On the basis of the physical mechanism, a body-fitted coordinate system is developed. By using this system the boundaries in simulation and in real are fitted well, and simulation with great accuracy is achieved. A co...On the basis of the physical mechanism, a body-fitted coordinate system is developed. By using this system the boundaries in simulation and in real are fitted well, and simulation with great accuracy is achieved. A computation example indicates that compared to traditional two-dimensional computation methods, the body-fitted simulation has an advantange of better coincidence with the real and can be adopted in simulating flow fields in tidal estuaries.展开更多
Generating body-fitted particle distribution for arbitrarily complex geometry underpins the applications of particle-based method to engineering and bioengineering and is highly challenging,and thus hinders the potent...Generating body-fitted particle distribution for arbitrarily complex geometry underpins the applications of particle-based method to engineering and bioengineering and is highly challenging,and thus hinders the potential of particle methods.In this paper,we present a new computer-aided design(CAD)compatible body-fitted particle generator,termed as CAD-BPG,for arbitrarily complex 3-D geometry.By parsing a CAD model,the present method can accurately tackle arbitrarily complex geometry representation and describe the corresponding geometry surface by constructing an implicit zero level-set function on Cartesian background mesh.To achieve a body-fitted and isotropic particle distribution,physics-driven relaxation process with surface bounding governed by the transport-velocity formulation of smoothed particle hydrodynamics(SPH)methodology is conducted to characterize the particle evolution.A set of examples,ranging from propeller,stent structures and anatomical heart models,show simplicity,accuracy and versatility of the present CAD-BPG for generating body-fitted particle distribution of arbitrarily complex 3-D geometry.Last but not least,the present CAD-BPG is applied for modeling wave-structure interaction,where wave interaction with an oscillating wave surge converter is studied,and the results show that the present method not only provides an efficient and easy-to-implement pre-processing tool for particle-based simulation but also improves the numerical accuracy compared with lattice particle distribution.Consequently,the propose CAD-BPG sheds light on simulating real-world applications by particle-based methods for researchers and engineers.展开更多
Numerical analysis of three-dimensional(3-D)two-phase reacting flowfield in an annular combustor wity the dump diffuser is developed in arbitrary curvilinear coordi-nates.Combustor performances are estimated by the em...Numerical analysis of three-dimensional(3-D)two-phase reacting flowfield in an annular combustor wity the dump diffuser is developed in arbitrary curvilinear coordi-nates.Combustor performances are estimated by the em-pirical-analytical desing method.Ths influence of three inlet velocity profiles of the prediffuser and two operating conditions on combustor preformance and flow character-istic is predicted.展开更多
Body-fitted coordinate transformation equation was deduced and used to generate the body-fitted grids of molten pool for twin-roll strip casting.The orthogonality of the grids on the boundary was modified by adjusting...Body-fitted coordinate transformation equation was deduced and used to generate the body-fitted grids of molten pool for twin-roll strip casting.The orthogonality of the grids on the boundary was modified by adjusting source item.The energy equation and the boundary conditions were transformed from physical space to computational space.The velocity field model proposed by Hirohiko Takuda was used to calculate the temperature field of molten steel,and the influence of technical factors was also discussed.展开更多
The 3-D turbulent flows in a valve pipe were described by the incompressibleReynolds-averaged Navier-Stokes equations with an RNG k-ε turbulence model. With the finite volumemethod and a body-fitted coordinate system...The 3-D turbulent flows in a valve pipe were described by the incompressibleReynolds-averaged Navier-Stokes equations with an RNG k-ε turbulence model. With the finite volumemethod and a body-fitted coordinate system, the discretised equations were solved by the SIMPLESTalgorithm. The numerical result of a cut-off valve with curved inlet shows the flow characteristicsand the main cause of energy loss when fluid flows through a valve. And then, the boundaries ofvalve were modified in order to reduce the energy loss. The computational results of modified valveshow that the numerical value of turbulent kinetic energy is lower, and that the modified design ofthe 3-D valve boundaries is much better. The analysis of the result also shows that RNG k-εturbulence model can successfully be used to predict the 3-D turbulent separated flows and thesecondary flow inside valve pipes.展开更多
A numerical model of transverse mixing in natural rivers has been presented by using the body-fitted coordinate systems,which is capable of describing the complex flow and mixing characteristics of rivers.To study the...A numerical model of transverse mixing in natural rivers has been presented by using the body-fitted coordinate systems,which is capable of describing the complex flow and mixing characteristics of rivers.To study the validity and to illustrate the applicability of this model,field measurement date in the Gan River near Nanchang have been used to compare the numerical results.展开更多
The co-located grid, SIMPLEC and Chen-Kim modified k - E turbulence model are applied to investigate numerically the multi-stream flow and temperature fields in the complex channel with a forced mixer lobe at room tem...The co-located grid, SIMPLEC and Chen-Kim modified k - E turbulence model are applied to investigate numerically the multi-stream flow and temperature fields in the complex channel with a forced mixer lobe at room temperature and at elevated temperature. The body-fitted coordinate grids are generated respectively in sub-domains according to the shapes of the channel by solving Poisson’s equations to compose the whole grid of the domain. The large viscosity, linear and simultaneous under-relaxation factors are used to solve the coupling of fluid and solid. The solid grid is complemented at the upper inlet of the secondary flow to keep the same node number at the inlet and at double-wall sub-domains. The numerical results and experimental data show good agreement at room temperature. It is illustrated that the cooling air ejected into the slot between the double plates decreases the temperature of the wall.展开更多
The main goal of this paper is to develop the coupled double-distributionfunction(DDF)lattice Boltzmann method(LBM)for simulation of subsonic and transonic turbulent flows.In the present study,we adopt the second-orde...The main goal of this paper is to develop the coupled double-distributionfunction(DDF)lattice Boltzmann method(LBM)for simulation of subsonic and transonic turbulent flows.In the present study,we adopt the second-order implicit-explicit(IMEX)Runge-Kutta schemes for time discretization and the Non-Oscillatory and NonFree-Parameters Dissipative(NND)finite difference scheme for space discretization.The Sutherland’s law is used for expressing the viscosity of the fluid due to considerable temperature change.Also,the Spalart-Allmaras(SA)turbulence model is incorporated in order for the turbulent flow effect to be pronounced.Numerical experiments are performed on different turbulent compressible flows around a NACA0012 airfoil with body-fitted grid.Our numerical results are found to be in good agreement with experiment data and/or other numerical solutions,demonstrating the applicability of the method presented in this study to simulations of both subsonic and transonic turbulent flows.展开更多
文摘On the basis of the physical mechanism, a body-fitted coordinate system is developed. By using this system the boundaries in simulation and in real are fitted well, and simulation with great accuracy is achieved. A computation example indicates that compared to traditional two-dimensional computation methods, the body-fitted simulation has an advantange of better coincidence with the real and can be adopted in simulating flow fields in tidal estuaries.
基金supported by the National Nature Science Foundation of China(Nos.41504102 and 41604037)National Science and Technology Major Project(No.2016ZX05015-006)Yangtze University Youth Found(No.2015cqn32)
基金the National Natural Science Foundation of China(Grant No.91952110)the Deutsche Forschungsgemeinschaft under(Grant Nos.DFG HU 1572/10-1,DFG HU1527/12-1).
文摘Generating body-fitted particle distribution for arbitrarily complex geometry underpins the applications of particle-based method to engineering and bioengineering and is highly challenging,and thus hinders the potential of particle methods.In this paper,we present a new computer-aided design(CAD)compatible body-fitted particle generator,termed as CAD-BPG,for arbitrarily complex 3-D geometry.By parsing a CAD model,the present method can accurately tackle arbitrarily complex geometry representation and describe the corresponding geometry surface by constructing an implicit zero level-set function on Cartesian background mesh.To achieve a body-fitted and isotropic particle distribution,physics-driven relaxation process with surface bounding governed by the transport-velocity formulation of smoothed particle hydrodynamics(SPH)methodology is conducted to characterize the particle evolution.A set of examples,ranging from propeller,stent structures and anatomical heart models,show simplicity,accuracy and versatility of the present CAD-BPG for generating body-fitted particle distribution of arbitrarily complex 3-D geometry.Last but not least,the present CAD-BPG is applied for modeling wave-structure interaction,where wave interaction with an oscillating wave surge converter is studied,and the results show that the present method not only provides an efficient and easy-to-implement pre-processing tool for particle-based simulation but also improves the numerical accuracy compared with lattice particle distribution.Consequently,the propose CAD-BPG sheds light on simulating real-world applications by particle-based methods for researchers and engineers.
文摘Numerical analysis of three-dimensional(3-D)two-phase reacting flowfield in an annular combustor wity the dump diffuser is developed in arbitrary curvilinear coordi-nates.Combustor performances are estimated by the em-pirical-analytical desing method.Ths influence of three inlet velocity profiles of the prediffuser and two operating conditions on combustor preformance and flow character-istic is predicted.
文摘Body-fitted coordinate transformation equation was deduced and used to generate the body-fitted grids of molten pool for twin-roll strip casting.The orthogonality of the grids on the boundary was modified by adjusting source item.The energy equation and the boundary conditions were transformed from physical space to computational space.The velocity field model proposed by Hirohiko Takuda was used to calculate the temperature field of molten steel,and the influence of technical factors was also discussed.
文摘The 3-D turbulent flows in a valve pipe were described by the incompressibleReynolds-averaged Navier-Stokes equations with an RNG k-ε turbulence model. With the finite volumemethod and a body-fitted coordinate system, the discretised equations were solved by the SIMPLESTalgorithm. The numerical result of a cut-off valve with curved inlet shows the flow characteristicsand the main cause of energy loss when fluid flows through a valve. And then, the boundaries ofvalve were modified in order to reduce the energy loss. The computational results of modified valveshow that the numerical value of turbulent kinetic energy is lower, and that the modified design ofthe 3-D valve boundaries is much better. The analysis of the result also shows that RNG k-εturbulence model can successfully be used to predict the 3-D turbulent separated flows and thesecondary flow inside valve pipes.
文摘A numerical model of transverse mixing in natural rivers has been presented by using the body-fitted coordinate systems,which is capable of describing the complex flow and mixing characteristics of rivers.To study the validity and to illustrate the applicability of this model,field measurement date in the Gan River near Nanchang have been used to compare the numerical results.
文摘The co-located grid, SIMPLEC and Chen-Kim modified k - E turbulence model are applied to investigate numerically the multi-stream flow and temperature fields in the complex channel with a forced mixer lobe at room temperature and at elevated temperature. The body-fitted coordinate grids are generated respectively in sub-domains according to the shapes of the channel by solving Poisson’s equations to compose the whole grid of the domain. The large viscosity, linear and simultaneous under-relaxation factors are used to solve the coupling of fluid and solid. The solid grid is complemented at the upper inlet of the secondary flow to keep the same node number at the inlet and at double-wall sub-domains. The numerical results and experimental data show good agreement at room temperature. It is illustrated that the cooling air ejected into the slot between the double plates decreases the temperature of the wall.
基金financially supported mainly by the Aeronautical Science Fund of China(Grant No.20061453020)The funds from the Foundation for Basic Research of Northwestern Polytechnical University,P.R.Chinafrom the Discovery Grant of the Natural Sciences and Engineering Research Council of Canada(NSERC)were also used to support this research work.
文摘The main goal of this paper is to develop the coupled double-distributionfunction(DDF)lattice Boltzmann method(LBM)for simulation of subsonic and transonic turbulent flows.In the present study,we adopt the second-order implicit-explicit(IMEX)Runge-Kutta schemes for time discretization and the Non-Oscillatory and NonFree-Parameters Dissipative(NND)finite difference scheme for space discretization.The Sutherland’s law is used for expressing the viscosity of the fluid due to considerable temperature change.Also,the Spalart-Allmaras(SA)turbulence model is incorporated in order for the turbulent flow effect to be pronounced.Numerical experiments are performed on different turbulent compressible flows around a NACA0012 airfoil with body-fitted grid.Our numerical results are found to be in good agreement with experiment data and/or other numerical solutions,demonstrating the applicability of the method presented in this study to simulations of both subsonic and transonic turbulent flows.
