A surface with gradient surface energy was fabricated on a silicon wafer by using the chemical vapor deposition (CVD) technology with the dodecyltrichlorosilane (C12H25Cl3Si) vapor which was adsorbed chemically on the...A surface with gradient surface energy was fabricated on a silicon wafer by using the chemical vapor deposition (CVD) technology with the dodecyltrichlorosilane (C12H25Cl3Si) vapor which was adsorbed chemically on the surface of the silicon wafer to form a self-assemble monolayer (ASM); thus a gradient profile of wettability. The microscopic contours of the gradient surface were measured with Seiko SPA400 atom force microscope (AFM). And the surface wettability profile was characterized by the sessile drop method, measuring the contact angle of fine water droplets that lay on the gradient surface, to represent the distribution of the surface energy on the surface. Using a high-speed video imaging system, the motion of water droplet on the horizontal gradient surface was visualized; the transient velocity was measured under ambient condition. The experimental results show that the liquid droplets can be driven to move from hydrophobic side to hydrophilic side on the horizontal gradient surface; the velocity of droplet can reach up to 40 mm/s. In addition, the motion of the water droplet can be generally divided into two stages: an acceleration stage; a deceleration stage. The droplet presents a squirming movement on the surface with a lower peak velocity; a larger extent of deceleration motion. And the static advancing contact angle of the droplet is obviously larger than the dynamic advancing contact angle on the gradient energy surface.展开更多
The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonline...The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonlinear ordinary differential equation is obtained by the Adomian decomposition method （ADM）. The physical quantities are derived including the pressure profile, the velocity profile, the maximum residue time, the stationary points, the volume flow rate, the average film velocity, the uniform film thickness, the shear stress, the surface tension profile~ and the vorticity vector. It is found that the velocity of the Sisko fluid film decreases when the fluid behavior index and the Sisko fluid parameter increase, whereas it increases with an increase in the inverse capillary number. An increase in the inverse capillary number results in an increase in the surface tension which in turn results in an increase in the surface tension gradient on the Sisko fluid film. The locations of the stationary points are shifted towards the moving plate with the increase in the inverse capillary number, and vice versa locations for the stationary points are found with the increasing Sisko fluid parameter. Furthermore, shear thinning and shear thickening characteristics of the Sisko fluid are discussed. A comparison is made between the Sisko fluid film and the Newtonian fluid film.展开更多
Little is known about the surface energy balance problem for a complex underlying surface.Taking data from the Loess Plateau Land-surface Processes Experiment(LOPEX) and investigating the characteristics of the surfac...Little is known about the surface energy balance problem for a complex underlying surface.Taking data from the Loess Plateau Land-surface Processes Experiment(LOPEX) and investigating the characteristics of the surface energy balance over a complex underlying surface,this paper calculates the soil heat storage and vertical sensible heat advection,analyzes their contributions to the surface energy imbalance,and discusses the mechanism by which the vertical velocity and temperature gradient in the surface layer affect the vertical sensible heat advection transfer.We found that the vertical velocity in the surface layer provides the necessary dynamic power for vertical sensible heat advection,and a relatively strong temperature gradient is the energy source generating vertical sensible heat advection.Under an ascending condition,the effect of vertical sensible heat advection on the surface energy budget is more obvious.It is also found that when the soil heat storage term and the vertical sensible heat advection term are added to the energy balance equation,the imbalance significantly improves.The peak of average diurnal residuals decreases from 125.1 to 41.5 W m-2,the daily average absolute value of residuals falls from 59.0 to 26.4 W m-2,and the surface energy balance closure increases from 78.4% to 94.0%.展开更多
This article concerns the construction of high-order energy-decaying numerical methods for gradient flows of evolving surfaces with curvature-dependent energy functionals.The semidiscrete evolving surface finite eleme...This article concerns the construction of high-order energy-decaying numerical methods for gradient flows of evolving surfaces with curvature-dependent energy functionals.The semidiscrete evolving surface finite element method is derived based on the calculus of variation of the semidiscrete surface energy functional.This makes the semidiscrete problem naturally inherit the energy decay structure.With this property,the semidiscrete problem is furthermore formulated as a gradient flow system of ODEs.The averaged vector-field collocation method is used for time discretization of the ODEs to preserve energy decay at the fully discrete level while achieving high-order accuracy in time.Extensive numerical examples are provided to illustrate the accuracy and energy diminishing property of the proposed method,as well as the effectiveness of the method in capturing singularities in the evolution of closed surfaces.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.50276072).
文摘A surface with gradient surface energy was fabricated on a silicon wafer by using the chemical vapor deposition (CVD) technology with the dodecyltrichlorosilane (C12H25Cl3Si) vapor which was adsorbed chemically on the surface of the silicon wafer to form a self-assemble monolayer (ASM); thus a gradient profile of wettability. The microscopic contours of the gradient surface were measured with Seiko SPA400 atom force microscope (AFM). And the surface wettability profile was characterized by the sessile drop method, measuring the contact angle of fine water droplets that lay on the gradient surface, to represent the distribution of the surface energy on the surface. Using a high-speed video imaging system, the motion of water droplet on the horizontal gradient surface was visualized; the transient velocity was measured under ambient condition. The experimental results show that the liquid droplets can be driven to move from hydrophobic side to hydrophilic side on the horizontal gradient surface; the velocity of droplet can reach up to 40 mm/s. In addition, the motion of the water droplet can be generally divided into two stages: an acceleration stage; a deceleration stage. The droplet presents a squirming movement on the surface with a lower peak velocity; a larger extent of deceleration motion. And the static advancing contact angle of the droplet is obviously larger than the dynamic advancing contact angle on the gradient energy surface.
文摘The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonlinear ordinary differential equation is obtained by the Adomian decomposition method （ADM）. The physical quantities are derived including the pressure profile, the velocity profile, the maximum residue time, the stationary points, the volume flow rate, the average film velocity, the uniform film thickness, the shear stress, the surface tension profile~ and the vorticity vector. It is found that the velocity of the Sisko fluid film decreases when the fluid behavior index and the Sisko fluid parameter increase, whereas it increases with an increase in the inverse capillary number. An increase in the inverse capillary number results in an increase in the surface tension which in turn results in an increase in the surface tension gradient on the Sisko fluid film. The locations of the stationary points are shifted towards the moving plate with the increase in the inverse capillary number, and vice versa locations for the stationary points are found with the increasing Sisko fluid parameter. Furthermore, shear thinning and shear thickening characteristics of the Sisko fluid are discussed. A comparison is made between the Sisko fluid film and the Newtonian fluid film.
基金supported by the National Natural Science Foundation of China(No.51674187)the International Joint Research Center for Value-added Metallurgy and Processing of Non-ferrous Metals,China(No.2019SD0010)the Key Industry Chain(Group)-Industrial Field in Shaanxi Province,China(No.2019ZDLGY05-03)。
基金supported by the National Natural Science Foundation of China (Grant No.40830597)the Public Welfare Research Project of China (Grant No.GYHY200806021)
文摘Little is known about the surface energy balance problem for a complex underlying surface.Taking data from the Loess Plateau Land-surface Processes Experiment(LOPEX) and investigating the characteristics of the surface energy balance over a complex underlying surface,this paper calculates the soil heat storage and vertical sensible heat advection,analyzes their contributions to the surface energy imbalance,and discusses the mechanism by which the vertical velocity and temperature gradient in the surface layer affect the vertical sensible heat advection transfer.We found that the vertical velocity in the surface layer provides the necessary dynamic power for vertical sensible heat advection,and a relatively strong temperature gradient is the energy source generating vertical sensible heat advection.Under an ascending condition,the effect of vertical sensible heat advection on the surface energy budget is more obvious.It is also found that when the soil heat storage term and the vertical sensible heat advection term are added to the energy balance equation,the imbalance significantly improves.The peak of average diurnal residuals decreases from 125.1 to 41.5 W m-2,the daily average absolute value of residuals falls from 59.0 to 26.4 W m-2,and the surface energy balance closure increases from 78.4% to 94.0%.
基金partly supported by NSFC 11871092 and NSAF U1930402,ChinaPostdoctoral Science Foundation(Project No.2020M682895)a grant from the Research Grants Council of the Hong Kong Special Administrative Region,China(GRF Project No.Poly U15300920)。
文摘This article concerns the construction of high-order energy-decaying numerical methods for gradient flows of evolving surfaces with curvature-dependent energy functionals.The semidiscrete evolving surface finite element method is derived based on the calculus of variation of the semidiscrete surface energy functional.This makes the semidiscrete problem naturally inherit the energy decay structure.With this property,the semidiscrete problem is furthermore formulated as a gradient flow system of ODEs.The averaged vector-field collocation method is used for time discretization of the ODEs to preserve energy decay at the fully discrete level while achieving high-order accuracy in time.Extensive numerical examples are provided to illustrate the accuracy and energy diminishing property of the proposed method,as well as the effectiveness of the method in capturing singularities in the evolution of closed surfaces.
