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刘天羽, 胡海豹, 宋健, 任峰. 均匀旋转对圆柱水动力及流动结构的影响. 力学学报, 2024, 56(4): 1-15. DOI: 10.6052/0459-1879-23-441
引用本文: 刘天羽, 胡海豹, 宋健, 任峰. 均匀旋转对圆柱水动力及流动结构的影响. 力学学报, 2024, 56(4): 1-15. DOI: 10.6052/0459-1879-23-441
Liu Tianyu, Hu Haibao, Song Jian, Ren Feng. Hydrodynamics and flow structures of a uniformly rotating circular cylinder. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(4): 1-15. DOI: 10.6052/0459-1879-23-441
Citation: Liu Tianyu, Hu Haibao, Song Jian, Ren Feng. Hydrodynamics and flow structures of a uniformly rotating circular cylinder. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(4): 1-15. DOI: 10.6052/0459-1879-23-441

均匀旋转对圆柱水动力及流动结构的影响

HYDRODYNAMICS AND FLOW STRUCTURES OF A UNIFORMLY ROTATING CIRCULAR CYLINDER

  • 摘要: 基于格子Boltzmann方法(LBM)对均匀旋转控制下的低雷诺数(Re = 100)圆柱绕流问题进行了数值模拟, 得到了转速比从0 ~ 10变化下, 旋转控制对圆柱水动力及流动结构的影响规律. 使用动态模态分解(DMD)对流场特征进行提取, 并分析了施加旋转控制之后转速比对流场不同模态和增长率的影响. 结果表明, 随着转速比增大, 圆柱下游流动结构依次呈现出卡门涡街、剪切层、反向剪切层、单侧涡和附着涡5种结构; 阻力系数时均值先减小, 随后在转速进入单侧涡区间后增大, 升力系数与力矩系数的时均值均单调增加, 同时, 在出现涡脱落的两个转速区间内, 水动力出现了明显的波动, 且二次失稳时波动幅度更大. DMD的结果表明, 圆柱下游的流动结构主要受圆柱壁面的旋转影响而发生改变并产生全新流动模态; 旋转会对流动稳定性产生影响: 在未充分发展阶段, 旋转对流动稳定性的影响不显著, 而在充分发展后, 各转速下的流场不稳定模态数均远少于未充分发展阶段, 随着转速比的增大, 流动稳定性会产生不同程度的增强或减弱, 且无涡脱落时的稳定性高于有涡脱落时, 因此, 通过旋转控制抑制尾涡脱落可以有效增强流动的稳定性.

     

    Abstract: Flow past a uniformly rotating circular cylinder in laminar regime is modeled by the lattice Boltzmann method (LBM), so as to obtain variations of the wake mode with the rotational speed α between 0 and 10. The dynamic mode decomposition (DMD) is then adopted to establish the reduced order model and to figure out the flow stability characteristics. The effect of rotary control on the hydrodynamic force exerted on the cylinder as well as the vorticity field are highlighted. According to the growth rate computed by the DMD, detailed trend of the impact of control parameters on the flow stability is presented. Results show that as the rotational speed increases, five modes can be observed: the Kármán vortex street mode, the shear layer mode, the reverse shear layer mode, the single-side vortex mode, and the attached vortex mode. As the rotational speed increases, the mean drag decreases first, but encounters a dramatic increase when the single-side vortex mode occurs. Meanwhile, the mean lift and mean moment coefficient retain the increasing trend. Within the two rotational speeds intervals where vortex shedding occurs, the hydrodynamic force fluctuates with higher amplitudes than those accompanied with the secondary instability. Results of the DMD show that flow structures in the downstream of the cylinder is mainly affected by the rotary motion of the cylinder wall that leads to new modes. As evidenced by the DMD growth rate, the rotary control also significantly affects the flow stability: in the underdevelopment stage, the effect of rotation on flow stability is not significant. After the full development, the flow field instability modes at each rotational speed are far less than those in the underdevelopment stage. With the increase of the rotational speed, the flow stability will be enhanced or weakened to varying degrees. In general, the flow stability without vortex shedding is better than that with vortex shedding. Therefore, the flow stability can be effectively enhanced via suppressing the vortex shedding using rotary control.

     

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