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Role of Dipole Jet in inclined Stroke Plane Kinematics of Insect Flight

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Journal of Bionic Engineering 2020年第1期17卷 161-173页

作者： Shanmugam Deepthi Sankaranarayanan Vengadesan Department of Applied Mechanics Indian Institute of Technology MadrasChennai 600036Tamil NaduIndia Department of Mechanical Engineering Virginia TechBlacksburgVAUSA

The two-dimensional(2D)inclined stroke plane kinematics of insect wing is studied for various stroke plane angles using the Immersed Boundary(IB)solver.The numerical results revealed the dominant lift enhancement mechanisms for this class of flows.The generated dipole was analyzed to find the maximum velocity,inclination and spread.The analysis of these dipole characteristics for the different stroke plane angles exposed the alternate method to study the vertical force variation with the stroke plane angles.Lift enhancement mechanisms and dipole characteristics complement the high vertical force coefficient for the stroke plane angle of 60?commonly used by dragonflies during hover.The location of the dipole identified a region of influence around the wing and demonstrated the role of the dipole jet in multi-body dynamics and wall effects.

关键词： insect flight bionic inclined stroke plane dipole jet flapping wing

Comparative study of AC and DC inclined plane tests on silicone rubber(SiR)insulation

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High Voltage 2017年第2期2卷 119-128页

作者： Sharif F.Kaaiye Cuthbert Nyamupangedengu School of Electrical and Information Engineering University of WitwatersrandJohannesburgSouth Africa

Currently there are no international standards for evaluating the tracking and erosion resistance of DC polymeric insulation under contaminated conditions.Researchers often modify the existing AC inclined plane test standards such as the IEC-60587 to accommodate DC voltage conditions but this has been reported to give various inconsistences.This paper presents comprehensive experimental results on inclined plane tests of silicone rubber(SiR)insulation at 3.5 and 4.5 kV AC and positive DC using intravenous(IV)system as the pollutant supply.The leakage currents(LC)were recorded throughout the entire tests.In addition,various physiochemical tests namely,Fourier Transform Infrared analysis,thermo-gravimetric analysis,scanning electron microscopy and energy dispersive spectroscopy were performed on the aged and unaged samples.Results show that DC LC is bigger(about three times)than that under AC for the same equivalent voltages.Furthermore,DC LC variations are less random and the average magnitudes increase with duration of voltage application compared with AC.The physiochemical analyses show that 3.5 kV_(rms) AC and 3.5 kV DC aged samples have comparable chemical characteristics albeit with electrode corrosion elements detected on the DC aged samples.Under 4.5 kV DC the degradation becomes significantly more severe and unrepeatable.It is therefore concluded that at 0.3 ml/min,pollutant flow rate,3.5 kV positive DC and 3.5 kV_(rms) AC are comparable as test voltages for inclined plane accelerated ageing of SiR insulation.

关键词： corrosion inclined plane

Dynamic response and optimization of an inclined steel rock shed by the graded energy dissipating method

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Journal of Mountain Science 2019年第1期16卷 138-152页

作者： WU Yong HE Si-ming LI Xin-po Wang Dong-po Key Laboratory of Mountain Hazards and Earth Surface Process Chinese Academy of Sciences Institute of Mountain Hazards and Environment Chinese Academy of Sciences State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology

Blocking rockfalls directly by reinforced concrete(RC) flat sheds with thick sand cushions is an outdated method. Such conventional sheds typically accumulate rock heavily, and become progressively damaged and are difficult to repair, and are very costly. To address these problems, we propose a new structure called a Graded Dissipating inclined Steel Rock(GDISR) shed that utilizes the graded energy dissipation method. Here, we study the dynamic response of the GDISR shed with model test and numerical simulation, and give its optimization design combining with a practical engineering case. Our results show that the optimized modular E-block and corrugated steel tube can deform to sufficiently absorb the energy of different impact intensities. This efficiently and economically provides GDISR sheds with two security lines. Compared with conventional RC sheds, GDISR sheds with optimal incline have a more efficient anti-impact function, are faster and easier to repair, and are much simpler and cheaper to build.

关键词： Dynamic response Optimization design Graded dissipating inclined steel rock shed

Numerical investigation on flow and heat transfer characteristics of supercritical RP-3 in inclined pipe

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Chinese Journal of Aeronautics 2019年第8期32卷 1885-1894页

作者： Zhi TAO Liangwei LI Jianqin ZHU Xizhuo HU Longyun WANG Lu QIU National Key Laboratory of Science and Technology on Aero-engine Aero-thermodynamics School of Energy and Power EngineeringBeihang UniversityBeijing 100083China College of Aeronautical Engineering Civil Aviation University of ChinaTianjin 300300China

Numerical simulations of flow and heat transfer to supercritical RP-3 through the inclined tubes have been performed using LS k–e model embedded in Fluent. The physical properties of RP-3 were obtained using the generalized corresponding state laws based on the fourcomponent surrogate model. Mass flow rate is 0.3 g/s, system pressure is 3 MPa, inlet temperature is 373 K. Inclination of the inclined pipe varied from -90° to 90°, with heat flux varied from 300 k W/m^2 to 400 kW/m^2. Comparison between the calculated result and the experimental data indicates the range of error reasonable. The results of ±45° show that temperature inhomogeneity in inclined pipe produce the secondary flow in its cross section due to the buoyancy force. Depending on the strength of the temperature inhomogeneity, there will be two different forms of secondary flow and both contribute to the convective heat transfer in the pipe. The secondary flow intensity decreases when the inhomogeneity alleviates and thermal acceleration will play a leading role. It will have a greater impact on the turbulent flow to affect the convective heat transfer in the pipe. When changing the inclination, it affects the magnitude of the buoyant component in flow direction. The angle increases, the buoyancy component decreases. And the peak temperature of wall dominated by the secondary flow will move forward and increase in height.

关键词： Heat transfer Hydrocarbon fuel inclined pipe Supercritical pressure Variable properties

Numerical Simulation on Flow Past Two Side-by-Side inclined Circular Cylinders at Low Reynolds Number

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China Ocean Engineering 2019年第3期33卷 344-355页

作者： LIU Cai GAO Yang-yang QU Xin-chen WANG Bin ZHANG Bao-feng Ocean College Zhejiang University Zhoushan 316021 China Powerchina Huadong Engineering Corporation Limited Hangzhou 311122 China

A series of three-dimensional numerical simulations is carried out to investigate the effect of inclined angle on flow behavior behind two side-by-side inclined cylinders at low Reynolds number Re=100 and small spacing ratio T/D=1.5 (T is the center-to-center distance between two side-by-side cylinders, D is the diameter of cylinder). The instantaneous and time-averaged flow fields, force coefficients and Strouhal numbers are analyzed. Special attention is focused on the axial flow characteristics with variation of the inclined angle. The results show that the inclined angle has a significant effect on the gap flow behaviors behind two inclined cylinders. The vortex shedding behind two cylinders is suppressed with the increase of the inclined angle as well as the flip-flop gap flow. Moreover, the mean drag coefficient, root-mean-square lift coefficient and Strouhal numbers decrease monotonously with the increase of the inclined angle, which follows the independent principle at small inclined angles.

关键词： two side-by-side inclined cylinders inclined angle wake flow pattern low Reynolds number axial flow

Static mechanics analysis of no bumping or vibration welding structure applied in high-speed & heavy-load CWR with single inclined surface

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Science China(Technological Sciences) 2010年第12期53卷 3153-3160页

作者： SONG YuQuan1, LUO WuWei2 & TAO Yi2 1 Jilin University, Changchun 130022, China 2 Shenyang Railway Bureau, Shenyang 110013, China Jilin University Changchun China Shenyang Railway Bureau Shenyang China

Nowadays, the sleeper, railroad bed, welding technology and materials of the high-speed & heavy-load Continuous Welded Rail (CWR) have been improved greatly. However, the orientation relationship between welding surface and rail is still orientation structure, which appeared 185 years ago in UK, namely, the welding surface is normal to the longitudinal direction of the rail. Thus rail welds are subject to vertical pure shear stress, lateral pure shear stress and axial pure tensile stress. Pure shear stress and pure tensile stress are both dangerous stresses, which result in failure of welds under high-speed & heavy-load condition for a long time. When the wheels pass rail welds, it is difficult to avoid vertical bumping and lateral vibration. In order to solve these problems, in this paper we put forward the single inclined welding surface having dip angle α with the lateral rail or dip angle β with the vertical rail and analyze the position geometry and stress state. Thus the vertical bumping and lateral vibration are basically eliminated, then the bearing capacity of the welding surface is significantly improved, and the stress of axial pure tensile and lateral pure shear of the welding surface is reduced.

关键词： continuous welded rail single inclined welding surface bearing capacity stress state regularity

A practical geometrical comparison between free-repelled hydraulic jumps within inclined channels

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Science China(Technological Sciences) 2009年第11期52卷 3363-3367页

作者： John Demetriou Eugene Retsinis National Technical University of Athens School of Civil Engineering. JD Research Hydrolab-A non Profit Foundation 12 Polykarpou St. N. Smymi Athens 17123 Greece National Technical University of Athens School of Civil Engineering. 23 Loid Tzortz St. Athens 11744 Greece

In this experimental study a practical geometrical comparison between inclined (angle φ) free and repelled hydraulic jumps (the latter in non prismatic but abruptly expanding channels) is presented, analysed and discussed. For repelled hydraulic jumps a considerable parameter is the expansion ratio r (=channels' width ratio), which here is changing from r =0.5 to r =0.7. The comparison is made with the free jump (in prismatic channel, r =1), in the same ranges of angles φ (0°≤φ≤8°) and Froude numbers (2≤Fr1≤8). A practical arithmetic example is presented to show the behavioral change of conjugate depths, lengths L and depths at 0.5L, in order to receive a comparison among all pertinent geometrical quantities. The present results may be useful for the hydraulic engineering when designing open channels.

关键词： free jumps repelled jumps inclined channels

Evolution of a mining induced fracture network in the overburden strata of an inclined coal seam

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International Journal of Mining Science and Technology 2012年第6期22卷 775-779页

作者： Wei Xiujun Gao Mingzhong Lv Youchang Shi Xiangchao Gao Hailian Zhou Hongwei Institue of Energy & Chemical Industry China Pingmei Shenma Group School of Hydraulic and Hydropower Engineering Sichuan University State Key Laboratory of Coal Resources and Safe Mining China University of Mining & Technology

The geological conditions of the Pingdingshan coal mining group were used to construct a physical model used to study the distribution and evolution of mining induced cracks in the overburden strata.Digital graphics technology and fractal theory are introduced to characterize the distribution and growth of the mining induced fractures in the overburden strata of an inclined coal seam.A relationship between fractal dimension of the fracture network and the pressure in the overburden strata is suggested.Mining induced fractures spread dynamically to the mining face and up into the roof as the length of advance increases.Moreover,the fractal dimension of the fracture network increases with increased mining length,in general,but decreases during a period from overburden strata separation until the main roof collapses.It is a1so shown that overburden strata pressure plays an important role in the evolution of mining induced fractures and that the fractal dimension of the fractures increases with the pressure of the overburden.

关键词： inclined coal seam Fracture network Evolution Fractal dimension

Cavitating Propeller Performance in inclined Shaft Conditions with OpenFOAM:PPTC 2015 Test Case

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Journal of Marine Science and Application 2018年第1期17卷 1-20页

作者： Stefano Gaggero Diego Villa Department of Electric ElectronicTelecommunications Engineering and Naval ArchitectureUniversity of Genoa16145 GenoaItaly

In this paper,we present our analysis of the non-cavitating and cavitating unsteady performances of the Potsdam Propeller Test Case(PPTC)in oblique flow.For our calculations,we used the Reynolds-averaged Navier-Stokes equation(RANSE)solver from the open-source OpenFOAM libraries.We selected the homogeneous mixture approach to solve for multiphase flow with phase change,using the volume of fluid(VoF)approach to solve the multiphase flow and modeling the mass transfer between vapor and water with the Schnerr-Sauer model.Comparing the model results with the experimental measurements collected during the SecondWorkshop on Cavitation and Propeller Performance– SMP’15 enabled our assessment of the reliability of the open-source calculations.Comparisons with the numerical data collected during the workshop enabled further analysis of the reliability of different flow solvers from which we produced an overview of recommended guidelines(mesh arrangements and solver setups)for accurate numerical prediction even in off-design conditions.Lastly,we propose a number of calculations using the boundary element method developed at the University of Genoa for assessing the reliability of this dated but still widely adopted approach for design and optimization in the preliminary stages of very demanding test cases.

关键词： Propeller Cavitation OpenFOAM RANSE BEM Unsteady flow PPTC inclined shaft