The effect of flow control devices（FCDs） on the uniformity of flow characteristics in a seven-strand symmetrical trapezoidal tundish was studied using both an experimental 1：2.5 hydraulic model and a numerical simu...The effect of flow control devices（FCDs） on the uniformity of flow characteristics in a seven-strand symmetrical trapezoidal tundish was studied using both an experimental 1：2.5 hydraulic model and a numerical simulation of a 1：1 geometric model.The variation coefficient（CV） was defined to evaluate the flow uniformity of the seven-strand tundish.An optimized FCD configuration was proposed on the basis of the evaluation of experimental results.It is concluded that a turbulence inhibitor（TI） and U-type dam are essential to improve the uniformity of fluid flow in the seven-strand tundish.In addition,the configuration of inclination T-type dams with a height of 200 mm between the second and third strands and with a height of 300 mm between the third and fourth strands can minimize the proportion of dead zone.After optimizing the configuration of FCDs,the variation coefficient reduces below 20%of the mean value,and the average proportion of dead zone is just 14.6%;in addition,the temperature fluctuation between the strands could be controlled within 0.6 K.In summary,the uniformity of flow and temperature in the seven-strand tundish is greatly improved.展开更多
Abstract A transonic, high Reynolds number natural laminar flow airfoil is designed and studied. The γ-θ transition model is combined with the shear stress transport （SST） k-w turbulence model to predict the trans...Abstract A transonic, high Reynolds number natural laminar flow airfoil is designed and studied. The γ-θ transition model is combined with the shear stress transport （SST） k-w turbulence model to predict the transition region for a laminar-turbulent boundary layer. The non-uniform free-form deformation （NFFD） method based on the non-uniform rational B-spline （NURBS） basis function is introduced to the airfoil parameterization. The non-dominated sorting genetic algorithm-II （NSGA-II） is used as the search algo- rithm, and the surrogate model based on the Kriging models is introduced to improve the efficiency of the optimization system. The optimization system is set up based on the above technologies, and the robust design about the uncertainty of the Mach number is carried out for NASA0412 airfoil. The optimized airfoil is analyzed and compared with the original airfoil. The results show that natural laminar flow can be achieved on a supercritical airfoil to improve the aerodynamic characteristic of airfoils.展开更多
以传统式张力腿平台(Tension Leg Platform)为对象,采用数值模拟与水池实验相结合的方法研究TLP涡激运动问题,以及张力腿和立管涡激振动特性;采用计算流体力学的方法,建立TLP涡激运动数值分析模型,分析均匀流作用下不同流速、来流方向...以传统式张力腿平台(Tension Leg Platform)为对象,采用数值模拟与水池实验相结合的方法研究TLP涡激运动问题,以及张力腿和立管涡激振动特性;采用计算流体力学的方法,建立TLP涡激运动数值分析模型,分析均匀流作用下不同流速、来流方向、以及规则波波流联合下TLP涡激运动规律,对张力腿、立管的涡激振动特性进行分析;将数值模拟计算结果与拖曳水池、全水深系泊水池试验结果对比,验证数值模拟与水池试验的一致性。分析结果表明,当流的折合速度在5.5~8.5之间时,TLP涡激运动出现锁频现象,系泊有减小平台横向涡激运动的作用,规则波对于流致涡激运动横荡方向运动有减小作用,而对纵荡的影响是其响应随规则波波高的增加而增加。本文得到的结论可为TLP的运动性能研究和工程设计提供参考。展开更多
基金supported by the National Natural Science Foundation of China (No.51404018)the Fundamental Research Funds for the Central Universities of China (No.FRF-TP-15-008A3)
文摘The effect of flow control devices（FCDs） on the uniformity of flow characteristics in a seven-strand symmetrical trapezoidal tundish was studied using both an experimental 1：2.5 hydraulic model and a numerical simulation of a 1：1 geometric model.The variation coefficient（CV） was defined to evaluate the flow uniformity of the seven-strand tundish.An optimized FCD configuration was proposed on the basis of the evaluation of experimental results.It is concluded that a turbulence inhibitor（TI） and U-type dam are essential to improve the uniformity of fluid flow in the seven-strand tundish.In addition,the configuration of inclination T-type dams with a height of 200 mm between the second and third strands and with a height of 300 mm between the third and fourth strands can minimize the proportion of dead zone.After optimizing the configuration of FCDs,the variation coefficient reduces below 20%of the mean value,and the average proportion of dead zone is just 14.6%;in addition,the temperature fluctuation between the strands could be controlled within 0.6 K.In summary,the uniformity of flow and temperature in the seven-strand tundish is greatly improved.
文摘Abstract A transonic, high Reynolds number natural laminar flow airfoil is designed and studied. The γ-θ transition model is combined with the shear stress transport （SST） k-w turbulence model to predict the transition region for a laminar-turbulent boundary layer. The non-uniform free-form deformation （NFFD） method based on the non-uniform rational B-spline （NURBS） basis function is introduced to the airfoil parameterization. The non-dominated sorting genetic algorithm-II （NSGA-II） is used as the search algo- rithm, and the surrogate model based on the Kriging models is introduced to improve the efficiency of the optimization system. The optimization system is set up based on the above technologies, and the robust design about the uncertainty of the Mach number is carried out for NASA0412 airfoil. The optimized airfoil is analyzed and compared with the original airfoil. The results show that natural laminar flow can be achieved on a supercritical airfoil to improve the aerodynamic characteristic of airfoils.
文摘以传统式张力腿平台(Tension Leg Platform)为对象,采用数值模拟与水池实验相结合的方法研究TLP涡激运动问题,以及张力腿和立管涡激振动特性;采用计算流体力学的方法,建立TLP涡激运动数值分析模型,分析均匀流作用下不同流速、来流方向、以及规则波波流联合下TLP涡激运动规律,对张力腿、立管的涡激振动特性进行分析;将数值模拟计算结果与拖曳水池、全水深系泊水池试验结果对比,验证数值模拟与水池试验的一致性。分析结果表明,当流的折合速度在5.5~8.5之间时,TLP涡激运动出现锁频现象,系泊有减小平台横向涡激运动的作用,规则波对于流致涡激运动横荡方向运动有减小作用,而对纵荡的影响是其响应随规则波波高的增加而增加。本文得到的结论可为TLP的运动性能研究和工程设计提供参考。
