When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve(SWCC).The occurrence of the contact angle hysteresis can be divided i...When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve(SWCC).The occurrence of the contact angle hysteresis can be divided into slipping and pinning.It is difficult to determine the effect of pinning existence on SWCC by tests.In this study,the effect of contact angle hysteresis on SWCC was analyzed either in the case of no variations in soil dry bulk density with changes in soil water content or no variations in soil water content with changes in soil dry bulk density.In both cases,soil particles were simplified to the spherical particle model.Based on the geometrically mechanic relationship between the particles and connecting liquid bridges,a physical model for predicting the SWCC was derived from the spherical particle model.Adjusting parameters made the model applicable to various soils,that is,the cohesive soil was considered as micron-sized spherical particles.Through the simulations on SWCC test data of sand,silt,clay,and swelling soil,it was confirmed that the physical model possessed good reliability and practicability.Finally,the analysis of rationality of contact angle was performed based on the basic assumptions of the model.展开更多
The capillary interactions, including the capillary force and capillary suction, between two unequal-sized particles with a fixed liquid volume are investigated. The cap- illary interaction model is used within the Yo...The capillary interactions, including the capillary force and capillary suction, between two unequal-sized particles with a fixed liquid volume are investigated. The cap- illary interaction model is used within the Young-Laplace framework. With the profile of the meridian of the liquid bridge, the capillary suction, and the liquid volume as state variables, the governing equations with two-fixed-point boundary axe first derived using a variable substitution technique, in which the gravity effects are neglected. The capillary suction and geometry of the liquid bridge with a fixed volume are solved with a shooting method. In modeling the capillary force, the Gorge method is applied. The effects of var- ious parameters including the distance between two particles, the ratio of particle radii, and the liquid-solid contact angles are discussed.展开更多
The influence of the thickness of a covering liquid layer and its viscosity as well as the impact velocity on energy loss during the normal impact on a flat steel wall of spherical granules with a liquid layer was stu...The influence of the thickness of a covering liquid layer and its viscosity as well as the impact velocity on energy loss during the normal impact on a flat steel wall of spherical granules with a liquid layer was studied. Free-fall experiments were performed to obtain the restitution coefficient of elastic-plastic γ- Al2O3 granules by impact on the liquid layer, using aqueous solutions of hydroxypropyl methylcellulose with different concentrations for variation of viscosity （1-300 mPa s）, In the presence of a liquid layer, increase of liquid viscosity decreases the restitution coefficient and the minimum thickness of the liquid layer at which the granule sticks to the wall. The measured restitution coefficients were compared with experiments performed without liquid layer. In contrast to the dry restitution coefficient, due to viscous losses at lower impact velocity, higher energy dissipation was obtained, A rational explanation for the effects obtained was given by results of numerically solved force and energy balances for a granule impact on a liquid layer on the wall. The model takes into account forces acting on the granule including viscous, surface tension, capillary, contact, drag, buoyancy and gravitational forces. Good agreement between simulations and experiments has been achieved.展开更多
A computational study of the stretching mechanism of a liquid bridge and the effect of the liquid properties on the DPN(dip-pen nanolithography)process is presented.The results show that the viscosity and contact angl...A computational study of the stretching mechanism of a liquid bridge and the effect of the liquid properties on the DPN(dip-pen nanolithography)process is presented.The results show that the viscosity and contact angle can have an appreciable influence on these processes.The greater the viscosity,the harder the liquid bridge is to break,which allows more molecular transfer during the DPN spotting process.Besides,when the contact angle between the liquid and substrate is less than 60 degrees,the time required to stretch the bridge and break it grows with the contact angle.During the stretching process,the pressure in the midsection(along the vertical direction)of the liquid bridge is relatively unstable,with frequent changes in its value.Furthermore,this pressure increases sharply when the liquid bridge breaks.展开更多
基金Supported by the National Natural Science Foundation of China (No. 50979028)the Program of the Chinese Ministry of Water Resources (No. 200801065)
文摘When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve(SWCC).The occurrence of the contact angle hysteresis can be divided into slipping and pinning.It is difficult to determine the effect of pinning existence on SWCC by tests.In this study,the effect of contact angle hysteresis on SWCC was analyzed either in the case of no variations in soil dry bulk density with changes in soil water content or no variations in soil water content with changes in soil dry bulk density.In both cases,soil particles were simplified to the spherical particle model.Based on the geometrically mechanic relationship between the particles and connecting liquid bridges,a physical model for predicting the SWCC was derived from the spherical particle model.Adjusting parameters made the model applicable to various soils,that is,the cohesive soil was considered as micron-sized spherical particles.Through the simulations on SWCC test data of sand,silt,clay,and swelling soil,it was confirmed that the physical model possessed good reliability and practicability.Finally,the analysis of rationality of contact angle was performed based on the basic assumptions of the model.
基金Project supported by the National Natural Science Foundation of China(Nos.51368038 and11162008)the Alumni Foundation of Civil Engineering of Lanzhou University of Technology(No.TM-QK-0701)the Environmental Protection Department of Gansu Province of China(No.GSEP-2014-23)
文摘The capillary interactions, including the capillary force and capillary suction, between two unequal-sized particles with a fixed liquid volume are investigated. The cap- illary interaction model is used within the Young-Laplace framework. With the profile of the meridian of the liquid bridge, the capillary suction, and the liquid volume as state variables, the governing equations with two-fixed-point boundary axe first derived using a variable substitution technique, in which the gravity effects are neglected. The capillary suction and geometry of the liquid bridge with a fixed volume are solved with a shooting method. In modeling the capillary force, the Gorge method is applied. The effects of var- ious parameters including the distance between two particles, the ratio of particle radii, and the liquid-solid contact angles are discussed.
文摘The influence of the thickness of a covering liquid layer and its viscosity as well as the impact velocity on energy loss during the normal impact on a flat steel wall of spherical granules with a liquid layer was studied. Free-fall experiments were performed to obtain the restitution coefficient of elastic-plastic γ- Al2O3 granules by impact on the liquid layer, using aqueous solutions of hydroxypropyl methylcellulose with different concentrations for variation of viscosity （1-300 mPa s）, In the presence of a liquid layer, increase of liquid viscosity decreases the restitution coefficient and the minimum thickness of the liquid layer at which the granule sticks to the wall. The measured restitution coefficients were compared with experiments performed without liquid layer. In contrast to the dry restitution coefficient, due to viscous losses at lower impact velocity, higher energy dissipation was obtained, A rational explanation for the effects obtained was given by results of numerically solved force and energy balances for a granule impact on a liquid layer on the wall. The model takes into account forces acting on the granule including viscous, surface tension, capillary, contact, drag, buoyancy and gravitational forces. Good agreement between simulations and experiments has been achieved.
基金by the basic scientific research project of Wenzhou,China(No.G20190014)supported by Key Laboratory of Air-driven Equipment Technology of Zhejiang.
文摘A computational study of the stretching mechanism of a liquid bridge and the effect of the liquid properties on the DPN(dip-pen nanolithography)process is presented.The results show that the viscosity and contact angle can have an appreciable influence on these processes.The greater the viscosity,the harder the liquid bridge is to break,which allows more molecular transfer during the DPN spotting process.Besides,when the contact angle between the liquid and substrate is less than 60 degrees,the time required to stretch the bridge and break it grows with the contact angle.During the stretching process,the pressure in the midsection(along the vertical direction)of the liquid bridge is relatively unstable,with frequent changes in its value.Furthermore,this pressure increases sharply when the liquid bridge breaks.
