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high-speed flow EROSION ON A NEW ROLLER COMPACTED CONCRETE DAM DURING CONSTRUCTION

Journal of Hydrodynamics 2012年第1期24卷 32-38页

作者： WANG Xin LUO Shao-ze HU Ya-an YUAN Qiang WANG He-sheng ZHAO Lan-hao Hydraulic Engineering Department Nanjing Hydraulic Research InstituteNanjing 210029China State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering -Nanjing 210098China College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing 210098China

A new roller compacted concrete dam of Fengman Hydropower Station is to be built in the toe of the old dam,which was identified as a dangerous *** new dam during construction would be influenced by the high-speed flow discharged from the old dam,which is an important problem to be considered for the first time in China,and which would affect the construction of the whole ***,a series of erosion experiments were conducted in this article.A high-speed flow erosion test apparatus was developed for the erosion experiments of the new dam *** maximum jet velocity goes up to 40 m/s and the section area of the nozzle is 0.0025 *** the process of experiments,the equipment shows a good *** wear tests for two types of materials used in the new dam,a roller compacted concrete and a distorted concrete with four kinds of ages were carried out with the flow velocity in the range of 30 m/s-35 m/*** parameters and erosion laws for the two types of concretes with different ages were determined,and a general relationship between the erosion rate and the flow velocity is obtained as：,with the velocity exponent between 3.33 and *** is concluded that the erosion resistance of the distorted concrete is better than that of the roller compacted concrete and the mechanical properties of the concretes of over 14 d age are influenced slightly by the water *** test results might serve as a practical technique guide for the safety of this project during its construction in the flood season.

关键词： high-speed flow impact apparatus erosion test roller compacted concrete hydraulic structures

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Drag Reduction Characteristics of Microstructure Inspired by the Cross Section of Barchan Dunes under high speed flow Condition

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Journal of Renewable Materials 2022年第3期10卷 781-797页

作者： Jiawei Jiang Yizhou Shen Jie Tao Zhenfeng Jia Xinyu Xie Chaojiao Zeng College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing210016China

A new type of microstructure inspired by the cross section of barchan dunes was proposed to reduce windage,which was considered as a passive drag reduction technology in aerospace manufacturing *** fluid dynamics method was carried out to discuss the effect of the microstructure on the skin friction reduction under high velocity flow *** microstructure heights were employed to survey the reduction of *** results illustrated that the appearance of microstructure led to a generation of pressure drag in non-smooth model(with microstructures inspired by cross section of barchan dune)in contrast to smooth ***,the microstructure significantly increased the thickness of the low-speed fluid by 11.4%in the near-wall flow field,causing the low-speed fluid to rise and decreasing the velocity gradient near the wall,thereby reducing viscous *** addition,high-speed fluid flowed above the microstructure units instead of along the inner side of the units due to the influence of micro-vortex,resulting in a reduction of friction near the ***-more,micro-vortex was considered to be the significant internal factor to achieve turbulent drag reduction since it could not only reduce the viscous resistance by promoting the fluid flow above the microstructure but also pro-vide a reverse thrust *** understanding of the mechanism of drag reduction provides theoretical guidance for further fabrication of drag reduction coatings using renewable materials.

关键词： Barchan dunes microstructure high-speed flow micro-vortex

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Gas-surface interaction features under effects of gas-gas molecules interaction in high-speed flows

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Chinese Journal of Aeronautics 2024年第5期37卷 228-242页

作者： Ruiling TAO Zhihui WANG School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Understanding interactions between gas molecules and solid surface is key to the aerodynamic design of high-speed,high-altitude aerospace vehicles,but there is a large dispersion of gas-surface interaction parameters or namely accommodation *** uncertainty results partly from different considerations of the interaction between gas molecules in various experimental and numerical *** this study,effects of gas-gas molecules interaction are systematically discussed by comparing two different approaches of molecular dynamics simulation of high-speed argon molecules scattering on a graphite *** popularly-used“single scattering”approach repeats the scattering process of a single gas molecule without considering the gas-gas molecules *** newly-developed“continual scattering”approach continually shoots gas molecules at the surface,considering collisions between gas molecules in addition to gas molecules’collisions with ***-surface interaction features in the two approaches are compared and discussed under various affecting factors including rarefaction degree,gas-surface interaction strength,surface temperature and incident *** is shown that these two approaches usually produce different accommodation coefficients,and the corresponding mechanisms are *** study could help clarify some doubts about the selection of accommodation coefficients in engineering practice,and also provide an instruction on design of an appropriate molecular dynamics simulation approach.

关键词： Gas-surface interaction Molecular dynamics Accommodation coefficient Aerospace vehicles high-speed flow

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Application of an impact plate-Bedload transport measuring system for high-speed flows

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International Journal of Sediment Research 2018年第1期33卷 35-46页

作者： Takahiro Koshiba Christian Auel Daizo Tsutsumi Sameh A.Kantoush Tetsuya Sumi Water Resources Research Center Disaster Prevention Research Institute Kyoto University ILF Consulting Engineers Hodaka Sedimentation Observatory Research Center for Fluvial and Coastal Disasters Disaster Prevention Research Institute Kyoto University

To achieve the sustainable use of dams, the development of methods for sediment management in reservoirs is required. One such method includes the use of Sediment Bypass Tunnels(SBTs) to divert sediment around a dam, thereby preventing sedimentation in the reservoir. However, SBTs are prone to severe invert abrasion caused by the high sediment flux. Therefore, it is necessary to establish a measurement system of the sediment transport rate in these tunnels. One system to measure sediment transport in rivers is the Swiss plate geophone, which can register plate vibrations caused by particle impact. In Japan, the Japanese pipe microphone is used, and sediment transport is measured based on the sound emitted by the particle impact. In this study an attempt was made to optimize the advantages of both systems by fixing a microphone and an acceleration sensor to a steel plate. The results of calibration experiments with this new system are presented and compared with the existing methods. It was found that the acceleration sensor can detect sediment particles larger than 2 mm in ***, a new parameter, referred to as the detection rate, was introduced to describe the correlation between the actual amount of sediment and the registered output. Finally, two parameters-the saturation rate and hit rate-are introduced and exhibit strong correlation with the detection rate.(?) 2018 International Research and Training Centre on Erosion and Sedimentation/the World Association

关键词： Sediment Bypass Tunnel Bedload Acoustic measurement Geophone Hydrophone high-speed flow

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A Comparison of Experimental and Numerical Studies Performed on a Low-Pressure Turbine Blade Cascade at high-speed Conditions, Low Reynolds Numbers and Various Turbulence Intensities

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Journal of Thermal Science 2013年第5期22卷 413-423页

作者： Jan Michalek Petr Straka VZLU - Aerospace Research and Test Establishment Beranovych 130 19500 PragueCzech Republic

This paper focuses on a comparison of experimental and numerical investigations performed on a low-pressure mid-loaded turbine blade at operating conditions comprised of a wide range of Math numbers （from 0.5 - 1.1）, Reynolds numbers （from 0.4e＋5 - 3.0e＋5）, flow incidence （-15 - 15 degrees） and three levels of free-stream tur- bulence intensities （2, 5 and 10%）. The experimental part of the work was performed in a high-speed linear cas- cade wind tunnel. The increased levels of turbulence were achieved by a passive grid placed at the cascade inlet. A two-dimensional flow field at the center of the blade was traversed pitch-wise upstream and downstream the cascade by means of a five-bole probe and a needle pressure probe, respectively. The blade loading was measured using the surface pressure taps evenly deployed at the blade mid-span along the suction and the pressure side. The inlet turbulence was investigated using the constant temperature anemometer technique with a dual sensor probe. Experimentally evaluated values of turbulent kinetic energy and its dissipation rate were then used as inputs for the numerical simulations. An in-house code based on a system of the Favre-averaged Navier-Stokes equation closed by a two-equation k-co turbulence model was adopted for the predictions. The code utilizes an algebraic model of bypass transition valid both for attached as for separated flows taking in account the effect of free-stream turbulence and pressure gradient. The resulting comparison was carried out in terms of the kinetic en- ergy loss coefficient, distributions of downstream wakes and blade velocity. Additionally a flow visualization was performed by means of the Schlieren technique in order to provide a further understanding of the studied phe- nomena. A few selected cases with a particular interest in the attached and separated flow transition are compared and discussed.

关键词： low pressure turbine high-speed flow low Reynolds number flow separation transition RANS

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Broadband design of acoustic metasurfaces for the stabilization of a Mach 4 boundary layer flow

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Advances in Aerodynamics 2022年第1期4卷 286-303页

作者： Rui Zhao Xiao Liu Chihyung Wen Xiaoyong Wang School of Aerospace Engineering Beijing Institute of TechnologyBeijing100081China Department of Aeronautical and Aviation Engineering The Hong Kong Polytechnic UniversityHong KongChina State Key Laboratory of high Temperature Gas Dynamics Institute of MechanicsChinese Academy of Sciences100190BeijingChina

A piecewise acoustic metasurface is designed to suppress the first mode while marginally amplifying the Mack second mode in a Mach 4 flat-plate boundary layer(BL)*** results of linear stability theory(LST)and the eN method demonstrate the stabilization effect and transition delay performance,***,the direct numerical simulation(DNS)results indicate that the designed broadband acoustic metasurface actually weakly excites the first mode with a slightly larger fluctuating pressure amplitude at the surface,which is in contrast to the analysis of *** discrepancies are found to lie in the‘roughness’effect caused by the recirculation zones inside the microslits and the alternating expansion and compression waves induced at the slit edges,which significantly amplifies the first *** further clarification of the competitive mechanism between the acoustic stabilization and‘roughness’destabilization effects of metasurfaces on the first mode,a carefully designed metasurface is installed at the maximum growth rate region,which excites the first mode on the metasurface but inhibits its development downstream.

关键词： Boundary layer stabilization Acoustic metasurfaces Mack modes high-speed flow

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THEMIS双卫星对磁尾高速流减速的联合观测

THEMIS双卫星对磁尾高速流减速的联合观测

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中国空间科学学会空间物理学专业委员会第十五届全国日地空间物理学研讨会

作者：商文赛尧中华史全岐孙为杰傅绥燕刘江田安民宗秋刚濮祖荫肖婷山东大学(威海)空间科学与物理学院北京大学地球与空间科学学院 IGPP/ESS University of California Los AngelesCA90095-1567USA

The motion and deceleration process of plasma sheet high speed flows have great significance to magnetospheric particle acceleration,magnetic field perturbation,triggering of substorm and formation of the substorm current *** February to April 2009 THEMIS and THEMIS are separated only along Z *** special configuration allows joint observations of high-speed flows at both the center and boundary of the plasma *** on case study and statistical analysis,we found that for 89%of the earthward high-speed flows,the probe far from the neutral sheet observed the high-speed flow first and the flow is mainly *** results also show that the X-component of the high-speed flow in the plasma sheet boundary is greater than that in central plasma *** the hypothesis that parallel flow remains the same speed during its propagation and central plasma sheet stream uniformly brakes,we deduced the location where the stream deceleration begins to be between 15Re and 20Re *** is consistent with near-earth reconnection site which have been proposed before in *** addition,the statistics showed that high speed flows in the central plasma sheet are accompanied by stronger dipolarization fronts than those in the plasma sheet boundary.

关键词： high-speed flow plasma sheet dipolarization fronts magnetic reconnection substorm

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