Drag Reduction Experiments Research Articles

Synthesis and Evaluation of Plugging Gel Resistant to 140 °C for Lost Circulation Control: Effective Reduction in Leakage Rate in Drilling Process.

Gel plugging agents have become one of the preferred methods for plugging in complex and severe loss conditions during drilling due to their good adaptability to loss channels. To address the common issue of poor temperature resistance in gel-based plugging agents, high-temperature-resistant gel plugging materials were synthesized through the molecular design of polymers, modifying existing agents. Based on the temperature and salt resistance of the aqueous solution of an acrylamide (AM)/N-vinylpyrrolidone (NVP) binary copolymer, temperature-resistant monomer sodium styrene sulfonate (SSS) was introduced and reacted in a polyvinyl alcohol (PVA) aqueous solution. Using ammonium persulfate (APS) as an initiator and crosslinking with N,N-methylenebisacrylamide (MBA), a gel plugging material resistant to 140 °C was synthesized. The structure, thermal stability, water absorption and expansion, and plugging performance of the gel were studied through hot rolling aging, thermogravimetric analysis, infrared spectroscopy, electron microscopy scanning, sand bed experiments, and drag reduction experiments. The results show that the gel material has good thermal stability and water absorption and expansion at 140 °C, and its temperature-resistant plugging performance is excellent, significantly slowing down the loss rate of drilling fluid. This provides a basis for the further development of gel materials.

Drag reduction design and experiments for the chisel-shaped shovel tip

To address the issue of high resistance encountered by traditional chisel-shaped shovel tips during tillage, this study drew inspiration from the micro V-shaped structures found in shark skin. Using laser cladding technology, a V-shaped wear-resistant coating was applied to the front surface of the shovel, with different drag-reducing V-shaped structures achieved by controlling the coating overlap ratio H (including 20%, 40%, and 60%). Additionally, the rear surface of the shovel tip was designed to mimic the V-shaped morphology of shark skin, proportionally amplified, and given a certain backward tilt angle θ to further reduce resistance. Through the discrete element simulation experiments while maintaining θ at 0°, it was found that the shovel tip achieved the best drag reduction effect when H was 40%. Based on this, the study varied the values of θ (including 0°, 1°, 3°, and 5°) while keeping H at 40%. Discrete element simulation experiments were conducted at depths of 250mm, 275mm, and 300mm to analyze the disturbance effect, fragmentation effect, and resistance of the shovel tip. Considering all factors, the shovel tip with θ of 5° was selected as the optimal choice. Finally, a soil trench experiment was conducted to verify the performance of the V-shaped shovel tip with H of 40% and θ of 5°, as well as the chisel-shaped shovel tip, in tillage operations. The experimental results showed good agreement with the simulation results, and the designed V-shaped shovel tip achieved a maximum drag reduction of 12.87%. This design provides valuable references for the structural optimization of subsoiler, contributing to the improvement of their performance and efficiency.

Bio-based synthesis of a sustainable Nano drag reducing agent for sprinkler irrigation systems

High-grade silica Nano particles were extracted from rice husk using a straightforward thermochemical method. The specifications of the isolated Nano particles were verified using a variety of material characterization techniques. Siloxane and silanol groups were notably visible in the spectra obtained using Fourier transform infrared spectroscopy. Scanning Electron Microscopy images revealed main Nano particles alongside secondary Micro particles. The size of the particles varied from 14.56 to 33.72 nm. The drag reduction experiments were took place in a facility that uses a forced closed loop. The extracted Nano silica was mixed with faucet water at a weight concentration of 50 to 400 mg/l to reduce drag. Records of pressure loss were obtained along a 186 cm carbon steel tube with internal diameters of 1.6 and 2.7 cm and variable flow rates of solutions at a comfortable temperature of 25 °C. The friction factor values were found to be around Blasuis asymptote for pure water but they were found to be near maximum drag reduction asymptotes when using the Nano material. A maximal drag reduction of nearly 68 % was achieved by using 400 ppm of Nano silica. It was observed that there is a crucial Reynolds number around 96000 that should not be surpassed since any additional increase results in a drop in drag reduction. Furthermore, a relationship between wall shear stress and velocity of the fluid was established.

Minimizing airfoil drag at low angles of attack with DBD-based turbulent drag reduction methods

Dielectric Barrier Discharge (DBD) based turbulent drag reduction methods are used to reduce the total drag on a NACA 0012 airfoil at low angels of attack. The interaction of DBD with turbulent boundary layer was investigated, based on which the drag reduction experiments were conducted. The results show that unidirectional steady discharge is more effective than oscillating discharge in terms of drag reduction, while steady impinging discharge fails to finish the mission (i.e. drag increase). In the best scenario, a maximum relative drag reduction as high as 64 % is achieved at the freestream velocity of 5 m/s, and a drag reduction of 13.7 % keeps existing at the freestream velocity of 20 m/s. For unidirectional discharge, the jet velocity ratio and the dimensionless actuator spacing are the two key parameters affecting the effectiveness. The drag reduction magnitude varies inversely with the dimensionless spacing, and a threshold value of the dimensionless actuator spacing of 540 (approximately five times of the low-speed streak spacing) exists, above which the drag increases. When the jet velocity ratio smaller than 0.05, marginal drag variation is observed. In contrast, when the jet velocity ratio larger than 0.05, the experimental data bifurcates, one into the drag increase zone and the other into the drag reduction zone, depending on the value of dimensionless actuator spacing. In both zones, the drag variation magnitude increases with the jet velocity ratio. The total drag reduction can be divided into the reduction in pressure drag and turbulent friction drag, as well as the increase in friction drag brought by transition promotion. The reduction in turbulent friction drag plays an important role in the total drag reduction.

Drag Reduction of AL-Ahdab Crude Oil Using Chemical Additives

The viscosity of crude oil has a crucial role in drag reduction during pipeline transportation; hence additives are required to enhancing the flow properties of AL-Ahdab crude oil. In this work, the potato starch biopolymer and CTAB surfactant are utilized to achieve the target. The drag reduction experiments were carried out at different crude oil flow rates (20-35-50 liters/min), pipe diameters (0.5-0.75 -1 inch), and different concentrations of potato starch (500-2000 ppm) and CTAB (100-500 ppm). The results showed that these additives had minimized flow resistance in various operating conditions, the drag reduction percent increased with increasing of additives concentration increase. The maximum drag reduction achieved using CTAB and potato starch is 41.6% and 36.3%, respectively, at 50 liters/min and 1-inch pipe diameter.

Research on Turbulent Drag Reduction of Surfactant-Polymer Mixed Solution Using Flow Visualization Technique

Objective: To explore the drag reduction effect of surfactant-polymer composite system in a turbulent flow. Methods: The turbulent drag reduction experiment of the one-component solution and the composite solution was carried out in a rectangular pipeline platform, respectively. Moreover, Particle Image Velocimetry (PIV) was utilized to measure the turbulent flow field of the drag-reducing flow. Results: Experimental results show that the composite drag reduction system has a drag reduction gain effect in comparison with the one-component surfactant or polymer solution. Especially in the destroyed drag reduction zone, the composite drag reduction system has a strong shear resistance. When Polyacrylamide (PAM) is added, the Reynolds drag reduction range of Cetyltrimethylammonium Chloride (CTAC) solution is broadened and the drag reduction gain efficiency reaches 46%, which will provide favorable conditions for oil transportation and other industries. Conclusion: Compared with a one-component CTAC solution, the mean velocity distribution of the composite solution moves up in the logarithmic-law layer, the velocity fluctuation peaks of the streamwise direction shift away from the inner wall of pipe, and the inhibition degree of the normal velocity fluctuation increases with the augment of PAM concentration. In contrast with water, the Reynolds shear stress of one-component CTAC solution and composite solution is reduced significantly, and the vortex structures in the region near the wall are suppressed dramatically with the decrease of vorticity intensity.

Experimental study on microbubble drag reduction on soil-steel interface

The soil-structure interface behavior is an important concern in ocean engineering design. In some cases, it is necessary to reduce the drag of structure, especially the shear stress on the soil-structure interface. In this study, a series of microbubble drag reduction experiments were first carried out on soil-steel interface. The effects of microbubble volume, moisture content, rotation speed and water types (freshwater and seawater) were investigated. It is shown that the average drag reduction ratio ranged from 15% to 92% under various conditions. With the increase of microbubble volume, the drag reduction effect is improved. Meanwhile, the characteristics of drag reduction were also explored under different moisture content. The drag reduction effect of microbubbles is relatively stable at different speeds.Its is proved that the microbubble drag reduction method can obviously reduce the soil-steel interface drag.

Drag reduction of stable biomimetic superhydrophobic steel surface by acid etching under an oxygen-sufficient environment

Superhydrophobic surfaces have shown utility applications in drag reduction field. A novel method based on simulation analysis and test experiments is proposed to fabricate a superhydrophobic surface with 3D flower-like micro and nano-structures on a steel ball under an O2 rich environment. The superhydrophobic steel surface has water CA of 166 ± 1.5°. The sliding angle is less than 2°. The experiment and the simulation of the superhydrophobic and the untreated steel ball fall under water are built to prove the validity of the method of reducing water resistance. The drag reduction ratio of the superhydrophobic steel ball is beyond 53% opposed to the untreated surface under water. A model simulation is built to simulate and analyze the solid-liquid interface drag reduction mechanism of superhydrophobic surface based on theoretical analysis. The result testifies the rationality of the drag reduction experiment.

Study on drag reduction of annular heavy oil transport based on thin oil boundary layer

In this paper, thin oil is used as the boundary layer fluid to carry out the drag reduction experiment of heavyoil. The research shows that when the ratio of the thin oil reaches 45%~50%, the decrement of annular dilution pressure is nearly the same as that of the mixed dilution method, and the annular dilution pressure decreases rapidly with the increasing of dilution ratio; while the ratio reaches 65%,the annular dilution pressure drop is only 25% to 35% of the mixed dilution pressure drop.Fixed thin oil ratio to 50%,when the conveying temperature is higher than 55°C,the annular dilution pressure is lower than the mixed dilution pressure drop; when the ratio is 60%, the annular dilution pressuredrop is lower than the mixed dilution pressure drop in the whole test temperature range, which proves that the drag reduction effect is remarkable.

Soft Robot Actuation Strategies for Locomotion in Granular Substrates

Soft-bodied organisms such as annelids may exploit body compliance using their hydrostatic skeletons and muscles to burrow in granular substrates. In this letter, we investigate the design of soft digging robots inspired by the bristled worm, (polychaetas). The behavior of soft structures in dry granular environments is complex and still not well understood. We describe the design and fabrication of a soft robot capable of locomotion in granular substrates and investigate actuation strategies for drag reduction inspired by the bristled worms biomechanical behaviors. The drag reduction experiments focus on an actuated soft leading segment. We implemented and studied two methods of actuation for the leading segment: periodic radial expansion and bi-directional bending, both of which we find to have an impact on the locomotion in granular substrates. Soft robots performing periodic radial expansion of the leading segments experienced the least overall drag force, while those with unactuated tips experienced the largest drag force, emphasizing the importance of controlling the tip stiffness to enable effective subsurface movement. Based on these results, we designed and tested a tethered, three-segment soft robot capable of digging through dry granular media.

Plastron Regeneration on Submerged Superhydrophobic Surfaces Using In Situ Gas Generation by Chemical Reaction

Superhydrophobic surfaces submerged under water appear shiny due to total internal reflection of light from a thin layer of air (plastron) trapped in their surface texture. This entrapped air is advantageous for frictional drag reduction in various applications ranging from microfluidic channels to marine vessels. However, these aerophilic textures are prone to impregnation by water due to turbulent pressure fluctuations from external flows and dissolution of the trapped gas into the water. We demonstrate a novel chemical method to replenish the plastron in situ by using the decomposition reaction of hydrogen peroxide on superhydrophobic surfaces prepared with a catalytic coating. We also provide a thermodynamic framework for designing superhydrophobic surfaces with optimal texture and chemistry for underwater plastron regeneration. We finally demonstrate the practical utility of this method by fabricating periodic microtextures on aluminum surfaces that incorporate a cheap catalyst, manganese dioxide. We perform drag-reduction experiments under turbulent flow conditions in a Taylor-Couette cell (TC cell), which show that more than half of the drag increase ensuing from plastron collapse can be recovered spontaneously by injection of dilute H2O2 into the TC cell. Thus, we present a low-cost, scalable method to enable in situ plastron regeneration on large surfaces for marine applications.

New mechanism and correlation for degradation of drag-reducing agents in turbulent flow with measured data from a double-gap rheometer

Flow drag reduction with polymer additives has been studied and applied for many years. But degradation of the drag-reducing agent (DRA) is still not well understood. In this study, a new theory for the mechanism of DRA degradation is proposed: the degradation of polymers in flow drag reduction process is a first-order chemical reaction based on the molecular weight. A modified Arrhenius equation can be used to predict the chemical reaction constant. This brings physicochemical meaning to the previously empirical degradation coefficient k in existing correlations. We then conduct a series of flow drag reduction experiments with PEO (polyethylene oxide) of three different molecular weights in a double-gap rheometer to investigate the degradation phenomena. A new correlation is developed to predict the lifespan of DRAs. Predictions with this correlation agree with measured data with an average relative error of 15%, better than previous correlations. The results indicate validity of the proposed new mechanism of DRA degradation.

Wind-Tunnel Experiments of Friction Drag Reduction on an Airfoil Using Passive Blowing

Wind-Tunnel Experiments of Friction Drag Reduction on an Airfoil Using Passive Blowing

The Use of Biobased Surfactant Obtained by Enzymatic Syntheses for Wax Deposition Inhibition and Drag Reduction in Crude Oil Pipelines

Crude oil plays an important role in providing the energy supply of the world, and pipelines have long been recognized as the safest and most efficient means of transporting oil and its products. However, the transportation process also faces the challenges of asphaltene-paraffin structural interactions, pipeline pressure losses and energy consumption. In order to determine the role of drag-reducing surfactant additives in the transportation of crude oils, experiments of wax deposition inhibition and drag reduction of different oil in pipelines with a biobased surfactant obtained by enzymatic syntheses were carried out. The results indicated that heavy oil transportation in the pipeline is remarkably enhanced by creating stable oil-in-water (O/W) emulsion with the surfactant additive. The wax appearance temperature (WAT) and pour point were modified, and the formation of a space-filling network of interlocking wax crystals was prevented at low temperature by adding a small concentration of the surfactant additive. A maximum viscosity reduction of 70% and a drag reduction of 40% for light crude oil flows in pipelines were obtained with the surfactant additive at a concentration of 100 mg/L. Furthermore, a successful field application of the drag-reducing surfactant in a light crude oil pipeline in Daqing Oilfield was demonstrated. Hence, the use of biobased surfactant obtained by enzymatic syntheses in oil transportation is a potential method to address the current challenges, which could result in a significant energy savings and a considerable reduction of the operating cost.

A mechanism of wave drag reduction in the thermal energy deposition experiments

Many experimental studies report reduced wave drag when thermal energy is deposited in the supersonic flow upstream of a body. Though a large amount of research on this topic has been accumulated, the exact mechanism of the drag reduction is still unknown. This paper is to fill the gap in the understanding connecting multiple stages of the observed phenomena with a single mechanism. The proposed model provides an insight on the origin of the chain of subsequent transformations in the flow leading to the reduction in wave drag, such as typical deformations of the front, changes in the gas pressure and density in front of the body, the odd shapes of the deflection signals, and the shock wave extinction in the plasma area. The results of numerical simulation based on the model are presented for three types of plasma parameter distribution. The spherical and cylindrical geometry has been used to match the data with the experimental observations. The results demonstrate full ability of the model to exactly explain all the features observed in the drag reduction experiments. Analytical expressions used in the model allow separating out a number of adjustment parameters that can be used to optimize thermal energy input and thus achieve fundamentally lower drag values than that of conventional approaches.

Turbulent Drag Reduction by Biopolymers in Large Scale Pipes

In this work, we describe drag reduction experiments performed in a large diameter pipe (i.d. 100 mm) using a semirigid biopolymer Xanthan Gum (XG). The objective is to build a self-consistent data base which can be used for validation purposes. To aim this, we ran a series of tests measuring friction factor at different XG concentrations (0.01, 0.05, 0.075, 0.1, and 0.2% w/w XG) and at different values of Reynolds number (from 758 to 297,000). For each concentration, we obtain also the rheological characterization of the test fluid. Our data is in excellent agreement with data collected in a different industrial scale test rig. The data is used to validate design equations available from the literature. Our data compare well with data gathered in small scale rigs and scaled up using empirically based design equations and with data collected for pipes having other than round cross section. Our data confirm the validity of a design equation inferred from direct numerical simulation (DNS) which was recently proposed to predict the friction factor. We show that scaling procedures based on this last equation can assist the design of piping systems in which polymer drag reduction can be exploited in a cost effective way.

Large-proportional shrunken bio-replication of shark skin based on UV-curing shrinkage

The shark skin effect has attracted worldwide attention because of its superior drag reduction. As the product of natural selection, the maximum drag reduction of shark skin is found in its normal living environment. Large-proportional shrinkage of shark skin morphology is greatly anticipated for its adaptation to faster fluid flow. One novel approach, large-proportional shrunken bio-replication, is proposed as a method to adjust the optimal drag reduction region of shark skin based on the shrinkage of UV-cured material. The shark skin is taken as a replica template to allow large-proportional shrinking in the drag reduction morphology by taking advantage of the shrinkage of UV-curable material. The accuracy of the large-proportional shrunken bio-replication approach is verified by a comparison between original and shrunken bio-replicated shark skin, which shows that the shrinking ratio can reach 23% and the bio-replication accuracy is higher than 95%. In addition, the translation of the optimum drag reduction peak of natural surface function to various applications and environments is proved by drag reduction experiments.

Synthetic Effect of Vivid Shark Skin and Polymer Additive on Drag Reduction Reinforcement

Natural shark skin has a well-demonstrated drag reduction function, which is mainly owing to its microscopic structure and mucus on the body surface. In order to improve drag reduction, it is necessary to integrate microscopic drag reduction structure and drag reduction agent. In this study, two hybrid approaches to synthetically combine vivid shark skin and polymer additive, namely, long-chain grafting and controllable polymer diffusion, were proposed and attempted to mimic such hierarchical topography of shark skin without waste of polymer additive. Grafting mechanism and optimization of diffusion port were investigated to improve the efficiency of the polymer additive. Superior drag reduction effects were validated, and the combined effect was also clarified through comparison between drag reduction experiments.

Seepage model and experiments of drag reduction by nanoparticle adsorption

The hydrophobic nanoparticle (HNP) adsorption is a new technique of drag reduction, which changes the wettability of the porous walls of the core, generates the slip-boundary of the fluid flow and consequently enhances the oil recovery. In the present work, a seepage model with consideration of the slip effect in the micro-channels and the influence of the equivalent pore radius modified by the HNP adsorption is proposed based on the Darcy's law. The permeability of the non-wetting phase in the porous media is calculated according to its dependence on the slip length, while the slip length is determined by a function of the contact angle and the equivalent pore radius. Numerical simulations are performed by use of the COMSOL multiphysics, and an acceptable agreement between experimental and simulation results is achieved (with an error less than 2.5%). The present model can then be used for the mechanism investigation and the prediction of the oilfield performance.

Mechanism analysis of one-dimensional short groove quasicrystal structure drag-reduction

Short groove arranged in one-dimensional quasicrystal structure is designed by mechanical method in this paper and drag reduction experiments are performed by viscometer. The results show that there is a novel drag reduction effect compared with periodic structure of one-dimensional short groove, in which 12-fold quasicrystal structure of one-dimensional short groove has the best drag reduction, and has an equal effect compared with one-dimensional periodic groove structure. An two-dimensional grating model is proposed to investigate the mechanism. It is found that in comparison with two-dimensional periodic grating, the intensity spectrum of coherent wave passing through two-dimensional quasiperiodic grating has several characteristic structure factors. Corresponding to the quasicrystal structures of one-dimensional short groove, the quasiperiodic structure in spanwise direction can activate little disturbance on boundary layer and make the secondary vortex more uniform, which restrains the strong disturbance in spanwise, consequently reducing the drag.