This study puts forward an active control method for circular cylinder flow by placing two small affiliated rotating cylinders adjacent to the main cylinder, and their effects on the drag and lift forces acting on the...This study puts forward an active control method for circular cylinder flow by placing two small affiliated rotating cylinders adjacent to the main cylinder, and their effects on the drag and lift forces acting on the main cylinder as well as the heat trans- fer effectiveness are numerically investigated. According to the diameter of the main cylinder the Reynolds number is chosen as Re=200. The well-proven finite volume method is employed for the calculation. The code is validated by comparing the present computed results of flow passing an isolated rotating cylinder with those available from the literature. To describe the present control model, two parameters are defined： the rotation direction of the two small cylinders （including co-current rota- tion and counter-current rotation） and the dimensionless rotation rate a. In the simulation, the rotation rate a varies from 0 to 2.4. The results indicate that the optimum rotation direction of the subsidiary cylinders, which is beneficial to both drag reduc- tion and beat transfer enhancement, is the co-current rotating （the upper affiliated cylinder spins clockwise and the lower affili- ated cylinder spins counter-clockwise）. We observe noticeable suppression of the vortex shedding and favorable reduction of the fluid forces acting on the main cylinder as the rotation rate increases. Besides, the pressure and viscous components of the drag force are analyzed. Energy balance between energy cost for activating the rotating cylinders and energy saving by the momentum injection is considered. In addition, the influence of the affiliated rotating cylinders on heat transfer is also investi- gated. The average Nusselt number is found to increase with the rotation rate.展开更多
文摘为探讨电液伺服系统的同步控制方法,以一个四液压缸大型平台电液伺服同步控制系统为对象,采用实验数据辨识4个液压缸的数学模型,对神经元自适应控制器用于同步控制进行了研究和改进,提出了虚拟主动缸和混合同步神经元控制结构.仿真结果表明:采用虚拟主动缸的同步效果好,最大同步误差为0.2606 mm,但需要建立1个液压缸的数学模型;采用混合同步神经元控制结构,不需要建立数学模型,可通过调节参数控制同步误差,较好地实现同步控制,3和8Hz正弦信号输入时最大同步误差分别为0.4313和0.3825 mm.
文摘This study puts forward an active control method for circular cylinder flow by placing two small affiliated rotating cylinders adjacent to the main cylinder, and their effects on the drag and lift forces acting on the main cylinder as well as the heat trans- fer effectiveness are numerically investigated. According to the diameter of the main cylinder the Reynolds number is chosen as Re=200. The well-proven finite volume method is employed for the calculation. The code is validated by comparing the present computed results of flow passing an isolated rotating cylinder with those available from the literature. To describe the present control model, two parameters are defined： the rotation direction of the two small cylinders （including co-current rota- tion and counter-current rotation） and the dimensionless rotation rate a. In the simulation, the rotation rate a varies from 0 to 2.4. The results indicate that the optimum rotation direction of the subsidiary cylinders, which is beneficial to both drag reduc- tion and beat transfer enhancement, is the co-current rotating （the upper affiliated cylinder spins clockwise and the lower affili- ated cylinder spins counter-clockwise）. We observe noticeable suppression of the vortex shedding and favorable reduction of the fluid forces acting on the main cylinder as the rotation rate increases. Besides, the pressure and viscous components of the drag force are analyzed. Energy balance between energy cost for activating the rotating cylinders and energy saving by the momentum injection is considered. In addition, the influence of the affiliated rotating cylinders on heat transfer is also investi- gated. The average Nusselt number is found to increase with the rotation rate.
