Percentage Drag Reduction Research Articles

Cocoa Husk Waste Mucilage as New Flow Improver in Pipelines

Liquid transportation through pipelines for very long distances is one of the most power consuming sectors in the industry. Synthetic polymers were used as flow improvers for many years to solve the power dissipation problem. These polymers are toxic and expensive. An environmentally friendly and more natural product that can replace the usage of polymers as flow improvers is needed. The present study focused on a new, cheap, natural and environmentally friendly flow improver that was extracted from the cocoa husk wastes. Mucilage was prepared from the cocoa husk waste and tested in aqueous media at concentrations between 100 ppm and 400 ppm using pipes with an internal diameter of 0.0125, 0.0254 and 0.0381 m and five different fluid velocities represented by the corresponding Reynolds Numbers (Re). It was found that the cocoa husk mucilage was an effective drag reducing agent. A maximum drag reduction percentage of 44% could be achieved by adding as little as 400 ppm of mucilage. Drag reduction was found to increase by increasing Reynolds Numbers, additive concentrations and pipe lengths. It also increased with decreasing pipe diameters.

Drag Reduction Characteristics Using Aloe Vera Natural Mucilage: An Experimental Study

In the present study, a new natural and environmentally friendly drag reducing agent is introduced as a flow improver in pipelines carrying liquids in turbulent flow mode. The new drag reducing agent is extracted from the Aloe Vera leaves. The extracted mucilage drag reduction performance was tested using a closed loop liquid circulation system. The experimental work was carried out in 0.0254 m I.D. pipe with 100 to 400 ppm addition concentrations, four testing sections lengths and five different flow rates. It was found that the Aloe Vera mucilage was an effective drag reducing agent. A maximum drag reduction percentage of 63% could be achieved by adding 400 ppm of mucilage to the main flow. Drag reduction was found to increase with increasing Reynolds Numbers, additive concentrations and pipe lengths. Finally, a new correlation equation representing the experimental data is introduced.

Aluminum Powder and Zwitrionic Surfactants as Drag Reducing Agents in Pipe Lines

Problem statement: One of the most power consuming sector in the industry is the liquid transportation through pipelines due to the turbulent mode the liquids are transported with. Drag reducing agents were used as a solution for the pumping power losses in pipelines. One of the inportant drag reducing agents suggested to improve the flow in pipelines are the suspended powders. Approach: In the present study, aluminum powders and zwitrionic surfactant ((3-(Decyldimethyleammonio) propanesulfonate inner salt and 3-(n-n Dimethylpalmityl-ammonio propanesulfonate) were investigated as drag reducing agent in aqueous media. The effect of additive concentration, Reynolds number and the testing section length are the main variables investigated. All the experimental work was carried in a build up experimental rig that consist of a closed loop experimental piping system. Results: The experimental results showed that, the percentage drag reduction Dr (%) increases by increasing the additive concentration and Reynolds number with maximum percentage drag reduction up to 50% with only 500 ppm addition concentration. Conclusion: The effect of testing section length was not so clear due to the way of introducing the additive to the main flow, that the additive is mixed in the main tank and not injected.

A massively parallel hybrid scheme for direct numerical simulation of turbulent viscoelastic channel flow

This paper describes in detail a numerical scheme designed for direct numerical simulation (DNS) of turbulent drag reduction. The hybrid spatial scheme includes Fourier spectral accuracy in two directions and sixth-order compact finite differences for first and second-order wall-normal derivatives, while time marching can be up to fourth-order accurate. High-resolution and high-drag reduction viscoelastic DNS are made possible through domain decomposition with a two-dimensional MPI Cartesian grid alternatively splitting two directions of space (‘pencil’ decomposition). The resulting algorithm has been shown to scale properly up to 16384 cores on the Blue Gene/P at IDRIS–CNRS, France. Drag reduction is modeled for the three-dimensional wall-bounded channel flow of a FENE-P dilute polymer solution which mimics injection of heavy-weight flexible polymers in a Newtonian solvent. We present results for four high-drag reduction viscoelastic flows with friction Reynolds numbers Re τ0 = 180, 395, 590 and 1000, all of them sharing the same friction Weissenberg number We τ0 = 115 and the same rheological parameters. A primary analysis of the DNS database indicates that turbulence modification by the presence of polymers is Reynolds-number dependent. This translates into a smaller percent drag reduction with increasing Reynolds number, from 64% at Re τ0 = 180 down to 59% at Re τ0 = 1000, and a steeper mean current at small Reynolds number. The Reynolds number dependence is also visible in second-order statistics and in the vortex structures visualized with iso-surfaces of the Q-criterion.

Influence of grafted copolymer structures (polyacrylamide-g-polyoxide) on drag-reduction

This article reports the results of experiments to synthesize a family of copolymers based on polyacrylamide (PAAM), poly(ethylene oxide) (PEO), and poly(propylene oxide) (PPO) to obtain PAAM-g-PEO and PAAM-g-PPO copolymers with varied grafted chain lengths and contents. The influence of the chemical structure, composition, and molecular architecture on the drag-reduction properties was evaluated. The PAAM-g-PEO systems were prepared by solution polymerization using hydrogen peroxide as initiator, whereas the PAAM-g-PPO systems were obtained by micellar polymerization using potassium persulfate as initiator and sodium dodecyl sulfate as surfactant agent. The synthesized polymers were characterized by carbon-13 nuclear magnetic resonance (13 C-NMR) and size-exclusion chromatography. The drag-reduction tests were carried out in a capillary viscosimeter in bench scale, and the performance was expressed in terms of drag-reduction percentage (%DR). The results suggest that, a determined chemical structure for each copolymer family evaluated probably promotes the ideal conformation of the chains under flow, favoring each polymer's drag-reduction action. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Drag reduction in co-current down flow packed column using xanthan gum

Drag reduction is one of the most important techniques for reducing energy consumption in a packed bed contactor. The present work involves an experimental investigation on flow regime transition for air-water system with and without drag reducing agent (DRA), two-phase pressure drop, friction factor and drag reduction using xanthan gum as DRA. Drag reduction was quantified from the two-phase pressure drop data. Based on the present observations it was found that the percentage drag reduction increases with an increase in the concentration of DRA and it is only effective in the range of 300 ppm to 800 ppm. The experimental results indicate that a maximum of 80% drag reduction was achievable using xanthan gum (800 ppm) as DRA. Furthermore, the experimental data were validated with the available literature correlations.

Counterflow Drag Reduction Studies for a Blunt Cone in High Enthalpy Flow

Drag reduction by counterflow supersonic jet for a 60-degree apex angle blunt cone in high enthalpy flow is investigated in a free piston driven hypersonic shock tunnel, HST3. For flow Mach number of 8 with specific flow enthalpy of 5 MJ/kg, it has been observed that the drag force decreases with increase in the ratio of supersonic jet total pressure to the freestream pitot pressure until the critical injection pressure ratio is reached. Maximum percentage drag reduction of 44 is measured at the critical injection pressure ratio of 22.36. Further increase in injection pressure ratio has reduced the percentage drag reduction. Experimentally obtained drag signals portray the change in nature of the flowfield, around the model, across the critical injection pressure ratio.

Temporal large eddy simulations of turbulent viscoelastic drag reduction flows

We report on temporal large eddy simulations (TLES) of the turbulent channel flow of a dilute polymer solution modeled with the FENE-P (finitely extensible nonlinear elastic in the Peterlin approximation) constitutive equation. The large eddy simulations are based upon an approximate temporal deconvolution method [Pruett et al., Phys. of Fluids, 18, 028104–1, (2006)] for residual Newtonian stress modeling and secondary regularization for unresolved subfilter Newtonian stress. The filtered conformation tensor equation involves deconvolution for stretching and for the nonlinear spring force, as well as secondary regularization. Results are shown at a friction Reynolds number 180 for Weissenberg numbers and molecular extensibilities spanning the moderate to high drag reducing regimes. Excellent agreement is obtained between TLES and direct numerical simulations (DNS) in terms of percent drag reduction prediction. TLES is also able to reproduce the high level of anisotropy of turbulence, which confirms recent findings by Frohnapfel et al. [J. Fluid Mech. 577, 457 (2007)] who present high anisotropy as a general mechanism to obtain significant drag reduction. The TLES model proves itself stable and its overall computational workload some 60 times less than DNS.

DRAG REDUCTION BY USING ANIONIC SURFACTANTS

The aim of reducing drag is to increase the flow efficiency by using the same pipes and pumps. As a result the amount of crude oil transported will increase without using new pipes and pumps.In the present work, the effectiveness of two surfactants (Sodium dodecyl benzene sulfonate (SDBS) and Sodium lauryl sulfate (SLS)) are studied by using a closed loop system. This system consists of three pipes made from commercial steel, each one with different diameter (0.75, 1 and 1.5 inch). The length of each individual test section of the pipe is two meters. The experimental work is achieved under three different temperatures (30º, 40º and 50°C). The concentrations of both surfactants used are ranging between 50 to 300 weight ppm. Laboratory tests showed that there is a direct proportionality between the percentage ofdrag reduction (%DR) on one hand and in Reynolds number and pipe diameter on the other hand.Inverse proportionality is observed between %DR and temperature. The %DR increases as concentration increases, but at a certain higher concentration, this relation will reverse. The final results showed that the highest drag reduction (%DR) was 23.67%. This value is obtained when 200 ppm SDBS is added at 30°C.The calculated values of friction factor were found to be situated between Blasius and Virk asymptote adjacent.

SLES SURFACTANT AS DRAG REDUCING AGENT WITHIN GASOIL FLOWING THROUGH PIPELINES

Sodium Lauryl Ether Sulfate (SLES) with five different concentrations (from 50 to 100 ppm) were used as drag reducer. This surfactant was studied using gasoil with seven different fluid flow rates (from 1.9 to 4.5 m3 /h) and a testing section length of 4 m. Percentage drag reduction (%Dr) was found to increase by increasing the surfactant concentration and Reynolds number. Maximum drag reduction (45.5%) was acheved by using 300 ppm of SLES dissolved in gas oil for flow rate equals to 4.5 m3 /h. Friction factor was calculated from the experimental data. For pure solvent; friction factor values lies near or at Blasuis asymptote. While, by producing the surfactants into the flow, the friction factor values were positioned below Blasius asymptote towards Virk maximum drag reduction asymptote. Correlation equation was suggested for surfactant solutions. This correlation shows the friction factor as a function of Reynolds number (Re) and surfactant concentration (C). The results showed good agreement between the observed friction factor values and the predicted ones from the correlation equation.

Flow Control Using Synthetic Jet and Plasma Actuators on a Rotorcraft Tail Boom Model

This paper shows the time-averaged effect of synthetic jet and plasma actuators on flow over a representative two-dimensional rotorcraft tail boom for delaying flow separation and, therefore, reducing pressure drag, whereas previous studies have evaluated these flow control devices on a circular cylinder. The percentage of pressure drag reduction is used to evaluate the effectiveness of these two unique actuators for varied applied voltage under device independent conditions such as actuator position and flow velocity. Two non-dimensional parameters were used to evaluate the effect of the actuators: coefficient of momentum (Cμ) and non-dimensional surface distance between the location of the actuator and the flow separation point (SDTB). Both actuation techniques beneficially affect the pressure distribution by decreasing the pressure near the location of the actuators and increasing the pressure in the separated flow region. Contour plots displaying the variation of the percentage of pressure drag reduct...

Enhancement in counterflow drag reduction by supersonic jet in high enthalpy flows

Counterflow drag reduction by supersonic jet for a 60° apex angle blunt cone flying at hypersonic Mach number is investigated for two different flow enthalpies using conventional and free piston driven hypersonic shock tunnels. Enhancement in drag reduction has been observed with increase in freestream stagnation enthalpy. It is shown that the percentage of drag reduction goes up by a factor of 2 when the flow enthalpy increases by a factor of 2.5 for a given ratio of total pressure of supersonic jet and freestream flow.

Drag Reduction of Crude Oil Flow in Pipelines Using Sodium Dodecyl Benzene Sulfonate Surfactant

In the present work, a closed loop circulation system consist of three testing sections was designed and constructed. The testing sections made from (3m) of commercial carbon steel pipe of diameters(5.08, 2.54 and 1.91 cm) . Anionic surfactant (SDBS )with concentrations of (50, 100, 150, 200 and 250 ppm) was tested as a drag reducing agent. The additive(SDBS)studied using crude oil from south of Iraq. The flow rates of crude oil were used in 5.08 and 2.54 cm I.D. pipes are (1 - 12) m3/hr while (1-6) m3/hr were used in 1.91 cm J .D. pipe . Percentage drag reduction (%Dr) was found to increase by increasing solution velocity, pipe diameter and additives concentration (i.e. increasing Renolds number). Also it was found that there is no change in apparent physical properties (viscosity) of crude oil after the addition of SDBS. The higher value of drag reduction of 54% in 5.08 cm I.D. was observed using 250 ppm SDBS surfactant dissolved in the used crude oil at flow rate of 12 m3/hr. Friction factor was calculated from experimental data. The friction factors values for pure solvent lies near or at Blasius asymptote suggested for flow of Newtonian fluids. After the addition of small amount of SDBS, the friction factor values were positioned below Blasius asymptote toward Virk maximum drag reduction asymptote, which was never reached.

Computational Study of Shock Mitigation and Drag Reduction by Pulsed Energy Lines

A series of numerical experiments were performed in which energy was deposited ahead of a cone traveling at supersonic/hypersonic speeds. The angle of attack was zero, and the cone half-angles ranged from 15 to 45 deg. The Mach numbers simulated were 2, 4, 6, and 8. The energy was deposited instantaneously along a finite length of the cone axis, ahead of the cone’s bow shock, causing a cylindrical shock wave to push air outward from the line of deposition. The shock wave would sweep the air out from in front of the cone, leaving behind a low-density column/tube of air, through which the cone (vehicle) propagated with significantly reduced drag. The greatest drag reduction observed was 96%. (One-hundred percent drag reduction would result in the complete elimination of drag forces on the cone.) The propulsive gain was consistently positive, meaning that the energy saved as a result of drag reduction was consistently greater than the amount of energy “invested” (i.e., deposited ahead of the vehicle). The highest ratio of energy saved/energy invested was approximately 6500% (a 65-fold “return” on the invested energy). We explored this phenomenon with a high-order-accurate multidomain weighted essentially nonoscillatory finite difference algorithm, using interpolation at subdomain boundaries. This drag-reduction/shock-mitigation technique can be applied locally or globally to reduce the overall drag on a vehicle.

Turbulent channel flow of dilute polymeric solutions: Drag reduction scaling and an eddy viscosity model

Direct numerical simulation of viscoelastic turbulent channel flows up to the maximum drag reduction (MDR) limit has been performed. The simulation results in turn have been used to develop relationships between the flow and fluid rheological parameters, i.e. maximum chain extensibility, Reynolds number, Re τ , and Weissenberg number, We τ and percent drag reduction (%DR) as well as the slope increment of the mean velocity profile. Moreover, based on the trends observed in the mean velocity profile and the overall momentum balance three different regimes of drag reduction (DR), namely, low drag reduction (LDR; 0 ≤ %DR ≤ 20), high drag reduction (HDR; 20 ≤ %DR ≤ 52) and MDR (52 ≤ %DR ≤ 74) have been identified and mathematical expressions for the eddy viscosity in these regimes are presented. It is found that both in LDR and HDR regimes the eddy viscosity varies with the distance from the channel wall. However, in the MDR regime the ratio of the eddy viscosity to the Newtonian one tends to a very small value around 0.1 within the channel. Based on these expressions a procedure that relies on the DNS predictions of the budgets of momentum and viscoelastic shear stress is developed for evaluating the mean velocity profile.

Drag reduction by compressible bubbles

Drag reduction by bubbles in stationary turbulent flows is sensitive to the compressibility of the bubbles. Without this dynamical effect the bubbles only renormalize the fluid density and viscosity, an effect that by itself can only lead to a small percentage of drag reduction. We show in this paper that the dynamics of bubbles and their effect on the compressibility of the mixture can lead to a much higher drag reduction.

Effects of Coiled-Tubing Curvature on Drag Reduction of Polymeric Fluids

Summary This paper presents experimental results of the effects of coiled-tubing curvature on the drag-reduction behavior of polymeric fluids in turbulent flow. The experimental setup consists of a 10-ft section of ½-in. outside diameter (OD) straight tubing and four reels of coiled tubing of the same diameter. Fluids investigated included water, guar, hydroxypropyl guar (HPG), and xanthan fluids at various polymer concentrations. It was found that the coiled-tubing curvature could reduce the drag reduction by 10 to 30% compared to straight tubing, depending on the flow conditions. The tubing curvature also delays the onset of drag reduction. The percentage of drag reduction in coiled tubing may be improved if fluid is pumped at higher rates. The results of the present study were also verified with full-scale experiments and were found to be representative of the drag-reduction behavior of similar fluids under field flow conditions.

Experimental study of drag reduction by a polymeric additive in slug two-phase flow of crude oil and air in horizontal pipes

In this study the effect of the presence of a drag reducing agent (DRA) on the pressure drop in cocurrent horizontal pipes carrying slug two-phase flow of air and crude oil is investigated. An experimental set-up is erected. The test section of the experimental set-up is consisted of: a smooth pipe of polycarbonate with 10.3 m long and 2.54 cm ID, a rough pipe of galvanized iron with 8.8 m long and 2.54 cm ID and a rough pipe of galvanized iron with 8.8 m long and 1.27 cm ID. The employing DRA is a Polyalpha-olefin (Polyisobutylene). The percent drag reduction (%DR) is calculated using the obtained experimental data, in presence of the DRA. The results show that addition of DRA could be effective up to some doses of DRA after which the pressure drop is kept constant. A %DR of about 40 is obtained for some experimental conditions.

Drag reduction of a circular cylinder at subcritical flow regime using base shield plates

Experimental studies on drag reduction of a circular cylinder of diameter D were conducted in the subcritical flow regime at Reynolds numbers in the range <TEX>$4{\times}10^4{\leq}Re{\leq}10^5$</TEX>. To shield the cylinder rear surface from the pressure deficit of the unsteady vortex generation in the near wake, two shield plates were attached downstream of the separation points to form a cavity at the base region. The chord of the shield plates, L, ranged from 0.22 to 1.52 D and the cavity width, G, was in the range from 0 to 0.96 D. It is concluded that significant drag reductions from that of a plain cylinder may be achieved by proper sizing of the shield plates and the base cavity. The study shows that using a pair of shield plates at G/D of 0.86 and angular position <TEX>${\theta}$</TEX> of <TEX>${\pm}121^{\circ}$</TEX> results in a configuration with percentage drag reduction of 40% for L/D of 0.5, and 55% for L/D of 1.0.

Polymer-induced drag reduction: Effects of the variations in elasticity and inertia in turbulent viscoelastic channel flow

In this work we systematically investigate the effects of the flow elasticity and inertia in polymer-induced drag reduction through (pseudo)spectral simulations of a turbulent channel flow of a dilute polymer solution. Viscoelastic effects are modeled by the finite-extensibility nonlinear elastic dumbbell model with the Peterlin approximation. The present work updates the low Weissenberg results (Weτ0⩽50) reported in earlier works by Sureshkumar et al. [Phys. Fluids 9, 743 (1997)] and Dimitropoulos et al. [J. Non-Newtonian Fluid Mech. 79, 433 (1998)] for a zero shear rate friction Reynolds number, Reτ0=125, by allowing for a lower value for the numerical diffusivity. In addition, we examine two effects on drag reduction: (A) high elasticity, by varying Weτ0 from 62.5 to 125 for a constant Reτ0=125, (B) friction Reynolds number, Reτ0=180, 395, and 590, for a constant Weτ0=50. In the high elasticity region, the mean Reynolds, Remean, continues to increase with increasing Weτ0, albeit at a smaller rate. Thus, the drag reduction achieved at the highest Weτ0 number, Weτ0=125, is about 37.5%, as compared to about 30% for Weτ0=50. On the other hand, the percent drag reduction remains virtually unchanged as Reτ0 is increased to 180, 395, and 590 for a constant Weτ0=50. Increasing the friction Reynolds number while keeping the friction Weissenberg number constant, does affect the detailed turbulent statistics. However, the boundary and the buffer layers approach an asymptote at a friction Reynolds number of 395 as it has also been observed in the Newtonian limit. The effect of variations in the computational domain, mesh resolution and the numerical diffusivity on the turbulent statistics is also reported.