It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up a...It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up and flow field was simulated by using k-ε turbulence equations of COMSOL Multi-physics. The influence and regularity of number(n),diameter(d) and arrangement of middle hole,and main control parameters of new air-cushion nozzle on aerodynamic characteristics and flow field were studied. The results show that:1) with n increases,airflow vortexes in air-cushion area increase in multiple; d decreases or n increases,air cushion pressure(p_c) becomes uniform; 2) average of p_c is proportional to pressure in nozzle box(p_t),when n increases,ratio of average of p_c to p_t increases,and when n ≤ 3 and d < b / 2,they have little effect on ratio of p_c average to p_t; 3) when n is an even number,n ≥4,and d ≤ b/2,p_c shows good uniformity; when n is an odd number,the center hole affects p_c uniformity greatly,and,when diameter of center hole is less than b / 4 and diameter of non-center is between b / 4 and b / 2,p_c has good uniformity. A new air-cushion jet model was presented,and the deviation of this new model with simulation data and experimental measured data are less than 7.75% and 7.76%,respectively. The present research is valuable for improving air-cushion stability,Al strip temperature homogeneity,and temperature control precision.展开更多
A three-dimensional （3D） finite element model of air-cushion isolated arch dam is presented with the nonlinear gas-liquid-solid multi-field dynamic coupling effect taken into account.In this model,the displacement f...A three-dimensional （3D） finite element model of air-cushion isolated arch dam is presented with the nonlinear gas-liquid-solid multi-field dynamic coupling effect taken into account.In this model,the displacement formulation in Lagrange method,pressure formulation in Euler method,nonlinear contact model based on Coulomb friction law are applied to the air-cushion,reservoir and contraction joint domain,respectively.The dynamic response of Jinping I arch dam with a height of 305 m is analyzed using the seismic records of the Wenchuan Earthquake in 2008.Numerical results show that the air-cushion isolation reduces significantly the hydrodynamic pressure as well as the opening width for the contraction joints of high arch dam.展开更多
To focus on the key scientific problem of process control of dynamic catastrophe of high dams,presented for the first time are the modelling theory of liquid-gas-solid tri-phase coupling of the air-cushion isolation c...To focus on the key scientific problem of process control of dynamic catastrophe of high dams,presented for the first time are the modelling theory of liquid-gas-solid tri-phase coupling of the air-cushion isolation control of high dams and its numerical simulation method,and theoretical description of the complicated dynamics problem of the tri-phase coupling-thermodynamics state-material-contact bi-nonlinearity,as well as the simulation analysis of the key effects of dynamic catastrophe of the air-cushion isolated high dam engineering.The analytic solution of plane-wave with rigid-dam body was created.The simulation comparison of dynamic catastrophe processes of 305 m Jinping arch dam with and without seismic control was carried out,and the results were basically in agreement with that obtained from the large shaking table tests,and verify each other.The entire air-chamber and optimized air-cushion with varying thickness were presented to develop a optimization method.The large shaking table tests of the isolated dam model,which is satisfied with the basic dynamic similarity relations,were performed for the first time.The test data seemed to be convincing and were in agreement with the dynamic simulation results of the tested model,thereby providing an experimental verification to the simulation theory and method.The combination experiments of theoretical model and physical model demonstrated that the hydrodynamic pressure of high arch dams can be reduced by more than 70% as well as the first and third principle stresses of the dam body reduced by more than 20%-30%,thereby the global anti-seismic capacity of the high dam being improved significantly.The results have shown that the air-cushion isolation is the prior developing direction of structural control technology of high concrete dams.展开更多
The 3-D characteristics of the water-air flow patterns in a corridor-shaped air-cushion surge chamber during hydraulic transients need to be considered in the shape optimization. To verify the reliability of the water...The 3-D characteristics of the water-air flow patterns in a corridor-shaped air-cushion surge chamber during hydraulic transients need to be considered in the shape optimization. To verify the reliability of the water-air two-phase model, namely, the volume of fluid model, the process of charging water into a closed air chamber is successfully simulated. Using the model, the 3-D flow characteristics under the load rejection and acceptance conditions within the air-cushion surge chamber of a specific hydro- power station are studied. The free surface waves, the flow patterns, and the pressure changes during the surge wave process are analyzed in detail. The longitudinal flow of water in the long corridor-shaped surge chamber is similar to the open channel flow with respect to the wave propagation, reflection and superposition characteristics. The lumped parameters of the 3-D numerical simulation agree with the results of a 1-D calculation of hydraulic transients in the whole water conveying system, which validates the 3-D method. The 3-D flow structures obtained can be applied to the shape optimization of the chamber.展开更多
基金Sponsored by Science and Technology Project of Liaoning Province(Grant No.L2013113)the Fundamental Research Funds for the Central Universities(Grant No.N140703002)
文摘It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up and flow field was simulated by using k-ε turbulence equations of COMSOL Multi-physics. The influence and regularity of number(n),diameter(d) and arrangement of middle hole,and main control parameters of new air-cushion nozzle on aerodynamic characteristics and flow field were studied. The results show that:1) with n increases,airflow vortexes in air-cushion area increase in multiple; d decreases or n increases,air cushion pressure(p_c) becomes uniform; 2) average of p_c is proportional to pressure in nozzle box(p_t),when n increases,ratio of average of p_c to p_t increases,and when n ≤ 3 and d < b / 2,they have little effect on ratio of p_c average to p_t; 3) when n is an even number,n ≥4,and d ≤ b/2,p_c shows good uniformity; when n is an odd number,the center hole affects p_c uniformity greatly,and,when diameter of center hole is less than b / 4 and diameter of non-center is between b / 4 and b / 2,p_c has good uniformity. A new air-cushion jet model was presented,and the deviation of this new model with simulation data and experimental measured data are less than 7.75% and 7.76%,respectively. The present research is valuable for improving air-cushion stability,Al strip temperature homogeneity,and temperature control precision.
基金supported by the National Natural Science Foun-dation of China (90715026)
文摘A three-dimensional （3D） finite element model of air-cushion isolated arch dam is presented with the nonlinear gas-liquid-solid multi-field dynamic coupling effect taken into account.In this model,the displacement formulation in Lagrange method,pressure formulation in Euler method,nonlinear contact model based on Coulomb friction law are applied to the air-cushion,reservoir and contraction joint domain,respectively.The dynamic response of Jinping I arch dam with a height of 305 m is analyzed using the seismic records of the Wenchuan Earthquake in 2008.Numerical results show that the air-cushion isolation reduces significantly the hydrodynamic pressure as well as the opening width for the contraction joints of high arch dam.
基金supported by the National Natural Science Foundation of China (Grant No. 90715026)
文摘To focus on the key scientific problem of process control of dynamic catastrophe of high dams,presented for the first time are the modelling theory of liquid-gas-solid tri-phase coupling of the air-cushion isolation control of high dams and its numerical simulation method,and theoretical description of the complicated dynamics problem of the tri-phase coupling-thermodynamics state-material-contact bi-nonlinearity,as well as the simulation analysis of the key effects of dynamic catastrophe of the air-cushion isolated high dam engineering.The analytic solution of plane-wave with rigid-dam body was created.The simulation comparison of dynamic catastrophe processes of 305 m Jinping arch dam with and without seismic control was carried out,and the results were basically in agreement with that obtained from the large shaking table tests,and verify each other.The entire air-chamber and optimized air-cushion with varying thickness were presented to develop a optimization method.The large shaking table tests of the isolated dam model,which is satisfied with the basic dynamic similarity relations,were performed for the first time.The test data seemed to be convincing and were in agreement with the dynamic simulation results of the tested model,thereby providing an experimental verification to the simulation theory and method.The combination experiments of theoretical model and physical model demonstrated that the hydrodynamic pressure of high arch dams can be reduced by more than 70% as well as the first and third principle stresses of the dam body reduced by more than 20%-30%,thereby the global anti-seismic capacity of the high dam being improved significantly.The results have shown that the air-cushion isolation is the prior developing direction of structural control technology of high concrete dams.
基金support by the National Natural Science Foundation of China(Grant Nos.51039005,50909076)
文摘The 3-D characteristics of the water-air flow patterns in a corridor-shaped air-cushion surge chamber during hydraulic transients need to be considered in the shape optimization. To verify the reliability of the water-air two-phase model, namely, the volume of fluid model, the process of charging water into a closed air chamber is successfully simulated. Using the model, the 3-D flow characteristics under the load rejection and acceptance conditions within the air-cushion surge chamber of a specific hydro- power station are studied. The free surface waves, the flow patterns, and the pressure changes during the surge wave process are analyzed in detail. The longitudinal flow of water in the long corridor-shaped surge chamber is similar to the open channel flow with respect to the wave propagation, reflection and superposition characteristics. The lumped parameters of the 3-D numerical simulation agree with the results of a 1-D calculation of hydraulic transients in the whole water conveying system, which validates the 3-D method. The 3-D flow structures obtained can be applied to the shape optimization of the chamber.
