A thermal lattice Boltzmann method(LBM)for two-phase fluid flows in nucleate pool boiling process is proposed.In the present method,a new function for heat transfer is introduced to the isothermal LBM for two-phase im...A thermal lattice Boltzmann method(LBM)for two-phase fluid flows in nucleate pool boiling process is proposed.In the present method,a new function for heat transfer is introduced to the isothermal LBM for two-phase immiscible fluids with large density differences.The calculated temperature is substituted into the pressure tensor,which is used for the calculation of an order parameter representing two phases so that bubbles can be formed by nucleate boiling.By using this method,twodimensional simulations of nucleate pool boiling by a heat source on a solid wall are carried out with the boundary condition for a constant heat flux.The flow characteristics and temperature distribution in the nucleate pool boiling process are obtained.It is seen that a bubble nucleation is formed at first and then the bubble grows and leaves the wall,finally going up with deformation by the buoyant effect.In addition,the effects of the gravity and the surface wettability on the bubble diameter at departure are numerically investigated.The calculated results are in qualitative agreement with other theoretical predictions with available experimental data.展开更多
The lattice Boltzmann method(LBM)with an elastic model is applied to the simulation of two-phase flows containing a deformable body with a viscoelastic membrane.The numerical method is based on the LBM for incompressi...The lattice Boltzmann method(LBM)with an elastic model is applied to the simulation of two-phase flows containing a deformable body with a viscoelastic membrane.The numerical method is based on the LBM for incompressible two-phase fluid flows with the same density.The body has an internal fluid covered by a viscoelastic membrane of a finite thickness.An elastic model is introduced to the LBM in order to determine the elastic forces acting on the viscoelastic membrane of the body.In the present method,we take account of changes in surface area of the membrane and in total volume of the body as well as shear deformation of the membrane.By using this method,we calculate two problems,the behavior of an initially spherical body under shear flow and the motion of a body with initially spherical or biconcave discoidal shape in square pipe flow.Calculated deformations of the body(the Taylor shape parameter)for various shear rates are in good agreement with other numerical results.Moreover,tank-treading motion,which is a characteristic motion of viscoelastic bodies in shear flows,is simulated by the present method.展开更多
基金This work was partly supported by the Grant-in-Aid for Young Scientists(B)[No.18760121]the Ministry of Education,Culture,Sports,Science and Technology(MEXT)in Japan.
文摘A thermal lattice Boltzmann method(LBM)for two-phase fluid flows in nucleate pool boiling process is proposed.In the present method,a new function for heat transfer is introduced to the isothermal LBM for two-phase immiscible fluids with large density differences.The calculated temperature is substituted into the pressure tensor,which is used for the calculation of an order parameter representing two phases so that bubbles can be formed by nucleate boiling.By using this method,twodimensional simulations of nucleate pool boiling by a heat source on a solid wall are carried out with the boundary condition for a constant heat flux.The flow characteristics and temperature distribution in the nucleate pool boiling process are obtained.It is seen that a bubble nucleation is formed at first and then the bubble grows and leaves the wall,finally going up with deformation by the buoyant effect.In addition,the effects of the gravity and the surface wettability on the bubble diameter at departure are numerically investigated.The calculated results are in qualitative agreement with other theoretical predictions with available experimental data.
基金supported in part by the Satellite Venture Business Laboratory,Shinshu University and by the Grant-in-Aid for Young Scientists(B)[No.21760123]of the Ministry of Education,Culture,Sports,Science and Technology,Japan.
文摘The lattice Boltzmann method(LBM)with an elastic model is applied to the simulation of two-phase flows containing a deformable body with a viscoelastic membrane.The numerical method is based on the LBM for incompressible two-phase fluid flows with the same density.The body has an internal fluid covered by a viscoelastic membrane of a finite thickness.An elastic model is introduced to the LBM in order to determine the elastic forces acting on the viscoelastic membrane of the body.In the present method,we take account of changes in surface area of the membrane and in total volume of the body as well as shear deformation of the membrane.By using this method,we calculate two problems,the behavior of an initially spherical body under shear flow and the motion of a body with initially spherical or biconcave discoidal shape in square pipe flow.Calculated deformations of the body(the Taylor shape parameter)for various shear rates are in good agreement with other numerical results.Moreover,tank-treading motion,which is a characteristic motion of viscoelastic bodies in shear flows,is simulated by the present method.
