heat transfer between the fluid and the pipe wall obviously decreases. The heat transfer reduction can reach up to 80~90%, which is greater than the drag reduction. A new method is proposed for characterizing the effect of drag reducing polymer on the heat transfer in two-phase flow with Stanton Number.

Effects of drag-reducing polymers on microcirculation of normal rat hindlimb skeletal muscle.

To observe the effects of polyethylene oxide (PEO) on microcirculation of normal rat hindlimb skeletal muscle. Sixteen male Wistar rats were anesthetized and equally and randomly divided into PEO group (administered with 10 ppm PEO solution) and control group (administered with equal volume of normal saline). The PEO solution or saline was separately injected through the caudal vein at a constant rate of 5 ml/h for 20 minutes. Using short axis view at right mid thigh region, contrast-enhanced ultrasonography was performed before and after the administration of solution. Electrocardiogram, blood pressure, and central venous pressure were also monitored. In the PEO group, after the administration of PEO, microcirculation capillary volume increased from (20.78±2.63) dB to (22.40±1.94) dB (P=0.023), red blood cell velocity from (0.27±0.08) s-1 to (0.35±0.13) s-1(P=0.010), and capillary blood flow from (5.65±1.81) dB/s to (7.91±3.28) dB/s (P=0.013). In the control group, there were no significant changes in microcirculation capillary volume, red blood cell velocity, and capillary blood flow (all Pþ0.05) after the injection of normal saline. The changes of heart rates, blood pressures and central venous pressure were not significant after the administration of either PEO or saline (all Pþ0.05). PEO can remarkably increase capillary volume, red blood cell velocity, and capillary blood flow in normal rat hindlimb skeletal muscle.

Effect of drag-reducing polymers on horizontal oil–water flows

The effect of a drag-reducing polymer (DRP) in the water phase during horizontal oil–water flow was investigated in a 14 mm ID acrylic pipe. Oil (5.5 mPa s, 828 kg/m 3) and a co-polymer (Magnafloc 1011) of polyacrylamide and sodium acrylate were used. Two polymer concentrations were tested, 20 ppm and 50 ppm, made from a 1000 ppm master solution. The results showed a strong effect of DRP on flow patterns. The presence of DRP extended the region of stratified flow and delayed transition to slug flow. The addition of the polymer clearly damped interfacial waves. Annular flow changed in all cases investigated to stratified or dual continuous flow, while slug flow changed in most cases to stratified flow. In the cases where the slug and bubble flow patterns still appeared after the addition of the polymer, the oil slugs and bubbles were seen to flow closer together than in the flow without the polymer. The DRP caused a decrease in pressure gradient and a maximum drag reduction of about 50% was found when the polymer was introduced into annular flow. The height of the interface and the water hold up increased with DRP. There were no large differences on pressure gradient and hold up between the two DRP concentrations. Using a two-fluid model it was found that the addition of the polymer results in a decrease in both the interfacial and the water wall shear stresses.

Effect of drag reducing polymer on air–water annular flow in an inclined pipe

Drag reduction (DR) for air and water flowing in an inclined 0.0127 m diameter pipe was investigated experimentally. The fluids had an annular configuration and the pipe is inclined upward. The injection of drag reducing polymer (DRP) solution produced drag reductions as high as 71% with concentration of 100 ppm in the pipeline. A maximum drag reduction that is accompanied (in most cases) by a change to a stratified or annular-stratified pattern. The drag reduction is sensitive to the gas and liquid superficial velocities and the pipe inclination. Maximum drag reduction was achieved in the case of pipe inclination of 1.28° at the lowest superficial gas velocity and the highest superficial liquid velocity. For the first time in literature, the drag reduction variations with the square root of the superficial velocities ration for flows with the same final flow patterns have self-similar behaviors.

Liquid−Solid Mass Transfer at a Fixed Bed of Lessing Rings, in Relation to Electrochemical Reactor Design

The mass-transfer behavior of a fixed bed of Lessing rings, under single- and two-phase flow, was studied by measuring the limiting current of the cathodic reduction of the ferricyanide ion. Variables studied included ring diameter (d), solution flow rate, gas flow rate, physical properties of the solution, and the effect of drag-reducing polymers. The single-phase mass-transfer data were correlated for the conditions of 1390 < Sc < 4763 (where Sc is the Schmidt number, which represents a dimensionless kinematic viscosity/molecular diffusivity coefficient), 166 < Re < 722 (where Re is the solution Reynolds number, which represents a dimensionless flow parameter), and 1 cm < d < 1.4 cm by the equation Sh = 1.57Sc0.33Re0.46 (where Sh is the Sherwood number, which represents a dimensionless mass-transfer coefficient). The two-phase mass-transfer data were correlated for the conditions 1390 < Sc < 4763, 144 < Re < 748, 60 < Reg < 818 (where Reg is the gas Reynolds number), and 1 cm < d < 1.4 cm by the equation Sh = 1.93Sc0.33Re0.34Reg0.11. Polyox WSR-301 drag-reducing polymer was found to reduce the rate of mass transfer by an amount of 17.2%−32.7% for single-phase flow; for two-phase flow, the decrease in the rate of mass transfer was 27%−34%. Implication of the present results for the design and operation of electrochemical reactorsespecially those involving gas absorptionwas noted.

Effect of drag-reducing polymers on pseudo-slugs––interfacial drag and transition to slug flow

Drag-reducing polymers were added to air and water flowing in a stratified configuration in a horizontal 2.54 cm pipe. The interface was covered with large amplitude roll waves, that have been called pseudo-slugs, over a range of flow conditions. The damping of small wavelength waves causes a large decrease in the interfacial stress and, therefore, an increase in the liquid holdup. At superficial gas velocities greater than 4 m/s the transition to slug flow is delayed in that it occurs at larger liquid holdups. This observation is interpreted by assuming that turbulence in slugs is damped. This increases the shedding rate of a slug and, therefore, its stability. The pressure drop can increase or decrease when polymers are added. The increase in holdup is accompanied by an increase in gas velocity, which causes an increase in the pressure drop. The decrease in the interfacial stress has the opposite effect.

Effect of drag-reducing polymers on annular gas–liquid flow in a horizontal pipe

Measurements of drag-reduction are presented for air and water flowing in a horizontal 0.0953 m pipe. The fluids had an annular configuration. The injection of polymer solution produced drag-reductions of about 48% with concentrations of only 10–15 ppm in the liquid. The effectiveness of the drag-reducing polymer is sensitive to the method of injection and the concentration of the polymer solution that is injected.

Effect of drag-reducing polymers on the rate of flow-induced corrosion of metals

Abstract Rates of diffusion-controlled corrosion of copper rotating cylinders in acidified chromate solutions containing Polyox WSR-301 drag-reducing polymer, were measured under turbulent flow conditions. The variables studied were the acid concentration, the cylinder rotational speed and the polymer concentration. The rate of corrosion was found to decrease in the presence of Polyox, depending on the operating conditions. At a given polymer concentration, the maximum inhibition efficiency was found to be a decreasing function of the acid concentration and occurred between a Reynolds number of 4500 and 6000, depending on the acid concentration. The maximum observed corrosion inhibition efficiency was about 23% for an acid concentration of 0.25 M bearing 250 ppm Polyox. Possible practical applications of drag-reducing polymers in operating chemical engineering equipment, to benefit from their dual function as corrosion inhibitors and drag reducers, were highlighted.

Effect of Drag-Reducing Polymers on the Rate of Liquid-Solid Mass Transfer in Fixed Beds of Spheres under Forced Convection Conditions

The effect of drag–reducing polymers on the rate of liquid – solid mass transfer in a packed bed reactor under forced convection conditions was studied by measuring the rate of diffusion–controlled dissolution of copper spheres in acidified chromate solutions. The variables investigated were superficial liquid velocity, sphere diameter, bed height, and polymer concentration. The mass transfer coefficient was found to increase with increasing superficial liquid velocity. Increasing both sphere diameter and bed height were found to decrease the mass transfer coefficient. Polymer addition was found to decrease the rate of mass transfer by an amount ranging from 29.2 to 56.9% depending on superficial liquid velocity and polymer concentration. Mass transfer data were correlated in absence and in the presence of drag–reducing polymer, using the following equations, respectively: Jd = 3.71Re–0.54 and, Jd = 2.5 Re–0.61where Jd is mass transfer J-factor and Re is the Reynolds number.

Effect of drag-reducing polymers on the structure of the stagnant zones and eddies in models of constricted and branching blood vessels

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