The current paper presents the result of a study on determining the pressure distribution along the surface of a foil section by using measured velocity field data and the Reynolds Averaged Navier-Stokes equations. Th...The current paper presents the result of a study on determining the pressure distribution along the surface of a foil section by using measured velocity field data and the Reynolds Averaged Navier-Stokes equations. The results are compared with the measured pressure data and show its satisfaction. It is a try to find a new way to determine pressure by combining the experimental data and CFD method.展开更多
Submarine maneuverability has been analyzed by means of computational fluid dynamics(CFD).This approach provides an alternative,accurate,and cost-effective method for simulating actual flow.The numerical results show ...Submarine maneuverability has been analyzed by means of computational fluid dynamics(CFD).This approach provides an alternative,accurate,and cost-effective method for simulating actual flow.The numerical results show that the numerical simulation of the viscous flow related to a moving submarine based on the RANS equation with a relevant turbulence model can not only provide rich flow field details such as flow separation,but also accurately predict its hydrodynamic performance.The present study indicates that CFD can be used to forecast the submarine’s maneuverability in the initial design stage.The present results will be used in the future as a basis for analyzing methods to reduce the vibration and noise generated by the submarine.展开更多
Planing vessels are applied widely in civil and military situations.Due to their high speed,the motion of planning vessels is complex.In order to predict the motion of planning vessels,it is important to analyze the h...Planing vessels are applied widely in civil and military situations.Due to their high speed,the motion of planning vessels is complex.In order to predict the motion of planning vessels,it is important to analyze the hydrodynamic performance of planning vessels at high speeds.The computational fluid dynamic method（CFD） has been proposed to calculate hydrodynamic performance of planning vessels.However,in most traditional CFD approaches,model tests or empirical formulas are needed to obtain the running attitude of the planing vessels before calculation.This paper presents a new CFD method to calculate hydrodynamic forces of planing vessels.The numerical method was based on Reynolds-Averaged Navier-Stokes（RANS） equations.The volume of fluid（VOF） method and the six-degrees-of-freedom equation were applied.An effective process was introduced to solve the numerical divergence problem in numerical simulation.Compared with experimental results,numerical simulation results indicate that both the running attitude and hydrodynamic performance can be predicted well at high speeds.展开更多
This work is aimed at optimizing a settler structure in a mixer-settler.Two different aspects have been considered.Firstly,the flowcharacteristics of a settler have been examined by computational fluid dynamics(CFD)si...This work is aimed at optimizing a settler structure in a mixer-settler.Two different aspects have been considered.Firstly,the flowcharacteristics of a settler have been examined by computational fluid dynamics(CFD)simulation with various agitation speeds of the mixer,as well as organic phase volume fractions ranging from 0.075 to 0.6.The aqueous and organic phase turbulent flow fields were measured by particle image velocimetry(PIV)technique to verify the CFD simulation.Two organic phases with different physical properties were assessed in the CFD simulation to simulate the liquid-liquid systems related to rare earth element extraction,i.e.,0.072 mol·L^-1 P507/kerosene and 1.8 mol·L^-1 P507/kerosene.Secondly,the CFD simulation was carried out in a settler equipped with baffles.The effects of number and location of the baffle in the settler on flow features and entrainments of the aqueous and organic outlet were analyzed.Meanwhile,different settler/mixer volume ratios were also examined.By analyses and comparisons,an optimal design for settler was proposed.CFD can provide a significant guidance to better mixer-settler design.展开更多
Wing-body junction turbulence flow is simulated by using RANS equation and boundary fitted coordinate technique. Three order differential scheme is used in the computation of convection term and two layers turbulence ...Wing-body junction turbulence flow is simulated by using RANS equation and boundary fitted coordinate technique. Three order differential scheme is used in the computation of convection term and two layers turbulence model are employed in the calculation.展开更多
A global optimization approach to turbine blade design based on hierarchical fair competition genetic algorithms with dynamic niche （HFCDN-GAs） coupled with Reynolds-averaged Navier-Stokes （RANS） equation is prese...A global optimization approach to turbine blade design based on hierarchical fair competition genetic algorithms with dynamic niche （HFCDN-GAs） coupled with Reynolds-averaged Navier-Stokes （RANS） equation is presented. In order to meet the search theory of GAs and the aerodynamic performances of turbine, Bezier curve is adopted to parameterize the turbine blade profile, and a fitness function pertaining to optimization is designed. The design variables are the control points＇ ordinates of characteristic polygon of Bezier curve representing the turbine blade profile. The object function is the maximum lift-drag ratio of the turbine blade. The constraint conditions take into account the leading and trailing edge metal angle, and the strength and aerodynamic performances of turbine blade. And the treatment method of the constraint conditions is the flexible penalty function. The convergence history of test function indicates that HFCDN-GAs can locate the global optimum within a few search steps and have high robustness. The lift-drag ratio of the optimized blade is 8.3% higher than that of the original one. The results show that the proposed global optimization approach is effective for turbine blade.展开更多
This paper presents a numerical model that simulates the wind fields, turbulence fields, and dispersion of gaseous substances in urban areas on building to city block scales. A Computational Fluid Dynamics（CFD） appr...This paper presents a numerical model that simulates the wind fields, turbulence fields, and dispersion of gaseous substances in urban areas on building to city block scales. A Computational Fluid Dynamics（CFD） approach using the steady-state, Reynolds-Averaged Navier-Stokes（RANS） equations with the standard k-ε turbulence model within control volumes of non-uniform cuboid shapes has been employed. Dispersion field is computed by solving an unsteady transport equation of passive scalar. Another approach based on Gaussian plume model is used to correct the turbulent Schmidt number of tracer, in order to improve the dispersion simulation. The experimental data from a wind tunnel under neutral conditions are used to validate the numerical results of velocity, turbulence, and dispersion fields. The numerical results show a reasonable agreement with the wind tunnel data. The deviation of concentration between the simulation with corrected turbulent Schmidt number and the wind tunnel experiments may arise from 1） imperfect point sources, 2） heterogeneous turbulent difusivity, and 3） the constant turbulent Schmidt assumption used in the model.展开更多
The variations of ship stern flow field structure and its corresponding hydrodnamic performance under full scale Reynolds numbal (5 109) and model scale Reynolds numbal(5 106) are investigated numerically in this pape...The variations of ship stern flow field structure and its corresponding hydrodnamic performance under full scale Reynolds numbal (5 109) and model scale Reynolds numbal(5 106) are investigated numerically in this paper. The governing equations for 3-D incompressible turbulent flow which consist of RANS equation and K-ε two equation turbulence model are solved by finite difference scheme. Derailed computational results are presented graphically. The comparisons between present calculation, existing measurement and other calculation are made.展开更多
A calculation code of numeriCal simulation of complete Reynolds-averaged Navier-Stokes(RANS) equations for three-dimensional viscous flow around a ship is developed in this paper using an improved separated-layer fini...A calculation code of numeriCal simulation of complete Reynolds-averaged Navier-Stokes(RANS) equations for three-dimensional viscous flow around a ship is developed in this paper using an improved separated-layer finite analytic(SLFA) method. And the k-εmodel is used to compute the turbulent stress. An improvement is also made for grid generation in the aspectS of saving the run time and controlling the grid density in the near wall region. The SIMPLEM algorithm, superior to the well-known SIMILER algorithm, is adopted for speeding up the iterations of the coupling between the pressure and velocity under the unstaggered gild.Rather satisfied agreements with the experimental results are achieved for the Wigley mathematic hull at the Reynolds number of 1. 0×106.展开更多
A method is presented to calculate the resistance of a high-speed displacement ship taking the effect of sinkage and trim and viscosity of fluid into account.A free surface flow field is evaluated by solving Reynolds ...A method is presented to calculate the resistance of a high-speed displacement ship taking the effect of sinkage and trim and viscosity of fluid into account.A free surface flow field is evaluated by solving Reynolds averaged Navier-Stokes(RANS) equations with volume of fluid(VoF) method.The sinkage and trim are computed by equating the vertical force and pitching moment to the hydrostatic restoring force and moment.The software Fluent,Maxsurf and MATLAB are used to implement this method.With dynamic mesh being used,the position of a ship is updated by the motion of "ship plus boundary layer" grid zone.The hull factors are introduced for fast calculating the running attitude of a ship.The method has been applied to the ship model INSEAN2340 for different Froude numbers and is found to be efficient for evaluating the flow field,resistance,sinkage and trim.展开更多
On the basis of the transient water wave(TWW) theory,focused wave is generated in the circulating water channel.Numerical simulation of the focused wave is carried out by solving the Reynolds averaged NavierStokes(RAN...On the basis of the transient water wave(TWW) theory,focused wave is generated in the circulating water channel.Numerical simulation of the focused wave is carried out by solving the Reynolds averaged NavierStokes(RANS) equations.The dynamic grid technique is adopted to simulate the motion of the wave maker,and the volume of fluid(VOF) method is used to capture the free surface of the wave.The simulation results are compared with the measured data,and good agreement is obtained.For quantitative estimation of the numerical simulation error and uncertainty,the uncertainty analysis method recommended by the International Towing Tank Conference(ITTC) procedure is performed for the simulation results of the surface elevations at different positions.Both grid-convergence and time-step-size convergence studies are conducted using three types of grids and time step sizes.The simulation results are all monotonously convergent in the verification procedure,and the validations of the simulated surface elevations with the positions at 3.5,4.0 and 4.5 m are all achieved by comparing with the validation uncertainty.It is found that the numerical simulation errors caused by the grid and time-step-size in the convergence studies have the same order of magnitude.In addition,the numerical errors and uncertainties for the surface elevations at different positions are compared and discussed in detail.This paper presents the first attempt to carry out the uncertainty analysis of the simulation of focused wave,and the effectiveness of the proposed verification and validation procedures in the uncertainty analysis is demonstrated.展开更多
文摘The current paper presents the result of a study on determining the pressure distribution along the surface of a foil section by using measured velocity field data and the Reynolds Averaged Navier-Stokes equations. The results are compared with the measured pressure data and show its satisfaction. It is a try to find a new way to determine pressure by combining the experimental data and CFD method.
基金supported by Scientific Research Fund of Ministry of Education Innovation platform open fund Project(No.2018C01044)and(No.2018A03025).
文摘Submarine maneuverability has been analyzed by means of computational fluid dynamics(CFD).This approach provides an alternative,accurate,and cost-effective method for simulating actual flow.The numerical results show that the numerical simulation of the viscous flow related to a moving submarine based on the RANS equation with a relevant turbulence model can not only provide rich flow field details such as flow separation,but also accurately predict its hydrodynamic performance.The present study indicates that CFD can be used to forecast the submarine’s maneuverability in the initial design stage.The present results will be used in the future as a basis for analyzing methods to reduce the vibration and noise generated by the submarine.
基金Supported by the National Natural Science Foundation of China （51009038/E091002）
文摘Planing vessels are applied widely in civil and military situations.Due to their high speed,the motion of planning vessels is complex.In order to predict the motion of planning vessels,it is important to analyze the hydrodynamic performance of planning vessels at high speeds.The computational fluid dynamic method（CFD） has been proposed to calculate hydrodynamic performance of planning vessels.However,in most traditional CFD approaches,model tests or empirical formulas are needed to obtain the running attitude of the planing vessels before calculation.This paper presents a new CFD method to calculate hydrodynamic forces of planing vessels.The numerical method was based on Reynolds-Averaged Navier-Stokes（RANS） equations.The volume of fluid（VOF） method and the six-degrees-of-freedom equation were applied.An effective process was introduced to solve the numerical divergence problem in numerical simulation.Compared with experimental results,numerical simulation results indicate that both the running attitude and hydrodynamic performance can be predicted well at high speeds.
基金the National Basic Research Program of China(No.2012CBA01203)National Natural Science Foundation of China(No.21636004)the Specialized Research Fund for Doctoral Program of Higher Education of MOE of China(No.20130002110018)in the State Key Laboratory of Chemical Engineering of Tsinghua University,Beijing,China。
文摘This work is aimed at optimizing a settler structure in a mixer-settler.Two different aspects have been considered.Firstly,the flowcharacteristics of a settler have been examined by computational fluid dynamics(CFD)simulation with various agitation speeds of the mixer,as well as organic phase volume fractions ranging from 0.075 to 0.6.The aqueous and organic phase turbulent flow fields were measured by particle image velocimetry(PIV)technique to verify the CFD simulation.Two organic phases with different physical properties were assessed in the CFD simulation to simulate the liquid-liquid systems related to rare earth element extraction,i.e.,0.072 mol·L^-1 P507/kerosene and 1.8 mol·L^-1 P507/kerosene.Secondly,the CFD simulation was carried out in a settler equipped with baffles.The effects of number and location of the baffle in the settler on flow features and entrainments of the aqueous and organic outlet were analyzed.Meanwhile,different settler/mixer volume ratios were also examined.By analyses and comparisons,an optimal design for settler was proposed.CFD can provide a significant guidance to better mixer-settler design.
文摘Wing-body junction turbulence flow is simulated by using RANS equation and boundary fitted coordinate technique. Three order differential scheme is used in the computation of convection term and two layers turbulence model are employed in the calculation.
基金This project is supported by National Natural Science Foundation of China (No,50776056)National Hi-tech Research and Development Program of China (863 Program,No.2006AA05Z250).
文摘A global optimization approach to turbine blade design based on hierarchical fair competition genetic algorithms with dynamic niche （HFCDN-GAs） coupled with Reynolds-averaged Navier-Stokes （RANS） equation is presented. In order to meet the search theory of GAs and the aerodynamic performances of turbine, Bezier curve is adopted to parameterize the turbine blade profile, and a fitness function pertaining to optimization is designed. The design variables are the control points＇ ordinates of characteristic polygon of Bezier curve representing the turbine blade profile. The object function is the maximum lift-drag ratio of the turbine blade. The constraint conditions take into account the leading and trailing edge metal angle, and the strength and aerodynamic performances of turbine blade. And the treatment method of the constraint conditions is the flexible penalty function. The convergence history of test function indicates that HFCDN-GAs can locate the global optimum within a few search steps and have high robustness. The lift-drag ratio of the optimized blade is 8.3% higher than that of the original one. The results show that the proposed global optimization approach is effective for turbine blade.
基金Supported by the China Meteorological Administration Special Public Welfare Research Fund (GYHY201106033)
文摘This paper presents a numerical model that simulates the wind fields, turbulence fields, and dispersion of gaseous substances in urban areas on building to city block scales. A Computational Fluid Dynamics（CFD） approach using the steady-state, Reynolds-Averaged Navier-Stokes（RANS） equations with the standard k-ε turbulence model within control volumes of non-uniform cuboid shapes has been employed. Dispersion field is computed by solving an unsteady transport equation of passive scalar. Another approach based on Gaussian plume model is used to correct the turbulent Schmidt number of tracer, in order to improve the dispersion simulation. The experimental data from a wind tunnel under neutral conditions are used to validate the numerical results of velocity, turbulence, and dispersion fields. The numerical results show a reasonable agreement with the wind tunnel data. The deviation of concentration between the simulation with corrected turbulent Schmidt number and the wind tunnel experiments may arise from 1） imperfect point sources, 2） heterogeneous turbulent difusivity, and 3） the constant turbulent Schmidt assumption used in the model.
文摘The variations of ship stern flow field structure and its corresponding hydrodnamic performance under full scale Reynolds numbal (5 109) and model scale Reynolds numbal(5 106) are investigated numerically in this paper. The governing equations for 3-D incompressible turbulent flow which consist of RANS equation and K-ε two equation turbulence model are solved by finite difference scheme. Derailed computational results are presented graphically. The comparisons between present calculation, existing measurement and other calculation are made.
文摘A calculation code of numeriCal simulation of complete Reynolds-averaged Navier-Stokes(RANS) equations for three-dimensional viscous flow around a ship is developed in this paper using an improved separated-layer finite analytic(SLFA) method. And the k-εmodel is used to compute the turbulent stress. An improvement is also made for grid generation in the aspectS of saving the run time and controlling the grid density in the near wall region. The SIMPLEM algorithm, superior to the well-known SIMILER algorithm, is adopted for speeding up the iterations of the coupling between the pressure and velocity under the unstaggered gild.Rather satisfied agreements with the experimental results are achieved for the Wigley mathematic hull at the Reynolds number of 1. 0×106.
基金the National Natural Science Foundation of China (No.50879090)the Advanced Research Program of GAD of the P.L.A (No.7131005)
文摘A method is presented to calculate the resistance of a high-speed displacement ship taking the effect of sinkage and trim and viscosity of fluid into account.A free surface flow field is evaluated by solving Reynolds averaged Navier-Stokes(RANS) equations with volume of fluid(VoF) method.The sinkage and trim are computed by equating the vertical force and pitching moment to the hydrostatic restoring force and moment.The software Fluent,Maxsurf and MATLAB are used to implement this method.With dynamic mesh being used,the position of a ship is updated by the motion of "ship plus boundary layer" grid zone.The hull factors are introduced for fast calculating the running attitude of a ship.The method has been applied to the ship model INSEAN2340 for different Froude numbers and is found to be efficient for evaluating the flow field,resistance,sinkage and trim.
基金the National Natural Science Foundation of China(No.51379124)the Knowledge-Based Ship-Design Hyper-Integrated Platform(KSHIP) 2nd Term(No.GKZY010004)
文摘On the basis of the transient water wave(TWW) theory,focused wave is generated in the circulating water channel.Numerical simulation of the focused wave is carried out by solving the Reynolds averaged NavierStokes(RANS) equations.The dynamic grid technique is adopted to simulate the motion of the wave maker,and the volume of fluid(VOF) method is used to capture the free surface of the wave.The simulation results are compared with the measured data,and good agreement is obtained.For quantitative estimation of the numerical simulation error and uncertainty,the uncertainty analysis method recommended by the International Towing Tank Conference(ITTC) procedure is performed for the simulation results of the surface elevations at different positions.Both grid-convergence and time-step-size convergence studies are conducted using three types of grids and time step sizes.The simulation results are all monotonously convergent in the verification procedure,and the validations of the simulated surface elevations with the positions at 3.5,4.0 and 4.5 m are all achieved by comparing with the validation uncertainty.It is found that the numerical simulation errors caused by the grid and time-step-size in the convergence studies have the same order of magnitude.In addition,the numerical errors and uncertainties for the surface elevations at different positions are compared and discussed in detail.This paper presents the first attempt to carry out the uncertainty analysis of the simulation of focused wave,and the effectiveness of the proposed verification and validation procedures in the uncertainty analysis is demonstrated.
