为获取南方地区黏弹性壤土颗粒离散元接触模型的本征物理参数和接触力学参数,建立其用于离散元仿真的接触模型。以试验测定的堆积角为40.95°的壤土为研究对象,选取Hertz–Mindlin with JKR接触模型,通过实测试验获取壤土的本征物...为获取南方地区黏弹性壤土颗粒离散元接触模型的本征物理参数和接触力学参数,建立其用于离散元仿真的接触模型。以试验测定的堆积角为40.95°的壤土为研究对象,选取Hertz–Mindlin with JKR接触模型,通过实测试验获取壤土的本征物理参数值;借助GEMM数据库推荐的土壤接触力学参数初选范围,通过最陡爬坡试验得到接触力学参数值的最优值区间。利用Design–Expert软件对最优值区间的接触力学参数进行4因素3水平二次正交旋转组合试验,获取堆积角回归模型,以实测土壤堆积角40.95°为目标,对回归模型进行接触力学参数寻优,得到接触力学参数的最优组合为:JKR表面能13.05 J/m2,恢复系数0.5,动摩擦因数0.15,静摩擦因数1.06,该最优组合参数仿真堆积角均值为41.07°,与实测堆积角误差为0.3%。展开更多
Nature is a huge gallery of art involving nearly perfect structures and properties over the millions of years of development. Many plants and animals show water-repellent properties with fine micro-structures, such as...Nature is a huge gallery of art involving nearly perfect structures and properties over the millions of years of development. Many plants and animals show water-repellent properties with fine micro-structures, such as lotus leaf, water skipper and wings of butterfly. Inspired by these special surfaces, the artificial superhydrophobic surfaces have attracted wide attention in both basic research and industrial applications. The wetting properties of superhydrophobic surfaces in nature are affected by the chemical compositions and the surface topographies. So it is possible to realize the biomimetic superhydrophobic surfaces by tuning their surface roughness and surface free energy correspondingly. This review briefly introduces the physical-chemical basis of superhydrophobic plant surfaces in nature to explain how the superhydrophobicity of plant surfaces can be applied to different biomimetic functional materials with relevance to technological applications. Then, three classical effects of natural surfaces are classified： lotus effect, salvinia effect, and petal effect, and the promising strategies to fabricate biomimetic su- perhydrophobic materials are highlighted. Finally, the prospects and challenges of this area in the future are proposed.展开更多
The seasonal changes in leaf particulate matter （PM） accumulation, surface wettability and micromor- phology in urban tree species, including Sophorajaponica （S. japonica）, Platanus acerifolia （P. acerifolia） an...The seasonal changes in leaf particulate matter （PM） accumulation, surface wettability and micromor- phology in urban tree species, including Sophorajaponica （S. japonica）, Platanus acerifolia （P. acerifolia） and Cedrus deodara （C. deodara）, were studied during a single growing season. The three species showed distinct seasonal trends in PM accumulation, increasing from spring to autumn （or winter） even during the rainy season, but at different rates. During the study, the leaf PM retention amount ofP acerifolia, a species with ridged leaf surfaces, was significantly higher than that of S. japonica and C. deodara, species with waxy leaf surfaces. The contact angles of water droplets on leaves decreased with leafage except on the abaxial surface orS.japonica, which remained non-wettable or highly non-wettable throughout the growing season; the decrease in the contact angle on adaxial surface of S. japonica was greater when compared with P acerifolia and C. deodara. A significant and negative relationship existed between leaf PM retention amounts and contact angles on adaxial surface of leaves of all three species. The increase in wettability, probably caused when epicuticular wax was destroyed by mechan- ical and chemical abrasion, seemed to be the main factor leading to seasonal variations in leaf PM accumulation.展开更多
The dynamics of two-phase flows with a constant driving force inside a micro-channel is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this article. Flow regimes under diff...The dynamics of two-phase flows with a constant driving force inside a micro-channel is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this article. Flow regimes under different wall wettabilities and over smooth and grooved geometric surfaces are investigated. It is found that flow behaviors are strongly affected by the wall wettability and topography. Our results show that the LBM is efficient and accurate, and has very good application prospect in the study of drag reduction of microscopic seepage of reservoir.展开更多
Mine dust is classified as one of five natural coal mining disasters because it can harm the health of miners and poses a serious threat to the safety of the coal mine. Therefore, preparation of an effective dust supp...Mine dust is classified as one of five natural coal mining disasters because it can harm the health of miners and poses a serious threat to the safety of the coal mine. Therefore, preparation of an effective dust suppression agent is highly desired. To improve the capture efficiency of fine dust, this study examines the dust suppression effects of various combinations of wetting agents, additives, and coagulation agents by using the optimum seeking method to reduce mine dust, particularly respirable particles. The optimal formula is shown to contain 10wt% fatty alcohol polyoxyethylene ether（JFC）, 4.96wt% cationic polyacrylamide, and 4wt% calcium chloride. The dust suppression effect can be achieved at 96.1% in 5 min by using the optimal formula.展开更多
The apparent slip between solid wall and liquid is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this paper. With a no-slip bounce-back scheme applied to the interface, fl...The apparent slip between solid wall and liquid is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this paper. With a no-slip bounce-back scheme applied to the interface, flow regimes under different wall wettabilities are investigated. Because of the wall wettability, liquid apparent slip is observed. Slip lengths for different wall wettabilities are found to collapse nearly onto a single curve as a function of the static contact angle, and thereby a relationship between apparent slip length and contact angle is suggested. Our results also show that the wall wettability leads to the formation of a low-density layer between solid wall and liquid, which produced apparent slip in the micro-scale.展开更多
目的采用离散元法(DEM)模拟中药浸膏粉休止角,确定颗粒之间、颗粒与几何体之间的接触参数。方法以生甘草浸膏粉、独活浸膏粉、微晶纤维素(MCC)和乙基纤维素(EC)4种粉末为研究对象,在Hertz-Mindlin with JKR Cohesion接触模型和颗粒缩放...目的采用离散元法(DEM)模拟中药浸膏粉休止角,确定颗粒之间、颗粒与几何体之间的接触参数。方法以生甘草浸膏粉、独活浸膏粉、微晶纤维素(MCC)和乙基纤维素(EC)4种粉末为研究对象,在Hertz-Mindlin with JKR Cohesion接触模型和颗粒缩放的基础上,通过Plackett-Burman设计筛选出对休止角模拟测定影响显著的接触参数,进而通过最陡爬坡设计确定关键接触参数的最佳区域。根据Box-Behnken试验结果,建立接触参数和模拟休止角之间的回归模型,优选最佳接触参数值并验证。结果筛选得到的关键接触参数为颗粒-颗粒滚动摩擦系数、颗粒-颗粒恢复系数和颗粒-不锈钢恢复系数,所建回归模型对休止角的标定范围为33.30°~43.64°,4种粉末休止角模拟测定值与实验值的相对误差绝对值均小于2.0%,表明所建标定方法准确可靠。结论证明了通过宏观物性参数间接标定中药颗粒体系DEM微观力学参数的可行性,为混合、输送等中药制药过程的精确模拟奠定了基础。展开更多
The special gas wettability phenomenon of reservoir rocks has been recognized by more and more researchers.It has a significant effect on efficient development of unconventional reservoirs.First,based on the preferent...The special gas wettability phenomenon of reservoir rocks has been recognized by more and more researchers.It has a significant effect on efficient development of unconventional reservoirs.First,based on the preferentially gas-covered ability and surface free energy changes,definition and evaluation methods have been established.Second,a method for altering rock wettability and its mechanisms have been studied,surface oriented phenomena of functional groups with low surface energy are the fundamental reason for gas wettability alteration of rock.Third,the effect of gas wettability on the surface energy,electrical properties and dilatability are investigated.Last,the effects of gas wettability on capillary pressure,oil/gas/water distribution and flow are investigated with capillary tubes and etchedglass network models.The gas wettability theory of reservoir rocks has been initially established,which provides theoretical support for the efficient production of unconventional reservoirs and has great significance.展开更多
It is well known that surface roughness has a very important effect on superhydrophobicity.The Wenzel and Cassie-Baxter models,which correspond to the homogeneous and heterogeneous wetting respectively,are currently p...It is well known that surface roughness has a very important effect on superhydrophobicity.The Wenzel and Cassie-Baxter models,which correspond to the homogeneous and heterogeneous wetting respectively,are currently primary instructions for designing superhydrophobic surfaces.However,the particular drop shape that a drop exhibits might depend on how it is formed. A water drop can occupy multiple equilibrium states,which relate to different local minimal energy.In some cases,both equilibrium states can even co-exist on a same substrate.Thus the apparent contact angles may vary and have different values.We discuss how the Wenzel and Cassie-Baxter equations determine the homogeneous and heterogeneous wetting theoretically. Contact angle analysis on hierarchical surface structure and contact angle hysteresis has been put specific attention.In particular, we study the energy barrier of transition from Cassie-Baxter state to Wenzel state,based on existing achievement by previous researchers,to determine the possibility of the transition and how it can be interpreted.It has been demonstrated that surface roughness and geometry will influence the energy required for a drop to get into equilibrium,no matter it is homogeneous or heterogeneous wetting.展开更多
Natural surfaces with super hydrophobic properties often have micro or hierarchical structures.In this paper, the wettingbehaviours of a single droplet on biomimetic micro structured surfaces with different roughness ...Natural surfaces with super hydrophobic properties often have micro or hierarchical structures.In this paper, the wettingbehaviours of a single droplet on biomimetic micro structured surfaces with different roughness parameters are investigated.Atheoretical model is proposed to study wetting transitions.The results of theoretical analysis are compared with those of experimentindicating that the proposed model can effectively predict the wetting transition.Furthermore, a numerical simulationbased on the meso scale Lattice Boltzmann Method （LBM） is performed to study dynamic contact angles, contact lines, andlocal velocity fields for the case that a droplet displays on the micro structured surface.A spherical water droplet with r= 15 μmfalls down to a biomimetic square-post patterned surface under the force of gravity with an initial velocity of 0.01 m·sand aninitial vertical distance of 20 μm from droplet centre to the top of pots.In spite of a higher initial velocity, the droplet can stillstay in a Cassie state; moreover, it reaches an equilibrium state at t≈17.5 ms, when contact angle is 153.16° which is slightlylower than the prediction of Cassie-Baxter’s equation which gives θ=154.40°.展开更多
文摘为获取南方地区黏弹性壤土颗粒离散元接触模型的本征物理参数和接触力学参数,建立其用于离散元仿真的接触模型。以试验测定的堆积角为40.95°的壤土为研究对象,选取Hertz–Mindlin with JKR接触模型,通过实测试验获取壤土的本征物理参数值;借助GEMM数据库推荐的土壤接触力学参数初选范围,通过最陡爬坡试验得到接触力学参数值的最优值区间。利用Design–Expert软件对最优值区间的接触力学参数进行4因素3水平二次正交旋转组合试验,获取堆积角回归模型,以实测土壤堆积角40.95°为目标,对回归模型进行接触力学参数寻优,得到接触力学参数的最优组合为:JKR表面能13.05 J/m2,恢复系数0.5,动摩擦因数0.15,静摩擦因数1.06,该最优组合参数仿真堆积角均值为41.07°,与实测堆积角误差为0.3%。
基金Acknowledgments This work is supported by the National Nature Science Foundation of China （Nos. 31070155 and 11172301）, the ＂Western Light Talent Culture＂ Project, the Distinguished Young Scientists Project of Hubei Province （2012FFA002）, the Co-joint project of Chinese Academy of Sciences and the ＂Top Hundred Talents＂ Program of Chinese Academy of Sciences.
文摘Nature is a huge gallery of art involving nearly perfect structures and properties over the millions of years of development. Many plants and animals show water-repellent properties with fine micro-structures, such as lotus leaf, water skipper and wings of butterfly. Inspired by these special surfaces, the artificial superhydrophobic surfaces have attracted wide attention in both basic research and industrial applications. The wetting properties of superhydrophobic surfaces in nature are affected by the chemical compositions and the surface topographies. So it is possible to realize the biomimetic superhydrophobic surfaces by tuning their surface roughness and surface free energy correspondingly. This review briefly introduces the physical-chemical basis of superhydrophobic plant surfaces in nature to explain how the superhydrophobicity of plant surfaces can be applied to different biomimetic functional materials with relevance to technological applications. Then, three classical effects of natural surfaces are classified： lotus effect, salvinia effect, and petal effect, and the promising strategies to fabricate biomimetic su- perhydrophobic materials are highlighted. Finally, the prospects and challenges of this area in the future are proposed.
文摘The seasonal changes in leaf particulate matter （PM） accumulation, surface wettability and micromor- phology in urban tree species, including Sophorajaponica （S. japonica）, Platanus acerifolia （P. acerifolia） and Cedrus deodara （C. deodara）, were studied during a single growing season. The three species showed distinct seasonal trends in PM accumulation, increasing from spring to autumn （or winter） even during the rainy season, but at different rates. During the study, the leaf PM retention amount ofP acerifolia, a species with ridged leaf surfaces, was significantly higher than that of S. japonica and C. deodara, species with waxy leaf surfaces. The contact angles of water droplets on leaves decreased with leafage except on the abaxial surface orS.japonica, which remained non-wettable or highly non-wettable throughout the growing season; the decrease in the contact angle on adaxial surface of S. japonica was greater when compared with P acerifolia and C. deodara. A significant and negative relationship existed between leaf PM retention amounts and contact angles on adaxial surface of leaves of all three species. The increase in wettability, probably caused when epicuticular wax was destroyed by mechan- ical and chemical abrasion, seemed to be the main factor leading to seasonal variations in leaf PM accumulation.
基金supported by the National Natural Science Foundation of China(Grant No.50874071)the National High Technology Research and Development Program of China(863 Program,Grant No.2008AA06Z201)+3 种基金the Program of Science and Technology Commission of Shanghai Municipality(Grant No.071605102)the project of Shanghai Education Commission Research Innovation(Grand No.08ZZ45)the Program for Changjiang Scholars and Innovative Research Team in Universities(Grant No.IRT0844)the China Postdoctoral Science Foundation(Grant No.20090450687)
文摘The dynamics of two-phase flows with a constant driving force inside a micro-channel is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this article. Flow regimes under different wall wettabilities and over smooth and grooved geometric surfaces are investigated. It is found that flow behaviors are strongly affected by the wall wettability and topography. Our results show that the LBM is efficient and accurate, and has very good application prospect in the study of drag reduction of microscopic seepage of reservoir.
基金National Natural Science Funds-Coal Joint Funds Key Support Project (No. U1261205)Basic Research Plan Project of Science and Technology of Qingdao (No. 13-1-4-149-jch)Key Technology Development Projects of Qingdao Economic and Technological Development Zone (No. 2013-1-66) for providing the financial support to this research
文摘Mine dust is classified as one of five natural coal mining disasters because it can harm the health of miners and poses a serious threat to the safety of the coal mine. Therefore, preparation of an effective dust suppression agent is highly desired. To improve the capture efficiency of fine dust, this study examines the dust suppression effects of various combinations of wetting agents, additives, and coagulation agents by using the optimum seeking method to reduce mine dust, particularly respirable particles. The optimal formula is shown to contain 10wt% fatty alcohol polyoxyethylene ether（JFC）, 4.96wt% cationic polyacrylamide, and 4wt% calcium chloride. The dust suppression effect can be achieved at 96.1% in 5 min by using the optimal formula.
基金the National Natural Science Foundation of China (Grant No. 50874071)the National High Technology Research and Development of China (863 Program,Grant No. 2008AA06Z201)+1 种基金the Key Program of Science and Technology Commission of Shanghai Municipality (Grant No.071605102)the Leading Talent Funding of Shanghai
文摘The apparent slip between solid wall and liquid is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this paper. With a no-slip bounce-back scheme applied to the interface, flow regimes under different wall wettabilities are investigated. Because of the wall wettability, liquid apparent slip is observed. Slip lengths for different wall wettabilities are found to collapse nearly onto a single curve as a function of the static contact angle, and thereby a relationship between apparent slip length and contact angle is suggested. Our results also show that the wall wettability leads to the formation of a low-density layer between solid wall and liquid, which produced apparent slip in the micro-scale.
文摘目的采用离散元法(DEM)模拟中药浸膏粉休止角,确定颗粒之间、颗粒与几何体之间的接触参数。方法以生甘草浸膏粉、独活浸膏粉、微晶纤维素(MCC)和乙基纤维素(EC)4种粉末为研究对象,在Hertz-Mindlin with JKR Cohesion接触模型和颗粒缩放的基础上,通过Plackett-Burman设计筛选出对休止角模拟测定影响显著的接触参数,进而通过最陡爬坡设计确定关键接触参数的最佳区域。根据Box-Behnken试验结果,建立接触参数和模拟休止角之间的回归模型,优选最佳接触参数值并验证。结果筛选得到的关键接触参数为颗粒-颗粒滚动摩擦系数、颗粒-颗粒恢复系数和颗粒-不锈钢恢复系数,所建回归模型对休止角的标定范围为33.30°~43.64°,4种粉末休止角模拟测定值与实验值的相对误差绝对值均小于2.0%,表明所建标定方法准确可靠。结论证明了通过宏观物性参数间接标定中药颗粒体系DEM微观力学参数的可行性,为混合、输送等中药制药过程的精确模拟奠定了基础。
基金supported by the Basic Research on Drilling & Completion of Critical Wells for Oil & Gas (Grant No. 51221003)National Science Fund for Petrochemical Industry (Project No. U1262201)+2 种基金"863" National Project (Project No. 2013AA064803)National Science Fund for Distinguished Young Scholars (Project No. 50925414)National Natural Science Foundation (Project No. 51074173)
文摘The special gas wettability phenomenon of reservoir rocks has been recognized by more and more researchers.It has a significant effect on efficient development of unconventional reservoirs.First,based on the preferentially gas-covered ability and surface free energy changes,definition and evaluation methods have been established.Second,a method for altering rock wettability and its mechanisms have been studied,surface oriented phenomena of functional groups with low surface energy are the fundamental reason for gas wettability alteration of rock.Third,the effect of gas wettability on the surface energy,electrical properties and dilatability are investigated.Last,the effects of gas wettability on capillary pressure,oil/gas/water distribution and flow are investigated with capillary tubes and etchedglass network models.The gas wettability theory of reservoir rocks has been initially established,which provides theoretical support for the efficient production of unconventional reservoirs and has great significance.
文摘It is well known that surface roughness has a very important effect on superhydrophobicity.The Wenzel and Cassie-Baxter models,which correspond to the homogeneous and heterogeneous wetting respectively,are currently primary instructions for designing superhydrophobic surfaces.However,the particular drop shape that a drop exhibits might depend on how it is formed. A water drop can occupy multiple equilibrium states,which relate to different local minimal energy.In some cases,both equilibrium states can even co-exist on a same substrate.Thus the apparent contact angles may vary and have different values.We discuss how the Wenzel and Cassie-Baxter equations determine the homogeneous and heterogeneous wetting theoretically. Contact angle analysis on hierarchical surface structure and contact angle hysteresis has been put specific attention.In particular, we study the energy barrier of transition from Cassie-Baxter state to Wenzel state,based on existing achievement by previous researchers,to determine the possibility of the transition and how it can be interpreted.It has been demonstrated that surface roughness and geometry will influence the energy required for a drop to get into equilibrium,no matter it is homogeneous or heterogeneous wetting.
基金supported by the Royal Society(UK)-NSFC(China)joint project,2009-2011by China Natural Science Foundation major International collaborative project 2010-2013 under grant No.50920105504
文摘Natural surfaces with super hydrophobic properties often have micro or hierarchical structures.In this paper, the wettingbehaviours of a single droplet on biomimetic micro structured surfaces with different roughness parameters are investigated.Atheoretical model is proposed to study wetting transitions.The results of theoretical analysis are compared with those of experimentindicating that the proposed model can effectively predict the wetting transition.Furthermore, a numerical simulationbased on the meso scale Lattice Boltzmann Method （LBM） is performed to study dynamic contact angles, contact lines, andlocal velocity fields for the case that a droplet displays on the micro structured surface.A spherical water droplet with r= 15 μmfalls down to a biomimetic square-post patterned surface under the force of gravity with an initial velocity of 0.01 m·sand aninitial vertical distance of 20 μm from droplet centre to the top of pots.In spite of a higher initial velocity, the droplet can stillstay in a Cassie state; moreover, it reaches an equilibrium state at t≈17.5 ms, when contact angle is 153.16° which is slightlylower than the prediction of Cassie-Baxter’s equation which gives θ=154.40°.
