In order to speed underwater launch of minor-caliber weapons,a sealing device can be set in front of underwater muzzle to separate water,preventing the muzzle from water immersion.By establishing and simplifying the m...In order to speed underwater launch of minor-caliber weapons,a sealing device can be set in front of underwater muzzle to separate water,preventing the muzzle from water immersion.By establishing and simplifying the model of underwater weapon sealing device and unstructured mesh computing domain model based on computational fluid dynamics（CFD）,dynamic mesh and user defined function（UDF）,the N-S equation is solved and the numerical analysis and calculation of the complex two-phase flow inside the sealing device are carried out.The results show that the gas discharged from the sealing device is conducive to the formation of the projectile supercavity.When the projectile is launched at 5munder water,the shock wave before and after the projectile has impact on the box body up to 100 MPa,therefore the sealing device must be strong enough.The research results have the vital significance to the design of underwater weapon sealing device and the formation of the projectile supercavitation.展开更多
The flow around airfoil NACA0012 enwrapped by the body-fitted grid is simulated by a coupled doubledistribution-function （DDF） lattice Boltzmann method （LBM） for the compressible Navier-Stokes equations. Firstly, ...The flow around airfoil NACA0012 enwrapped by the body-fitted grid is simulated by a coupled doubledistribution-function （DDF） lattice Boltzmann method （LBM） for the compressible Navier-Stokes equations. Firstly, the method is tested by simulating the low Reynolds number flow at Ma =0. 5,a=0. 0, Re=5 000. Then the simulation of flow around the airfoil is carried out at Ma：0. 5, 0. 85, 1.2; a=-0.05, 1.0, 0.0, respectively. And a better result is obtained by using a local refined grid. It reduces the error produced by the grid at Ma=0. 85. Though the inviscid boundary condition is used to avoid the problem of flow transition to turbulence at high Reynolds numbers, the pressure distribution obtained by the simulation agrees well with that of the experimental results. Thus, it proves the reliability of the method and shows its potential for the compressible flow simulation. The suecessful application to the flow around airfoil lays a foundation of the numerical simulation of turbulence.展开更多
Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of orien...Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of oriented valves within a tray and meshed into two parts with different grid types and sizes.The volume fraction correlation concerning inter-phase momentum transfer source was fitted based on experimental data,and built in UDF for simulation.The flow pattern of oriented valve tray under different operating conditions was simulated under Eulerian-Eulerian framework with realizable k-ε model.The predicted liquid height from CFD simulation was in good agreement with the results of pressure drop and volume fraction correlations.Meanwhile,the velocity distribution and volume fraction of the two phases were demonstrated and analyzed,which are useful in design and analysis of the column trays.展开更多
Numerical simulation on conjugate heat transfer of an internal cooled turbine vane was carried out. Numerical techniques employed included the third-order accuracy TVD scheme, multi-block structured grids and the tech...Numerical simulation on conjugate heat transfer of an internal cooled turbine vane was carried out. Numerical techniques employed included the third-order accuracy TVD scheme, multi-block structured grids and the technique of arbitrary curved mesh. Comparison between results of commercial CFD codes with several turbulence models and those of this code shows that it is incorrect of commercial CFD codes to predict the thermal boundary layer with traditional turbulence models, and that turbulence models considering transition lead to more accurate heat transfer in thermal boundary layer with some reliability and deficiency yet. The results of this code are close to those of CFX with transition model.展开更多
Shape optimization of the caudal fin of the three-dimensional self-propelled swimming fish,to increase the swimming efficiency and the swimming speed and control the motion direction more easily,is investigated by com...Shape optimization of the caudal fin of the three-dimensional self-propelled swimming fish,to increase the swimming efficiency and the swimming speed and control the motion direction more easily,is investigated by combining optimization algorithms,unsteady computational fluid dynamics and dynamic control in this study.The 3D computational fluid dynamics package contains the immersed boundary method,volume of fluid method,the adaptive multi-grid finite volume method and the control strategy of fish swimming.Through shape optimizations of various swimming speeds,the results show that the optimal caudal fins of different swimming modes are not exactly the same shape.However,the optimal fish of high swimming speed,whose caudal fin shape is similar to the crescent,also have higher efficiency and better maneuverability than the other optimal bionic fish at low and moderate swimming speeds.Finally,the mechanisms of vorticity creation of different optimal bionic fish are studied by using boundary vorticity-flux theory,and three-dimensional wake structures of self-propelled swimming of these fish are comparatively analyzed.The study of vortex dynamics reveals the nature of efficient swimming of the 3D bionic fish with the lunate caudal fin.展开更多
Numerical simulations and the control of self-propelled swimming of three-dimensional bionic fish in a viscous flow and the mechanism of fish swimming are carried out in this study,with a 3D computational fluid dynami...Numerical simulations and the control of self-propelled swimming of three-dimensional bionic fish in a viscous flow and the mechanism of fish swimming are carried out in this study,with a 3D computational fluid dynamics package,which includes the immersed boundary method and the volume of fluid method,the adaptive multi-grid finite volume method,and the control strategy of fish swimming.Firstly,the mechanism of 3D fish swimming was studied and the vorticity dynamics root was traced to the moving body surface by using the boundary vorticity-flux theory.With the change of swimming speed,the contributions of the fish body and caudal fin to thrust are analyzed quantitatively.The relationship between vortex structures of fish swimming and the forces exerted on the fish body are also given in this paper.Finally,the 3D wake structure of self-propelled swimming of 3D bionic fish is presented.The in-depth analysis of the 3D vortex structure in the role of 3D biomimetic fish swimming is also performed.展开更多
基金National Natural Science Foundation of China(No.51175481)
文摘In order to speed underwater launch of minor-caliber weapons,a sealing device can be set in front of underwater muzzle to separate water,preventing the muzzle from water immersion.By establishing and simplifying the model of underwater weapon sealing device and unstructured mesh computing domain model based on computational fluid dynamics（CFD）,dynamic mesh and user defined function（UDF）,the N-S equation is solved and the numerical analysis and calculation of the complex two-phase flow inside the sealing device are carried out.The results show that the gas discharged from the sealing device is conducive to the formation of the projectile supercavity.When the projectile is launched at 5munder water,the shock wave before and after the projectile has impact on the box body up to 100 MPa,therefore the sealing device must be strong enough.The research results have the vital significance to the design of underwater weapon sealing device and the formation of the projectile supercavitation.
基金Supported by the Aeronautical Science Foundation of China(20061453020)Foundation for Basic Research of Northwestern Polytechnical University(03)~~
文摘The flow around airfoil NACA0012 enwrapped by the body-fitted grid is simulated by a coupled doubledistribution-function （DDF） lattice Boltzmann method （LBM） for the compressible Navier-Stokes equations. Firstly, the method is tested by simulating the low Reynolds number flow at Ma =0. 5,a=0. 0, Re=5 000. Then the simulation of flow around the airfoil is carried out at Ma：0. 5, 0. 85, 1.2; a=-0.05, 1.0, 0.0, respectively. And a better result is obtained by using a local refined grid. It reduces the error produced by the grid at Ma=0. 85. Though the inviscid boundary condition is used to avoid the problem of flow transition to turbulence at high Reynolds numbers, the pressure distribution obtained by the simulation agrees well with that of the experimental results. Thus, it proves the reliability of the method and shows its potential for the compressible flow simulation. The suecessful application to the flow around airfoil lays a foundation of the numerical simulation of turbulence.
文摘Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of oriented valves within a tray and meshed into two parts with different grid types and sizes.The volume fraction correlation concerning inter-phase momentum transfer source was fitted based on experimental data,and built in UDF for simulation.The flow pattern of oriented valve tray under different operating conditions was simulated under Eulerian-Eulerian framework with realizable k-ε model.The predicted liquid height from CFD simulation was in good agreement with the results of pressure drop and volume fraction correlations.Meanwhile,the velocity distribution and volume fraction of the two phases were demonstrated and analyzed,which are useful in design and analysis of the column trays.
基金Sponsored by the National Natural Science Foundation of China (Grant No.5047028 and 50476017)
文摘Numerical simulation on conjugate heat transfer of an internal cooled turbine vane was carried out. Numerical techniques employed included the third-order accuracy TVD scheme, multi-block structured grids and the technique of arbitrary curved mesh. Comparison between results of commercial CFD codes with several turbulence models and those of this code shows that it is incorrect of commercial CFD codes to predict the thermal boundary layer with traditional turbulence models, and that turbulence models considering transition lead to more accurate heat transfer in thermal boundary layer with some reliability and deficiency yet. The results of this code are close to those of CFX with transition model.
基金supported by the National Natural Science Foundation of China (Grant No. 10672183)
文摘Shape optimization of the caudal fin of the three-dimensional self-propelled swimming fish,to increase the swimming efficiency and the swimming speed and control the motion direction more easily,is investigated by combining optimization algorithms,unsteady computational fluid dynamics and dynamic control in this study.The 3D computational fluid dynamics package contains the immersed boundary method,volume of fluid method,the adaptive multi-grid finite volume method and the control strategy of fish swimming.Through shape optimizations of various swimming speeds,the results show that the optimal caudal fins of different swimming modes are not exactly the same shape.However,the optimal fish of high swimming speed,whose caudal fin shape is similar to the crescent,also have higher efficiency and better maneuverability than the other optimal bionic fish at low and moderate swimming speeds.Finally,the mechanisms of vorticity creation of different optimal bionic fish are studied by using boundary vorticity-flux theory,and three-dimensional wake structures of self-propelled swimming of these fish are comparatively analyzed.The study of vortex dynamics reveals the nature of efficient swimming of the 3D bionic fish with the lunate caudal fin.
基金the support of National Natural Science Foundation of China (Grant No.10672183)
文摘Numerical simulations and the control of self-propelled swimming of three-dimensional bionic fish in a viscous flow and the mechanism of fish swimming are carried out in this study,with a 3D computational fluid dynamics package,which includes the immersed boundary method and the volume of fluid method,the adaptive multi-grid finite volume method,and the control strategy of fish swimming.Firstly,the mechanism of 3D fish swimming was studied and the vorticity dynamics root was traced to the moving body surface by using the boundary vorticity-flux theory.With the change of swimming speed,the contributions of the fish body and caudal fin to thrust are analyzed quantitatively.The relationship between vortex structures of fish swimming and the forces exerted on the fish body are also given in this paper.Finally,the 3D wake structure of self-propelled swimming of 3D bionic fish is presented.The in-depth analysis of the 3D vortex structure in the role of 3D biomimetic fish swimming is also performed.
