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Numerical Study on Reduction in Aerodynamic Drag and Noise of High-Speed Pantograph 被引量:1
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作者 Deng Qin Xing Du +1 位作者 Tian Li Jiye Zhang 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第5期2155-2173,共19页
Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly,energy efficient and rapid advances in train technology.Using computational fluid dynamics t... Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly,energy efficient and rapid advances in train technology.Using computational fluid dynamics theory and the K-FWH acoustic equation,a numerical simulation is conducted to investigate the aerodynamic characteristics of high-speed pantographs.A component optimization method is proposed as a possible solution to the problemof aerodynamic drag and noise in high-speed pantographs.The results of the study indicate that the panhead,base and insulator are the main contributors to aerodynamic drag and noise in high-speed pantographs.Therefore,a gradual optimization process is implemented to improve the most significant components that cause aerodynamic drag and noise.By optimizing the cross-sectional shape of the strips and insulators,the drag and noise caused by airflow separation and vortex shedding can be reduced.The aerodynamic drag of insulator with circular cross section and strips with rectangular cross section is the largest.Ellipsifying insulators and optimizing the chamfer angle and height of the windward surface of the strips can improve the aerodynamic performance of the pantograph.In addition,the streamlined fairing attached to the base can eliminate the complex flow and shield the radiated noise.In contrast to the original pantograph design,the improved pantograph shows a 21.1%reduction in aerodynamic drag and a 1.65 dBA reduction in aerodynamic noise. 展开更多
关键词 High-speed pantograph aerodynamic drag aerodynamic noise REDUCTION optimizing
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Preparation and performance evaluation of the slickwater using novel polymeric drag reducing agent with high temperature and shear resistance ability
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作者 Ming-Wei Zhao Zhen-Feng Ma +5 位作者 Cai-Li Dai WeiWu Yong-Quan Sun Xu-Guang Song Yun-Long Cheng Xiang-Yu Wang 《Petroleum Science》 SCIE EI CAS CSCD 2024年第2期1113-1121,共9页
Slickwater fracturing fluids are widely used in the development of unconventional oil and gas resources due to the advantages of low cost,low formation damage and high drag reduction performance.However,their performa... Slickwater fracturing fluids are widely used in the development of unconventional oil and gas resources due to the advantages of low cost,low formation damage and high drag reduction performance.However,their performance is severely affected at high temperatures.Drag reducing agent is the key to determine the drag reducing performance of slickwater.In this work,in order to further improve the temperature resistance of slickwater,a temperature-resistant polymeric drag reducing agent(PDRA)was synthesized and used as the basis for preparing the temperature-resistant slickwater.The slickwater system was prepared with the compositions of 0.2 wt%PDRA,0.05 wt%drainage aid nonylphenol polyoxyethylene ether phosphate(NPEP)and 0.5 wt%anti-expansion agent polyepichlorohydrindimethylamine(PDM).The drag reduction ability,rheology properties,temperature and shear resistance ability,and core damage property of slickwater were systematically studied and evaluated.In contrast to on-site drag reducing agent(DRA)and HPAM,the temperature-resistant slickwater demonstrates enhanced drag reduction efficacy at 90℃,exhibiting superior temperature and shear resistance ability.Notably,the drag reduction retention rate for the slickwater achieved an impressive 90.52%after a 30-min shearing period.Additionally,the core damage is only 5.53%.We expect that this study can broaden the application of slickwater in high-temperature reservoirs and provide a theoretical basis for field applications. 展开更多
关键词 Unconventional resources Polymeric drag reducing agent Slickwater High drag reduction rate Temperature resistance
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Numerical investigation on the aerodynamic drag reduction based on bottom deflectors and streamlined bogies of a high-speed train
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作者 JIANG Chen LONG jn-lan +2 位作者 LI Yan-ong GAO Guang-jun FRANKLIN Eze 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第9期3312-3328,共17页
The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In th... The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In this study,computational fluid dynamics(CFD)based on three-dimensional steady incompressible Reynolds-average Naiver-Stokes(RANS)equations and Realizable k-ε turbulence model were utilized for numerical simulations.Inspired by the concept of streamlined design and the idea of bottom flow field control,this study iteratively designed the bogies in a streamlined shape and combined them with the bottom deflectors to investigate the joint drag reduction mechanism.Three models,i.e.,single-bogie model,simplified train model,and eight-car high-speed train model,were created and their aerodynamic characteristics were analyzed.The results show that the single-bogie model with streamlined design shows a noticeable drag reduction,whose power bogie and trailer bogie experience 13.92%and 7.63%drag reduction,respectively.The range of positive pressure area on the bogie is reduced.The aerodynamic drag can be further reduced to 15.01%by installing both the streamlined bogie and the deflector on the simplified train model.When the streamlined bogies and deflectors are used on the eight-car model together,the total drag reduction rate reaches 2.90%.Therefore,the proposed aerodynamic kit for the high-speed train bottom is capable to improve the flow structure around the bogie regions,reduce the bottom flow velocity,and narrow the scope of the train’s influence on the surrounding environment,achieving the appreciable reduction of aerodynamic drag.This paper can provide a new idea for the drag reduction of high-speed trains. 展开更多
关键词 high-speed train numerical simulation drag reduction DEFLECTOR streamlined design
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Airfoil friction drag reduction based on grid-type and super-dense array plasma actuators
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作者 方子淇 宗豪华 +2 位作者 吴云 梁华 苏志 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第2期94-103,共10页
To improve the cruise flight performance of aircraft, two new configurations of plasma actuators(grid-type and super-dense array) were investigated to reduce the turbulent skin friction drag of a low-speed airfoil. Th... To improve the cruise flight performance of aircraft, two new configurations of plasma actuators(grid-type and super-dense array) were investigated to reduce the turbulent skin friction drag of a low-speed airfoil. The induced jet characteristics of the two actuators in quiescent air were diagnosed with high-speed particle image velocimetry(PIV), and their drag reduction efficiencies were examined under different operating conditions in a wind tunnel. The results showed that the grid-type plasma actuator was capable of producing a wall-normal jet array(peak magnitude: 1.07 m/s) similar to that generated in a micro-blowing technique, while the superdense array plasma actuator created a wavy wall-parallel jet(magnitude: 0.94 m/s) due to the discrete spanwise electrostatic forces. Under a comparable electrical power consumption level,the super-dense array plasma actuator array significantly outperformed the grid-type configuration,reducing the total airfoil friction drag by approximately 22% at a free-stream velocity of 20 m/s.The magnitude of drag reduction was proportional to the dimensionless jet velocity ratio(r), and a threshold r = 0.014 existed under which little impact on airfoil drag could be discerned. 展开更多
关键词 plasma actuator flow control drag reduction AIRFOIL
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Numerical Study on the Effect of Vortex Generators on the Aerodynamic Drag of a High-Speed Train
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作者 Tian Li Hao Liang +1 位作者 Zerui Xiang Jiye Zhang 《Fluid Dynamics & Materials Processing》 EI 2024年第2期463-473,共11页
A relatively high aerodynamic drag is an important factor that hinders the further acceleration of high-speed trains.Using the shear stress transport(SST)k-ωturbulence model,the effect of various vortex generator typ... A relatively high aerodynamic drag is an important factor that hinders the further acceleration of high-speed trains.Using the shear stress transport(SST)k-ωturbulence model,the effect of various vortex generator types on the aerodynamic characteristics of an ICE2(Inter-city Electricity)train has been investigated.The results indi-cate that the vortex generators with wider triangle,trapezoid,and micro-ramp arranged on the surface of the tail car can significantly change the distribution of surface pressure and affect the vorticity intensity in the wake.This alteration effectively reduces the resistance of the tail car.Meanwhile,the micro-ramp vortex generator with its convergent structure at the rear exhibits enhancedflow-guiding capabilities,resulting in a 15.4%reduction in the drag of the tail car. 展开更多
关键词 Vortex generator aerodynamic drag REDUCTION numerical simulation
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Estimation of Displacement and Extension due to Reverse Drag of Normal Faults: Forward Method
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作者 Shunshan Xu Angel Francisco Nieto-Samaniego +1 位作者 Huilong Xu Susana Alicia Alaniz-Álvarez 《International Journal of Geosciences》 CAS 2024年第1期25-39,共15页
In the case of reverse drag of normal faulting, the displacement and horizontal extension are determined based on the established equations for the three mechanisms: rigid body, vertical shear and inclined shear. Ther... In the case of reverse drag of normal faulting, the displacement and horizontal extension are determined based on the established equations for the three mechanisms: rigid body, vertical shear and inclined shear. There are three sub-cases of basal detachment for the rigid body model: horizontal detachment, antithetic detachment and synthetic detachment. For the rigid body model, the established equations indicate that the total displacement on the synthetic base (D<sub>t2</sub>) is the largest, that on the horizontal base (D<sub>t1</sub>) is moderate, and that on the antithetic base (D<sub>t3</sub>) is the smallest. On the other hand, the value of (D<sub>t1</sub>) is larger than the displacement for the vertical shear (D<sub>t4</sub>). The value of (D<sub>t1</sub>) is larger than or less than the displacement for the inclined shear (D<sub>t5</sub>) depending on the original fault dip δ<sub>0</sub>, bedding angle θ, and the angle of shear direction β. For all original parameters, the value of D<sub>t5</sub> is less than the value of D<sub>t4</sub>. Also, by comparing three rotation mechanisms, we find that the inclined shear produces largest extension, the rigid body model with horizontal detachment produces the smallest extension, and the vertical shear model produces moderate extension. 展开更多
关键词 Fault Rotation Fault drag Fault Displacement EXTENSION Forward Model
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Parametric Optimization of Wheel Spoke Structure for Drag Reduction of an Ahmed Body
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作者 Huihui Zhai Dongqi Jiao Haichao Zhou 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第4期955-975,共21页
The wheels have a considerable influence on the aerodynamic properties and can contribute up to 25%of the total drag on modern vehicles.In this study,the effect of the wheel spoke structure on the aerodynamic performa... The wheels have a considerable influence on the aerodynamic properties and can contribute up to 25%of the total drag on modern vehicles.In this study,the effect of the wheel spoke structure on the aerodynamic performance of the isolated wheel is investigated.Subsequently,the 35°Ahmed body with an optimized spoke structure is used to analyze the flow behavior and the mechanism of drag reduction.The Fluent software is employed for this investigation,with an inlet velocity of 40 m/s.The accuracy of the numerical study is validated by comparing it with experimental results obtained from the classical Ahmed model.To gain a clearer understanding of the effects of the wheel spoke parameters on the aerodynamics of both the wheel and Ahmedmodel,and five design variables are proposed:the fillet angleα,the inside arc radius R1,the outside radius R2,and the same length of the chord L1 and L2.These variables characterize the wheel spoke structure.The Optimal Latin Hypercube designmethod is utilized to conduct the experimental design.Based on the simulation results of various wheel spoke designs,the Kriging model and the adaptive simulated annealing algorithm is selected to optimize the design parameters.The objective is to achieve the best combination for maximum drag reduction.It is indicated that the optimized spoke structure resulted in amaximum drag reduction of 5.7%and 4.7%for the drag coefficient of the isolated wheel and Ahmed body,respectively.The drag reduction is primarily attributed to changes in the flow state around the wheel,which suppressed separation bubbles.Additionally,it influenced the boundary layer thickness around the car body and reduced the turbulent kinetic energy in the wake flow.These effects collectively contributed to the observed drag reduction. 展开更多
关键词 Ahmed body wheel spoke design parameter optimization drag reduction numerical simulation
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Effects of Crosswise Appendage Plate Flexibility on the Drag Reduction Characteristics of Cylinder
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作者 Jiyao Yang Xiaomei Ye +1 位作者 Guoyi He Feng Yu 《Journal of Applied Mathematics and Physics》 2024年第6期2032-2040,共9页
In engineering applications (Like an ocean riser), fluid flow around bluff bodies generates substantial resistance, which can jeopardize structural integrity, lifespan, and escalate resource consumption. Therefore, em... In engineering applications (Like an ocean riser), fluid flow around bluff bodies generates substantial resistance, which can jeopardize structural integrity, lifespan, and escalate resource consumption. Therefore, employing drag reduction measures becomes particularly crucial. This paper employs the immersed boundary method to investigate the impact of transversely oriented appendage plate flexibility on the drag of cylinders under different Reynolds numbers and distances. The results indicate that flexible appendage plate exerts drag reduction effects on the downstream cylinder, with this effect gradually diminishing as Reynolds numbers increase. At identical Reynolds numbers, the drag reduction effect initially increases and then decreases with distance, with the optimal drag reduction distance observed at D = 2.5. Compared to cylinders without appendage plate, the maximum drag reduction achieved is 30.551%. Addressing the drag reduction issue in cylinders holds significant importance for ensuring engineering structural integrity, enhancing engineering efficiency, and developing novel underwater towing systems. 展开更多
关键词 Appendage Plate FLEXIBILITY Cylinder Flow drag Reduction
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TRANSONIC DRAG REDUCTION ON SUPERCRITICAL WING SECTION USING SHOCK CONTROL BUMPS 被引量:3
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作者 杨洋 刘学强 Asif Saeed 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2012年第3期207-214,共8页
Two-dimensional and three-dimensional shock control contour bumps are designed for a supercritical wing section with the aim of transonic wave drag reduction. The supercritical airfoil (NASA SC (02)-0714) is selec... Two-dimensional and three-dimensional shock control contour bumps are designed for a supercritical wing section with the aim of transonic wave drag reduction. The supercritical airfoil (NASA SC (02)-0714) is selected considering the fact that most modern jet transport aircrafts that operate in the transonic flow regime (cruise at transonic speeds) employ supercritical airfoil sections. Here it is to be noted that a decrease in the transonic wave drag without loss in lift would result in an increased lift to drag ratio, which is a key range parameter that can potentially increase both the range and endurance of the aircraft. The major geometric bump parameters such as length, height and span are altered for both the two-dimensional and three-dimensional bumps in order to obtain the optimum location and shape of the bump. Once an optimum standalone three-dimensional bump is acquired, an array of bumps is manually placed spanwise of an unswept supercritical wing and analyzed under fully turbulent flow conditions. Different configurations are tested with varying three-dimensional bump spacing in order to determine the contribution of bump spacing on overall performance. The results show a 14% drag reduction and a consequent 16% lift to drag ratio rise at the design Mach number for the optimum arrangement of bumps along the wing span. 展开更多
关键词 shock control bumps TRANSONIC supercritical wing drag reduction
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Drag-free卫星编队的发展现状和趋势研究 被引量:4
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作者 张锦绣 曹喜滨 +1 位作者 董晓光 王继河 《哈尔滨工业大学学报》 EI CAS CSCD 北大核心 2010年第5期673-677,共5页
分析了Drag-free卫星编队的发展历程,就动力学建模与系统控制方法进行了综合调研和分析,提出了Drag-free卫星编队的应用前景和需要解决的关键技术,为我国未来空间环境与空间天气等超高精密探测奠定一定的基础.
关键词 drag-free卫星 卫星编队 空间环境探测
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Multi-SPline Technique for the Extraction of Drag Coeffidents from Radar Data 被引量:2
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作者 祁载康 《Journal of Beijing Institute of Technology》 EI CAS 1994年第1期42+33-42,共11页
In the preparation of firing tables, the determination of projectile drag coefficientsthrough firing test radar data reduction is very important. Many methods have been developed for this work but none of them appear ... In the preparation of firing tables, the determination of projectile drag coefficientsthrough firing test radar data reduction is very important. Many methods have been developed for this work but none of them appear to be satisfactory in one Way or another. Inthis paper a multi-spline model of drag coefficient (cd) curve is developed that can guaranteefirst derivative continuity of the cd curve and has good flexibility of fitting accurately to acd curve from subsonic up to supersonic range. Practical firing data reduction tests showboth fast convergence and accurate fitting results. Typical velocity fitting RMS errors are0.05-0.08 m/s. 展开更多
关键词 aerodynamic drag data reduction firing tables/aerodynarnic identification radar data reduction
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近地单质量块Drag-Free卫星自适应控制方法 被引量:2
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作者 董晓光 曹喜滨 +1 位作者 张锦绣 施梨 《哈尔滨工业大学学报》 EI CAS CSCD 北大核心 2013年第1期1-6,共6页
为了实现Drag-Free卫星中卫星本体对内部质量块的高精度跟踪,首先推导了近地环境下卫星与质量块的相对运动动力学方程,并分析了影响二者相对运动的主要干扰源,针对单质量块Drag-Free卫星的位移模式设计了自适应控制器,适用于卫星质量和... 为了实现Drag-Free卫星中卫星本体对内部质量块的高精度跟踪,首先推导了近地环境下卫星与质量块的相对运动动力学方程,并分析了影响二者相对运动的主要干扰源,针对单质量块Drag-Free卫星的位移模式设计了自适应控制器,适用于卫星质量和空间干扰为定常或慢变未知量的情况,且在卫星质量和外部干扰为未知常值的假设下,控制器能够保证卫星对质量块跟踪误差的全局渐近收敛,最后给出了仿真场景以说明本文方法的有效性. 展开更多
关键词 drag-Free卫星 位移模式 自适应控制 参数估计 干扰补偿
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仅有单个陀螺的Drag-free卫星初始速率阻尼模糊控制研究 被引量:1
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作者 党朝辉 项军华 刘昆 《上海航天》 2012年第1期6-11,共6页
研究了在仅有偏航姿态测量陀螺时,利用Drag-free卫星与其内部定向体间的相对状态观测值实现姿态确定的方法。针对Drag-free卫星的特点,建立了定向体的空间姿态观测模型和Drag-free卫星的姿态动力学方程,据此推导了用于姿态确定的Kalman... 研究了在仅有偏航姿态测量陀螺时,利用Drag-free卫星与其内部定向体间的相对状态观测值实现姿态确定的方法。针对Drag-free卫星的特点,建立了定向体的空间姿态观测模型和Drag-free卫星的姿态动力学方程,据此推导了用于姿态确定的Kalman滤波算法。为实现初始速率阻尼阶段Drag-free卫星的三轴姿态稳定,设计了模糊控制律。仿真结果验证了方法的有效性。 展开更多
关键词 drag—free卫星 单个陀螺 初始速率阻尼 模糊控制
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基于大气阻力实时辨识的Drag-free卫星最优控制研究 被引量:1
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作者 党朝辉 项军华 曾国强 《上海航天》 2010年第6期6-10,60,共6页
研究了基于大气阻力实时辨识的Drag-free卫星最优控制。将Drag-free卫星和其内部的验证质量等效为两颗内、外编队卫星并建立动力学方程,推导了基于卫星和验证质量的相对运动状态观测值反演大气阻力的算法。建立了状态最优调节器模型,采... 研究了基于大气阻力实时辨识的Drag-free卫星最优控制。将Drag-free卫星和其内部的验证质量等效为两颗内、外编队卫星并建立动力学方程,推导了基于卫星和验证质量的相对运动状态观测值反演大气阻力的算法。建立了状态最优调节器模型,采用动态规划求解经典的二次型最优控制。对低轨圆轨道Drag-free卫星的仿真计算结果表明方法的求解精度较高,计算消耗较小。 展开更多
关键词 drag-free卫星 跟踪保持 最优控制 大气阻力 实时辨识
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Relevance of zero lift drag coefficient and lift coefficient to Mach number for large aspect ratio winged rigid body
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作者 董素荣 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2015年第3期270-274,共5页
Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics mo... Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics model of the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body is amended.The research indicates that the change trends of zero lift drag coefficient and lift coefficient to Mach number are similar.The calculation result and wind tunnel experiment data all verify the validity of the amended dynamics model by which to estimate the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body,and thus providing some technical reference to aerodynamics character analysis of the same types of winged rigid body. 展开更多
关键词 winged rigid body zero lift drag coefficient lift coefficient wind tunnel experiment dynamic characteristics
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Review on the applications and developments of drag reducing polymer in turbulent pipe flow 被引量:13
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作者 M.A.Asidin E.Suali +1 位作者 T.Jusnukin F.A.Lahin 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2019年第8期1921-1932,共12页
Drag reduction phenomenon in pipelines has received lots of attention during the past decades due to its potential engineering applications, especially in fluid transporting industries. Various methods to enhance drag... Drag reduction phenomenon in pipelines has received lots of attention during the past decades due to its potential engineering applications, especially in fluid transporting industries. Various methods to enhance drag reduction have been developed throughout the years and divided into two categories;non-additives method and additives method. Both categories have different types of methods, with different formulations and applications which will generally be discussed in this review. Among all the methods discussed, drag reduction using polymer additive is as one of the most enticing and desirable methods. It has been the subject of research in this field and has been studied extensively for quite some time. It is due to its ability to reduce drag up to 80% when added in minute concentrations. Reducing drag in the pipe will require less pumping power thus offering economic relieves to the industries. So, this paper will be focusing more on the use of polymer additives as drag reducing agent, the general formulations of the additives, major issues involving the use of drag reducing polymers, and the potential applications of it. However, despite the extensive works of drag reduction polymer, there are still no models that accurately explain the mechanism of drag reduction. More studies needed to be done to have a better understanding of the phenomenon. Therefore, future research areas and potential approaches are proposed for future work. 展开更多
关键词 Pipe LINES drag reduction POLYMER ADDITIVES drag REDUCING AGENTS
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Experimental Research and Mathematical Model of Drag Torque in Single-plate Wet Clutch 被引量:26
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作者 YUAN Shihua PENG Zengxiong JING Chongbo 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2011年第1期91-97,共7页
Reduction of drag torque is one of important potentials to improve transmission efficiency.Existing mathematical model of drag torque was not accurate to predict the decrease after oil film shrinking because of the di... Reduction of drag torque is one of important potentials to improve transmission efficiency.Existing mathematical model of drag torque was not accurate to predict the decrease after oil film shrinking because of the difficulty in modeling the flow pattern between two plates.Flow pattern was considered as laminar flow and full oil film in the gap between two plates in traditional model.Subsequent equivalent circumferential degree model presented an improvement in oil film shrinking due to centrifugal force,but was also based on full oil film in the gap,which resulted difference between model prediction and experimental data.The objective of this paper is to develop an accurate mathematical model for the above problem by using experimental verification.An experimental apparatus was set up to test drag torque of disengaged wet clutch consisting of single friction and separate plate.A high speed camera was used to record the flow pattern through transparent quartz disk plate.The visualization of flow pattern in the clearance was investigated to evaluate the characteristics of oil film shrinking.Visual test results reveal that the oil film begins to shrink from outer radius to inner radius at the stationary plate and only flows along the rotating plate after shrinking.Meanwhile,drag torque decreases sharply due to little contact area between the stationary plate and the oil.A three-dimensional Navier-Stokes (N-S) equation based on laminar flow is presented to model the drag torque.Pressure distributions in radial and circumferential directions as well as speed distributions are deduced.The model analysis reveals that the acceleration of flow in radial direction caused by centrifugal force is the key reason for the shrinking at the constant feeding flow rate.An approach to descript flow pattern was presented on the basis of visual observation.The drag torque predicted by the model agrees well with test data for non-grooved wet clutch.The proposed model enhances the precision for predicting drag torque,and lays down a framework on which some subsequent models are developed. 展开更多
关键词 wet clutches drag torque mathematical model laminar flow
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IMPROVED FORECASTING OF COLD AIR OUTBREAKS OVER SOUTHERN CHINA THROUGH OROGRAPHIC GRAVITY WAVE DRAG PARAMETERIZATION 被引量:8
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作者 钟水新 陈子通 +2 位作者 王刚 蒙伟光 黄荣 《Journal of Tropical Meteorology》 SCIE 2016年第4期522-534,共13页
The parameterization of gravity wave drag induced by sub-grid scale orography(GWDO), which has been used in the regional model based on the Global/Regional Assimilation and Prediction System for Tropical Mesoscale Mod... The parameterization of gravity wave drag induced by sub-grid scale orography(GWDO), which has been used in the regional model based on the Global/Regional Assimilation and Prediction System for Tropical Mesoscale Model(GRAPES_TMM), is extended to include the effect of mountain flow blocking drag(MBD). The extended scheme is evaluated against non-GWDO parameterization, including a cold air outbreak over southern China and a monthly verification in February 2012. The experiment results show that the GWDO and MBD parameterization both improves the forecasting of the cold air outbreaks over southern China, as well as alleviations of system bias of GRAPES_TMM.(1) The extended scheme alleviates the strong southerly wind and high surface temperature simulation during the cold air outbreak, especially over northern Guangxi and Guangdong(NGG) province, where local high surface temperature simulation reduces nearly 5 degree.(2) The MBD parameterization improves southerly wind simulations over NGG, as well as surface temperature forecasts improvement over Guangxi, Guizhou province and southern Yunnan-Guizhou plateau(YUP), and low level southerly wind simulation improvement over intertidal zone over south China.(3) The formation of MBD is mainly in the mountain area(Wuyi, Daba mountain, east of YUP) and coastal area. The MBD over plateau, which is mainly formed at the west of 105°E, is stronger and thicker than that over Nanling mountain.(4) The improvement of GWDO and MBD parameterization is stable in model physics. MBD parameterization demonstrates more overall improvements in the forecasts than GWDO, and the larger of the model forecast error is, the greater improvements of MBD contribute to. Overall, the extended GWDO scheme successfully improves the simulations of meteorological elements forecasting during cold air outbreaks. 展开更多
关键词 GRAPES_TMM GRAVITY wave drag induced by orographics MOUNTAIN flow BLOCKING drag southerly windbias
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Drag reduction behavior of hydrolyzed polyacrylamide/xanthan gum mixed polymer solutions 被引量:9
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作者 Mehdi Habibpour Peter E. Clark 《Petroleum Science》 SCIE CAS CSCD 2017年第2期412-423,共12页
Partially hydrolyzed polyacrylamide(HPAM)as the main component of slickwater fracturing fluid is a shear-sensitive polymer,which suffers from mechanical degradation at turbulent flow rates.Five different concentrati... Partially hydrolyzed polyacrylamide(HPAM)as the main component of slickwater fracturing fluid is a shear-sensitive polymer,which suffers from mechanical degradation at turbulent flow rates.Five different concentrations of HPAM as well as mixtures of polyacrylamide/xanthan gum were prepared to investigate the possibility of improving shear stability of HPAM.Drag reduction(DR)measurements were performed in a closed flow loop.For HPAM solutions,the extent of DR increased from 30%to67%with increasing HPAM concentration from 100 to1000 wppm.All the HPAM solutions suffered from mechanical degradation and loss of DR efficiency over the shearing period.Results indicated that the resistance to shear degradation increased with increasing polymer concentration.DR efficiency of 600 wppm xanthan gum(XG)was 38%,indicating that XG was not as good a drag reducer as HPAM.But with only 6%DR decline,XG solution exhibited a better shear stability compared to HPAM solutions.Mixed HPAM/XG solutions initially exhibited greater DR(40%and 55%)compared to XG,but due to shear degradation,DR%dropped for HPAM/XG solutions.Compared to 200 wppm HPAM solution,addition of XG did not improve the drag reduction efficiency of HPAM/XG mixed solutions though XG slightly improved the resistance against mechanical degradation in HPAM/XG mixed polymer solutions. 展开更多
关键词 Slickwater POLYACRYLAMIDE Xanthan gum drag reduction Shear stability
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Experimental demonstration of a new concept of drag reduction and thermal protection for hypersonic vehicles 被引量:18
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作者 Zonglin Jiang Yunfeng Liu Guilai Han Wei Zhao Key Laboratory of High Temperature Gas Dynamics, Institute of Mechanics, Chinese Academy of Sciences, 100190 Beijing, China 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2009年第3期417-419,共3页
A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front o... A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front of a blunt body into a conical shock, and the lateral jets work to protect the spike tip from overheating and to push the conical shock away from the blunt body when a pitching angle exists during flight. Experiments are conducted in a hypersonic wind tunnel at a nominal Mach number of 6. It is demonstrated that the shock/shock interaction on the blunt body is avoided due to injection and the peak pressure at the reattachment point is reduced by 70% under a 4° attack angle. 展开更多
关键词 Hypersonic vehicle Shock-reconstruction. drag reduction Thermal protection Spike and lateral jets
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