Abstract:Vortex breakdown of swirl flow in an enclosed conical chamber with a rotating bottom wall was studied by numerical simulation, and the influences of Reynolds number and geometric parameters on the development mechanism of vortex breakdown phenomenon were analyzed. The flow was go-verned by the unsteady three-dimensional incompressible Navier-Stokes equations. The finite volume method was used to discretize the governing equations and the Semi-Implicit Method for Pressure Linked Equation(SIMPLE)algorithm was employed to couple the solutions of the system. The unstructured grid is applied to divide the computational domain. The development characteristics of vortex breakdown in the conical chamber derived from the simulation results are as follows: the low pressure region of vortex breakdown with local fluid recirculation would appear near the axis in the conical chamber when the Reynolds number reaches a critical value. As the Reynolds number increases further, the size of the vortex breakdown bubble increases first and then decreases until it disappears and it moves away from the driving surface within the parameter range studied. However, the position where the vortex breakdown first appears and disappears doesn′t change with the variation of the geometry for the conical chamber with the same aspect ratio. From the values of the critical Reynolds number when the vortex breakdown bubble appears, conical chamber suppresses the generation of vortex breakdown compared with cylindrical chambers and the conical chamber(H1/H=0)with the maximum diameter of the top surface has the best suppress effect.
[1]Escudier M P. Observations of the flow produced in a cylindrical container by a rotating endwall[J]. Experiments in Fluids, 1984, 2(4): 189-196.[2]Lopez J M. Axisymmetric vortex breakdown, Part 1: Confined swirling flow[J].Journal of Fluid Mechanics,1990,221:533-552.[3]Brown G L, Lopez J M. Axisymmetric vortex breakdown, Part 2: Physical mechanisms[J].Journal of Fluid Mechanics,1990,221:553-576.[4]刘应征, 陈汉平. 圆柱空腔内涡破裂的LDA三维流动测量[J]. 实验力学, 1999, 14(4): 477-483. Liu Yingzheng, Chen Hanping. 3-D measurement for vortex breakdown in a cylindrical container by LDA[J]. Chinese Journal of Experimental Mechanics, 1999, 14(4): 477-483.(in Chinese)[5]刘应征, 陈汉平, 罗次申, 等. 圆柱空腔内旋转流动涡破裂随Re变化的实验研究[J]. 上海交通大学学报, 2000, 34(4): 513-516. Liu Yingzheng, Chen Hanping, Luo Cishen, et al. Experiment investigation on vortex breakdown at different Reynolds number[J]. Journal of Shanghai Jiaotong University, 2000, 34(4): 513-516.(in Chinese)[6]刘应征, 陈汉平. 圆柱空腔内旋转流动中轴对称涡破裂现象的数值模拟[J]. 计算物理, 1999, 16(6): 656-660. Liu Yingzheng, Chen Hanping. Numerical simulation of axisymmetric vortex breakdown in a cylindrical container with a rotating lid[J]. Chinese Journal of Computational Physics, 1999, 16(6): 656-660.(in Chinese)[7]Husain H, Shtern V, Hussain F. Control of vortex breakdown by addition of near-axis swirl[J].Physics of Fluids, 2003, 15(2):271-279.[8]Piva M, Meiburg E. Steady axisymmetric flow in an open cylindrical with a partially rotating bottom wall[J]. Physics of Fluids,2005,17(6):063603-063615.[9]Lopez J M, Cui Y D, Lim T T. Experimental and numerical investigation of the competition between axisymmetric time-periodic modes in an enclosed swirling flow[J].Physics of Fluids,2006,18(10):104106-104117.[10]Yu P, Lee T S, Zeng Y, et al. Characterization of flow behavior in an enclosed cylinder with a partially rotating end-wall[J].Physics of Fluids,2007,19(5):057104-057115.[11]Yu P, Lee T S, Zeng Y, et al. Effects of conical lids on vortex breakdown in an enclosed cylindrical chamber[J]. Physics of Fluids,2006,18(11):117101-117111.[12]Yu P, Lee T S, Zeng Y, et al. Steady axisymmetric flow in an enclosed conical frustum chamber with a rotating bottom wall[J]. Physics of Fluids,2008,20(8):087103-087115.