The bubbles rise up and burst at the free surface is a complex two-phase process.A free energy lattice Boltzmann method(LBM)model is adopted in this paper to study this phenomenon.The interface capturing technique[Zhe...The bubbles rise up and burst at the free surface is a complex two-phase process.A free energy lattice Boltzmann method(LBM)model is adopted in this paper to study this phenomenon.The interface capturing technique[Zheng et al.,2006]is used to deal with the high density ratio problem.The Laplace law and the air-water interface capturing ability are validated for the multiphase model.The interaction between the single bubble or multiple bubbles and the free surface are studied by the multiphase model.The force acting on the bubble and the evolution of the free surface is studied.Meanwhile,effect of the initial distance between two adjacent bubbles on interaction effects of multiple bubbles is investigated as well.展开更多
For the growth and departure of bubbles from an orifice, a free energy lattice Boltzmann model is adopted to deal with this complex multiphase flow phenomenon. A virtual layer is set at the boundary of the flow domain...For the growth and departure of bubbles from an orifice, a free energy lattice Boltzmann model is adopted to deal with this complex multiphase flow phenomenon. A virtual layer is set at the boundary of the flow domain to deal with the no-slip boundary condition. Effects of the viscosity, surface tension, gas inertial force and buoyancy on the characteristics of bubbles when they grow and departure from an orifice in quiescent liquid are studied. The releasing period and departure diameter of the bubble are influenced by the residual gas at the orifice, and the interaction between bubbles is taken into consideration. The relations between the releasing period or departure diameter and the gravity acceleration show fair agreements with previous numerical and theoretical results. And the influence of the gas outflow velocity on bubble formation is discussed as well. For the bubbles growing in cross-flow field, effects of the cross-flow speed and the gas outflow velocity on the bubble formation are discussed, which is related to the application in ship resistance reduction. And optimal choice of the ship speed and gas outflow velocity is studied. Cases in this paper also prove that this high density ratio LBM model has its flexibility and effectiveness on multiphase flow simulations.展开更多
We derive the mesoscopic interparticle potentials from macroscopic thermodynamics for van der Waals,Redlich-Kwong,and Redlich-Kwong-Soave equations of state and find that all these potentials are very similar to the L...We derive the mesoscopic interparticle potentials from macroscopic thermodynamics for van der Waals,Redlich-Kwong,and Redlich-Kwong-Soave equations of state and find that all these potentials are very similar to the Lennard-Jones potential.To investigate the interfacial property at the mesoscale level,we incorporate free energy functions into the single-component multiphase lattice Boltzmann model and obtain the saturated density coexistence curves and interface mass density profiles across the interface using this method with different equations of state.The simulation results accurately reproduce the properties of equilib-rium thermodynamics.Numerical results for single-component phase transitions indicate that a bubble-growth process is obtained and the equilibrium phase diagram is achieved at a given temperature.Bulk free energy,the interfacial energy coefficient,and other properties of nonequilibrium thermodynamic parameters,which are used to examine interfacial properties,are obtained in these simulations,and all these parameters are found to obey irreversible thermodynamics.展开更多
基金supported by the National Natural Science Foundation of China (11672081)
文摘The bubbles rise up and burst at the free surface is a complex two-phase process.A free energy lattice Boltzmann method(LBM)model is adopted in this paper to study this phenomenon.The interface capturing technique[Zheng et al.,2006]is used to deal with the high density ratio problem.The Laplace law and the air-water interface capturing ability are validated for the multiphase model.The interaction between the single bubble or multiple bubbles and the free surface are studied by the multiphase model.The force acting on the bubble and the evolution of the free surface is studied.Meanwhile,effect of the initial distance between two adjacent bubbles on interaction effects of multiple bubbles is investigated as well.
基金financially supported by the National Key R&D Program of China(Grant No.2018YFC0308900)the Industrial Technology Development Program(Grant No.JCKY2018604C010)Shenzhen Special Fund for Future Industries(Grant No.JCYJ20160331163751413)
文摘For the growth and departure of bubbles from an orifice, a free energy lattice Boltzmann model is adopted to deal with this complex multiphase flow phenomenon. A virtual layer is set at the boundary of the flow domain to deal with the no-slip boundary condition. Effects of the viscosity, surface tension, gas inertial force and buoyancy on the characteristics of bubbles when they grow and departure from an orifice in quiescent liquid are studied. The releasing period and departure diameter of the bubble are influenced by the residual gas at the orifice, and the interaction between bubbles is taken into consideration. The relations between the releasing period or departure diameter and the gravity acceleration show fair agreements with previous numerical and theoretical results. And the influence of the gas outflow velocity on bubble formation is discussed as well. For the bubbles growing in cross-flow field, effects of the cross-flow speed and the gas outflow velocity on the bubble formation are discussed, which is related to the application in ship resistance reduction. And optimal choice of the ship speed and gas outflow velocity is studied. Cases in this paper also prove that this high density ratio LBM model has its flexibility and effectiveness on multiphase flow simulations.
基金supported by the, National Natural Science Foundation of China (50406012, 51076172)the National Key Laboratory of Bubble Physics and Natural Circulation of NPIC (9140C710901090C71, 9140C7101020802)the Specialized Research Fund for the Doctoral Program of Higher Education of China (20090191120017)
文摘We derive the mesoscopic interparticle potentials from macroscopic thermodynamics for van der Waals,Redlich-Kwong,and Redlich-Kwong-Soave equations of state and find that all these potentials are very similar to the Lennard-Jones potential.To investigate the interfacial property at the mesoscale level,we incorporate free energy functions into the single-component multiphase lattice Boltzmann model and obtain the saturated density coexistence curves and interface mass density profiles across the interface using this method with different equations of state.The simulation results accurately reproduce the properties of equilib-rium thermodynamics.Numerical results for single-component phase transitions indicate that a bubble-growth process is obtained and the equilibrium phase diagram is achieved at a given temperature.Bulk free energy,the interfacial energy coefficient,and other properties of nonequilibrium thermodynamic parameters,which are used to examine interfacial properties,are obtained in these simulations,and all these parameters are found to obey irreversible thermodynamics.
