The terminal velocity of a liquid droplet settling in a sulfactant solution has been studied for the non-linear adsorption Langmuir frameworks accounting for monolayer saturation and non-ideal surfactant interactions....The terminal velocity of a liquid droplet settling in a sulfactant solution has been studied for the non-linear adsorption Langmuir frameworks accounting for monolayer saturation and non-ideal surfactant interactions. Most prior research uses a linear adsorption model which cannot capture these effects, The Maragoni migration of a liquid drop settling through a surfactant solution is examined by using Langmuir framework. The solution concentration Ceq is assumed large enough for the surfactant mass transfer to be adsorption-controlled. Langmuir model generates non-linear Marangoni stresses which diverge in the limit of approaching ∝, strongly retarding U'.展开更多
In this paper,monolayer saturation and nonideal surfactant interactions are captured with a nonlinear adsorption framework.The migration of a droplet in surfactant solution with electrolyte is discussed.Most prior res...In this paper,monolayer saturation and nonideal surfactant interactions are captured with a nonlinear adsorption framework.The migration of a droplet in surfactant solution with electrolyte is discussed.Most prior research studied the migration of a bubble or a droplet in surfactant solution without electrolyte.When the surfactants in solution with electrolyte are adsorbed at the surface of a bubble or a droplet,an electrical double layer will form near the surface of the bubble or the droplet,which will affect the subsequent adsorption of the surfactants.A group of dimensionless parameters(the interaction coefficient of the adsorbed surfactants K ∞ ,the Marangoni number Ma ,the Biot number Bi and the viscosity ratio k )are discussed in detail.The surface concentration of the adsorbed surfactants,the surface velocity and the migration velocity of the droplet are obtained by a boundary collocation technique.The terminal velocity U 0 of the droplet increases as K ∞ increases.展开更多
A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat ...A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved with the finite element differential equation solver COMSOL Multiphysics.The magnetic field was aligned perpendicularly to the welding direction.The main objective of these simulations was to estimate the critical value of the magnetic field needed to suppress convective flows in the weld pool during high-power(up to 20 kW)laser beam welding of aluminum alloys with up to 20 mm deep weld pool.It reveals that steady magnetic fields with corresponding Hartmann numbers Ha2-104 based on the half-width of the weld pool can effectively suppress convective flows in the weld pool.Moreover,the typically occurring wineglass-shape of the weld cross section caused by thermo-capillary flow is weakened.展开更多
A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick alumin...A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum.The three-dimensional heat transfer,fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics.Dominant physical effects of the process were taken into account:Thermo-capillary(Marangoni)convection at the upper and lower weld pool surfaces,natural convection due to the gravity influence and the latent heat of solid-liquid phase transition.Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatic pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT(rms)at an oscillation frequency of 450 Hz.The inductive support system allows for single-pass laser beam welding of thick aluminum plates.The flow pattern in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool.展开更多
文摘The terminal velocity of a liquid droplet settling in a sulfactant solution has been studied for the non-linear adsorption Langmuir frameworks accounting for monolayer saturation and non-ideal surfactant interactions. Most prior research uses a linear adsorption model which cannot capture these effects, The Maragoni migration of a liquid drop settling through a surfactant solution is examined by using Langmuir framework. The solution concentration Ceq is assumed large enough for the surfactant mass transfer to be adsorption-controlled. Langmuir model generates non-linear Marangoni stresses which diverge in the limit of approaching ∝, strongly retarding U'.
文摘In this paper,monolayer saturation and nonideal surfactant interactions are captured with a nonlinear adsorption framework.The migration of a droplet in surfactant solution with electrolyte is discussed.Most prior research studied the migration of a bubble or a droplet in surfactant solution without electrolyte.When the surfactants in solution with electrolyte are adsorbed at the surface of a bubble or a droplet,an electrical double layer will form near the surface of the bubble or the droplet,which will affect the subsequent adsorption of the surfactants.A group of dimensionless parameters(the interaction coefficient of the adsorbed surfactants K ∞ ,the Marangoni number Ma ,the Biot number Bi and the viscosity ratio k )are discussed in detail.The surface concentration of the adsorbed surfactants,the surface velocity and the migration velocity of the droplet are obtained by a boundary collocation technique.The terminal velocity U 0 of the droplet increases as K ∞ increases.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12027801,11621202,12272372,and 11902318)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2018491).
基金Item Sponsored by the Deutsche Forschungsgemeinschaft (BonnGermany) Under Grant No.DFG GU 1211/2-1
文摘A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved with the finite element differential equation solver COMSOL Multiphysics.The magnetic field was aligned perpendicularly to the welding direction.The main objective of these simulations was to estimate the critical value of the magnetic field needed to suppress convective flows in the weld pool during high-power(up to 20 kW)laser beam welding of aluminum alloys with up to 20 mm deep weld pool.It reveals that steady magnetic fields with corresponding Hartmann numbers Ha2-104 based on the half-width of the weld pool can effectively suppress convective flows in the weld pool.Moreover,the typically occurring wineglass-shape of the weld cross section caused by thermo-capillary flow is weakened.
基金Item Sponsored by the Deutsche Forschungsgemeinschaft (BonnGermany) under Grant No.DFG GU 1211/2-1
文摘A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum.The three-dimensional heat transfer,fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics.Dominant physical effects of the process were taken into account:Thermo-capillary(Marangoni)convection at the upper and lower weld pool surfaces,natural convection due to the gravity influence and the latent heat of solid-liquid phase transition.Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatic pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT(rms)at an oscillation frequency of 450 Hz.The inductive support system allows for single-pass laser beam welding of thick aluminum plates.The flow pattern in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool.
