Friction stir welding （FSW） has been widely adopted in aerospace industry for fabricating high-strength aluminum alloy structures, such as large volume fuel tanks, due to its exceptional advantages includ- ing low d...Friction stir welding （FSW） has been widely adopted in aerospace industry for fabricating high-strength aluminum alloy structures, such as large volume fuel tanks, due to its exceptional advantages includ- ing low distortion, less defects and high mechanical properties of the joint. This article systematically reviews the key technical issues in producing large capacity aluminum alloy fuel tanks by using FSW, including tool design. FSW process optimization, nondestructive testing （NDT） techniques and defect repairing techniques, etc. To fulfill the requirements of Chinese aerospace industry, constant-force FSW, retractable tool FSW, lock joint FSW, on-line NDT and solid-state equal-strength FSW techniques, as well as a complete set of aerospace aluminum FSW equipment, have been successfully developed. All these techniques have been engineered and validated in rocket tanks, which enormously improved the fabrication ability of Chinese aerospace industry.展开更多
The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the sti...The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the stirred tank, such as gas cavity andaccumulation of gas at the two sides of wall baffles, can be capturedby the simulation. The simulated results agree well with availableexperimental data. Since the improved inner-outer iterative algorithmdemands on empirical formula and experimental data for the impellerregion, and the approach seems generally applicable for simulatinggas-liquid stirred tanks.展开更多
Particle suspension characteristics are predicted computationally in a stirred tank driven by a Smith turbine. In order to verify the hydrodynamic model and numerical method, the predicted power number and flow patter...Particle suspension characteristics are predicted computationally in a stirred tank driven by a Smith turbine. In order to verify the hydrodynamic model and numerical method, the predicted power number and flow pattern are compared with designed values and simulated results from the literature, respectively. The effects of particle density, particle diameter, liquid viscosity and initial solid loading on particle suspension behavior are investigated by using the Eulerian-Eulerian two-fluid model and the standard k-ε turbulence model. The results indicate that solid concentration distribution depends on the flow field in the stirred tank. Higher particle density or larger particle size results in less homogenous distribution of solid particles in the tank. Increasing initial solid loading has an adverse impact on the homogeneous suspension of solid particles in a low-viscosity liquid, whilst more uniform particle distribution is found in a high-viscosity liquid.展开更多
Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid（VOF） method.Extreme waves are generated based on wave focusing in a 2-D numerical model.To validate the capability of the...Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid（VOF） method.Extreme waves are generated based on wave focusing in a 2-D numerical model.To validate the capability of the VOF-based model described in this article,the propagation of regular waves is computed and compared with the theoretical results.By adjusting the phases of wave components,extreme waves are formed at given time and given position in the computation.The numerical results are compared with theoretical solutions and experimental data.It is concluded that the present model based on the VOF technique can provide acceptably accurate numerical results to serve practical purposes.展开更多
The seismic response of an isolated vertical, cylindrical, extra-large liquefied natural gas （LNG） tank by a multiple friction pendulum system （MFPS） is analyzed. Most of the extra-large LNG tanks have a fundament...The seismic response of an isolated vertical, cylindrical, extra-large liquefied natural gas （LNG） tank by a multiple friction pendulum system （MFPS） is analyzed. Most of the extra-large LNG tanks have a fundamental frequency which involves a range of resonance of most earthquake ground motions. It is an effective way to decrease the response of an isolation system used for extra-large LNG storage tanks under a strong earthquake. However, it is difficult to implement in practice with common isolation bearings due to issues such as low temperature, soft site and other severe environment factors. The extra-large LNG tank isolated by a MFPS is presented in this study to address these problems. A MFPS is appropriate for large displacements induced by earthquakes with long predominant periods. A simplified finite element model by Malhotra and Dunkerley is used to determine the usefulness of the isolation system. Data reported and statistically sorted include pile shear, wave height, impulsive acceleration, convective acceleration and outer tank acceleration. The results show that the isolation system has excellent adaptability for different liquid levels and is very effective in controlling the seismic response of extra-large LNG tanks.展开更多
Simulation of solitary wave run-up on a vertical circular cylinder is carried out in a viscous numerical wave tank developed based on the open source codes Open FOAM. An incompressible two-phase flow solver naoe-FOAM-...Simulation of solitary wave run-up on a vertical circular cylinder is carried out in a viscous numerical wave tank developed based on the open source codes Open FOAM. An incompressible two-phase flow solver naoe-FOAM-SJTU is used to solve the Reynolds-Averaged Navier–Stokes（RANS） equations with the SST k ？？ turbulence model. The PISO algorithm is utilized for the pressure-velocity coupling. The air-water interface is captured via Volume of Fluid（VOF） technique. The present numerical model is validated by simulating the solitary wave run-up and reflected against a vertical wall, and solitary wave run-up on a vertical circular cylinder. Comparisons between numerical results and available experimental data show satisfactory agreement. Furthermore, simulations are carried out to study the solitary wave run-up on the cylinder with different incident wave height H and different cylinder radius a. The relationships of the wave run-up height with the incident wave height H, cylinder radius a are analyzed. The evolutions of the scattering free surface and vortex shedding are also presented to give a better understanding of the process of nonlinear wave-cylinder interaction.展开更多
文摘Friction stir welding （FSW） has been widely adopted in aerospace industry for fabricating high-strength aluminum alloy structures, such as large volume fuel tanks, due to its exceptional advantages includ- ing low distortion, less defects and high mechanical properties of the joint. This article systematically reviews the key technical issues in producing large capacity aluminum alloy fuel tanks by using FSW, including tool design. FSW process optimization, nondestructive testing （NDT） techniques and defect repairing techniques, etc. To fulfill the requirements of Chinese aerospace industry, constant-force FSW, retractable tool FSW, lock joint FSW, on-line NDT and solid-state equal-strength FSW techniques, as well as a complete set of aerospace aluminum FSW equipment, have been successfully developed. All these techniques have been engineered and validated in rocket tanks, which enormously improved the fabrication ability of Chinese aerospace industry.
基金the National Natural Science Foundation of China (No. 29792074) and SINOPEC.
文摘The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the stirred tank, such as gas cavity andaccumulation of gas at the two sides of wall baffles, can be capturedby the simulation. The simulated results agree well with availableexperimental data. Since the improved inner-outer iterative algorithmdemands on empirical formula and experimental data for the impellerregion, and the approach seems generally applicable for simulatinggas-liquid stirred tanks.
基金Financial support from National Natural Science Foundationof China(20976191 and 51025624)Program for New Century Excellent Talents in University(NCET-09-0342)111 Project(B12034)
文摘Particle suspension characteristics are predicted computationally in a stirred tank driven by a Smith turbine. In order to verify the hydrodynamic model and numerical method, the predicted power number and flow pattern are compared with designed values and simulated results from the literature, respectively. The effects of particle density, particle diameter, liquid viscosity and initial solid loading on particle suspension behavior are investigated by using the Eulerian-Eulerian two-fluid model and the standard k-ε turbulence model. The results indicate that solid concentration distribution depends on the flow field in the stirred tank. Higher particle density or larger particle size results in less homogenous distribution of solid particles in the tank. Increasing initial solid loading has an adverse impact on the homogeneous suspension of solid particles in a low-viscosity liquid, whilst more uniform particle distribution is found in a high-viscosity liquid.
基金support by the National Natural Science Foundation of China (Grant No. 50779004)
文摘Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid（VOF） method.Extreme waves are generated based on wave focusing in a 2-D numerical model.To validate the capability of the VOF-based model described in this article,the propagation of regular waves is computed and compared with the theoretical results.By adjusting the phases of wave components,extreme waves are formed at given time and given position in the computation.The numerical results are compared with theoretical solutions and experimental data.It is concluded that the present model based on the VOF technique can provide acceptably accurate numerical results to serve practical purposes.
基金Foundation of Basic Research Program of State Key Laboratory from Ministry of Science and Technology of China Under Grant No. SLDRCE10-D-01Foundation of Shanghai Engineering Technical Research Centre Under Grant No. 10DZ2252000
文摘The seismic response of an isolated vertical, cylindrical, extra-large liquefied natural gas （LNG） tank by a multiple friction pendulum system （MFPS） is analyzed. Most of the extra-large LNG tanks have a fundamental frequency which involves a range of resonance of most earthquake ground motions. It is an effective way to decrease the response of an isolation system used for extra-large LNG storage tanks under a strong earthquake. However, it is difficult to implement in practice with common isolation bearings due to issues such as low temperature, soft site and other severe environment factors. The extra-large LNG tank isolated by a MFPS is presented in this study to address these problems. A MFPS is appropriate for large displacements induced by earthquakes with long predominant periods. A simplified finite element model by Malhotra and Dunkerley is used to determine the usefulness of the isolation system. Data reported and statistically sorted include pile shear, wave height, impulsive acceleration, convective acceleration and outer tank acceleration. The results show that the isolation system has excellent adaptability for different liquid levels and is very effective in controlling the seismic response of extra-large LNG tanks.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51379125,51411130131,and 11432009)Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning(Grant No.2013022)the National Basic Research Program of China(973 Program,Grant No.2013CB036103)
文摘Simulation of solitary wave run-up on a vertical circular cylinder is carried out in a viscous numerical wave tank developed based on the open source codes Open FOAM. An incompressible two-phase flow solver naoe-FOAM-SJTU is used to solve the Reynolds-Averaged Navier–Stokes（RANS） equations with the SST k ？？ turbulence model. The PISO algorithm is utilized for the pressure-velocity coupling. The air-water interface is captured via Volume of Fluid（VOF） technique. The present numerical model is validated by simulating the solitary wave run-up and reflected against a vertical wall, and solitary wave run-up on a vertical circular cylinder. Comparisons between numerical results and available experimental data show satisfactory agreement. Furthermore, simulations are carried out to study the solitary wave run-up on the cylinder with different incident wave height H and different cylinder radius a. The relationships of the wave run-up height with the incident wave height H, cylinder radius a are analyzed. The evolutions of the scattering free surface and vortex shedding are also presented to give a better understanding of the process of nonlinear wave-cylinder interaction.
