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Shape ratio effects on the mechanical characteristics of rectangular prism rocks and isolated pillars under uniaxial compression

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International Journal of Mining Science and Technology 2022年第2期32卷 347-362页

作者： Kun Du Xuefeng Li Rui Su Ming Tao Shizhan Lv Jia Luo Jian Zhou School of Resources and Safety Engineering Central South UniversityChangsha 410083China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China Hunan Research Institute for Nonferrous Metals CO. LTDChangsha 410100China

Isolated pillars in underground mines are subjected to uniaxial stress,and the load bearing cross-section of pillars is commonly rectangularly *** addition,the uniaxial compression test(UCT)is widely used for determining the basic mechanical properties of rocks and revealing the mechanism of isolated pillar disasters under unidimensional *** shape effects of rock mechanical properties under uniaxial compression are mainly quantitatively reflected in the specific shape ratios of ***,it is necessary to study the detailed shape ratio effects on the mechanical properties of rectangular prism rock specimens and isolated pillars under uniaxial compressive *** this study,granite,marble and sandstone rectangular prism specimens with various height to width ratios(r)and width to thickness ratios(u)were prepared and *** study results show that r and u have a great influence on the bearing ability of rocks,and thin or high rocks have lower uniaxial compressive *** the level of r can enhance the u effect on the strength of rocks,and increasing the level of u can enhance the r effect on the strength of *** lateral strain on the thickness side of the rock specimen is larger than that on the width side,which implies that crack growth occurs easily on the thickness *** r and u,a novel strength prediction model of isolated pillars was proposed based on the testing results,and the prediction model was used for the safety assessment of 179 isolated pillars in the Xianglu Mountain Tungsten Mine.

关键词： Uniaxial compression test Isolated pillar rectangular prism Shape ratio effect Failure property

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VORTEX FORMATION MECHANISM BEHIND THE rectangular prism WITH DEPTH TO HEIGHT RATIO OF 0.675

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 1990年第3期3卷 323-329页

作者： NAKAGAWA, T Max-Planck-Institut für Strömungsforschung Göttingen Federal Republic of Germany

This article is concerned with the vortex formation mechanism behind a rectangular prism with depth to height ratio of 0.675. A Mach-Zehnder interferometer is used for the high-speed flow visualization, and high-sensitivity pressure transducers are used for pressure measurement in the test section of the transonic wind tunnel. It is found that the main vortices primarily govern the vortex formation and vortex shedding from the rectangular prism, but motions of the cavities generated on the upper side surface or on the lower side surface, as well as those of the separating shear layers, are also essential in the vortex formation process. A detailed formation mechanism of the strong vortex behind the rectangular prism is discussed and proposed.

关键词： vortex shedding vortex formation flow separation rectangular prism

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Effect of wall proximity in fluid flow and heat transfer from a rectangular prism placed inside a wind tunnel

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2008年第3-4期51卷 736-746页

作者： Chakrabarty, Dipes Brahma, Ranajit Kumar MCKV Inst Engn Dept Automobile Engn Liluah 711204 W Bengal India Indian Inst Technol Dept Mech Engn Kharagpur 721302 W Bengal India

Experimental investigations in fluid flow and heat transfer have been carried out to study the effect of wall proximity due to flow separation around rectangular prisms. Experiments have been carried out for the Reynolds number 4.9 x 10(4), blockage ratios are 0.1, 0.2, 0.3 and 0.4, aspect ratio (d/c) are 1.5, 1.33, 0.667 and 0.333, different height-ratios and various angles of attack. The static pressure distribution has been measured on all faces of the rectangular prisms. The results have been presented in the form of pressure coefficient, drag coefficient for various height-ratios and blockage ratios. The pressure distribution shows positive values on the front face whereas on the rear face negative values of the pressure coefficient have been observed. The positive pressure coefficient for different height-ratios does not vary too much but the negative values of pressure coefficient are higher for all points on the surface as the bluff body approaches the upper wall of the wind tunnel. The drag coefficient decreases with the increase in angle of attack as the height-ratio decreases. There is no definite angle of attack for all blockage ratios and Reynolds numbers at which the value of drag coefficient is either maximum or minimum. The heat transfer experiments have been carried out under constant heat flux condition. Heat transfer coefficient are determined from the measured wall temperature and ambient temperature and presented in the form of Nusselt number. Both local and average Nusselt numbers have been presented for various height-ratios. The variation of local Nusselt number has been shown with non-dimensional distance for different angles of attack and blockage ratios. The variation of average Nusselt number has also been shown with different angles of attack for blockage ratios. The local as well as average Nusselt number decreases as the height-ratio decreases for all non-dimensional distance and angle of attack, respectively, for rectangular prisms. T

关键词： flow separation rectangular prism blockage ratio height-ratio angle of attack pressure coefficient drag coefficient Nusselt number

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Rankine combined vortex interaction with a rectangular prism

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INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS 2015年第1期29卷 120-132页

作者： Gorecki, Piotr Selvam, Rathinam Panneer Univ Arkansas Dept Civil Engn Fayetteville AR 72701 USA

Large eddy simulation is utilised to study the three-dimensional interaction between a travelling Rankine combined vortex and a rectangular prism. The study examines the strength and the topology of a vortex during the interaction with a prism that is much wider than the vortex core diameter. The physics of the interaction is revealed for the straight (beta = 0 degrees) and the oblique (beta = 45 degrees) impacts. For both cases, the low-level portion of the vortex undergoes displacements in the streamwise and the lateral directions. Also the vortex shape and the core vorticity are substantially disrupted. Behind the prism the full vortex circulation is recovered after a considerable distance. This created a low-velocity region. The sheltering effect of the prism is noticed for both straight and oblique impacts. The flow velocities in the sheltering region, right behind the prism, are reduced by more than 42% compared to the maximum flow speeds before the interaction.

关键词： large eddy simulation rectangular prism tornado-like flow Rankine combined vortex model vortex-structure interaction sheltering effect vortex flow

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Spatial Distribution of Gusty Loads on a rectangular prism in Boundary Layer Flows

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KSCE JOURNAL OF CIVIL ENGINEERING 2018年第8期22卷 3052-3065页

作者： Zeng, Jiadong Li, Mingshui Li, Shaopeng Ma, Ruwei Southwest Jiaotong Univ Res Ctr Wind Engn Chengdu Sichuan Peoples R China Key Lab Wind Engn Sichuan Prov Chengdu Sichuan Peoples R China Chongqing Univ Sch Civil Engn Chongqing Peoples R China

The pressure fluctuations acting on a stationary rectangular prism with cross configuration (2:1/1:2) are investigated by wind tunnel testing. The synchronous surface pressures on the rigid model were measured in simulated atmospheric boundary layer flow and the unsteady forces were calculated by numerical integral of surface pressures. The effects of the wind fields and the model's side ratio on the aerodynamic coefficients, spectral characteristics and spatial correlation of aerodynamic loading were investigated. The main purpose of this study is to further analyze the spatial structure of the fluctuating wind loads acting on a rectangular prism as well as to use the cross correlation coefficient and coherence function to explore their distribution trends. The results show that the along-wind gust loading is consistent with the longitudinal turbulence and the across-wind aerodynamic force is mainly induced by the vortex-shedding, recirculation and reattachment of separation shear layers on the lateral sides. In practical applications, the Strouhal number is approximately constant along the height. Extended empirical coherence models of the fluctuating along-wind and across-wind loads are proposed with consideration to the effects of wind fields, the structure characteristics and dimensions of the prism and length scale.

关键词： rectangular prism aerodynamic loads atmospheric boundary flow coherence function wind tunnel test

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VIBRATIONS AND HEATING OF A VISCOELASTIC rectangular prism AND VISCOELASTIC FINITE CYLINDER IN THE CASE OF KINEMATIC EXCITATION

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SOVIET APPLIED MECHANICS 1984年第10期20卷 923-929页

作者： SENCHENKOV, IK CHERVINKO, OP Acad of Sciences of the Ukrainian SSR Inst of Mechanics Kiev USSR Acad of Sciences of the Ukrainian SSR Inst of Mechanics Kiev USSR

The problem stated in the title is important in the design of rubber-metal vibration dampers which operate in the range of wave-resonance frequencies. Based on exact solutions of the problems of dynamics of linear viscoelasticity, the resonance spectra and modes of vibration of such bodies in the lower part of the high-frequency region the effect of viscosity on the character of the vibrations, and certain features of vibrational heating of the bodies are examined. The main attention is given to the case of an incompressible material with temperature-independent mechanical characteristics. A prism of rectangular cross-section and a short solid cylinder are considered.

关键词： Finite Cylinders rectangular prism Excitation Vibration Heating kinematics

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Computational simulation of the turbulent flow around a surface mounted rectangular prism

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JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS 2015年 142卷 173-187页

作者： Joubert, E. C. Harms, T. M. Venter, G. Univ Stellenbosch Dept Mech & Mechatron Engn ZA-7600 Stellenbosch South Africa

Engineering structures considered as bluff bodies are often associated with complex unsteady turbulent flow structures that are not yet fully understood and difficult to reproduce numerically. One of the main challenges is to find a numerical model that accurately account for turbulence in the flow without using too much computational resources. In this paper the Spalart-Allmaras improved delayed detached eddy simulation (IDDES) turbulence model with an all-y(+) wall treatment is used to numerically reproduce the flow features around a rectangular cross-sectioned beam in a wind tunnel at a Reynolds number of 7.6 x 10(4). The beam is orientated with the long edge of the cross-section parallel to the flow and can be characterised by the ratios of L/D=2.63 and H/L= 5. The simulation results are compared to time-averaged experimental data which includes particle image velocimetry (PIV) and pressure. The comparison of the simulation results against experimental data shows that the Spalart-Allmaras IDDES model accurately reproduces the flow field around the beam with only minor discrepancies. Furthermore, the complex time-varying three-dimensional flow field is discussed in detail. Alternating vortex shedding occurs but this seems to be periodically interrupted. The Strouhal number over the height of the beam was found to vary between 0.053 and 0.059 which corresponds well with studies of similar LID ratios in the literature. The maximum cyclic loading was found to occur at a height of y = 0.5H and along the side wall at 0.8L from the upstream edge of the beam. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Bluff body aerodynamics rectangular prism Wind tunnel tests Computational simulation Detached eddy simulation OpenFOAM

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Fluid-structure interaction analysis of a 4:1 rectangular prism undergoing vortex-induced vibration

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JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS 2024年 254卷

作者： Zhang, Zhanbiao Xu, Fuyou Wang, Yuqi Wang, Xu Dalian Univ Technol Sch Infrastruct Engn Dalian 116024 Peoples R China

The vortex-induced vibration (VIV) characteristics and fluid-structure interaction mechanism of a 4:1 rectangular prism is investigated in this study based on large-eddy simulations. Variations of the vibration amplitude, vortex- induced force, and surface pressure with the inflow velocity (U*) U *) are analyzed. Some significant questions regarding the VIV responses are raised and explained based on dynamic mode decomposition (DMD) and phase analyses of the flow fields. The cooperative shedding process of the motion-induced leading-edge vortex and the Karmon-type trailing-edge vortex that sustains the VIV is identified in the DMD mode. It is found that the phase difference between the leading and trailing-edge vortices in the near wake increases with U *, leading to the eventual disappearance of VIV at a critical U *. The root-mean-squared lift coefficient ( C L _ rms ) reaches its highest value in the initial phase of lock-in range, and then shows a monotonic reduction with increasing U *. However, the structure could maintain a relatively large vibration amplitude until VIV disappears, even though the CL_rms L _ rms may be as low as that for the static case. This phenomenon is explained in detail based on the variations in phase distributions of the surface pressure with increasing U *.

关键词： rectangular prism Vortex-induced vibration Dynamic mode decomposition Large-eddy simulation Phase analyses

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Solution processed ZnO rectangular prism as an effective photoanode material for dye sensitized solar cells

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MATERIALS LETTERS 2015年 147卷 119-122页

作者： Al-Agel, F. A. Akhtar, M. Shaheer Alshammari, H. Alshammari, A. Khan, Shamshad A. Univ Hail Dept Phys Hail Saudi Arabia Chonbuk Natl Univ New & Renewable Energy Mat Dev Ctr New REC Jeonju South Korea Univ Hail Dept Chem Hail Saudi Arabia St Andrews Coll Dept Phys Gorakhpur 273001 Uttar Pradesh India

Well crystalline ZnO rectangular prism (ZnO-RP) nanomaterials were synthesized by a low temperature solution process and employed as photoanode materials for the dye sensitized solar cells (DSSCs). Synthesized nanomaterials featured the define rectangular prism morphology with the average thickness of similar to 100 nm and possessed typical hexagonal wurtzite structure. ZnO-RP photoanode presented a reasonable conversion efficiency (eta) of similar to 33% along with high short circuit current (J(SC)) of similar to 8.91 mA/cm(2), open circuit voltage (V-OC) of similar to 0.725 V and fill factor (FF) of similar to 0.51 in DSSC The rectangular shape of ZnO could provide high surface to volume ratio for dye absorption and light harvesting efficiency, which significantly resulted in high J(SO) and conversion efficiency of DSSC. (C) 2015 Elsevier B.V. All rights reserved.

关键词： ZnO rectangular prism Interfaces Solar energy materials Surface area

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POLARIZING rectangular prism USED IN LASER TECHNIQUES

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APPLIED OPTICS 1994年第33期33卷 7717-7719页

作者： ZHAO, MS LI, GH The authors are with the Laser Institute Qufu Normal University Qufu Shandong 273165 China.

A polarizing rectangular prism is presented. The prism has the advantages of low loss and a high extinction ratio and can be used in laser oscillators to replace polarizers and reflecting prisms.

关键词： POLARIZATION rectangular prism LASER TECHNIQUES

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