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| 1 | Some open problems in granular matter mechanics显示文摘Granular matter is a large assemblage of solid particles, which is fundamentally different from any other type of matters, such as solid and liquid. Most models presented for granular matter are phenomenological and are only suitable for solving engineering problems. Many fundamental mechanical problems remain open. By analyzing characteristics of internal state structure, we propose that granular matter is intrinsically multiscale, i.e. microscale of particle size, mesoscale of force chain, and macroscale of the bulk of granular matter. The correlations among difference scales would be crucial. The mesoscale force chain network is determined by both particle properties and macroscopic boundary conditions. The evolution of the force the chain network contributes to macroscopic mechanical properties of granular matter. In addition, we discuss the drawbacks in simplifying contact forces in the current models, and the difficulties in analyzing the interaction of interstitial fluid in wet granular matter. As an appropriate application of granular matter, debris flow can be studied with granular matter mechanics; meanwhile, debris flow brings more challenges which certainly motivate future studies on granular matter. | Qicheng Sun a, Guangqian Wanga, Kaiheng Hub a Department of Hydraulic Engineering, State Key Laboratory for Hydroscience and Engineering, Tsinghua University, Beijing 100084, China b Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China | 2009 | Progress in Natural Science:Materials International2009，19，5： | 25 |
| 2 | A preliminary study of the failure mechanisms of cascading landslide dams显示文摘Landslide dams commonly form when mass earth or rock movements reach a river channel and cause a complete or partial blockage of the channel.Intense rainfalls can induce upstream flows along a sloping channel that significantly affect downstream landslide dams.If a series of landslide dams are collapsed by incoming mountain torrents(induced by intense rainfall),large debris flows can form in a very short period.Furthermore,the failure of these dams can amplify the magnitude and scale of debris flows in the flow direction.The catastrophic debris flows that occurred in Zhouqu County,China on 8 August 2010 were caused by intense rainfall and the upstream cascading failure of landslide dams along the gullies.Incorporating the role of outburst floods associated with the complete or partial failure of landslide dams is an interesting problem usually beyond the scope of analysis because of the inherent modeling complexity.To understand the cascading failure modes of a series of landslide dams,and the dynamic effect these failures have on the enlargement of debris flow scales,experimental tests are conducted in sloping channels mimicking field conditions,with the modeled landslide dams distributed along a sloping channel and crushed by different upstream flows.The failure modes of three different cascades of landslide dams fully or partially blocking a channel river are parametrically studied.This study illustrates that upstream flows can induce a cascading failure of the landslide dams along a channel.Overtopping is the primary failure mechanism,while piping and erosion can also induce failures for different constructed landslide dams.A cascading failure of landslide dams causes a gradually increasing flow velocity and discharge of the front flow,resulting in an increase in both diameter and percentage of the entrained coarse particles.Furthermore,large landslide blockages can act to enhance the efficiency of river incision,or conversely to induce aggradation of fluvial sediments,depending on the blockage factor of the landslide dams and upstream discharge. | Gordon G.D Peng Cui Xinghua Zhu Jinbo Tang Huayong Chen Qicheng Sun | 2015 | International Journal of Sediment Research2015，30，3： | 8 |
| 3 | Holocene volcanic rocks in Jingbo Lake region --Diversity of magmatism显示文摘During the time from 5500 a to 5200 a BP more than 10 Holocene volcanoes in Jingbo Lake region erupted and the volcanic rocks covered an area of about 500 km2. Holocene volcanic rocks in Jingbo Lake region belong to the potassium-rich rocks and contain three rock types: trachybasalts, basanites and phonotephrites. Various types of magmatism formed in a small area and in a short period of time came from partial melting of potassically-metasomatised lithospheric mantle. The diversity of magmatism can be explained by that Jingbo Lake is situated in the back-arc extensional region of East Asian continent subducted by the Pacific Ocean, and potassic fluid derived from mantle wedge or dehydration of subducted slab can result in a high heterogeneity of the mantle beneath this region. Based on the pressure estimation of clinopyroxene megacrysts, we estimate that phonotephrite magma fractionally crystallize at ca . 52-54 km down the earth. | FAN Qicheng SUN Qian LI Ni WANG Tuanhua | 2006 | Progress in Natural Science:Materials International2006，16，1： | 8 |
| 4 | Paddy System with a Hybrid Rice Enhances Cyanobacteria Nostoc and Increases N2 Fixation显示文摘Biological nitrogen (N) fixation (BNF) plays a significant role in maintaining soil fertility in paddy field ecosystems. Rice variety influences BNF, but how different rice varieties regulate BNF and associated diazotroph communities has not been quantified. Airtight, field-based 15N2-labelling grow th chamber experiments were used to assess the BNF capac 辻 y of different rice varie ties. In addition, both the 16S rRNA and nifH genes were sequenced to assess the influence of different rice varieties on bacterial and diazotrophic communities in paddy soils. After subjecting a rice-soil system to 74 d of continuous airtight, field-based 15N2 labelling in pots in a growth chamber, the amounts of fixed N were 22.3 and 38.9 kg ha^-1 in inbred japonica (W23) and hybrid indica (IIY) rice cultivars plan ted in the rice-soil systems, respectively, and only 1%—2.5% of the fixed N was allocated to the rice plants and weeds. A greater abundance of diazotrophs was found in the surface soil (0-1 cm) under IIY than under W23. Sequencing of the 16S rRNA gene showed significantly greater abundances of the cyanobacterial genera Nostoc, Anabaena, and Cylindrospermum under IIY than under W23. Sequencing of the nifH gene also showed a significantly greater abundance of Nostoc under IIY than under W23. These results indicate that the hybrid rice cultivar (IIY) promoted BNF to a greater extent than the inbred rice cultivar (W23) and that the increase in BNF might have been due to the enhanced heterocystous cyanobacteria Nostoc. | MA Jing BEI Qicheng WANG Xiaojie LIU Gang Georg CADISCH LIN Xingwu ZHU Jianguo SUN Xiaoli XIE Zubin | 2019 | Pedosphere2019，29，3： | 7 |
| 5 | Influence of gravity on narrow input forced drainage in 2D liquid foams显示文摘Liquid foam is a dense packing of gas bubbles in a small amount of liquid containing surfactants or other surface-active macromolecules, which is one of the highly organized materials and possesses hallmark rheological behaviour of soft matters. Forced foam drainage is the flow of constantly inputted liquid through the network of interstitial channels between bubbles under actions of gravity and capil-larity. This process involves two mechanisms: minimal viscous flow dissipation of liquid and minimal surface energy of bubbles. For constant surfactant solution, viscous dissipation usually varies with gravity. This work reports simulations of 2D forced foam drainage with narrow input in a Hele-Shaw cell under 8 different gravities, g, ranging from 9.8 to 0 ms?2. The spread of liquid both vertical due to gravity action, and horizontal due to capillary suction, is recorded over time. Positions of drainage wave fronts in both directions with time are found to be well described in the power law form, and the exponents are 0.536+5.29×10-3g and 0.479?7.27×10-3g, respectively, while the sum is close to a constant of 1.015 which is independent of gravity. For g=9.8 ms-2, the calculated exponents are in good agreement with experimental results by Hutzler et al. and Wang. | SUN QiCheng GE Wei HUANG Jin | 2007 | Chinese Science Bulletin2007，52，3： | 4 |
| 6 | Kinetic granular temperature and its measurement using speckle visibility spectroscopy显示文摘The occurrence of a mesoscopic scale in granular materials leads to a sharp increase in the number of interaction processes at both intra-and inter-scale levels.The mesoscopic scale is the main source of the complex macroscopic properties of granular materials.The quantification of mesoscopic disordered movements is often referred to as granular temperature.In this paper,we first introduce the physical meaning of the original granular temperature of a kinetic nature,Tk,and then briefly summarize the advances made over the past few decades.Our research group has focused on Tk measurement using speckle visibility spectroscopy.The principle of this technique and the instruments developed in our research group are briefly introduced.Our work shows great promise in the measurement of kinetic granular temperature.Finally,a summary of granular temperature and some recent developments in speckle visibility spectroscopy measurements are presented. | Hui Yang Yonghai Zhu Ran Li Qicheng Sun | 2020 | Particuology2020，18，1： | 4 |
| 7 | Simulations of Bingham plastic flows with the multiple-relaxation-time lattice Boltzmann model显示文摘Fresh cement mortar is a type of workable paste,which can be well approximated as a Bingham plastic and whose flow behavior is of major concern in engineering.In this paper,Papanastasiou’s model for Bingham fluids is solved by using the multiplerelaxation-time lattice Boltzmann model(MRT-LB).Analysis of the stress growth exponent m in Bingham fluid flow simulations shows that Papanastasiou’s model provides a good approximation of realistic Bingham plastics for values of m>108.For lower values of m,Papanastasiou’s model is valid for fluids between Bingham and Newtonian fluids.The MRT-LB model is validated by two benchmark problems:2D steady Poiseuille flows and lid-driven cavity flows.Comparing the numerical results of the velocity distributions with corresponding analytical solutions shows that the MRT-LB model is appropriate for studying Bingham fluids while also providing better numerical stability.We further apply the MRT-LB model to simulate flow through a sudden expansion channel and the flow surrounding a round particle.Besides the rich flow structures obtained in this work,the dynamics fluid force on the round particle is calculated.Results show that both the Reynolds number Re and the Bingham number Bn afect the drag coefcients CD,and a drag coefcient with Re and Bn being taken into account is proposed.The relationship of Bn and the ratio of unyielded zone thickness to particle diameter is also analyzed.Finally,the Bingham fluid flowing around a set of randomly dispersed particles is simulated to obtain the apparent viscosity and velocity fields.These results help simulation of fresh concrete flowing in porous media. | CHEN SongGui SUN QiCheng JIN Feng LIU JianGuo | 2014 | Science China(Physics,Mechanics & Astronomy)2014，57，3： | 4 |
| 8 | Numerical study of flow pattern modulation in a vertical phase separation condenser tube显示文摘The passive phase separation concept was proposed to modulate flow patterns for heat transfer enhancement. By the flow pattern modulation, the gas tends to be near the wall and the liquid tends to be in the tube core. Experiment has been performed to verify the fresh idea and the flow pattern modulation mechanism was analyzed qualitatively. This paper focuses on the numerical simulation of the bubble dynamics for a single bubble in the vertical phase separation condenser tube to quantitatively explore the flow pattern mechanism, based on a multiscale grid system and the volume-of-fluid (VOF) method. It is found that: (1) the modulated liquid film thickness can be decreased by 70% compared to that in the bare tube region; (2) the modulated bubble traveling velocity can be doubled, causing the increased liquid velocity and velocity gradient in the annular region to weaken the fluid boundary layer; (3) the significantly increased bubble traveling velocity in the annular region promotes the mass and momentum exchange between the annular region and the core region, and yields the self-sustained pulsating flow in the core region. The above three factors are benefit for the performance improvement of the heat transfer facilities. | SUN DongLiang XU JinLiang CHEN QiCheng CAO Zhen | 2013 | Chinese Science Bulletin2013，58，13： | 4 |
| 9 | Numerical simulation of ae-olian sediment transport显示文摘A discrete element model (DEM) is developed for aeolian sediment transport in the scope of investigation of the dynamic behavior of grains, in which the motion of individual grain is considered while velocity distribution of wind is given according to bed forms. The above model has been used for simulating the phenomenon of 4000 grains blown by wind, resulting in ripples and saltating paths, which shows good agreements with experimental observations. The result is helpful for revealing the intrinsic mechanism of sand flow. | Qicheng Sun Guangqian Wang | 2001 | Chinese Science Bulletin2001，46，9： | 3 |
| 10 | STUDIES ON STRUCTURAL AND MECHANICAL PROPERTIES UNDER ISOSTATIC COMPRESSION WITH LARGE-SCALE DISCRETE ELEMENT SIMULATIONS显示文摘Granular systems undergo a jamming transition at point J simply by increasing the packing fraction. A large-scale parallel discrete element code(THDEM: TsingHua Discrete Element Method) was used to obtain a satisfying statistical description of the structural and mechanical properties near point J. The isostatic compressions of 100,000 polydispersed frictionless particles were simulated on high performance computers to clearly observe the sophisticated configurations of force chains. The first peak of the pair correlation function, coordination number, spatial distribution of the packing fraction, and stress were calculated to analyze their variations with increasing packing fraction. The critical packing fraction at point J is determined to be 0.62. The incremental stress and coordination number from point J scale well with the power law, and coincide with previous theoretical predications. The distribution of the packing fraction is a normal distribution around the average value. The standard deviation decreases with increasing packing fraction, indicating the system is more uniform with a denser packing. | Jianguo Liu Qicheng Sun Feng Jin Qingkai Liu | 2014 | Acta Mechanica Solida Sinica2014，27，2： | 3 |
| 11 | Foam drainage wave coalescing and its energy evolution显示文摘Liquid foam is a dense packing of gas bubbles in a small amount of surfactant solution. Liquid drains out of foams until equilibrium is reached due to the compromise between gravity and capillarity, which greatly affects the stability of foam. Based on a series of work on foam structure and drainage we conducted previously, this paper reports the results on coalescence of an original forced drainage wave at a low flow rate with subsequent drainage waves with higher flow rates. The evolutions of viscous energy and surface energy during the process of coalescence are theoretically analyzed. | SUN QiCheng HUANG Jin WANG GuangQian | 2008 | Chinese Science Bulletin2008，53，20： | 3 |
| 12 | Microscopic study on stress-strain relation of granular materials显示文摘A biaxial shearing test on granular materials is numerically simulated by distinct element method (DEM). The evolution of the microstructures of granular materials during isotropic compression and shearing is investigated, on which a yield function is derived. The new yield function has a similar form as the one used in the modified Cam-clay model and explains the yield characteristics of granular materials under the isotropic compression and shear process through the change of the contact distribution N(θ) defining the contacts at particle contact angle θ. | LIU SiHong YAO YangPing SUN QiCheng LI TieJun LIU MinZhi | 2009 | Chinese Science Bulletin2009，54，23： | 2 |
| 13 | Condensation heat transfer enhancement mechanism for vertical upflows by the phase separation concept at small gravity显示文摘In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the small gravity environment, which leads to reduction in the service life of equipments. In this study, a passive condenser, developed on basis of the phase separation concept,is utilized to improve the performance of the condensation heat transfer under the small gravity environment. As a result of the limitation of experiments, the mechanisms of heat transfer enhancement of the phase separation condenser tube are revealed through numerical simulation based on the volume-of-fluid(VOF) method. The following conclusions could be obtained:(1) A novel phase distribution of ‘‘gas near the tube wall and liquid in the tube core'' is formed. The thin liquid film is indeed created after the flow pattern modulation by inserting mesh cylinder.(2)The condensation quantity for single bubble in the annular region increases about 16 times greater than that in the bare tube region in the case of Jl= 0.0574 m/s and Jg= 0.0229 m/s.(3) Gas volume fraction affects the parameters of liquid film thickness, bubble length and liquid bridge length. The increase in the gas volume fraction results in the decrease in the evaluation index from21.56 to 12.82. The evaluation index is defined as the ratio of the condensation quantities per unit tube length of the annular region and the bare tube region. | Qicheng Chen Dongliang Sun | 2015 | Science Bulletin2015，60，20： | 2 |
| 14 | The bubble leakage mechanism for vertical upflows by the phase separation concept显示文摘Recently,our research group proposed the phase separation condenser tube,in which a mesh cylinder was inserted to form the flow structure of‘‘gas near the tube wall and liquid in the tube core’’,significantly enhance the condensation heat transfer.But the bubble leakage towards the core region may worsen the heat transfer enhancement.In order to prevent the bubble leakage,the critical criterion was proposed based on the Young–Laplace equation,considering the inertia force,viscous force and pulsating flow.It was found that the critical criterion depends on the dimensionless parameter G*,the We number and a coefficient C.The numerical model was developed in terms of the volume of fluid method to predict the two-phase laminar flow in the phase separation condenser tube.The results show that the bubble leakage takes place at the bubble tip,which is agreed with the experimental observations.The critical curve distinguishing the non-bubble-breaking and bubble-breaking was obtained by comparing the bubble dynamics at different G*and We.The coefficient C was determined.The critical criterion for the bubble leakage is given as G We0:22We0:99349 G4:7 103 We0:00651t196:39We0:006514cosa DHW,providing the design and operation guidance for the phase separation condenser tube. | Qicheng Chen Jinliang Xu Dongliang Sun | 2014 | Chinese Science Bulletin2014，59，21： | 2 |
| 15 | Free-surface Simulations of Newtonian and Non-Newtonian Fluids with the Lattice Boltzmann Method显示文摘This paper describes the application of a three-dimensional lattice Boltzmann method(LBM) to Newtonian and non-Newtonian(Bingham fluid in this work) flows with free surfaces. A mass tracking algorithm was incorporated to capture the free surface, whereas Papanastasiou's modified model was used for Bingham fluids. The lattice Boltzmann method was first validated using two benchmarks: Newtonian flow through a square cross-section tube and Bingham flow through a circular cross-section tube. Afterward, the dam-break problem for the Newtonian fluid and the slump test for Bingham fluid were simulated to validate the free-surface-capturing algorithm. The numerical results were in good agreement with analytical results, as well as other simulations, thereby proving the validity and correctness of the current method. The proposed method is a promising substitute for time-consuming and costly physical experiments to solve problems encountered in geotechnical and geological engineering, such as the surge and debris flow induced by a landslide or earthquake. | ZHANG Chuanhu CHEN Songgui SUN Qicheng JIN Feng | 2016 | Acta Geologica Sinica(English Edition)2016，90，3： | 2 |
| 16 | Simulations of granular flow along an inclined plane using the Savage-Hutter model显示文摘In this work a velocity-dependent friction is introduced into a depth-averaged Savage-Hutter dynamical model for shallow granular flows. The process of granular material flowing along an inclined plane and then depositing on a horizontal plane is simulated. The surface profiles and evolution of various types of energy are investigated and compared when using the standard Coulomb-type friction versus velocity-dependent friction. Interestingly, there is a small difference between the two different types of friction. | Minglong Fei Qicheng Sun Deyu Zhong Gordon G.D.Zhou | 2012 | Particuology2012，10，2： | 2 |
| 17 | Simulations of Bingham plastic flows with the multiple-relaxation-time lattice Boltzmann model显示文摘 | Chen Songgui Sun Qicheng Jin Feng & Liu Jianguo | | SCIENCE CHINA Physics Mechanics & Astronomy 00，，： | 1 |
| 18 | Crack spacing of unsaturated soils in the critical state显示文摘The cracking mechanism of unsaturated soils due to evaporation is poorly understood, and the magnitude of crack spacing is usually hard to estimate. In this work, cracks were postulated to occur succedently rather than simultaneously, that is, secondary cracks appear after primary cracks as evaporation continues. Formulae of the secondary crack spacing and secondary trend crack spacing were then derived after stress analysis. The calculated spacing values were consistent with the published experimental data. Meanwhile, the effect of the Poisson ratio on the crack spacing was analyzed, which showed that the magnitude of crack spacing was proportional to the Poisson ratio in the range of [0.30, 0.35]. | SUN JiChao WANG GuangQian SUN QiCheng | 2009 | Chinese Science Bulletin2009，54，12： | 1 |
| 19 | Application of granular solid hydrodynamics to a well-graded unbound granular material undergoing triaxial tests显示文摘Unbound granular materials(UGMs)are widely used as a base or a subbase in pavement construction.They are generally well graded and exhibit a higher peak strength than that of conventional cohesionless granular materials.By using a simplified version of granular solid hydrodynamics(GSH),a set of GSH material constants is determined for a UGM material.The deviatoric stress and volumetric strain caused by triaxial compression are calculated and then compared with experimental data.The results indicate that the GSH theory is able to describe such a special type of granular materials. | Shixiong SONG Qicheng SUN Feng JIN Chuhan ZHANG | 2013 | Frontiers of Structural and Civil Engineering2013，7，1： | 1 |
| 20 | Understanding force chains in dense granular materials 显示文摘 | SUN Qicheng JIN Feng LIU Jianguo | 2010 | International Journal of Modem Physics B2010，24，： | 1 |
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