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A prediction of drag reduction by entrapped gases in hydrophobic transverse grooves

Science China(Technological Sciences) 2013年第12期56卷 2973-2978页

作者： WANG Bao WANG JiaDao CHEN DaRong State Key Laboratory of Tribology Tsinghua University

The drag reduction effect of super-hydrophobic surface induced by the entrapped gas is unstable due to the gradual disappearance of the trapped *** this paper,a hydrophobic transverse grooved surface was designed to sustain gas in valleys.A detail numerical simulation was presented to investigate the flow field near the proposed *** water flowed over this surface,the entrapped gas was blocked by the ridges and the solid-liquid interface was replaced by the liquid-gas interface due to the entrapped gas,furthermore the micro-vortex formed in the *** there was an effective slippage between water and solid induced by the entrapped gas,the velocity gradient of boundary layer decreased,which contributed to a remarkable drag reduction ***,considering the extra undesired pressure drag reduction which negatively impacted the drag reduction effect of this method,the total drag coefficient including the viscous drag coefficient and the pressure coefficient was *** effective drag reduction rate of about 15%was achieved and the effect of this method was confirmed by experiments conducted in a high-speed water tunnel when grooves were optimized.

关键词： hydrophobic transverse groove gas skin-friction drag reduction computational fluid dynamics（cfd）

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Conceptual design and aerodynamic evaluation of hypersonic airplane with double flanking air inlets

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Science China(Technological Sciences) 2013年第10期56卷 1980-1988页

作者： CUI Kai HU ShouChao LI GuangLi QU ZhiPeng SITU Ming State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of Sciences The 31th Research Institute of CASIC

To aim at design requirements of high lift-to-drag ratio as well as high volumetric efficiency of next generation hypersonic airplanes,a body-wing-blending configuration with double flanking air inlets layout is ***,a novel forebody design methodology which by rotating and assembling two waverider-based surfaces is firstly introduced in this *** typical configurations are designed and their aerodynamic performances are evaluated by computational fluid *** results for forebodies analysis show that large volumetric efficiency,high lift-to-drag ratio,and uniformly distributed flowfield at the inlet cross section can be assured ***,results of numerical simulation of four integrated configurations with various leading edge shapes,including three power-law curves and a cosine curve clearly show the advantage of high lift-to-drag ***,the high pressure generated by the side wall of the airframe can be partly captured by the reasonably designed wings in the condition of small flight attack *** the order of lift-to-drag ratio of four configurations at 0 degree flight attack angle is completely different from the condition of 4-degree flight attack *** result demonstrates that the curve shape of the leading edge is very important for the lift-to-drag ratio of the aircraft,and it should be further optimized under the cruising attack angle in future work.

关键词： hypersonic flanking air inlet waverider computational fluid dynamics（cfd）

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cfd Simulation of Propane Cracking Tube Using Detailed Radical Kinetic Mechanism

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Chinese Journal of Chemical Engineering 2013年第12期21卷 1319-1331页

作者：张楠邱彤陈丙珍 Institute of Process Systems Engineering Tsinghua University Beijing 100080 China

In the radiant section of cracking furnace,the thermal cracking process is highly coupled with turbulent flow,heat transfer and mass *** this paper,a three-dimensional simulation of propane pyrolysis reactor tube is performed based on a detailed kinetic radical cracking scheme,combined with a comprehensive rigorous computational fluid dynamics(cfd)*** eddy-dissipation-concept(EDC)model is introduced to deal with turbulence-chemistry interaction of cracking gas,especially for the multi-step radical *** the high aspect ratio and severe gradient phenomenon,numerical strategies such as grid resolution and refinement,stepping method and relaxation technique at different levels are employed to accelerate *** scale of radial nonuniformity in the vicinity of the tube wall is *** distributions of each radical reaction rate are first studied,and made it possible to identify the dominant elementary ***,a series of operating conditions including the feedstock feed rate,wall temperature profile and heat flux profile towards the reactor tubes are *** obtained results can be used as scientific guide for further technical retrofit and operation optimization aiming at high conversion and selectivity of pyrolysis process.

关键词： numerical simulation cracking tube computational fluid dynamics（cfd） detailed radical kinetics

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Numerical Study on Flow-induced Noise for a Steam Stop-valve Using Large Eddy Simulation

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Journal of Marine Science and Application 2013年第3期12卷 351-360页

作者： Jiming Liu Tao Zhang Yong'ou Zhang School of Naval Architecture and Ocean Engineering Huazhong University of Science & Technology Wuhan 430074 China

The noise induced by the fluctuant saturated steam flow under 250 °C in a stop-valve was numerically *** simulation was carried out using computational fluid dynamics（cfd） and *** acoustic field was investigated with Lighthill＇s acoustic analogy based on the properties of the flow field obtained using a large-eddy simulation that employs the LES-WALE dynamic model as the sub-grid-scale ***,the validation of mesh was well conducted,illustrating that two million elements were sufficient in this ***,the treatment of the steam was deliberated,and conclusions indicate that when predicting the flow-induced noise of the stop-valve,the steam can be treated as incompressible gas at a low inlet ***,the flow-induced noises under different inlet velocities were *** findings reveal it has remarkable influence on the flow-induced ***,whether or not the heat preservation of the wall has influence on the noise was taken into *** results show that heat preservation of the wall had little influence.

关键词： flow-induced noise steam stop-valve flow field sound field large eddy simulation（LES） computational fluid dynamics（cfd） ACTRAN

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Limit Requirements Simulation of Sundial Solar Tracking Machine

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Chinese Journal of Mechanical Engineering 2012年第2期25卷 306-314页

作者： WANG Siyi SUN Youhong WANG Qingyan WANG Qinghua WEI Ming Construction Engineering School Jilin UniversityChangchun 130026China Jilin Sundial New Energy Resources Ltd. Changchun 130061China

Sundial solar tracking machines are machines that tracking the sun,and can promote sunshine receiving efficiency of solar *** operations are strongly influenced by wind *** studies were focused on tracking accuracy and tracking methods,the influence of wind load to the operation of the tracking machines has not caused enough attention,so that many tracking machines did not have the reasonable design basis,which led to unreasonable design and high maintenance costs,and had seriously influenced the application and popularization of the tracking ***,the 16 m2 sundial solar tracking machine is taken as research object from the perspective of wind load.A series of computational fluid dynamics（cfd） analyses are carried out on the model of the 16 m2 sundial solar tracking ***,in order to make cfd analyses carry on smoothly,after the three-dimensional solid model is established,the model is simplified,and grids are meshed on the simplified ***,in the virtual environment,to make the simulation closer to real but at the same time not too complex to make simulation hard to realize,assumptions of the nature of air flow are conducted,boundary conditions of the analyses are set reasonably,and appropriate cfd analysis solver is also ***,the results of the cfd analyses are also analyzed and sorted;and limit requirements（i.e.,force conditions of limit case）,such as the maximum load and the maximum total torque,are provided for the further finite element analyses（FEA） and the optimization design of the *** paper presents an effective computer simulation analysis method for the design and optimization of this type of solar tracking machine,and this method can greatly shorten the development cycle and cost.

关键词： gnomonics tracking machine wind load computational fluid dynamics（cfd） limit requirements

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A NOVEL DESIGN OF COMPOSITE WATER TURBINE USING cfd

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Journal of Hydrodynamics 2012年第1期24卷 11-16页

作者： PIECHNA Janusz MLLER Norbert Turbomachinery Laboratory Department of Mechanical EngineeringMichigan State UniversityEast LansingUSA

This paper presents computational investigation of a novel design of composite material axial water turbine using computational fluid dynamics（cfd）.Based on three-dimensional numerical flow analysis,the flow characteristics through the water turbine with nozzle,wheel and diffuser are *** extract power and torque of a composite water turbine at different rotating speeds were calculated and analyzed for a specific flow *** simulation results show that using nozzle and diffuser can increase the pressure drop across the turbine and extract more power from available water *** results provide a fundamental understanding of the composite water turbine,and this design and analysis method is used in the design process.

关键词： water turbine composite material computational fluid dynamics（cfd） extracted power

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Removal of SiC particles from solar grade silicon melts by imposition of high frequency magnetic field

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Transactions of Nonferrous Metals Society of China 2012年第11期22卷 2813-2821页

作者： Mehdi KADKHODABEIGI Jafar SAFARIAN Halvard TVEIT Merete TANGSTAD Stein Tore JOHANSEN Department of Materials Science and Engineering Norwegian University of Science and Technology (NTNU) P.O. Box 7491 Trondheim Norway SINTEF Materials and Chemistry Flow Technology Group P.O. Box 7465Trondheim Norway

Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon （MG-Si） was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics （cfd） were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.

关键词： SiC particle electromagnetic separation solar grade silicon （SoG-Si） photovoltaic cells computational fluid dynamics（cfd） non-metallic particles metallic impurities

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Effect of Radiant Spectral Characteristics on Performance of a Near-Infra-Red Heating Module

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Journal of Thermal Science 2011年第6期20卷 510-515页

作者： Ju-Hyun Kim Won-Taek Choi Minsub Han School of Mechanical System Engineering University of Incheon Araytech IncheonKorea

We simulated the heat transfer phenomena of the heating module that is primarily based on the radiant energy in the near-infra-red(NIR) *** the module,the power emitted by the lamp filament is distributed to the lamp glass,reflector,and the target medium,which are cooled by an air *** radiant heat transfer is simulated by using the ray-tracing scheme,in which the spectral characteristics of the emission and the materials are *** heat transport from the lamp glass to the cooling air is analyzed by using the finite volume *** the lamp-filament temperature rises in the range of 3000-3400K,the NIR radiant power on the target medium ***,the lamp-glass temperature also rises,and the proportion of the NIR power to the entire radiation has a peak in the temperature *** spectral distributions of the absorbed energies in all the components in the module are highly non-uniform,and a monochromatic model of the radiant heat transfer may result in a significant discrepancy.

关键词： computational fluid dynamics（cfd） Curing Drying Coating process

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Flow Field Characteristics for Parachute-projectile System

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Chinese Journal of Mechanical Engineering 2011年第5期24卷 813-819页

作者： ZHU Yong LIU Li WANG Zhengping School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China

In the current research for parachute flow field nowadays,the size of parachutes in previous research are so large compared with their carriers that the effects of the carriers wake flow to parachute are always *** from such large parachutes,the parachute size in this paper is on the same magnitude with the carrier,thus,the carrier can obviously affect the parachute flow *** this paper,flow field characteristics of small parachute for projectile decelerating are researched through two approaches,namely,computational fluid dynamics（cfd） simulation and wind tunnel *** parachutes with various sizes are chosen for ***,the cfd simulation of flow field around these parachutes is carried out,and then the cfd simulation of parachute-projectile systems is *** to the simulation results,the phenomenon is observed that in the simulations of parachutes there are two vortex-rings at the wind shadow of parachutes,however,in the second simulations of parachute-projectile systems,two additional vortex-rings emerge inside the *** to these two inner vortex-rings,the pressure inside parachutes *** a result,the drag of parachute in simulation of parachute-projectile systems is about 20% smaller compared with the prior *** order to verify the numerical results of cfd simulations,wind tunnel tests are *** terms of the data of the wind tunnel tests,the cfd simulation for flow field characteristics is reasonable and *** results of both cfd simulation and wind tunnel tests demonstrated the influence of projectile wake flow to parachute drag can not be neglected if the parachute size is on the same magnitude with *** influence to parachute drag from the ratio of projectile diameter to parachute diameter is also analyzed both in cfd simulations and wind tunnel *** approach combined cfd simulation and wind tunnel tests proposed can be used to guide the design of such parachute whose si

关键词： parachute projectile flow field computational fluid dynamics（cfd） wind tunnel test

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Flow-restricted Etching Method on Isotropic Substrates and Its Mechanism

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Chinese Journal of Mechanical Engineering 2010年第5期23卷 560-567页

作者： XIE Haibo ZHENG Yi FAN Yurun FU Xin YANG Huayong The State Key Lab of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

With the development of analytical instrumentation to minimization,integration and automation,the microfluidic chips,which are more integrated,complex and diversified,have been applied widely on the manufacturing of analytical ***,the present photolithography-based microfabrication technology,which is only able to pattern microchannels with simple inside structures,can not follow the rapid development of *** solving the problem,a fabrication method based on the restricting effect of laminar flow is proposed for the micro etching on isotropic *** were conducted inside glass-based microchannels,in which certain etchant was used to form complicated *** flow parameters＇ effects on the aspect ratio,side wall profile and etching rate were revealed by the *** experimental results reveal that the topography of micro structures patterned with the restricted flow etching method is mainly determined by the flowrates of separator and *** computational fluid dynamics（cfd） model on the interface between multiple streams was established for the etching process,and analysis on the causes of various micro topographies was conducted based on the cfd simulation *** experimental data consisted with the simulation results very *** investigation depicted in this paper indicate that the flow restricted etching method provides sufficient references for the research and understanding on the mass transport at the liquid-liquid surface in the microchannel and can be used to pattern complex micro structures with high aspect ratios,meantime,it greatly enriches the microfabrication technology for microfluidic chips.

关键词： microfluidics etching computational fluid dynamics（cfd） laminar

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