The southern margin of the Gurbantunggut Desert,China,is characterized by alternating layers of aeolian and alluvial deposits.Investigating the characteristics of arenaceous sediment in this area is of significant imp...The southern margin of the Gurbantunggut Desert,China,is characterized by alternating layers of aeolian and alluvial deposits.Investigating the characteristics of arenaceous sediment in this area is of significant importance for understanding the interactive processes of wind and water forces,as well as the provenance of sediment.However,there are relatively few investigations on the characteristics of such sediment at present.In this study,we researched three aeolian-alluvial interactive stratigraphic profiles and different types of surface sediment on the desert-oasis transitional zone of southern margin of the Gurbantunggut Desert.Based on the optically stimulated luminescence(OSL)dating of aeolian sand and analyses of quartz sand grain size and surface micro-texture,we explored the aeolian-alluvial environmental change at southern margin of the desert in Holocene,as well as the provenance of sediment.The results indicated that the grain size characteristics of different types of sediment in the stratigraphic profiles were similar to those of modern dune sand,interdune sand,muddy desert surface soil,and riverbed sand.Their frequency curves were unimodal or bimodal,and cumulative probability curves were two-segment or three-segment,mainly composed of suspension load and saltation load.The quartz sand in the sediment at southern margin of the desert had undergone alternating transformation of various exogenic forces,with short transportation distance and time,and sedimentary environment was relatively humid.In Holocene,southern margin of the desert primarily featured braided river deposits,and during intermittent period of river activity,there were also aeolian deposits such as sand sheet deposits,stabilized dune deposits,and mobile dune deposits.The provenance for Holocene alluvial deposits at southern margin of the desert remains relatively constant,with the debris of the Tianshan Mountains being the primary provenance.Aeolian sand is mainly near-source recharge,which is formed by in situ deposition of fluvial or lacustrine materials in southern margin of the desert transported by wind erosion,and its provenance was still the weathered debris of the Tianshan Mountains.In addition,the sand in interior of the desert may be transported by northwest wind in desert-scale,thus affecting the development of dunes in southern margin of the desert.The results of this study provide a reference for understanding the composition and provenance changes of desert sand in the context of global climate change.展开更多
Rectangular explosive charges are usually used in military or civilian explosive transportation and storage.The effects of shape parameters and detonation positions on the peak overpressure and maximum impulse of blas...Rectangular explosive charges are usually used in military or civilian explosive transportation and storage.The effects of shape parameters and detonation positions on the peak overpressure and maximum impulse of blasts lack comprehensive investigation,which is significant for the design of blast-resistant structures.In this paper,the side-length ratio of the rectangle,orientation,and detonation position of the charge are chosen as controlling parameters to investigate their influence on blast loads in the scaled distances of the gauges ranging from 0.63 to 10.54 m/kg^(1/3) with well validated 3D numerical simulations.The results show that there is a large difference in the near-field spatial distribution of the blast load of the rectangular charge;if the blast load of the rectangular charge is simply evaluated with the spherical charge,the maximum peak overpressure(maximum impulse)will be underestimated by a factor of 7.46(4.84).This must be taken seriously by blast-resistant structure designers.With the increase in the scaled distance,when the critical scaled distance is greater than 6.32(7.38)m/kg^(1/3),the influence of the charge shape on the maximum peak overpressure(maximum impulse)of the spatial blast load can be ignored.In general,the impact of detonation of the charge at the end on the maximum peak overpressure is greater compared with central detonation,but for the impact of the maximum impulse,it is necessary to pay attention to the side-length ratio of the rectangular charge and the specific detonation position on the end face.Furthermore,the structural response of steel plates placed at different azimuths under the blast load of a rectangular charge is preliminarily analyzed,and the results show that the deformation and energy of the plates are consistent with the distribution of the blast load.These analysis results provide a reference for the explosion protection design in near-field air explosions.展开更多
This study investigates the nonlinear dynamic properties of rotating functionally graded sandwich rectangular plates in a thermal environment.The nonlinear vibration equations for a rotating metal-ceramic functionally...This study investigates the nonlinear dynamic properties of rotating functionally graded sandwich rectangular plates in a thermal environment.The nonlinear vibration equations for a rotating metal-ceramic functionally graded sandwich rectangular plate in a thermal environment are derived using classical thin plate theory and Hamilton’s principle,considering geometric nonlinearity,temperature-dependent material properties,and power law distribution of components through the thickness.With cantilever boundary conditions,the flexural nonlinear differential equations of the rectangular sandwich plate are obtained via the Galerkin method.Since the natural vibration differential equations exhibit nonlinear characteristics,the multiscale method is employed to derive the expression for nonlinear natural frequency.An example analysis reveals how the natural frequency of a functionally graded sandwich rectangular plate varies with rotational speed and temperature.Results show that the nonlinear/linear frequency ratio increases with rotational angular velocity Ω and thickness-to-length ratio h/a,follows a cosine-like periodic pattern with the setting angle,and shows a sharp decrease followed by a rapid increase with increasing width-to-length ratio b/a.The derived analytical solutions for nonlinear frequency provide valuable insights for assessing the dynamic characteristics of functionally graded structures.展开更多
The growing need for enhanced heat dissipation is compelling the development of more effective heat exchangers.Innovation inspired by nature bionics,four types of leaf-shaped pin fins were proposed and four combinatio...The growing need for enhanced heat dissipation is compelling the development of more effective heat exchangers.Innovation inspired by nature bionics,four types of leaf-shaped pin fins were proposed and four combinations of them were considered.The leaf-shaped design of the cooling pin fin enhances uniformity and synergy,effectively creating an optimized flow path that boosts cooling performance.Eight three-dimensional conjugate heat transfer models in staggered arrangement were developed using ANSYS-Fluent software.Aluminum6061material was used as the heat sinkmaterial and single-phase liquid water flowed through the rectangular channel where the Reynolds(R_(e))number varies from 40 to 100.Using the same boundary conditions as the software simulations,two leaf-shaped channels were printed to validate numerical models.Velocity field and temperature differences of the eight proposed leaf-shaped pin fins configurations were discussed by comparison with cylindrical pin fins.Based on the findings of this study,at a Reynolds number of 80,the Leaf B Staggered Array(LBSA)records a maximum temperature that is 0.72 K lower than that of the cylindrical pin fins arrangement.Additionally,the LBSA exhibits a reduction in the friction factor by approximately 33.3%relative to the circular pin fins array under the same R_(e).This implies that the design of LBSA has been optimized to provide better heat dissipation performance while maintaining lower energy consumption.Furthermore,the LBSA demonstrates the most favorable thermal-hydraulic performance index(TPI),which is 1.18 times higher than that of the circular pin fins arrangement at R_(e)=80.The temperature reduction and friction factor reduction of the lobed channel is more pronounced than that of the conventional cooling channel,highlighting its potential to increase heat transfer efficiency and reduce energy consumption in practical applications.展开更多
Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation...Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation of rectangular jacked pipes and the distribution of the earth pressure on jacked pipes,we present an analytical solution for predicting the vertical earth pressure on deep-buried rectangular pipe jacking tunnels,incorporating the tunnelling-induced ground loss distribution.Our proposed analytical model consists of the upper multi-layer parabolic soil arch and the lower friction arch.The key parameters(i.e.,width and height of friction arch B and height of parabolic soil arch H 1)are determined according to the existing research,and an analytical solution for K l is derived based on the distribution characteristics of the principal stress rotation angle.With consideration for the transition effect of the mechanical characteristics of the parabolic arch zone,an analytical solution for soil load transfer is derived.The prediction results of our analytical solution are compared with tests and simulation results to validate the effectiveness of the proposed analytical solution.Finally,the effects of different parameters on the soil pressure are discussed.展开更多
The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areex...The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areexamined,particularly,the combinations of rectangular solid and perforated blocks,used to create a disturbancein the flow.The analysis focuses on several key aspects and related metrics,including the temperature distribution,the mean Fanning friction factor,the pressure drop,the Nusselt number,and the overall heat transfer coefficientacross a range of Reynolds numbers(80–870).It is shown that the introduction of such blocks significantlyenhances the heat transfer performances of the MCHS compared to the straight-through flow channel.Specifically,a case is found where the Nusselt number increases by 2.3 times relative to the reference case.The integrationof perforated blocks facilitates the generation of vorticity within the channel,promoting the mixing of coldand hot fluids.Notably,MCHS incorporating perforated rectangular blocks exhibit more pronounced heat transferbenefits at Reynolds numbers smaller than 400.展开更多
To study the efect of micro-texture on the cutting performance of polyrystalline cubic boron nitide(PCBN)tools,five types of micro-textures(circular pits,eliptical grooves,transverse grooves,composite grooves,and wavy...To study the efect of micro-texture on the cutting performance of polyrystalline cubic boron nitide(PCBN)tools,five types of micro-textures(circular pits,eliptical grooves,transverse grooves,composite grooves,and wavy grooves)were applied to the rake surface of PCBN tools by an optical fber laser marking machine.Through a combination of three dimensional cutting simulations and experiments,the influences of micro-texture on chip-tool contact area,cutting force,chip morphology,shear angle,and surface roughness during the cuting process were analyzed.The results indicated that the chip--tool contact area and cutting force of both non-textured and micro textured tools increased with increasing cutting speed,while the shear angle decreased with increasing cutting speed.The chip-tool contact area and cutting force of the five types of micro-textured tools were smaller than those of the non textured tool The chip-tool contact area and cutting force obtained by the wavy-groove micro textured tool were the smallest.The chip radius produced by the five types of micro-textured tools was smaller than that produced by the non-textured tool,and the chip morphology was more stable.The transverse-groove micro-textured tool had a better chip breaking efect.The chip rnadius generated by the lliptical groove micro textured tool was 0.96 cm,while that generated by the wavy-groove tool varied from 0.55 cm to 1.26 cm.The presence of a micro-texture reduced the surface roughness of the workpiece by 11.73%-56.7%.Under the same cutting conditions,the five types of micro-textured tools gave a smaller chip--tool contact area,cutting force,chip radius,and surface roughness and a larger shear angle than the non-textured tool.In addition,the elliptical groove and wavy-groove micro-textured tools had better cuting performance.展开更多
A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented fo...A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented for the first time. The identified micro-textures can be grouped into two categories： （i） Growth related textures in the form of coarse/fine-sieve morphology, fine-scale oscillatory zoning and resorption surfaces resulted when the equilibrium at the crystal-melt interface was fluctuated due to change in temperature or H20 or pressure or composition of the crystallizing melt; and （ii） morphological texture, like glomerocryst, synneusis, swallow-tailed crystal, microlite and broken crystals, formed by the influence of dynamic behavior of the crystallizing magma （convection, turbulence, degassing, etc.）. Each micro-texture has developed in a specific magmatic environment, accordingly, a first order magma plumbing model and crystallization dynamics are envisaged for the studied lava unit. Magma generated has undergone extensive fractional crystallization of An-rich plagioclase in stable magmatic environment at a deeper depth. Subsequently they ascend to a shallow chamber where the newly brought crystals and pre-existing crystals have undergone dynamic crystallization via dissolution-regrowth processes in a convective self- mixing environment. Such repeated recharge-recycling processes have produced various populations of plagioclase with different micro-textural stratigraphy in the studied lava unit. Intermittent degassing and eruption related decompression have also played a major role in the final stage of crystallization dynamics.展开更多
Fabrication of the surface micro-texture on the C-plane sapphire is undertaken by a355 nm Ultraviolet(UV)pulsed laser.The surface micro-textures of sapphire with different laser scanning line spacing ranging from 10 l...Fabrication of the surface micro-texture on the C-plane sapphire is undertaken by a355 nm Ultraviolet(UV)pulsed laser.The surface micro-textures of sapphire with different laser scanning line spacing ranging from 10 lm to 100 lm are obtained,where the selection range of scanning line spacing is controlled in the range of the groove width and plasma width to obtain a surface of high Peak-Valley(PV)value.A reasonable processing order is proposed to manufacture different types of surface micro-textures on sapphire by laser ablation trajectory regulation.In the multiple-passes laser ablation of sapphire by the UV nanosecond pulsed laser,the scanning lines in each direction is treated as once scanning.On this basis,the multiple processing can be carried out to avoid the influence of the subsequent scanning on the machined groove.In addition,the effect of different scanning line spacing on the PV value is quantified and different types of surface microtextures on sapphire,including the squares,the rhombuses and the hexagons,are successfully fabricated,which can be applied in the friction reduction or anti-reflection field.展开更多
Implicit large-eddy simulation of an over-expanded screeching rectangular jet is performed with a seventh-order finite difference scheme.Good agreement is found between the predicted flow-and acoustic fields with the ...Implicit large-eddy simulation of an over-expanded screeching rectangular jet is performed with a seventh-order finite difference scheme.Good agreement is found between the predicted flow-and acoustic fields with the experimental observations.Fourier decomposition,phase-averaging analysis and Spectral Proper Orthogonal Decomposition(SPOD)are used to investigate the origin of the screech,the shock leakage during the shear-layer flapping,and the distinguishing fluctuating characteristics in the minor-and major-axis plane of the rectangular jet.It finds that the screech is radiated from the end of the forth shock cell,where the interaction of the shock waves with the shear layer causes periodic leakages of shock-wave tips in the minor-axis plane,resulting in the generation of intense acoustic waves in the surrounding air.An obvious flapping mode at the same frequency of the screech is captured in the minor-axis plane and dominates the dynamic motions of the rectangular jet.The SPOD modes of pressure and velocity fluctuations at the screech frequency help to reveal the relationship between the screech generation and the coherent structures.展开更多
The microstructure and micro-texture in different areas of a friction stir(FS)-welded DP600 steel were investigated by means of electron backscatter diffraction.The volume fraction of martensite and non-polygonal ferr...The microstructure and micro-texture in different areas of a friction stir(FS)-welded DP600 steel were investigated by means of electron backscatter diffraction.The volume fraction of martensite and non-polygonal ferrite was evaluated based on the image quality(IQ)parameter.Analysis of grain boundaries revealed that the fraction of sub-grain boundaries as well as that of low-angle grain boundaries in the heat-affected zone(HAZ)and stir zone(SZ)was more than doubled compared to those in the DP600 steel base metal(BM).The micro-texture examination of the BM showed strong{112}<110>and{111}<112>components with an intensity 4.6 times of that random texture.The texture showed a memory effect in the HAZ,with a reduced overall intensity.Within the SZ,D_(1),D_(2) and E shear texture components together with a cube component were developed.Formation of these texture components of ferrite were attributed to the transformation of B and R texture components of prior austenite,which are evidences of continuous dynamic recrystallization mechanism in the SZ of the friction stir-welded DP600 steel.展开更多
The aim of this study is to numerically investigate the impact of boundary slip on electroosmotic flow(EOF) in curved rectangular microchannels. Navier slip boundary conditions were employed at the curved microchannel...The aim of this study is to numerically investigate the impact of boundary slip on electroosmotic flow(EOF) in curved rectangular microchannels. Navier slip boundary conditions were employed at the curved microchannel walls. The electric potential distribution was governed by the Poisson–Boltzmann equation, whereas the velocity distribution was determined by the Navier–Stokes equation. The finite-difference method was employed to solve these two equations. The detailed discussion focuses on the impact of the curvature ratio, electrokinetic width, aspect ratio and slip length on the velocity. The results indicate that the present problem is strongly dependent on these parameters. The results demonstrate that by varying the dimensionless slip length from 0.001 to 0.01 while maintaining a curvature ratio of 0.5 there is a twofold increase in the maximum velocity. Moreover, this increase becomes more pronounced at higher curvature ratios. In addition, the velocity difference between the inner and outer radial regions increases with increasing slip length. Therefore, the incorporation of the slip boundary condition results in an augmented velocity and a more non-uniform velocity distribution. The findings presented here offer valuable insights into the design and optimization of EOF performance in curved hydrophobic microchannels featuring rectangular cross-sections.展开更多
This study proposes a novel open-type rectangular breakwater combined with horizontal perforated plates on both sides to enhance the sheltering effect of the rectangular box-type breakwaters against longer waves.The h...This study proposes a novel open-type rectangular breakwater combined with horizontal perforated plates on both sides to enhance the sheltering effect of the rectangular box-type breakwaters against longer waves.The hydrodynamic characteristics of this breakwater are analyzed through analytical potential solutions and experimental tests.The quadratic pressure drop conditions are exerted on the horizontal perforated plates to facilitate assessing the effect of wave height on the dissipated wave energy of breakwater through the analytical solution.The hydrodynamic quantities of the breakwater,including the reflection,transmission,and energyloss coefficients,together with vertical and horizontal wave forces,are calculated using the velocity potential decomposition method as well as an iterative algorithm.Furthermore,the reflection and transmission coefficients of the breakwater are measured by conducting experimental tests at various wave periods,wave heights,and both porosities and widths of the horizontal perforated plates.The analytical predicted results demonstrate good agreement with the iterative boundary element method solution and measured data.The influences of variable incident waves and structure parameters on the hydrodynamic characteristics of the breakwater are investigated through further calculations based on analytical solutions.Results indicate that horizontal perforated plates placed on the water surface for both sides of the rectangular breakwater can enhance the wave dissipation ability of the breakwater while effectively decreasing the transmission and reflection coefficients.展开更多
The dynamic control equation of a new prestressed partially concrete-filled rectangular steel tube(CFRT)beam can be derived based on D’Alembert’s principle.It is used to infer the theoretical results of the dynamic ...The dynamic control equation of a new prestressed partially concrete-filled rectangular steel tube(CFRT)beam can be derived based on D’Alembert’s principle.It is used to infer the theoretical results of the dynamic characteristics for the prestressed CFRT beam.Additionally,the finite element model is set up by ABAQUS for simulation analysis.The results show that the natural vibration frequencies and mode function of the prestressed CFRT simply supported beam calculated by the theoretical formulas are reliable since the relative errors of the first-order frequencies under different prestressing levels are within 6%compared with the finite element results.Further analysis of the prestressing parameters is carried out using the theoretical formulas,in which factors such as the prestressing level,eccentricity of tendons,and tensile stiffness of prestressed tendons have different influences on the natural vibration frequencies.Finally,it provides a theoretical basis for the dynamic design of the prestressed CFRT beams.展开更多
Tunnel heading stability in two dimensions(2D)has been extensively investigated by numerous scholars in the past decade.One significant limitation of 2D analysis is the absence of actual tunnel geometry modeling with ...Tunnel heading stability in two dimensions(2D)has been extensively investigated by numerous scholars in the past decade.One significant limitation of 2D analysis is the absence of actual tunnel geometry modeling with a considerable degree of idealization.Nevertheless,it is possible to study the stability of tunnels in three dimensions(3D)with a rectangular shape using finite element limit analysis(FELA)and a nonlinear programming technique.This paper employs 3D FELA to generate rigorous solutions for stability numbers,failure mechanisms,and safety factors for rectangular-shaped tunnels.To further explore the usefulness of the produced results,multivariate adaptive regression spline(MARS)is used for machine learning of big dataset and development of design equations for practical design applications.The study should be of great benefit to tunnel design practices using the developed equations provided in the paper.展开更多
基金the National Natural Science Foundation of China(42071011)the 2023 Annual Postgraduate Research and Innovation Foundation of Fujian Normal University,China.
文摘The southern margin of the Gurbantunggut Desert,China,is characterized by alternating layers of aeolian and alluvial deposits.Investigating the characteristics of arenaceous sediment in this area is of significant importance for understanding the interactive processes of wind and water forces,as well as the provenance of sediment.However,there are relatively few investigations on the characteristics of such sediment at present.In this study,we researched three aeolian-alluvial interactive stratigraphic profiles and different types of surface sediment on the desert-oasis transitional zone of southern margin of the Gurbantunggut Desert.Based on the optically stimulated luminescence(OSL)dating of aeolian sand and analyses of quartz sand grain size and surface micro-texture,we explored the aeolian-alluvial environmental change at southern margin of the desert in Holocene,as well as the provenance of sediment.The results indicated that the grain size characteristics of different types of sediment in the stratigraphic profiles were similar to those of modern dune sand,interdune sand,muddy desert surface soil,and riverbed sand.Their frequency curves were unimodal or bimodal,and cumulative probability curves were two-segment or three-segment,mainly composed of suspension load and saltation load.The quartz sand in the sediment at southern margin of the desert had undergone alternating transformation of various exogenic forces,with short transportation distance and time,and sedimentary environment was relatively humid.In Holocene,southern margin of the desert primarily featured braided river deposits,and during intermittent period of river activity,there were also aeolian deposits such as sand sheet deposits,stabilized dune deposits,and mobile dune deposits.The provenance for Holocene alluvial deposits at southern margin of the desert remains relatively constant,with the debris of the Tianshan Mountains being the primary provenance.Aeolian sand is mainly near-source recharge,which is formed by in situ deposition of fluvial or lacustrine materials in southern margin of the desert transported by wind erosion,and its provenance was still the weathered debris of the Tianshan Mountains.In addition,the sand in interior of the desert may be transported by northwest wind in desert-scale,thus affecting the development of dunes in southern margin of the desert.The results of this study provide a reference for understanding the composition and provenance changes of desert sand in the context of global climate change.
基金supported by the National Science Foundation of China(Grant No.14102428)the Fundamental Research Funds for the Central Universities(Grant Nos.WK2090000019 and YD2480002002)the Open Research Fund of Anhui Province Key Laboratory of Green Building and Assembly Construction,Anhui Institute of Building Research&Design(Grant No.2021-JKYL-005).
文摘Rectangular explosive charges are usually used in military or civilian explosive transportation and storage.The effects of shape parameters and detonation positions on the peak overpressure and maximum impulse of blasts lack comprehensive investigation,which is significant for the design of blast-resistant structures.In this paper,the side-length ratio of the rectangle,orientation,and detonation position of the charge are chosen as controlling parameters to investigate their influence on blast loads in the scaled distances of the gauges ranging from 0.63 to 10.54 m/kg^(1/3) with well validated 3D numerical simulations.The results show that there is a large difference in the near-field spatial distribution of the blast load of the rectangular charge;if the blast load of the rectangular charge is simply evaluated with the spherical charge,the maximum peak overpressure(maximum impulse)will be underestimated by a factor of 7.46(4.84).This must be taken seriously by blast-resistant structure designers.With the increase in the scaled distance,when the critical scaled distance is greater than 6.32(7.38)m/kg^(1/3),the influence of the charge shape on the maximum peak overpressure(maximum impulse)of the spatial blast load can be ignored.In general,the impact of detonation of the charge at the end on the maximum peak overpressure is greater compared with central detonation,but for the impact of the maximum impulse,it is necessary to pay attention to the side-length ratio of the rectangular charge and the specific detonation position on the end face.Furthermore,the structural response of steel plates placed at different azimuths under the blast load of a rectangular charge is preliminarily analyzed,and the results show that the deformation and energy of the plates are consistent with the distribution of the blast load.These analysis results provide a reference for the explosion protection design in near-field air explosions.
基金supported by the National Natural Science Foundation of China(No.11772090).
文摘This study investigates the nonlinear dynamic properties of rotating functionally graded sandwich rectangular plates in a thermal environment.The nonlinear vibration equations for a rotating metal-ceramic functionally graded sandwich rectangular plate in a thermal environment are derived using classical thin plate theory and Hamilton’s principle,considering geometric nonlinearity,temperature-dependent material properties,and power law distribution of components through the thickness.With cantilever boundary conditions,the flexural nonlinear differential equations of the rectangular sandwich plate are obtained via the Galerkin method.Since the natural vibration differential equations exhibit nonlinear characteristics,the multiscale method is employed to derive the expression for nonlinear natural frequency.An example analysis reveals how the natural frequency of a functionally graded sandwich rectangular plate varies with rotational speed and temperature.Results show that the nonlinear/linear frequency ratio increases with rotational angular velocity Ω and thickness-to-length ratio h/a,follows a cosine-like periodic pattern with the setting angle,and shows a sharp decrease followed by a rapid increase with increasing width-to-length ratio b/a.The derived analytical solutions for nonlinear frequency provide valuable insights for assessing the dynamic characteristics of functionally graded structures.
基金supported by the Shandong Provincial Natural Science Foundation,China(Grant ZR2024ME136).
文摘The growing need for enhanced heat dissipation is compelling the development of more effective heat exchangers.Innovation inspired by nature bionics,four types of leaf-shaped pin fins were proposed and four combinations of them were considered.The leaf-shaped design of the cooling pin fin enhances uniformity and synergy,effectively creating an optimized flow path that boosts cooling performance.Eight three-dimensional conjugate heat transfer models in staggered arrangement were developed using ANSYS-Fluent software.Aluminum6061material was used as the heat sinkmaterial and single-phase liquid water flowed through the rectangular channel where the Reynolds(R_(e))number varies from 40 to 100.Using the same boundary conditions as the software simulations,two leaf-shaped channels were printed to validate numerical models.Velocity field and temperature differences of the eight proposed leaf-shaped pin fins configurations were discussed by comparison with cylindrical pin fins.Based on the findings of this study,at a Reynolds number of 80,the Leaf B Staggered Array(LBSA)records a maximum temperature that is 0.72 K lower than that of the cylindrical pin fins arrangement.Additionally,the LBSA exhibits a reduction in the friction factor by approximately 33.3%relative to the circular pin fins array under the same R_(e).This implies that the design of LBSA has been optimized to provide better heat dissipation performance while maintaining lower energy consumption.Furthermore,the LBSA demonstrates the most favorable thermal-hydraulic performance index(TPI),which is 1.18 times higher than that of the circular pin fins arrangement at R_(e)=80.The temperature reduction and friction factor reduction of the lobed channel is more pronounced than that of the conventional cooling channel,highlighting its potential to increase heat transfer efficiency and reduce energy consumption in practical applications.
基金Project(2022YJS073)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2024YFE0198500)supported by the National Key Research and Development Program of China:Intergovernmental International Science and Technology Innovation CooperationProject(U2469207)supported by the National Natural Science Foundation Railway Innovation and Development Joint Fund Project,China。
文摘Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation of rectangular jacked pipes and the distribution of the earth pressure on jacked pipes,we present an analytical solution for predicting the vertical earth pressure on deep-buried rectangular pipe jacking tunnels,incorporating the tunnelling-induced ground loss distribution.Our proposed analytical model consists of the upper multi-layer parabolic soil arch and the lower friction arch.The key parameters(i.e.,width and height of friction arch B and height of parabolic soil arch H 1)are determined according to the existing research,and an analytical solution for K l is derived based on the distribution characteristics of the principal stress rotation angle.With consideration for the transition effect of the mechanical characteristics of the parabolic arch zone,an analytical solution for soil load transfer is derived.The prediction results of our analytical solution are compared with tests and simulation results to validate the effectiveness of the proposed analytical solution.Finally,the effects of different parameters on the soil pressure are discussed.
基金funded by the Project of the Hubei Provincial Department of Science and Technology(Grant No.2022CFB957)the Project of Hubei Engineering University of Teaching Research(Grant No.JY2024032)+1 种基金Ministry of Education University-Industry Cooperation Collaborative Education Project(Grant No.220903584161245)College Students’Innovation and Entrepreneurship Training Program(Grant Nos.DC2024031,DC2024032).
文摘The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areexamined,particularly,the combinations of rectangular solid and perforated blocks,used to create a disturbancein the flow.The analysis focuses on several key aspects and related metrics,including the temperature distribution,the mean Fanning friction factor,the pressure drop,the Nusselt number,and the overall heat transfer coefficientacross a range of Reynolds numbers(80–870).It is shown that the introduction of such blocks significantlyenhances the heat transfer performances of the MCHS compared to the straight-through flow channel.Specifically,a case is found where the Nusselt number increases by 2.3 times relative to the reference case.The integrationof perforated blocks facilitates the generation of vorticity within the channel,promoting the mixing of coldand hot fluids.Notably,MCHS incorporating perforated rectangular blocks exhibit more pronounced heat transferbenefits at Reynolds numbers smaller than 400.
基金the Basic Scientific Research Program of the Educational Commission of Liaoning Province,China(Grant No.L2017LQN024).
文摘To study the efect of micro-texture on the cutting performance of polyrystalline cubic boron nitide(PCBN)tools,five types of micro-textures(circular pits,eliptical grooves,transverse grooves,composite grooves,and wavy grooves)were applied to the rake surface of PCBN tools by an optical fber laser marking machine.Through a combination of three dimensional cutting simulations and experiments,the influences of micro-texture on chip-tool contact area,cutting force,chip morphology,shear angle,and surface roughness during the cuting process were analyzed.The results indicated that the chip--tool contact area and cutting force of both non-textured and micro textured tools increased with increasing cutting speed,while the shear angle decreased with increasing cutting speed.The chip-tool contact area and cutting force of the five types of micro-textured tools were smaller than those of the non textured tool The chip-tool contact area and cutting force obtained by the wavy-groove micro textured tool were the smallest.The chip radius produced by the five types of micro-textured tools was smaller than that produced by the non-textured tool,and the chip morphology was more stable.The transverse-groove micro-textured tool had a better chip breaking efect.The chip rnadius generated by the lliptical groove micro textured tool was 0.96 cm,while that generated by the wavy-groove tool varied from 0.55 cm to 1.26 cm.The presence of a micro-texture reduced the surface roughness of the workpiece by 11.73%-56.7%.Under the same cutting conditions,the five types of micro-textured tools gave a smaller chip--tool contact area,cutting force,chip radius,and surface roughness and a larger shear angle than the non-textured tool.In addition,the elliptical groove and wavy-groove micro-textured tools had better cuting performance.
文摘A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented for the first time. The identified micro-textures can be grouped into two categories： （i） Growth related textures in the form of coarse/fine-sieve morphology, fine-scale oscillatory zoning and resorption surfaces resulted when the equilibrium at the crystal-melt interface was fluctuated due to change in temperature or H20 or pressure or composition of the crystallizing melt; and （ii） morphological texture, like glomerocryst, synneusis, swallow-tailed crystal, microlite and broken crystals, formed by the influence of dynamic behavior of the crystallizing magma （convection, turbulence, degassing, etc.）. Each micro-texture has developed in a specific magmatic environment, accordingly, a first order magma plumbing model and crystallization dynamics are envisaged for the studied lava unit. Magma generated has undergone extensive fractional crystallization of An-rich plagioclase in stable magmatic environment at a deeper depth. Subsequently they ascend to a shallow chamber where the newly brought crystals and pre-existing crystals have undergone dynamic crystallization via dissolution-regrowth processes in a convective self- mixing environment. Such repeated recharge-recycling processes have produced various populations of plagioclase with different micro-textural stratigraphy in the studied lava unit. Intermittent degassing and eruption related decompression have also played a major role in the final stage of crystallization dynamics.
基金supported by the National Natural Science Foundation of China(No.51805257)the China Postdoctoral Science Foundation(No.2019TQ0151)+3 种基金the National Natural Science Foundation of China for Creative Research Groups(No.51921003)the Foundation of Graduate Innovation Center in NUAA,China(No.KFJJ20190502)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.KYCX19_0162)the Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology,China。
文摘Fabrication of the surface micro-texture on the C-plane sapphire is undertaken by a355 nm Ultraviolet(UV)pulsed laser.The surface micro-textures of sapphire with different laser scanning line spacing ranging from 10 lm to 100 lm are obtained,where the selection range of scanning line spacing is controlled in the range of the groove width and plasma width to obtain a surface of high Peak-Valley(PV)value.A reasonable processing order is proposed to manufacture different types of surface micro-textures on sapphire by laser ablation trajectory regulation.In the multiple-passes laser ablation of sapphire by the UV nanosecond pulsed laser,the scanning lines in each direction is treated as once scanning.On this basis,the multiple processing can be carried out to avoid the influence of the subsequent scanning on the machined groove.In addition,the effect of different scanning line spacing on the PV value is quantified and different types of surface microtextures on sapphire,including the squares,the rhombuses and the hexagons,are successfully fabricated,which can be applied in the friction reduction or anti-reflection field.
基金support of the National Natural Science Foundation of China(No.12372221)is acknowledged。
文摘Implicit large-eddy simulation of an over-expanded screeching rectangular jet is performed with a seventh-order finite difference scheme.Good agreement is found between the predicted flow-and acoustic fields with the experimental observations.Fourier decomposition,phase-averaging analysis and Spectral Proper Orthogonal Decomposition(SPOD)are used to investigate the origin of the screech,the shock leakage during the shear-layer flapping,and the distinguishing fluctuating characteristics in the minor-and major-axis plane of the rectangular jet.It finds that the screech is radiated from the end of the forth shock cell,where the interaction of the shock waves with the shear layer causes periodic leakages of shock-wave tips in the minor-axis plane,resulting in the generation of intense acoustic waves in the surrounding air.An obvious flapping mode at the same frequency of the screech is captured in the minor-axis plane and dominates the dynamic motions of the rectangular jet.The SPOD modes of pressure and velocity fluctuations at the screech frequency help to reveal the relationship between the screech generation and the coherent structures.
文摘The microstructure and micro-texture in different areas of a friction stir(FS)-welded DP600 steel were investigated by means of electron backscatter diffraction.The volume fraction of martensite and non-polygonal ferrite was evaluated based on the image quality(IQ)parameter.Analysis of grain boundaries revealed that the fraction of sub-grain boundaries as well as that of low-angle grain boundaries in the heat-affected zone(HAZ)and stir zone(SZ)was more than doubled compared to those in the DP600 steel base metal(BM).The micro-texture examination of the BM showed strong{112}<110>and{111}<112>components with an intensity 4.6 times of that random texture.The texture showed a memory effect in the HAZ,with a reduced overall intensity.Within the SZ,D_(1),D_(2) and E shear texture components together with a cube component were developed.Formation of these texture components of ferrite were attributed to the transformation of B and R texture components of prior austenite,which are evidences of continuous dynamic recrystallization mechanism in the SZ of the friction stir-welded DP600 steel.
基金Project supported by the Natural Science Foundation of Inner Mongolia of China(Grant No.2021BS01008)the Program for Innovative Research Team in Universities of Inner Mongolia Autonomous Region(Grant No.NMGIRT2323)the Scientific Research Funding Project for introduced high level talents of IMNU(Grant No.2020YJRC014)。
文摘The aim of this study is to numerically investigate the impact of boundary slip on electroosmotic flow(EOF) in curved rectangular microchannels. Navier slip boundary conditions were employed at the curved microchannel walls. The electric potential distribution was governed by the Poisson–Boltzmann equation, whereas the velocity distribution was determined by the Navier–Stokes equation. The finite-difference method was employed to solve these two equations. The detailed discussion focuses on the impact of the curvature ratio, electrokinetic width, aspect ratio and slip length on the velocity. The results indicate that the present problem is strongly dependent on these parameters. The results demonstrate that by varying the dimensionless slip length from 0.001 to 0.01 while maintaining a curvature ratio of 0.5 there is a twofold increase in the maximum velocity. Moreover, this increase becomes more pronounced at higher curvature ratios. In addition, the velocity difference between the inner and outer radial regions increases with increasing slip length. Therefore, the incorporation of the slip boundary condition results in an augmented velocity and a more non-uniform velocity distribution. The findings presented here offer valuable insights into the design and optimization of EOF performance in curved hydrophobic microchannels featuring rectangular cross-sections.
基金supported by the National Natural Sci-ence Foundation of China(Nos.52201345,and 52001293)the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘This study proposes a novel open-type rectangular breakwater combined with horizontal perforated plates on both sides to enhance the sheltering effect of the rectangular box-type breakwaters against longer waves.The hydrodynamic characteristics of this breakwater are analyzed through analytical potential solutions and experimental tests.The quadratic pressure drop conditions are exerted on the horizontal perforated plates to facilitate assessing the effect of wave height on the dissipated wave energy of breakwater through the analytical solution.The hydrodynamic quantities of the breakwater,including the reflection,transmission,and energyloss coefficients,together with vertical and horizontal wave forces,are calculated using the velocity potential decomposition method as well as an iterative algorithm.Furthermore,the reflection and transmission coefficients of the breakwater are measured by conducting experimental tests at various wave periods,wave heights,and both porosities and widths of the horizontal perforated plates.The analytical predicted results demonstrate good agreement with the iterative boundary element method solution and measured data.The influences of variable incident waves and structure parameters on the hydrodynamic characteristics of the breakwater are investigated through further calculations based on analytical solutions.Results indicate that horizontal perforated plates placed on the water surface for both sides of the rectangular breakwater can enhance the wave dissipation ability of the breakwater while effectively decreasing the transmission and reflection coefficients.
基金the National Natural Science Foundation of China(No.51878407)。
文摘The dynamic control equation of a new prestressed partially concrete-filled rectangular steel tube(CFRT)beam can be derived based on D’Alembert’s principle.It is used to infer the theoretical results of the dynamic characteristics for the prestressed CFRT beam.Additionally,the finite element model is set up by ABAQUS for simulation analysis.The results show that the natural vibration frequencies and mode function of the prestressed CFRT simply supported beam calculated by the theoretical formulas are reliable since the relative errors of the first-order frequencies under different prestressing levels are within 6%compared with the finite element results.Further analysis of the prestressing parameters is carried out using the theoretical formulas,in which factors such as the prestressing level,eccentricity of tendons,and tensile stiffness of prestressed tendons have different influences on the natural vibration frequencies.Finally,it provides a theoretical basis for the dynamic design of the prestressed CFRT beams.
基金supported by the Thailand Science Research and Innovation Fundamental Fund fiscal year 2023The fifth author (V.Kamchoom)acknowledges the financial support from the National Science,Research and Innovation Fund (NSRF)at King Mongkut's Institute of Technology Ladkrabang (KMITL),Thailand (Grant No.FRB66065/0258-RE-KRIS/FF66/53)+1 种基金the Climate Change and Climate Variability Research in Monsoon Asia (CMON3)from the National Research Council of Thailand (NRCT) (Grant No.N10A650844)the National Natural Science Foundation of China (NSFC).
文摘Tunnel heading stability in two dimensions(2D)has been extensively investigated by numerous scholars in the past decade.One significant limitation of 2D analysis is the absence of actual tunnel geometry modeling with a considerable degree of idealization.Nevertheless,it is possible to study the stability of tunnels in three dimensions(3D)with a rectangular shape using finite element limit analysis(FELA)and a nonlinear programming technique.This paper employs 3D FELA to generate rigorous solutions for stability numbers,failure mechanisms,and safety factors for rectangular-shaped tunnels.To further explore the usefulness of the produced results,multivariate adaptive regression spline(MARS)is used for machine learning of big dataset and development of design equations for practical design applications.The study should be of great benefit to tunnel design practices using the developed equations provided in the paper.
